Automation of the water treatment plant WWTP in Gardabani, Georgia [307881]

Universitatea Tehnică a [anonimizat]: [anonimizat]: dr.conf. Ilie NUCA

Chișinău – 2018

Universitatea Tehnică a Moldovei

Facultatea de Energetică și Inginerie Electrică

Departamentul Inginerie Electrică

Admis la susținere

Șef departament dr.conf. Ilie NUCA

___________________________

„__”____________________ 2018

[anonimizat]:____________ (Moldovan Artiom)

Conducător:___________ (dr.conf. Ilie Nuca)

Chișinău – 2018

DECLARAȚIE

Subsemnatul (a) _______________________ [anonimizat], [anonimizat]. Declar că lucrarea nu a mai fost prezentată sub această formă la nici o instituție de învățământ superior în vederea obținerii unui grad sau titlu științific ori didactic.

Semnătura autorului, __________

ABSTRACT

This project contain: 79 pages, 31 illustrations, 3 tables, 20 bibliographical sources

Keywords: [anonimizat], [anonimizat], PLCMaster, PLC-Slave.

The object of study: SCADA systems for supervision and management of water treatment plant.

The aim of the project:. Creating a SCADA system for monitoring and control of water treatment plant.

In this project put the question of achievements of a [anonimizat]. [anonimizat].

This project includes:

Each system identification and description of the role and function of each. SCADA system type is determined according to the Caeté load requirements imposed.

Achieving communication between SCADA system topology (Master) and SCADA systems (Slave) are selected equipment Hardware and Software.

Making graphical user interfaces for SCADA system (with the role of monitoring and control), and established control condition.

Creation and implementation of SCADA system was conducted at the company's request „Elsaco” Botoșani, România, in collaboration with „Salonix” Chisinau.

[anonimizat], astfel încât apa obținută să corespundă normelor naționale și internaționale referitoare la apa potabilă. Pentru a asigura aceste norme e [anonimizat], anorganice și biologice până la normele standardelor în vigoare.

Obiectivul de studiu reprezintă o stație de tratare a apei, acest obiectiv este complex și compus din mai multe subsisteme care se întind pe suprafețe mari și distanțe considerabile între ele. În urma exploatări îndelungate sa constatat că omul nu poate asigura o [anonimizat] a greși, iar aceste greșeli pot duce la consecințe grave pentru utilizatori de apă potabilă. O altă problemă este că pentru a monitoriza și a dirija cu toate aceste subsisteme care intervin în procesul de tratare a apei, e necesar de mult personal care generează costuri suplimentare.

Scopul principal al lucrării este de a studia etapele de tratare a apei potabile, iar ulterior de proiectat și de implementat un sistem SCADA de gestionare și monitorizare în care intervenția operatorului uman va fi doar în cazuri de mentenanță. Sistemul SCADA proiectat reprezintă un sistem de generația a treia, de tipul structurat în rețea. La realizarea părții de comunicare, s-a apelat la tehnologii moderne prin folosirea unei infrastructuri de fibră optică la transportul semnalelor de date conform protocolului TCP/IP. În funcționarea sistemului SCADA, pe lângă funcțiile principale de control și comandă a elementelor, un aspect esențial în partea de analiză de proces constă în interpretarea datelor înregistrate. Prin intermediul acesteia, se poate reprezenta grafic, în mod selectiv, evoluția funcție de timp a valorilor mărimilor de proces precum și analiza parametrilor de funcționare.

Sistemul SCADA va asigura:

Posibilitatea de vizualizare, accesare și modificare a parametrilor de funcționare a stației

posibilitatea de înregitrare a informațiilor primite de la diferite echipamente, pentru o analiză mai eficientă;

control și monitorizare centralizate sau de la distanță;

cost de operare redus;

utilizarea eficientă a resurselor și serviciilor; productivitate crescută; – diagnosticarea rapida a alarmelor și a avariilor.

Flexibilitate astfel încât să se adapteze în cazul schimbării tehnologiei de control.

1. General description of the water treatment plant Gardabani

1.1. General description the chambers

Inlet chamber

Gardabani WWTP is receiving waste water at the inlet chamber through five inlet pipelines:

Main Collector 1: Tbilisi, Rustavi, Gardabani 1 Concrete Pipeline Dia. 3,300 mm

Main Collector 2: Nitrogen Concrete Pipeline Dia. 1,200 mm

Industrial 1: Power Plant Steel Pipeline Dia. 245 mm

Industrial 2: Power Plant Steel Pipeline Dia. 245 mm

Collector: Gardabani 2 Steel Pipeline Dia. 325 mm

Distribution chamber

The plant inflow is distributed towards the current eight (8) screen channels.

Screening

In the screening hall eight (8) bar screens, each in a single screen channel, with approx. 20

mm gap width serve to screen the waste water. Screenings are discharged on a conveyor belt

and subsequently in containers and then disposed of.

Grit Chambers

There are six (6) existing grit removal channels, which are solely gravitationally operated and

periodically exempted with submerged grit pumps, with the grit being discharged into the sand

drying beds through a pipeline.

Distribution Wells

Currently two (2) distribution chambers are used to hydraulically distribute the pretreated

waste water to the primary clarifiers through weirs, equipped with shut-off gates.

Primary clarification

There are ten (10) round shaped primary clarification basins in the plant of which five (5) units

are currently in operation. The diameter of the units is 50 m.

Outlet Channel

The clarified waste water is discharged into the outlet channel. The water then enters the

WWTP’s original bypass channel and subsequently the runoff channel of the plant.

Primary pumping stations

Raw sludge from the primary clarifiers is pumped through 2 (two) raw sludge pumping station

towards the sludge drying beds.

Sludge drying beds

Dewatered sludge is loaded to a tractor wagon and disposed of. There are three (3) of ten (10)

sludge beds in operation in the plant.

The following plant components will be described:

– Inlet Chamber (object 035)

– Admission Building (object 060)

– PU Coarse Screen (object 061)

– Fine Screen Building (object 065)

– PU Fine Screen (object 066)

– Aerated Grit and Grease Removal combined with High Loaded Aeration Tank A-stage (object 070)

– Distribution Well PST (object 105)

– PST 1 (object 111)

– PST 2 (object 112)

– PST 3 (object 113)

– PST 4 (object 114)

– PST 5 (object 115)

– Outlet Channel (object 200)

– Primary Sludge Pumping Station (object 120)

– Return Sludge Pumping Station (object 125)

– Digested sludge Pumping Station (object 315)

– Return Sludge Pumping Station (object 320)

– Primary Sludge Thickener (object 260)

– PU Picket Fence (object 261)

– Thickened Primary Sludge Pumping Station (object 265)

– Aerobic Digester (object 310)

– Machinery Station (object 410)

– Precipitation Station (object 350)

– Polymer Station (object 360)

– Air purification Pre-Thickener (object 270)

– Air purification Aerobic Digester (object 370)

– Potable Water Booster Station (object 390)

– Wastewater Pumping Station (object 300)

1.1.1 Inlet chamber (035)

The incoming wastewater enters to the wastewater treatment plant at the Inlet Chamber (object 035).

In front of inlet chamber a new shaft (object 030) will be built. This shaft will be constructed around existing inlet concrete pipe DN 3300 mm as well as steel pipe DN 1200, while both pipes are still in operation. The new shaft will also be connected to four smaller inlet pipes and to a new temporary bypass (DN 2200 mm) for bypassing screens plants and grit chambers.

1.1.2 Admission building (060)

Five coarse screens will be installed in existing channels. All existing channels will be refurbished and three will serve in future as bypass. The screens, penstocks and conveyors will be installed in a new building to protect the installation against low temperature, storm and rain. Each of the five screen channels can be isolated by a penstock. The screen building is equipped with a hoisting system.

The building is equipped with ventilation fan for additional ventilation. The ventilator is controlled by local room thermostat.

The enclosure is equipped with gas leakage detector to alarm if the H2S value or CO value or CH4 value rise above normal values. Sound and visual alarms are provided outside the enclosure to warn the operators if CO, CH4 and H2S atmosphere occur. In this case entering of the screen building is not allowed.

1.1.3 PU Coarse screen (061)

Five mechanically raked coarse screens, with a gap width of 20 mm are installed to separate rough material out of the incoming wastewater. If level difference up- and downstream a screen reaches a preselected level, the screen will start operation. The material retained on the screens is unloaded on belt conveyors in direction containers. Two screenings container with volume 4 m³ are located outside the building. The coarse screens, belt conveyor and penstocks are installed inside a new building.

The daily amount of screenings in the coarse screens is calculated with 5 l/(PE x a) and 358,000 inhabitants. The daily screenings quantity is calculated to approx. 5 m³/d of wet screenings. For the dimensioning of the transport system the peak flow is chosen to
4 m³/h. To avoid smell leaks screens channels are covered.

1.1.4 Fine screen building (065)

The fine screens, conveyors, screenings press and containers are enclosed in the building. Five channels are used for the installation of fine screen with automatic mechanical operation. Three screen channels will be used for bypass the screening plant. The screen building is equipped with a hoisting system.

The building for the fine screens, conveyors, press with their screening containers ensure operation in freezing conditions. Fan heaters are provided and ensure 10 °C in the building when the weather is cold for a proper operating process.

The building is equipped additionally with ventilation fans for additional ventilation. The ventilators are controlled by local room thermostat.

A gas leakage detector is installed in this building. In this case entering of the screen building is not allowed.

1.1.5 Fine screen PU (066)

Downstream of the coarse screens units (object 061), the wastewater is discharged to five fine screens channels via existent pipes DN1400. All five channels are fitted with mechanically cleaned fine screens. Four screens are capable to pass 100 % of the peak flow. The Fine screens are designed to remove solids greater than 5 mm. The screen cleaning operation is controlled by the measurement of water levels before and after the screens.

The screenings are dropped into a screenings press with a washing facility following two conveyors. This reduces the volume of screenings and the organic matters are washed out from the screenings and back into the wastewater flow. Hence, the screenings are less problematic to handle. The screenings are automatically transported by the screening press towards a rotatable conveyor and dropped into containers.

The daily amount of screenings in the fine screens is calculated with 10 l/(PE x a) and 358,000 inhabitants. The daily screenings quantity is calculated to approx. 10 m³/d of wet screenings. For the dimensioning of the transport system the peak flow is chosen to

4 m³/h. After pressing the screenings, the quantity will be approx. 5 m³/d.

To avoid smell leaks screens channels are covered.

