U.P.B. Sci. Bull., Series , Vol. , Iss. , 201 ISSN 1223-7027 [602896]

U.P.B. Sci. Bull., Series …, Vol. …, Iss. …, 201 ISSN 1223-7027
THE USE OF AMBR AND RO SYSTEM FOR WASTEWATER
TREATMENT
Ramona ZGAVAROGEA1,2, Violeta NICULESCU1, Marius
MIRICIOIU1, Andreea IORDACHE1, Marin NEACSA2
Domestic wastewater from Ramnicu Valcea town has been treated by
anaerobic membrane bioreactor (AMBR), followed by reverse osmosis (RO). Main
objectives were to study the reduction of organic matter and nutrient recovery, as
well as the production of gas. The results showed the reduction of organic matter, nitrogen and phosphorous. The quality of the concentrate is similar to source
separated human urine. However, it is necessary to add acid to prevent the
precipitation / fouling of the RO unit. Total use of electricity for running the system is estimated at 4-7 kWh / m
3.

Keywords : Anaerobic, domestic wastewater, nutrient recovery, reverse os mosis
1. Introduction
Various approaches for the use of recycling nutrients from wast ewater
have been tested. A first approach is to use 'end of pipe' wast ewater treatment. The
wastewater treatment station in a town using an anaerobic membr ane bioreactor
(AMBR) and reverse osmosis (RO) was studied. The results will b e used to design
a treatment plant for this area. Only domestic wastewater will be treated in the
local sewage plant, thus excluding water drainage and rainwater . Results from the
analysis showed that this concept will reduce the potential for eutrophication and
increase the potential for nutrient recycling. The use of a MBR is very beneficial
for both anaerobic and aerobic processes [1-3], one of the adva ntages being the
possibility of a solid long retention time. The membrane unit i s of the vibratory
shear enhanced processing (VSEP) type, implementing a vibration amplitude in
order to achieve transverse flow across the membrane. The main objective was to
assess the effectiveness and performance of an AMBR coupled wit h a RO unit. It
was monitored the reduction of organic matter, nitrogen and pho sphorous, as well
as the production of methane gas. The aim was to obtain a produ ct with a high

1National R&D Institute for Cryogenics and Isotopes Technologies – ICSI, Ramnicu Valcea,
Romania, e-mail: [anonimizat]
2 The Faculty of Engineering and Management of Technological Sys tems, POLITEHNICA
University of Bucharest, Romania
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Summary of Comments on Microsoft Word – 5105
Page: 1
Number: 1 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 9:51:17 AM
This is a very broad estimation, from simple to almost double. without any comparison with classical technologies, which is mandatory.

Number: 2 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 10:03:17 AM
The literature review is very scarce and incomplete, with rather old papers.
You should provide a better literature study, showing if the concept of AMBR – RO series is already studied, and what are the novelties of
your study, compared with others did already.

Number: 3 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 9:56:07 AM
Please, explain how do you separate the former from the latter – this is really important. Are there two networks dealing, separately, with
domestic wastewater and drainage/rainwater?

Number: 4 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 9:58:00 AM
When you have more than two citations in a row, you must separate each with some words justifying why it deserves to be cited.

Number: 5 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 9:59:18 AM
Please, explain better the role of the vibrations – the cross flow through membrane is due to a pressure difference.

Ramona Zgavarogea, Violeta Niculescu, Marius Miricioiu, Andreea Iordache, Marin Neacsa
content of nitrogen and phosphorus, but with a low content of h eavy metals,
which can be used in agriculture [4].

2. Materials and Methods
The system consisted of a pilot scale AMBR and RO unit. The com plete
mixed anaerobic bioreactor had a total volume of 1.5 m3. The volume of liquid in
the reactor was 0.75 m3, resulting in a hydraulic retention time of about 0.5