1.1.6 Aerated grit and grease removal combined with high loaded aeration tank A-stage (070)

The aerated grit chamber and grease trap are the first stage biological process, following the principals of an adsorption-activated-sludge-process (AB-process). The grit removal and the high loaded aeration tank are one unit. The combined function is biological treatment and sand plus grease removal.

Four grit and grease removal tanks will be constructed, each capable of handling 25% of the maximum flow under rainy conditions. Hydraulically even higher flows can be treated, but efficiency will decrease.

Grit will be removed in order to reduce the risk of damage to the mechanical equipment in the following treatment units, and grease will be removed to avoid non-aesthetic conditions caused by the volatile organics and malodorous floating sludge. The settled grit will be transported to the grit classifier then unloaded into a container. The retained grease will be scraped off and discharged into a grease collector shaft.

Highly loaded biological A-stage

The aerated grit chamber is calculated and proposed as a biological treatment (A-stage). The A-stage is a biological high loaded activated sludge stage. Aerobic and facultative anaerobic activated sludge is produced and pollutants can be removed by adsorbing and additionally by biodegradation. This operation has special advantages. The primary pollutants are adsorbed to the activated sludge flocs and will be removed by taking off primary sludge. This process is similar to the flocculants in a chemical enhanced primary sedimentation tank. The oxygen consumption is reduced.

The simultaneous use of an aerated grit chamber as an adsorption stage is achieved with additional air requirements and with a separate return sludge circle to activate growth of biomass and bioflocs for adsorption.

Aerated Grit and grease removal

A standing wave is produced with compressed air aeration on one side. The sands are separated on the tank floor. The average retention period is higher than 10 minutes and a sand removal for grit with a diameter bigger than 0.20 mm is realised. The scum is bloated with the fine bubble aeration and can be skimmed from the water surface. The bottoms of the activated sludge basins (aerated grit removal tank) are single-sided fitted with membrane diffusers to guarantee sufficient aeration capacity.

1.1.7 Distribution well PST (105)

The distribution chamber is designed to distribute 80 % of the flow from the aerated grit to four PST´s (object 111 -112 -113 -114).

The outlets of the distribution tank are fitted each with 2 penstocks (105HS101 – 102 /

201 – 202 / 301 – 302 / 401 – 402) to isolate any primary sedimentation tank in case of malfunction.

The overfall walls have the same height and the same length. Thus results in a uniform flow to each primary sedimentation tank.

1.1.8 Primary sedimentation tanks (111,112,113,114,115)

The primary clarifiers remove readily settleable solids and floating materials and reduce the suspended solids content. The purpose of the primary clarifiers is to remove a substantial portion of the organic solids from the untreated wastewater, with a resulting decrease in the organic and solid loadings in effluent channel.

Treated wastewater will be discharged into outlet channel (unit 200).

Settled sludge on one hand will be pumped to the aerated unit chamber to activate a biological treatment process and to increase efficiencies of the mechanical treatment stage. On the other hand primary sludge will be pumped to the static thickener (object 260).

1.1.9 Outlet channel (200)

The outlet channel (object 200) collects treated wastewater to discharge.

1.1.10 Primary sludge pumping station (object 120) + Return sludge pumping station (object 125)

The primary sludge pumping station (object 120) consist of two pumping units. The primary sludge pumps (object 120) for primary sludge from PST units 111 – 114 (object 110) and the return sludge pumps (object 125) from PST units 111 – 114 (object 110).

For evacuation of water a cellar evacuation pump (120AP002) is foreseen which starts automatic operation in case of leakage detected by a level switch (120ML101). The pump is installed in existing pump sump.

A ventilation fan (120AL001) provides an air exchange. The station is equipped additionally with a fan heater (120AL005) for heating and ensures 10 °C in the building when the weather is cold. The ventilators are controlled by local room thermostat (120MT001).

A Lifting facility allows the removal of the pumps.

1.1.11 Digested sludge pumping station (object 315) + Return sludge pumping station for PST 115 (object 320)

The Digested sludge pumping station (object 315) consist of two separated pumping unit. The return sludge pumps (object 320) for return sludge of PST 115 (object 110) and another the digested sludge pumps (object 315) for digested sludge from the aerobic digester (object 310).

For evacuation of water a cellar evacuation pump (315AP002) is foreseen which starts automatic operation in case of leakage detected by a level switch (315ML101). The pump is installed in existing pump sump.

A ventilation fan (315AL001) provides an air exchange. The station is equipped additionally with a fan heater (315AL006) for heating and ensures 10 °C in the building when the weather is cold. The ventilators are controlled by local room thermostat (315MT001).

A Lifting facility allows the removal of the pumps.

1.1.12 Primary sludge thickener (260) + PU Picket fence (261)

The primary sludge of the A-stage is gravitationally thickened. The thickener is a "continuous flow" type with diameter of 20 m equipped with a picket fence and with fixed overflow weir for the removal of sludge liquor. The thickener will be constructed as a circular concrete tank with its base sloping towards a bottom hopper located in the centre of the tank.

The feeding pipe ends in height of the water level at the centre of the tank. The sludge "draw-off" is installed at the bottom of the hopper. Inside the thickener, a sludge blanket level sensor is installed.

The thickener is covered. The foul air under the covered tank will be sucked and transferred to biofilter (unit 270).

1.1.13 Thickened primary sludge pumps (265)

The thickened sludge pumps are designed as (1 + 1) stream solution. The pumps transport sludge from the Primary sludge Thickener (object 260) to the Aerobic Digester (object 310).

1.1.14 Aerobic digester (310)

Sludge is stabilised in aerobic sludge digester. On the flat bottom a fine bubble aeration system will be installed.

A tank with defoaming agent and a dosing pump will be installed in chemical dosing building (object 350). The defoaming agent can be dosed into sludge feed line to the stabilisation tank. The stabilisation tank is covered with a plastic membrane textile. The cover is provided with service openings and a connection for exhaust air. Waste air will be extracted and treated in one biofilter (object 370). To prevent foam discharge to the biofilter a sprinkler system next to the waste air removal will be installed. The spraying equipment is connected to the potable water network (unit 390).

The aerated tank is equipped with a fixed overflow for the removal of digested sludge. The sludge flows in a shaft (object 400.4) which serves as pump sump for the 2 digested sludge pumps located in object 315. From this pumping station (object 315) sludge is pumped to existing sludge drying beds (object 520).

1.1.15 Sludge machinery station (410)

The pressured air for aerobic sludge stabilisation (object 310) and for A-stage is produced in the sludge machinery station (object 410). Inside the sludge machinery station three turbo blowers are installed in a separate room.

The turbo blowers are designed for 6,500 Nm³/h, each with a pressure difference of 650 mbar. The air demand is calculated for a fine bubble aeration system in the stabilisation tank. For details please see process calculation.

The blower capacities are adequate to keep the minimum oxygen concentration in the stabilisation tanks at 0.5 mg/l minimum.

The blower units aerating the sludge stabilisation stage are monitored through pressure, temperature and flow sensors and registered in the Process Control System (PCS). The amount of air delivered to the sludge stabilisation is adjustable from the Process Control System (PCS).

1.1.16 Precipitation station (350)

The ferric chloride dosing plant is a stand-alone plant started from a signal from the treatment works control system with the ability to accept a signal to pace the dosing pumps in response to flow through the WWTP Outlet channel.

Storage tank for the ferric chloride is located indoors, frost free and are isolated in a separate frame to protect from accidental leakage.

The ferric chloride is dosed into the two outlet shafts of the grit chambers (object 070) to the distribution chambers of the primary sedimentation tanks in proportion to their respective waste water flow rate.

1.1.17 Flocculant station (360)

The polymer preparation system is designed as an automatic preparation plant for polymer powder. The storage for the polymer powder is designed for the consumption of 10 days. The polymer solution shall be dosed into the distribution wells of the primary sedimentation tanks (object 111 – 115) in proportion to their respective wastewater flow rate. Flocculant station is equipped with totally four dosing pumps. Two redundant dosing pumps are provided for each of their dosing lines.

1.1.18 Air purification pre-thickener (270)

To avoid smell leaks from sludge thickening, the tank is covered and air below the covered spaces is extracted and treated in a biofilter.

1.1.19 Air purification aerobic digester (370)

To avoid smell leaks from sludge digester (object 310), the tank is covered and air from the covered space is extracted and treated in a biofilter.

1.1.20 Potable water booster station (390)

The potable water booster station (object 390) serves all facility parts with potable water. The booster station will be dry installed inside the chemical dosing building (object 350).

1.1.21 Dewatering pumping station (300)

Two submersible pumps (1 duty +1 stand-by) are designed in order to displace the wastewater from control room (object 500) as well as condensate from the biofilters (object 270 and 370) and drainage of the screenings and grit containers (object 060 and 065) towards the inlet chamber of the coarse screen building (unit 060).

1.2. Functional description the chambers

1.2.1 Inlet chamber (035)

After finalising the shaft object 030, the bypass DN 2200 and its connection to the existing transport sewer in direction to existing distribution chamber for eastern sedimentation tanks the existent pipe DN 3300 will be demolished inside the shaft and waste water will be routed via the new bypass. The opening to existing inlet chamber will be closed temporary with a steel-plate. This works will be done during a limited period. During this period incoming flow will be stopped and small flows from leaking will be pumped with temporary pumps. After sealing the steel-plate all downstream works can be done without being influenced by incoming waste water. When all works for the rehabilitation are completed, the steel-plate will be removed, and the temporary bypass will be closed and removed. Afterwards the new plant is in operation.

Each inlet will be equipped with flow measurement (035MF001 – 005) delivered by the Employer.

The inlet chamber (object 035) is equipped with a level measurement (035ML001).

In the inlet chamber pH-value (035MQ001) and temperature (035MT001) will be measured and transferred to SCADA system. The data is for information purposes only.

The effluent flows by gravity to the distribution chamber between the Admission Building (object 060) and the inlet chamber. It distributes the water to the coarse screens and bypass channels of the screens. A scum and oil evacuation are foreseen in the distribution chamber. At the corner of the distribution chamber, a rectangular pit is designed. The pit possesses an opening. In front of this opening, a lowerable penstock is installed. In case of scum accumulation on the water surface, the operator will operate the penstock manually.

During daily checks, the operator must check the situation and open the penstock for a limited period. The scum will spill over the penstock blade and falls into the collecting pit. Afterwards the operator will close the penstock manually. The collecting pit has a storage capacity of rd. 9 m³. From there a suction vehicle will suck the scum. An evacuation pipe with a coupling (035HH001) are installed for scum removal.

1.2.2 Admission building (060)

The coarse screens, bypass channels, and conveyors are enclosed in the building. Waste air is collected and transferred by forced ventilation (060AL101) to atmosphere.

The building is equipped with gas leakage detectors to alarm if the CH4, Benzine, Benzol value (060MQ001) or H2S value (060MQ002) or CO value (060MQ003) rise above a first limit (low values). Sound and visual alarms are provided outside the enclosure to warn the operators if CO, CH4 and H2S atmosphere occur.

An overhead lifting device (060AH001) is provided in the building to allow the removal/maintenance of installed equipment.

1.2.3 PU Coarse screen (061)

Five mechanically raked coarse screens (4 duty (061AK101 – 401) + 1 standby (061AK501)) are installed. The screens are designed to remove solids greater than 20 mm. The screenings are automatically transported by two belt conveyors (061AC001/002) and a rotatable belt conveyor (061AC003). The material is dropped into containers (060HK001/002). Two screenings containers with 4 m³ each are foreseen for installation outside the building. The screen cleaning operation is controlled by the measurement of water levels upstream and downstream the screens (061ML101 – 105). If level difference reaches a preselected level a screen will start cleaning. The conveyor will start the band movement and approx. 1 minute after than the cleaning process ends the conveyor will stop. Conveyors are dimensioned for maximum 4 m³/h.

Each screen channel can be isolated with penstocks installed upstream of coarse screens (060AS101 – 105) and downstream of the fine screen channels (065AS101 – 105). Three emergency bypass channels around the coarse screens are designed in case of total failure of the electrical panel. This bypass channel starts upstream of coarse screens with a fixed overfall weir.

An overhead lifting device (060AH001) is provided in the building to allow the maintenance of installed equipment.

Figure 1 Object 060. Electrical works.

The roof of the admission building is designed to dismantle the metallic construction above the coarse screens to allow the transport of each screen outside the building in case a replacement will be necessary in the future.

1.2.4 Fine screen building (065)

Waste air is collected and transferred by forced ventilation (1 duty (065AL201), 1 standby (065AL202)) to atmosphere. The building is equipped additionally with fan heaters (065AL004 – 006) for heating and ensures 10 °C in the building when the weather is cold. The building is equipped with gas leakage detectors to alarm if the CH4, Benzine, Benzol value (065MQ001) or H2S value (065MQ002) or CO value (065MQ003) rise above a first limit (low values). Sound and visual alarms are provided outside the enclosure to warn the operators if CH4, Benzine, Benzole, CO, or H2S atmosphere occur.

An overhead lifting device (065AH001) is provided in the building to allow the removal/maintenance of installed equipment.

The distribution chamber between the fine screen building (object 065) and the grit and grease removal (object 070) possesses a sampler (065AK001) for providing samples of waste water.

1.2.5 Fine screen PU (066)

Five (4 duty (066AK101 – 401) and 1 standby (066AK501)) parallel mechanically raked fine screens are installed. The screens are designed to remove solids greater than 5 mm. The screenings are automatically transported by two belt conveyors (066AC001/002) into one screening press (066AC101). From here, the material is dropped into containers (065HK001/002) by using a short rotatable belt conveyor (066AC003). Two screenings containers with 4 m³ each are foreseen for installation inside the building. The screen cleaning operation is controlled by the measurement of water levels upstream and downstream the screens (066ML101 – 105). If level difference reaches a preselected level a screen will start cleaning. The conveyor will start the band movement and approx. 1 minute after than the cleaning process ends the conveyor will stop. Also screen press starts operation and ends after a preselected time. During operation time of press the small rotatable band transports the pressed screenings into the preselected container. Presses and conveyors are dimensioned for maximum 6 m³/h.

Figure 2 Object 065. Electrical works.

Each screen channel can be isolated with penstocks installed upstream of coarse screens (060AS101 – 105) and downstream of the fine screen channels (065AS101 – 105). Three emergency bypass channels around the fine screens are designed in case of total failure of the electrical panel. This bypass channel starts upstream of coarse screens with a fixed overfall weir. The effluent water of the fine screen channels and the bypass channels flow to a distribution chamber upstream the Grit and Grease Removal Chamber (object 070).

1.2.6 Aerated grit and grease removal combined with high loaded aeration tank A-stage (070)

To avoid settlement of suspended solids in the existing channel between fine screens and grit chamber an aeration pipe system with coarse bubble aeration (070HK010) will be installed. This system provides sufficient turbulence in the channel and increase the active volume of A-stage.

The wastewater from the distribution chamber of fine screens flows to the new combined aerated grit chambers and grease removal tanks. Each line of the grit and grease removal chamber is fitted with penstocks at the inlet (070AS101 – 401) and outlet (070AS102 – 402) side to allow isolation of a line for maintenance purposes.

The fine bubble aeration is performed by membrane plate diffusers (070HK070) which produce a vertical flow velocity (wave) for avoiding sedimentation of organic matter and provide sufficient efficiency for oxygen transfer. The compressed air is produced in the common blower station (object 410) located in building (object 350) for both A-stage and aerobic sludge stabilisation.

Dissolved oxygen in inlet flow, in NOx-loads and oxygen transfer at min aeration capacity (1,790 Nm³/h) ensures sufficient oxygenation capacity for biological treatment in A-stage. In dead minimum aeration for the wave in a grit chamber leads to increasing oxygen concentrations.

Aeration is automatically regulated by electrically actuated control valve (070AS070) based on measurement of the average oxygen concentration measured by the two oxygen transmitters (070MQ101 – 201) in the common outlet channel of the tanks. Alternatively, one of these metered DO- values by each individual sensor can be selected as input for control of the assigned regulation valve.

The blowers for aeration are controlled by the air pressure that fluctuates relative to the control valve openings. The pressure is measured in the transport air pressure pipes by a pressure sensor and transmitter (410MP104).

The sands are separated with both, a helical standing wave and a special cross section of the building. They are collected in a trough at the tank bottom.

The sand-water-mixture is pumped into 2 collecting channels (one for two trains) and transported through this channel to the pit with 2 grit slurry pumps. It will be then pumped by the 2 (1 duty (070AP501) + 1 standby (070AP502)) grit slurry pumps to the grit classifier (070AK001). The level measurement (070ML101) located in the grit collecting chamber controls the grit pump operation. The level sensor (070ML102) located in the grit collecting chamber serves for pumps dry running protection and overflow of the sump. The grit pumps 070AP501 and 070AP502 will be interlocked with the grit classifier; the start of the pump causes the start of the grit classifier as well. The sand classifier separates the sand from the water on behalf of principle of gravity. The sand from the classifier is transported by screw conveyor to a container (070HK001/002). The container is able to accommodate 4 m³ of sand. Drainage water of the grit classifier is delivered to the effluent channel of fine screens (object 060) by gravity.

Scum, oil and grease is skimmed from the water surface by a blade, mounted on scraper bridge (070AK101 + 301), which transport the scum to a scum pipe and collects it in a grease collecting chamber at the outlet side of the grit removal tank. From there the grease will be sucked by a suction vehicle.

Figure 3 Object 070. Electrical works.

The waste water from four sand removal tanks passes a penstock at outlet of each tank and flows into a distribution chamber with a volume of approx. 300 m³. Additional dosing of precipitant is possible if CEPT operation is active. Dosing pumps located in the Technical building (object 350) dose via two dosing lines precipitant into the shafts in effluent Grit Chamber. Two fixed overflow weir divide the flow into 80 % and 20 %. The weirs can be separated by means of removable stop-logs. Smaller flow is directed into sedimentation tank No 115 and bigger flow is directed to the distribution chamber object 105 serving other four sedimentation tanks No 111 – 114.

1.2.7 Distribution well PST (105)

The distribution chamber (object 105) collects wastewater from the distribution chamber at the downstream side of the grit and grease removal chamber (object 070). It receives 80 % of total flow and is designed to distribute the flow to four primary sedimentation tanks (PST 1 – 4, object 110).

Flocculant from the polymer station (object 360) is dosed into the wastewater. The overfall walls have the same height and the same length. Thus results in a uniform flow to each primary sedimentation tank. The four outlets of the distribution tank are fitted each with manually operated penstocks to isolate any clarifier in case of malfunction or maintenance.

The chamber is fitted with a level measurement (105ML101).

1.2.8 Primary sedimentation tanks 110 (111,112,113,114,115)

The feeding of the tanks occurs via a pipe (DN 2000) into the central structure. The outflow of the tanks occurs via effluent weirs (111HK101, 112HK201, 113HK301, 114HK401, 115HK501) mounted at the new steel effluent channels (111HK102, 112HK202, 113HK302, 114HK402, 115HK502) located at supports at outside wall of the tanks. The channels are equipped with scum boards. Treated wastewater will be discharged into the outlet channel (unit 200).

The scraper (111AK101, 112AK201, 113 AK301, 114AK401, 115AK501) collects the settled sludge into the central hopper of the primary clarifier. Scum is collected in a scum hopper (111HK103, 112HK203, 113HK303, 114HK403, 115HK503) served by the scum beam at scraper bridge. The scum from PST 111-114 is collected in a scum chamber located near the outside wall and flows by gravity towards the primary sludge pumping station (object 120). The scum from PST 5 flows into a shaft (object 400.4) located in between the PST 115 and the aerobic digester (object 310). The scum is mixed with the discharged stabilised sludge into the shaft (object 400.4) and gravitates directly to the digested sludge pumping station (object 315)

The sludge hoppers of PST 1,2,3 and 4 are connected via new sludge discharge pipes with the primary sludge pumping station (object 120). The sludge hopper of PST 5 is connected with the sludge pumping station (object 315).

Figure 4 Object 110. Electrical works.

The primary sedimentation tanks include following measurements:

– Sludge level sensor (110ML101, 110ML201, 110ML301, 110ML401, 110ML501)

1.2.9 Outlet channel (200)

The outlet channel (object 200) collects the treated wastewater from the effluent channels of all primary sedimentation tanks 111 – 115.

The outlet channel includes:

– Level measurement (200ML002)

– Flow measurement (200MF001)

– pH measurement (200MQ001) and Temperature measurement (200MT001)

– Sampler (110AK001)

The flow in the outlet channel goes to discharge.

1.2.10 Primary sludge pumping station (object 120) + Return sludge pumping station (object 125)

Object 125:

The sludge hoppers of PST 111 – 114 (object 110) are connected via sludge discharge pipes DN 300 with the primary sludge pumping station (object 120). At each sludge discharge pipe, an electrical actuated valve (120AS101 – 120AS401) is installed. This pumping station consist also the return sludge pumping station (object 125), equipped with 2 centrifugal pumps (one duty (125AP101) + one standby (125AP201)) as return sludge pumps to the combined A- Stage and grit and grease removal chamber (object 070).

The return sludge pumps (125AP101/201) are controlled by frequency converters.

A pre-selected return sludge ratio (13.6 % at dry weather flow) calculates the necessary return sludge flow. The calculation is done with an average inlet flow, measured by a flow measurement (200MF001), over 1 h time period multiplied with the given ratio. The return sludge flow is measured by a flow measurement (125MF001). The four electric actuated gate valves (120AS101 – 120AS401) in the sludge pipelines from the sludge hopper of the tanks are open and the flow measurement (125MF001) regulate the calculated flow. 80 % of total return sludge flow will be pumped by installed pump capacity.

The sensors (110ML101, 110ML201, 110ML301, 110ML401) measure the sludge levels. If a sludge level is higher than a preset value (variable set point in SCADA) a fault report is set. Operator will enhance the evacuation of the accumulated sludge from concerned tank (111 – 114) by full open electric actuated valve and stop sludge evacuation from the tank with lower sludge level by closing for a pre-selected time i.e. 1 h the electric actuated gate valves (120AS101 – 120AS401) in the sludge pipelines from the sludge hopper of the tanks. Afterwards the operator has to open all electric valves again and observe the sludge levels.

Object 120:

The sludge hoppers of PST 111 – 114 (object 110) are connected via sludge discharge pipes with the primary sludge pumping station (object 120). At each sludge discharge pipe, an electrical actuated valve (120AS101 – 120AS401) is installed. Furthermore scum from primary sedimentation is routed to the pumping station. The four separate sludge discharge pipes are connected to a header located at the suction side of both pumping stations (object 125) and (object 120).

The primary sludge pumping station (unit 120) is connected to the suction header of the return sludge pumping station (object 125). The primary sludge pumping station will be equipped with three dry-installed rotary lobe pumps (two duty (120AP101/201) + one standby (120AP301)). Each primary sludge pump possesses an overpressure switch (120MP101 – 301) and a temperature sensor (120MT101 – 301) as protection device. The pipes are fitted with all necessary valves. The primary sludge will be conveyed by the rotary lobe pumps to the primary sludge thickener (object 260). The primary sludge flow is measured and recorded (120MF101). The daily quantity of primary sludge is approx. 1,415 m³/d in design flow conditions.

The control program for primary sludge pumping can be selected based on pre-selected base value of daily sludge quantity (e.g. 1,400 m³/d). The set point value of daily sludge quantity is calculated with the following formula.

QPS = 1,400 m³/d + deltaSSA-stage x VA-stage / SSRS

Volume VA-stage 3,580 m³

SSRS – content measured by dry solids sensor (120MQ101)

deltaSSA-stage (SSA-stage – SSset value)

SSset value- 1.6 g/l

SSA-stage determined in laboratory

The pressure pipe towards sludge thickener (object 260) is fitted with a measurement (120MQ101), which analyses dry solids content. This sensor measures the DS-content value in return sludge.

Example

Volume VA-stage 3,580 m³

SSRS -content 17 g/l

SSset value 1.6 g/l

SSA-stage 1.8 g/l

deltaSSA-stage 0.2 g/l = 1.8 – 1.6

QPS = 1,400 m³/d + deltaSSA-stage x VA-stage / SSRS

QPS = 1,400 m³/d + 0.2 x 3,580 / 17

QPS = 1,400 + 42 m³/d

Figure 5 Object 120 and 125. Electrical works.

The Operator makes every workday a manual control of DS-concentration in laboratory and SCADA system will calculate automatically the amount of the daily sludge quantity to be withdrawn. The daily sludge quantity is designed to be pumped in 18 h uniformly distributed over 24 h towards the sludge thickener (object 260). The daily primary sludge quantity will be pumped by help of a Start – Pause mode.

Daily operation time per pump QPS = 1,442 m³/d / (2 x 80 m³/h) = 9 h

Alternatively, manually controlled constant flow of primary sludge can be selected by operator, if the above mentioned automatically operation mode is not possible for operation.

1.2.11 Digested sludge pumping station (object 315) + Return sludge pumping station for PST 115 (object 320)

Object 320:

The sludge hopper of PST 115 (object 115) is connected via a sludge discharge pipe DN 300 with the return sludge pumps (object 320). At the sludge discharge pipe, electrical actuated valve (320AS501) is installed.

The return sludge pumping station (object 320) will be equipped with two dry-installed pumps (one duty (320AP301) + 1 standby (320AP401)). The return sludge pumps are controlled by frequency converters.

A pre-selected return sludge ratio (13.6 % at dry weather flow) calculates the necessary return sludge flow. 20 % of total return sludge flow will be pumped by installed pump capacity of 535 m³/h to the combined A- Stage and grit and grease removal chamber (object 070).

Object 315:

The aerobic digester (object 310) is connected via a sludge discharge pipe DN 250 with the shaft 400.4 upstream of the digested sludge pumps (object 315). Furthermore scum from primary sedimentation tank PST 115 gravitates to the shaft 400.4 and will be mixed with digested sludge. At the sludge discharge pipe from shaft 400.4 towards the digested sludge pumping station an electrical actuated valve (315AS601) is installed. The digested sludge pumping station will be equipped with two dry-installed pumps (one duty (315AP401) + 1 standby (315AP501)). One spare pump (315AP601) will be provided. Each digested sludge pump possesses an overpressure switch (315MP101/201) and a temperature sensor (315MT101/201) as protection device. A flow meter (315MF601) and a dry matter sensor (315MQ601) is installed in the collector pressure pipe. The flow meter shall primarily serve to register sludge volume transported. Both sensors are registered in the Scada. The digested sludge flows to the existent sludge drying beds (object 520).

Figure 6 Object 315 and 320. Electrical works.

In the suction header pH-value (315MQ002) and temperature (315MT002) will be measured and transferred to SCADA system. The data is for information purposes only.

1.2.12 Primary sludge thickener (260) + PU Picket fence (261)

Primary sludge of the primary sedimentation tanks (object 110) is pumped via rotary lobe pumps located in the Primary sludge pumping station (object 120) to the Primary Sludge Thickener (object 260). The feeding pipe ends in height of the water level at the centre of the tank. The thickener receives the flow and solids in the sludge settle down. A picket fence (261AM101) stirs the sludge continuously. Inside the thickener a sludge blanket level sensor (260ML101) is installed. As the gravitational thickener is a flow-through-tank, sludge liquor according to the inlet raw sludge quantity spills over an installed overflow weir (260HK101) into a pipe directing the sludge liquor by gravity to the distribution chamber between fine screen (object 065) and grit and grease removal (object 070). The thickened sludge is drawn off via a pipe at the bottom of the hopper to the thickened primary sludge pumps (object 265). For monitoring of pH-value a sensor (265MQ002) is installed in the discharge pipe from the sludge thickener towards the thickened sludge pumping station. Both pH- and temperature (265MT002) will be measured and transferred to SCADA system.

Figure 7 Object 260. Electrical works.

The data is for information purposes only. Waste air is delivered to a biofilter (object 270) for treatment.

1.2.13 Thickened primary sludge pumps (265)

Thickened sludge is drawn off by 2 pumps (1 duty (265AP101) + 1 standby (265AP201)) installed in object 265. The withdrawal pipe is fitted with a dry solid measurement (265MQ001), which together with the sludge blanket level sensor (260ML101) stops or starts the evacuation pumps. A sludge level approx. 0.20 m higher than a pre-selected level approx. 3.0 m will start the pumps operation. 30 cm below this level the pump stops operation. The suction pipe is fitted with a dry solid measurement (265MQ001). A dry solid minimum value of approx. 4.5 % corresponds to a minimum sludge blanket level which stops the evacuation pumps. A maximum dry solid value of approx. 5.0 % will correspond to maximum sludge blanket level which starts the evacuating pumps.

Each pump has an overpressure switch (265MP101/201) and a temperature sensor (265MT101/201) as protection device.

Figure 8 Object 265. Electrical works.

On the common pressure pipe of the pumps a flow measurement device (265MF001) is located to measure and record the quantity of thickened primary sludge towards the aerobic digester. The pipes can be flushed by using the up- and downstream installed flushing devices.

1.2.14 Aerobic digester (310)

The aerobic digester (object 310) is fed by sludge from the thickened primary sludge pumps (object 265). Before entering the digester, defoaming agent from the tank for defoaming agent (340HK001) can be dosed into the sludge feed line by two dosing pumps (one duty (340AP101) + 1 standby (340AP201)).

Pressurised air from the sludge machinery station (object 410) is delivered to the Aeration system (310HK310).

The digester is equipped with three combined oxygen and temperature sensor (310MQ101 / 310MT101), (310MQ102 / 310MT102) and (310MQ103 / 310MT103) and a level sensor (310ML101).

Digested sludge flows through a drowned pipe to a shaft (object 400.4). The shaft serves the digested sludge pumping station (object 315).

The thickened sludge pumps (265AP101 / 201) which are the feeding pumps of the digester are also interlocked with the level measurement (310ML101) inside the digester. If the digester water level reaches a preset value max-level (set value 310/11), a signal will be indicated and the thickened sludge feeding pump (265AP101 / 201) stops and an alarm is given to SCADA. The operator has to check the status of the digested sludge evacuation pump (315AP401 / 501).

The cover of the tank is provided with four service openings DN1400 positioned at 4, 6, 9 and 12 o`clock positions. The service openings are designed over the sludge feed pipe (12 o`clock position), the sludge evacuation pipe (6 o`clock position) and the dissolved oxygen sensors 310MQ102 respectively 310MQ103 (9 o`clock respectively 4 o`clock position). The service openings are provided with two view windows each. The view windows of service opening 1 (12 o`clock position) and service opening 2 (9 o`clock position) are open in normal operation, to assure fresh air supply into the tank. The cover of the tank is provided with a connection DN 700 for exhaust air. Waste air is delivered to a biofilter (object 370) for treatment.

The aerobic stabilisation tank possess a hydraulic Over-/ under-pressure safeguard (310HK312) for limiting highest and lowest pressure as protection device. The pressure safety device is connected via a pipe with the tank. With increasing pressure into the tank, the pressure cup is raised (above) and the waste air can flow through and escape through the blow-off pipe. The vacuum cup remains closed. Conversely at under-pressure, the vacuum cup is raised (below) and fresh air can flow into the device and into the tank. The pressure cup remains closed. The filling level of the overpressure cup (above) respectively the underpressure cup (below) can be controlled at the inspection glasses.

In order to prevent dangerous underpressure into the tank through suction of waste air by biofilter air extraction fan (370AL101) during standstill or failure of the turbo blowers (410AV201/202/203) an automatic interlock is foreseen. Therefore, the designed biofilter air extraction fan (370AL101) has to be interlocked to guarantee that it is in operation only if minimum one of the duty turbo blowers is in operation. In case of malfunction or standstill of the air blowers, a fault report is set. The biofilter air extraction fan (370AL101) stops and an alarm is given to SCADA.

Figure 9 Object 310. Electrical works.

To prevent foam transport towards the biofilter, a sprinkling system (310HK311) is installed on the top of the sludge level. The sprinkler system is fed with potable water. The potable water pipe is fitted with an electric actuated butterfly valve (310AS312). The spraying equipment for the digester will be switched on automatically by opening the electric actuated butterfly valve. The operation time is recorded in Scada. The operation time must be limited to prevent higher water inflow und thus reduction of the retention time.

1.2.15 Sludge machinery station (410)

The blowers will operate fully automatically based on a pre-set oxygen value monitored in the aerobic sludge stabilisation reactor and directly based on the air pressure in the header air pressure pipe.

The blowers are autonomous and locally controlled. Set point for the oxygen is controlled via the SCADA system and monitoring of the blowers is also done by the SCADA system.

All turbo blowers (2 duty (410AV201, 410AV202), 1 standby (410AV203)) deliver the air in a common header on the pressure side.

The header includes:

– Flow measurement (410MF101) in line to aerobic digester (object 310)

– Pressure measurement (410MP104)

– Temperature measurement (410MT104)

The flow measurement (410MF101) in the feed line to aerobic digester and three oxygen measurements (310MQ101 / 310MQ102 / 310MQ103) in the aerobic digester (object 310) controls the quantity of the pressured air, which has to be delivered by the turbo blowers. On one hand to ensure sufficient mixing and on the other hand to ensure sufficient oxygenation.

The SCADA will control the operation times of all blowers to be similar by changing duty and assist automatically.

The intake volume Flow of 14.460 m³/h of the turbo blowers is higher than its necessary cooling volume flow of approx. 13.000 m³/h, so that the turbo blowers are already sucking all cooling air into the room. We still use an exhaust fan to have a forced ventilation inside the room for cases in which the turbo blowers are not running. A thermostat (410MT001) inside the blower building controls the ventilator (410AL001) for ventilation of the blower room.

1.2.16 Precipitation station (350)

The precipitant tank (350HK101) is fit with level sensors (350ML101 – 350ML102 – 350ML103).

Four precipitant dosing pumps deliver the ferric chloride to the outlet shafts of the grit and grease removal (object 070). Two of these precipitant dosing pumps (1 duty (350AP101), 1 standby (350AP102)) deliver the ferric chloride to the shaft at grit chamber, which is feeding PST 111 – 114 (object 110) via the distribution chamber (object 105). This line includes a flow sensor (350MF101). The other two dosing pumps (1 duty (350AP201) and 1 standby (350AP202)) deliver the ferric chloride to the shaft at grit chamber, which is feeding PST 115 (object 110) via the connecting shaft (object 400.3). This line includes a flow sensor (350MF501).

1.2.17 Flocculant station (360)

Powder polymer from the powder polymer dosing station (360AC001) is mixed with potable water from potable water booster station (object 390) in the preparing tank. The tank is equipped with three mixers (360AM101 – 360AM103) and four level sensors (360ML001 – 360ML004).

Two polymer dosing pumps (1 duty (360AP101), 1 standby (360AP201)) deliver the polymer to the distribution chamber of PST 111 – 114 (object 105). The other two polymer dosing pumps (1 duty (360AP301), 1 standby (360AP401)) deliver the polymer to the Shaft No. 3 (object 400.3). Each pump is equipped with a temperature sensor (360MT101 – 360MT401) and a pressure sensor (360MP101 – 360MP401) as protection device.

Figure 10 Object 340,350,360 and 390. Electrical works.

Downstream of the pumps a flow sensor (360MF101, 360MF501) is designed for each line. Each stream has a dilution unit with an injector (360HK101, 360HK301) to achieve the post dilution with potable water.

1.2.18 Air purification pre-thickener (270)

The heart of the biofilter (270HK102) is the filter bed consisting of organic material. A natural microflora is colonising on the large surface of the chosen filter medium. Good biofilter media with a high biological activity stimulate multiplication and adaptation of micro-organisms by supplying optimal growth conditions. The pollutants are (ad)sorbed by the large inner surface of the biofilter medium and catabolised by the microorganisms within the biofilm.

To preserve the optimum conditions of growth and degradation for the microorganism waste air is convoyed by help of a ventilator (270AL101) towards an upstream scrubber unit before feeding in biofilter. This scrubber is a packed column integrated into the distribution chamber of the biofilter for conditioning of the inlet air: In the simplest application pre-conditioning relates to humidifying the waste air up to saturation. The humidification allows maintaining the water content of the biofilter medium at a sufficient level, needed for proper functioning of the microorganisms. The humidification works with potable water from the potable water booster station (object 390).

1.2.19 Air purification aerobic digester (370)

The heart of the biofilter (370HK102) is the filter bed consisting of organic material. A natural microflora is colonising on the large surface of the chosen filter medium. Good biofilter media with a high biological activity stimulate multiplication and adaptation of micro-organisms by supplying optimal growth conditions. The pollutants are (ad)sorbed by the large inner surface of the biofilter medium and catabolised by the microorganisms within the biofilm.

To preserve the optimum conditions of growth and degradation for the microorganism waste air is convoyed by help of a ventilator (370AL101) towards an upstream scrubber unit before feeding in biofilter. This scrubber is a packed column integrated into the distribution chamber of the biofilter for conditioning of the inlet air: In the simplest application pre-conditioning relates to humidifying the waste air up to saturation. The humidification allows maintaining the water content of the biofilter medium at a sufficient level, needed for proper functioning of the microorganisms. The humidification works with potable water from the potable water booster station (object 390).

1.2.20 Potable water booster station (390)

The potable water booster station (object 390) consist of three potable water pumps (390AP001/002/003) feed by an existent potable water network. The pumps convey the water to the coarse and fine screen buildings (object 060 and 065), the primary sludge pumping station (object 120), the aerobic digester (object 310), the digested sludge pumping station (object 315), the emergency combined eye shower and shower (350MH001), the precipitation station (object 350), the air purification pre-thickener (object 270), the air purification (object 370), the control room (object 500) and hydrants.

The potable water pumps possess an overpressure switch (390MP002) as protection device. The pipes are fitted with all necessary valves. The potable water flow is measured and recorded (390MF101). The pumps are controlled by pressure measurement (390MP001).

A pump sump for pump leakage with a level measurement (390ML102) is existing inside the chemical dosing building (object 350).

1.2.21 Dewatering pumping station (300)

The wastewater drainage pumps (300AP101/201) are controlled by an ultrasonic level measurement (300ML101) inside the wet chamber. If the water level is higher than a pre-selected level approx. 294.45 m (set point 300/11) one pump starts operation. If the level is below a pre selected level approx. 294.20 m (set point 300/12) the pump stops operation. A new start is possible after passing 10 minutes time period (set point 300/14) and with a level higher than necessary cover level above the pumps. The maximal permissible level inside the sump is 295.45 m (set point 300/13).

The cycling between the pumps will be done when a pre selected operation time (set value 300/15) has elapsed.

2. Making architecture and choosing hardware and software

2.1 General architecture for the SCADA system

The architecture of the SCADA system consists of four different levels:

1. field equipment;

2. PLC and RTU;

3. Communication networks;

4. SCADA Host computer.

Figure 11 General architecture for the SCADA system

The major function of SCADA is for acquiring data from remote devices and providing overall control remotely from a SCADA Host software platform. This provides the management of technological equipment so that these devices turn on and off at the right time, supporting the control strategy and a remote method of capturing data and events (alarms) for monitoring these processes and prevention the breakdowns of technological and auxiliary equipment.

The structure of the SCADA complex, for remote dispatching, gives the service personnel of the station the following possibilities:

– to monitoring the condition of equipment at a remote station (parameters of technological process, emergency and work lock conditions;

– to perform remote control of the system, without calling a specialist directly on the remote object;

– monitoring quality indicators of the water purification;

– archiving data (DBMS) on technological progress, keep an event log, view equipment crashes, and view graphs of time-adjusted parameter changes.

Base system and operator interface:

– base system: operator workstation based on an PC with the SCADA system installed

– operator interface: a set of graphical screens with a mnemonic representation of the treatment facilities structure, light indication and audible alarm.

2.2 Hardware components

2.2.1 PLC

The SIMATIC S7-1500 offers the easiest handling and the greatest level of user friendliness in numerous new details. Detailed plain text information offers full plant transparency. The standardized front connector provides simplified spare parts storage. Easy and practical assignment of clamp and label reduces wiring times and facilitates diagnostics in cases of failure.

Integrated potential bridges permit the simple and flexible formation of potential groups, and auxiliary components such as automatic circuit breakers and relays can be mounted quickly and easily. The shielding of analog signals ensures a high quality of signal reception and robustness with regard to external electromagnetic interference. Easy expandability, customized assembly, and upwards compatibility offer maximum cost efficiency and investment security.

The security concept of SIMATIC S7-1500 includes measures ranging from authorization stages and block protection to communication integrity. Security Integrated protects your investments, helps prevent the reproduction of machines, and helps to ensure a high level of plant availability.

On the SIMATIC memory card, individual blocks are linked to the serial numbers of the original memory card to prevent program copies. The controller detects modified engineering data or if data is being transmitted from an unauthorized source. Access protection safeguards against unauthorized configuration changes. (10)

Figure 12 PLC 1500

2.2.2 HMI

New, cost-efficient HMI generation meets the trend for high-quality visualization even in small machines and plants. Siemens meets the requirements of users for high-quality visualization and operation even in small and medium-size machines and plants with the second generation of SIMATIC HMI Basic Panels. While the price of the new devices is based on the current panels, their scope of performance has been expanded tremendously. The high resolution and a color depth of up to 65,500 colors are major factors contributing to the increased performance. Even the connectivity either by PROFINET or PROFIBUS interface plus USB port could be significantly improved. Configuration and operation of the new panels has become easier in connection with simplified programming by means of the new WinCC software version in the TIA Portal. (11)

Figure 13 HMI KTP900 Siemens

2.2.3 Server

Powerful performance

Whether you’re building 2D or 3D models or multitasking with demanding applications, the Precision T1700 Workstation can power through intensive tasks easily.

Intel® Xeon® processor E3-1200 v3 or 4th generation Intel® Core™ Processors enable fast and stable processing.

Choose Windows 7 Professional or Windows 8 Pro for easy productivity.

Powerful graphics options include AMD FirePro™ or NVIDIA® Quadro® professional-grade discrete graphics. Integrated Intel® graphics are standard.

Precision Optimizer helps your professional software run at its peak performance automatically.

Built to be dependable

The Precision T1700 has undergone extensive testing to ensure strong performance now and into the future.

Optional Dell Data Protection | Security Tools and optional Dell Data Protection | Encryption help make Precision T1700 a secure entry-level Workstation.

Optional mirrored RAID provides redundancy and fast recovery in the event of a drive failure.

Up to 32GB* of optional error-correcting code (ECC) memory corrects isolated soft-memory errors and provides a solid foundation for memory and system stability.

Available self-encrypting drives (SEDs) can reduce security risks and unauthorized access to your data.

Dell services, including Dell ProSupport, * can help you protect your hardware investment through a customizable suite of support options. (12)

Figure 14 Dell Precision T1700 MT CTO Base

2.2.4 Frequency converter

Features

Altivar Process is a Services Oriented Drive designed to reduce OPEX in Process & Utilities installations, thanks to embedded EcoStruxure Machine Advisor.

ATV600 is a range of ready-to-order drives and custom engineered drives focused on fluids management processing and energy saving.

Altivar Process is the first Services Oriented Drive with:

• Embedded Power measurement and Energy dashboard;

• Embedded process monitoring and control;

• Low Harmonics (THDi < 48% at 80% load or THDi < 5% with low harmonic offer);

• Stop and Go function to reduce energy consumption in standby mode;

• Asset monitoring and protection;

• Drift monitoring;

• Easy maintenance (Dynamic QR-Code);

• Seamless integration with embedded Ethernet:

– From device to process control with the Smart Process Object;

– From data to insights with the embedded Web Server.

Proven technical cooling and harmonics solutions:

• Modular and compact design;

• Easy grid integration;

• Embedded Control (PLC, RTU, HMI);

• A full set of control options;

• Fully load tested in a controlled laboratory environment;

• Complies with your country’s industry standards. (13)

Figure 15 Altivar 630

Benefits

Services Oriented Drives

This new concept of drives meets the major needs of process and utilities in terms of equipment efficiency and Total Cost of ownership by supporting the energy management, asset management and also the overall performance of the process.

• Sustainable cost savings thanks to predictive condition-based maintenance;

• Up to 20% downtime reduction without additional investment. (13)

Fluids Management Processing

• Embedded Pump curves embedded (easy to set 5 points curve);

• Anti-jam function prevents downtime;

• Limits leakage by reducing pressure when demand is low. (13)

Energy Saving

• Optimizes energy consumption;

• Accurate power measurement provides information for energy management;

• Reduced energy consumption in standby mode. (13)

Real Time Intelligence

Web server and services via Ethernet

• Embedded web server interface based on the Ethernet network gives you process monitoring with your daily working tools;

• Local and remote access to energy use and customized dashboards means your energy useage is visible anywhere, any time, on PC, tablet or smartphone. (13)

Custom Engineered Drives

Schneider Electric’s expertise in design and application services delivers solution-specific designs dedicated to your process requirements for seamless plant integration.

• Minimize design and delivery risks;

• Reduces the commissioning and adaptation time. (13)

Enhanced Drives Specifications

Compact and modular, suitable even in harsh environments, Altivar Process is perfect for upgrades, retrofits, or new installations.

• Withstand the harsh conditions of use, both from an electrical and environmental perspective. (13)

2.2.5 Other components

SCALANCE X-100 unmanaged Industrial Ethernet switches in machine-level applications for electrical or optical networks, even under extreme ambient conditions. The SCALANCE X-100 media converters support you in converting between two different media. (14)

Figure 16 SCALANCE X-100

The SIMATIC ET 200SP distributed I/O system is a scalable and highly flexible, distributed I/O system for connecting process signals to a central controller via PROFINET.

The SIMATIC ET 200SP is installed on a mounting rail and generally comprises:

an interface module, which communicates with all of the controllers that behave according to the PROFINET standard IEC 61158, up to 64 I/O modules, which are plugged into passive base units in any combination a server module, which completes the structure of the SIMATIC ET 200SP. The distributed I/O system is particularly easy to operate, and with its compact design it achieves maximum economy in the control cabinet. The SIMATIC ET 200SP communicates via PROFINET. Their high speed and transmission rate ensure significantly greater performance than conventional systems. Functional safety is certified in accordance with EN 61508 will be reached with the failsafe modules F-DI, F-DQ, F-PM-E until SIL 3/PL e. (15)

Figure 17 SIMATIC ET 200SP

Area of application

SIMATIC ET 200SP is a multi-functional distributed I/O system for various application areas. Thanks to the scalable structure, you can align the I/O station on-site to the exact needs. SIMATIC ET 200SP is approved for IP 20 degree of protection and designed for use in a control cabinet. (15)

The FortiGate 90E offers an excellent network security solution in a compact desktop form factor for enterprise branch offices and mid-sized businesses. Protect against cyber threats with industry-leading secure SD-WAN in a simple, affordable and easy to deploy solution. (16)

Figure 18 FortiGate 90E

2.3 Software components

2.3.1 Soft

1) WinCC 7.4 SP1 Runtime and Configuration.

Simatic WinCC (Windows Control Center) – a HMI system, software for creating a human-machine interface, an integral part of the Simatic automation system family, manufactured by Siemens AG. It runs under the operating systems of the Microsoft Windows family and uses the Microsoft SQL Server database (starting with version 6.0).

Main features of WinCC:

– Process Visualization (Graphic Designer);

– Configuring and configuring communication with controllers from different manufacturers (Tag -Management);

– Display, archiving and logging messages from the process (Alarm Logging);

– Display, archiving and logging of variables (Tag Logging);

– Expansion of system capabilities through the use of scripts in the languages ​​ANSI C, VBS and VBA;

– Designing a Reporting System (Report Designer);

– Interaction with other applications, including over the network, through the use of standard interfaces OLE, ODBC and SQL provides an easy integration of WinCC into the internal information network of the enterprise;

– Simple build client-server systems;

– Construction of redundant systems;

– Empowerment by using ActiveX controls;

– Open OPC interface (OLE for Process Control);

– Interaction with the package Simatic Step 7. (17)

2) Simatic Step 7 Profetional in TIA Portal V15.

TIA Portal (Totally Integrated Automation Portal) is an integrated development environment for software development of process automation systems from the level of drives and controllers to the level of a human-machine interface. It embodies the concept of integrated automation (Totally Integrated Automation) and the evolutionary development of the Simatic automation system family of Siemens AG.

The following software packages are integrated into TIA Portal:

– Simatic Step 7 for programming S7-1200, S71500, S7-300, S7-400 and WinAC controllers;

– Simatic WinCC for developing a man-machine interface (from the simplest keypads to complex SCADA level configurations);

– Sinamics StartDrive for parameterizing, programming and diagnosing Sinamics drives;

– Simatic PLCSIM – PLC simulator;

– Simatic Step 7 Safety;

– Simatic Visualization Architect;

– Simatic Energy Suite.

2.3.2 License

3. SCADA screens and object operation mod

3.1 Inlet chamber (035) and dewatering pumping station (300)

Normal operation 035:

The sensors (035MF001 – 005) measure the inlet flow;

The sensor (035ML001) measures the water level in the Inlet chamber;

The sensor (035MQ001) measures pH-value;

– The sensor (035MT001) measures temperature.

Figure 19 035 and 300 objects – "SCADA screen"

Normal operation 300:

The pumping station is operated automatically. One pump (300AP101 / 201) will be working;

The sensor (300ML101) measures the water level in the pump sump for discharge upstream coarse screens;

The sensor (300ML102) measures the water level in the pump sump and protects against pump dry running.

3.2 Admission building (060) and PU coarse screen (061)

The water level upstream and downstream the coarse screen is measured by level measurements (061ML101 – 105). A predefined water level difference (approx. 10 cm) starts the cleaning operation of one screen (set point 061/11).

The screenings fall into the skip of the belt conveyor. Screens and conveyors are interlocked and work synchronously. The conveyors start operation shortly before the screens start. When the screens stop a pre-selected time sequence (30 seconds) later, the conveyors stop, too.

Above the screenings containers a level measurement (061ML106) will be installed. The level sensor measures the filling level of the container and allows the change of discharge point for coarse screenings.

Figure 20 060 and 061 objects – "SCADA screen"

Set point values

Level difference measurement (061ML101 * 105)

Range 0 – 5 m

Set point 061/11: Water level difference starting screen operation 0.10 m

Set point 061/12: Water level difference 0.15 m

all screens are working continuously

Set point 061/13: Fixed time sequence 10 min

for cleaning fine screen if set value 061/11 is not attained

Set point 061/14: Time delay stopping conveyors

after screen cleaning stops 30 sec

Set point 061/15: Time delay stopping rotatable conveyor

after conveyors stop 30 sec

Set point 061/16: Filling level in containers 1.20 m

Set point 061/17: maximum level upstream coarse screens 299,57 m

The level difference and the time sequence to start operation of the coarse screens as well the time loop for the conveyors to stop after screen respectively conveyor operation are finished are adjustable. The filling level of containers to change discharge of screenings depends on container dimensions and is adjustable.

3.3 Fine screen building (065) and PU fine screen (066)

The water level in the channels upstream and downstream the fine screen plant is measured by level measurements (066ML101-105). A predefined water level difference (approx. 20 cm) starts the cleaning operation of one screen (set point 066/11).

The screenings fall in the skip of the screening conveyors (066AC001 – 002) and will be transported to the hopper of the screenings press. Screens, conveyors and press are interlocked and work synchronously. The conveyors starts operation shortly before the screens start. At the same moment, the screening press starts operation. When the screens stops a pre-selected time sequence (30 second) later, the conveyors stops, too, and the same time sequence (30 second) later the press stops operation.

Additional wash water is injected into the screenings through the hopper of the screening press. The wash water then absorbs and removes dissolvable organic matter from the screenings. The wash water will be drained into a sewer which ends upstream of the fine screens. Injection time of wash water is controlled by a runtime/pause switch in the local panel.

Above the screenings containers a level measurement (066ML106) will be installed. The level sensor measures the filling level of the container and allows the change of discharge point for coarse screenings.

Figure 21 065 and 066 objects – "SCADA screen"

Set point values

Level difference measurement (066ML101 – 105)

Range 0 – 3 m

Set point 066/11: Water level difference starting screen operation 0.15 m

Set point 066/21: Water level difference 0.20 m

all screens are working continuously

Set point 066/31: Fixed time sequence 10 min

for cleaning fine screen if set value 066/11 is not attained

Set point 066/41: maximum level upstream fine screens 2.5 m

Set point 066/51: Time delay stopping conveyors after screen cleaning stops 30 sec

Set point 066/61: Time delay stopping screenings press after conveyors stops 30 sec

Set point 066/71: Time delay stopping rotatable conveyors after screenings press stops 30 sec

Set point 066/81: Filling level in containers 1.20 m

The level difference and the time sequence to start operation of the fine screens as well the time loop for the conveyors respectively screenings presses to stop after screen respectively conveyor operation are finished are adjustable. The filling level of containers to change discharge of screenings depends on container dimensions and is adjustable.

3.4 Aerated grit and grease removal combined with high loaded aeration tank A-stage (070)

Normal operation 070:

The sensor (070ML001) measures the water level in the distribution chamber at inlet side;

The sensor (070ML002) measures the water level in the distribution chamber at outlet side;

The sensors (070MQ101 – 201) measure the oxygen concentration in the outlet channel of the combined aerated grit and grease removal chamber and high loaded aeration tank;

The sensor (070ML101) measures the water level in the pump sump for feeding grit classifier;

The sensor (070ML102) measures the water level in the pump sump, protects against pump dry running and sump overflow;

The sensor (070MF001) measures the flow towards grit classifier.

Figure 22 070 object – "SCADA screen"

Scraper bridge

Two tanks are fitted with a common scraper bridge. The scraper bridge removes sand and scum. The scraper bridge starts running from the park position at the influent side of the tank in direction to the outlet. Two submersible grit slurry pumps are installed at one bridge. During the movement to the end sand is pumped to a grit collecting channel, one channel per 2 trains. The sand-water-mixture flows by gravity from collecting channel to the common grit collecting pit. The scraper bridge will be interlocked with level in pit with grit transfer pumps. The grit transfer pump will be interlocked with the grit classifier; the start of the pump causes the start of the grit classifier as well. If the pump stops, the classifier keeps in operation for a predefined time sequence.

When reaching the end position of the tank the scum blade forms in a trough at the end of the tank and the scum will be evacuated towards the collecting pit.

After a pre-selected period the scraper changes his moving direction towards inlet. The sand pump is still working until the scraper bridge reaches the parking position at the inlet side of the tank. The scum blade will be lifted up and kept in the uplifted position while the scraper is running back to the inlet of the tank.

The scraper bridge operates cyclic time-controlled by package unit control cabinet. After a predefined time sequence (4 hours), the scraper starts running for a predefined amount of cycles. The scrapers are interlocked to each other because of capacity of grit classifier.

Pressured air system

The compressed air is produced by 3 blowers (2 duty + 1 stand-by), installed in the sludge machinery station (object 410) and delivered in a common delivery pipeline on the pressure side. This pipe will be distributed to two feeding lines, one for the aerated grit chamber incl. distribution channel and the other one for the aerobic stabilisation tank (object 310).

Aeration of combined grit chamber and A-stage is controlled by a control valve in the air feed line. The preselected DO-value of approx. 0.3 – 0.5 mg O2/l will be provided by opening and closing the regulation valve. As the system is sensitive, a time lag of approx. 30 seconds is foreseen in the Scada to prevent permanent operation of the regulation valve. Average value of the oxygen measurements (070MQ101-201) will be used for control loop. Alternatively, one of these metered DO- values by each individual sensor can be selected as input for control of the assigned regulation valve. Minimum air flow will be assured by minimum opening of control valve.

In every line five aeration grids each with 4 diffuser membrane plates are installed. Totally 80 diffuser membrane plates are installed, 20 pieces for each line. It is possible to isolate each of these grids by a ball valve in the drop pipe DN 50

3.5 Primary sedimentation tanks 110 (111,112,113,114,115) and outlet channel (200)

Normal operation 110:

PST 1, 2, 3 and 4 are fed with the flow coming from the distribution well PST (object 105);

PST 5 is fed with the flow coming from shaft no. 3 (object 400.3);

The sensors (110ML101, 110ML201, 110ML301, 110ML401, 110ML501) measure the sludge levels;

The scrapers (111AK101, 112AK201, 113AK301, 114AK401, 115AK501) are working continuously.

Figure 23 110 and 200 objects – "SCADA screen"

Normal operation 200:

The sensors are installed in the channel and measure water level, flow and pH values.

The sampler assays.

3.6 Primary sludge pumping station (object 120) + Return sludge pumping station (object 125)

Object 125:

The pumping station is operated automatically. The return sludge pumps are controlled by the flow measurement (125MF001). The return sludge flow from the primary sedimentation (unit 111-114) is nearly continuously and flows to the pumping station suction header. The flow sensor will increase or decrease the inverter of the pumps to maintain a predefined flow.

The cycling between the pumps will be done automatically when a pre-selected operation time has elapsed. The operational status of the pumps is monitored by the SCADA system.

For pump start at least one electric valve (120AS101 – 401) must be open.

Object 120:

The primary sludge pumps are operated automatically. A pre-selected daily sludge quantity will be pumped by use of a Start – Pause mode. The primary sludge flow is measured and recorded (120MF101).

The cycling between the pumps will be done automatically when a pre-selected operation time has elapsed. The operational status of the pumps is monitored by the SCADA system.

The sensor (120MP003) measures the pressure in the common scum pipe upstream the primary sludge pump (120AP101). The pump starts operation if a preset value is reached. The gate valves 120HS112 and 120HS212 are usually open. The valve 120HS005 is closed. The scum is discharged towards the sludge thickener object 260.

Figure 24 120 and 125 objects – "SCADA screen"

Set point values

Object 120:

Flow measurement (120MF101)

Range: 1 – 3,000 m³/d

Set point 120/11: chosen daily quantity of primary sludge 1,415 m³/d

Set point 120/12: operation time of an aggregate to change

duty and standby: 24 h

Dry solid concentration measurement (120MQ101)

Range: 1 – 50 g/l

Set point 120/21: Set point dry solids content: 17 g DS/l

Thermostat (120MT001)

Range: 0 – 50 °C

Set point 120/31: Set point level full capacity: approx. 35 °C

Object 125:

Flow measurement (120MF101)

Range: 0 – 2500 m³/h

Set point 125/11: Return sludge range between: 1,630 – 2,140 m³/h

Set point 125/21: Operation time of an aggregate to change

duty and standby: 24 h

The set point values which are visible in SCADA are changeable by the operator.

3.7 Digested sludge pumping station (object 315) + Return sludge pumping station for PST 115 (object 320)

Object 315:

The pumping station is operated automatically. The digested sludge pumps are controlled by a level sensor (400.4ML101) installed inside the shaft (object 400.4) located between the aerobic digester (object 310) and the primary sedimentation tank (object 115).

The thickened sludge pumps (265AP101 / 201) which are the feeding pumps of the digester (object 310) are also interlocked with the level measurement (400.4ML101) inside the shaft 400.4. If the water level reaches a preset value max-level (set value 315/22), a signal will be indicated and the thickened sludge feeding pump (265AP101 / 201) stops and an alarm is given to SCADA. The operator has to check the status of the digested sludge evacuation pump (315AP401 / 501).

If the level is lower than a pre-selected level (set value 315/21), the pump operation is stopped.

As the aerobic digester is a flow-through-tank, digested sludge according to the inlet raw sludge quantity spills over an installed overflow into a pipe directing the digested sludge by gravity via a shaft 400.4 to the digested sludge pumping station (unit 315) via opened draw off electrical actuated valve (315AS601).

In the suction header pH-value (315MQ002) and temperature (315MT002) will be measured and transferred to SCADA system. The data is for information purposes only.

The pumps are operated in an alternating sequence in order to minimise the wear of the pumps. The cycling between the pumps will be done automatically when a pre-selected operation time has elapsed.

Figure 25 315 and 320 objects – "SCADA screen"

Object 320

The pumping station is operated automatically. The return sludge flow from the primary sedimentation (object 115) is nearly continuously and flows to the pumping station suction header.

The pumps are operated in an alternating sequence in order to minimise the wear of the pumps. The cycling between the pumps will be done automatically when a pre-selected operation time has elapsed. The operational status of the pumps is monitored by the SCADA system.

For pump start electric valve (320AS501) has to be open.

Set point values

Object 315:

Set point 315/12: operation time of an aggregate to change

duty and standby: 24 h

Level measurement (400.4ML101)

Range: 0 – 5 m

Set point 315/21: Level min. (stop operating pumps 315AP401 / 501): 0.4 m

Set point 315/22: Level max. in shaft 400.4: 2.5 m

Set point 315/22: Level max and a fault report is set: 2.6 m

the thickened sludge feeding pump (265AP101 / 201)

stops and an alarm is given to SCADA

Thermostat (315MT001)

Range: 0 – 50 °C

Set point 315/41: Set point level full capacity: approx. 35 °C

Object 320:

Set point 320/11: Return sludge range between: 410 – 535 m³/h

Set point 320/12: Operation time of an aggregate to change

duty and standby: 24 h

The set point values which are visible in SCADA are changeable by the operator.

3.8 Primary sludge thickener (260) + PU Picket fence (261) and Thickened primary sludge pumps (265)

The thickener is a “continuous flow” type. This results in a continuous working picket fence (261AM101).

The sludge blanket level sensor (260ML101) controls the operation of the rotary lobe pumps (265AP101 – 201) located in the thickened sludge pumping station (object 265).

A sludge level approx. 0.20 m higher than a pre-selected level approx. 3.00 m will start the pumps operation. 30 cm below this level the pump stops operation. The suction pipe is fitted with a dry solid measurement (265MQ001). A dry solid minimum value of approx. 4.5 % corresponds to a minimum sludge blanket level which stops the evacuation pumps. A maximum dry solid value of approx. 5.0 % will correspond to maximum sludge blanket level which starts the evacuating pumps.

The local package unit control cabinet (261PU) for the picket fence is installed at thickener’s service bridge. The control panel for the pumps is located inside a MCB building (object 960).

Figure 26 260 and 265 objects – "SCADA screen"

Normal operation 265:

The sensor (260ML101) measures the sludge blanket level in the primary sludge thickener (object 260);

The sensor (265MQ001) measures the dry solid concentration in the withdrawal pipe;

The sensor (265MQ002) measure the pH value in the withdrawal pipe;

The sensor (265MF001) measures the sludge flow to the aerobic digester (object 310);

The sensors (265MT101/201) measure the temperature of the pumps;

The sensors (265MP101/201) measure the pressure on pump pressure side;

3.9 Aerobic digester (310) and defoaming agent (340)

Normal operation 310:

For a working sprinkling system the butterfly valve 310AS312 has to be open (by operator at SCADA or on site);

The sensors (310MQ101 / 102 / 103) measure the oxygen concentration;

The sensors (310MT101 / 102 / 103) measure the temperature;

The sensor (310ML101) measures the level.

Pressured air system

The compressed air is produced by 3 blowers (2 duty + 1 stand-by), installed in the sludge machinery station (object 410) and delivered in a common delivery pipeline on the pressure side. This pipe will be distributed to two feeding lines, one for the aerated grit chamber incl. distribution channel (object 070) and the other one for the aerobic stabilisation tank (object 310).

Aeration of aerobic stabilisation tank is controlled by a control valve (310AS310) in the air feed line. The preselected DO-value (310MQ101 / 102 / 103) of approx. 0.5 mg O2/l will be provided by opening and closing the regulation valve. As the system is sensitive, a time lag of approx. 30 seconds is foreseen in the Scada to prevent permanent operation of the regulation valve.

Average value of the oxygen measurements (310MQ101 / 102 / 103) will be used for control loop. Alternatively, one of these metered DO- values by each individual sensor can be selected as input for control of the assigned regulation valve.

Ensuring sufficient mixing is done by preselected minimum air flow to the stabilisation tank. Additionally, a pulse aeration could be chosen to increase mixing power. Details are described in operation modes of the blower station (object 410).

Figure 27 310 and 340 objects – "SCADA screen"

Normal operation 340:

Start-up

Defoaming agent is fed into the sludge feed line. At start-up a quantity of 0.2 % defoaming agent in relation to the SS-Load of the sludge in the digester is feed in a period of three days. This concludes the following initial dosing rate:

SS-Load: 9.430 m³ x 38.8 kg/m³ = 365.400 kg SS

Initial dosing rate: 365.400 kg SS x 0.2 % / 3 d = 243.6 kg/d =10.1 kg/h

Normal operation

At daily operation a quantity of 0.2 % defoaming agent is dosed in relation to the daily sludge feed:

Daily dosing rate: 23.066 kg SS/d x 0.2 % = 46 kg/d = 2.9 kg /h

3.10 Sludge machinery station (410)

Normal operation 410:

The sensor (410MP104) measures the pressure in the header pipe;

The sensor (410MT104) measures the temperature in the header pipe;

The sensor (410MF101) measures the airflow in the feed pipe of the digester;

The sensor (410MT001) measures the temperature in the blower building.

The minimum air demand of the aerobic stabilisation for mixing is i.e. 6,500 Nm³/h. To ensure the air demand two blowers have to operate. The butterfly valve (410HS201, 410HS202, 410HS203) are open under normal conditions. The blowers will operate fully automatically based on a preset pressure value (set value 410/31) based on the pressure sensor (410MP104) in the header pipe.

The minimum air flow for creating the required standing wave in the sand and grease trap (object 070) is rd. 1,790 Nm³/h and will be assured by minimum opening of control valve (070AS070) in the air feed pipe. The ventilator for air-cooling (410AL001) starts working based on a preset temperature value (set value 410/51) of thermostat (410MT001) in the building.

Figure 28 410 object – "SCADA screen"

Set point values

Measurement oxygen concentration (310MQ101 / 102 / 103) in digester

Range: 0 – 5 mg/l

Set point 410/11: Frequency control of blowers: approx. 1.0 mg O2/l

Set point 410/21: Set point O2: 0.5 mg/l

Set point 410/22: Set point min: 0.3 mg/l

Set point 410/23: Set point max: 2.0 mg/l

Pressure Measurement (410MP104)

Set point 410/31: Pressure in header: 600 mbar

range: 550 – 650

Set point 410/32: Minimum pressure: 530 mbar

range: 500 – 600

Set point 410/33: Maximum pressure: 630 mbar

range: 580 – 650

-Flow measurement (410MF101)

Set point 410/41: Minimum air flow to aerobic digester: 6,500 Nm³/h

range: 3,500 – 8,000 Nm³/h

Set point 410/42: Maximum air flow to aerobic digester: 7,000 Nm³/h

range: 6,500 – 10,000 Nm³/h

Set point 410/43: Preselected time between 2 cycles: 24 h (range 1 – 168 h)

Set point 410/44: Duration of pulse aeration: 5 h (range 1 – 60 Min.)

Set point 410/45: Chosen air flow for pulse aeration: 11,000 (range 9,000 – 13,000)

Thermostat (410MT001)

Set point 410/51: approx. 35 °C is full capacity

The set point values which are visible in SCADA are changeable by the operator.

3.11 Precipitation station (350) and potable water booster station (390).

Normal operation 350:

The sensors (350ML101 – 350ML102 – 350ML103) measures the level in the precipitant tank;

The sensors (350MF101 and 350MF501) measure the flow;

The control of dosing will be done automatically or manual.

Two possible operating modes are foreseen:

The precipitation flow rate is calculated in proportion to the discharge flow in the outlet channel (object 200). In case of rain weather (Qoutlet > 19,858 m³/h) the proportional dosing rate shall be limited (Set point 350/11). Dosing rate is controlled to be proportional to the outlet flow measured by the flow sensor (200MF001) in object 200;

If requested by process conditions or during maintenance the precipitation dosing rate can be adjusted manually independently from WWTP outlet flow (Set point 350/12).

Figure 29 350 and 390 objects – "SCADA screen"

Set point values

Flow Measurement (350MF101 and 350MF501)

Range: 0 – 200 l/h

Set point 350/11: Range

Automatic proportion Qprecipitant dosing / Qoutlet :

Dosing rate [%] = Qprecipitant dosing / Qoutlet x Dosing Factor

Set point 350/12:

PST 111 – 114 (80 %) Precipitation flow rate 0 – 200 l/h

PST 115 (20 %) Precipitation flow rate 0 – 40 l/h

Set point 350/13:

Minimum precipitant level value: = 0.5 m

(Operator has to order new precipitant)

The set point values which are visible in SCADA are changeable by the operator.

Normal operation 390:

The pumping station is operated automatically. One pump (390AP001/002/003) will be working. If the water demand is bigger than the capacity of the first duty pump and the pressure in the network decreases below pre-selected 4 bar the second pump will start automatically. The pumps are operated in an alternating sequence in order to minimise the wear of the pumps. The operational status of the pumps is monitored by the SCADA system

3.12 Flocculant station (360)

Normal operation:

The sensors (360ML001-360ML004) measure the polymer level;

The sensors (360MT101-360MT401) measure the pump temperature;

The sensors (360MP101-360MP401) measure the pressure at the pump stator;

The sensors (360MF101 and 360MF501) measure the flow;

The control of dosing will be done automatically or manual.

Two possible operating modes are foreseen:

The polymer flow rate is calculated in proportion to the discharge flow in the outlet channel (object 200). Dosing rate is controlled to be proportional to the outlet flow measured by the flow sensor (200MF001) (Set point 360/11);

If requested by process conditions or during maintenance the precipitation dosing rate can be adjusted manually independently from WWTP outlet flow (Set point 360/12, Set point 360/13).

Figure 30 360 object – "SCADA screen"

Set point values

Set point 360/11: Specific polymer dosing in g polymer / m³ outlet flow: 0.1 – 1

Flow Measurement (360MF101)

Range: 0 – 10 m³/h

Set point 360/12:

PST 111 – 114: Polymer solution flow rate 2.8 m³/h

Flow Measurement (360MF501)

Range: 0 – 10 m³/h

Set point 360/13:

PST 115 Polymer solution flow rate 1.0 m³/h

The set point values which are visible in SCADA are changeable by the operator.

CONCLUZII

Implementarea unui sistem SCADA asupra procesului tehnologic de funcționare a unei stații de tratare a apei este un aspect esențial în ceea ce privește asigurarea calității apei potabile.

Configurat corespunzător, sistemul este un instrument puternic în ceea ce privește atât gestionarea datelor de proces cât și optimizarea funcționării. În ceea ce privește managementul datelor de proces, avantajul major constă în versatilitatea funcțiilor specifice de arhivare, prelucrare, analiză și vizualizare a acestora. Astfel, există posibilitatea ca un tehnolog să realizeze analize specifice bazate pe datele reale preluate din câmp și să propună metode de optimizare pe termen lung. Acest aspect este mai relevant dacă luăm în considerare faptul că procesul tehnologic de tratare a apei potabile este un proces lent, a cărui periodicitate se extinde pe durate de ordinul orelor sau a zecilor de ore.

Un alt avantaj major al implementării unui sistem SCADA constă în posibilitatea optimizării funcționării procesului. În primul rând, prin compararea debitul influent, debitul de apă utilizat pentru spălare filtrelor și debitul de apă potabilă contorizat pe conducta de efluent se va putea verifica eficiența stației de tartare a apei, dar mai ales a evoluției acestora pe perioade extinse de timp ce va permite aplicarea unor corecții la nivelul de procesului tehnologic.

Scopul acestor corecții va fi acela de a obține o calitate a apei potabile conform normativelor, cu un consum energetic cât mai redus. Acest aspect este capital, având în vedere cantitățile mari de energie electrică consumată de către elementele din proces, cum ar fi de exemplu mixerile lente și rapide în etapa de Pre-oxidare. Aceste optimizări se pot realiza prin intervenția de la nivel ierarhic superior a sistemului, în zona subproceselor. Nu în ultimul rând ca importanță, este necesar să amintim și impactul pe care implementarea sistemului o are asupra securității procesului. Prin modul de gestionare a alarmelor de proces, este posibilă transmiterea informațiilor necesare, într-un mod foarte eficient, acolo unde este nevoie de ele. De asemenea, anumite decizii pot fi luat de către sistem, în concordanță cu informarea și acceptul operatorului.

Putem spune că implementarea de sisteme SCADA aduce, în cadrul tehnologiilor de tratare a apei potabile, un instrument deosebit de puternic și flexibil, a cărui avantaje se răsfrâng direct asupra performanțelor și a eficienței procesului tehnologic de tratare a apei.

BIBLIOGRAFIE

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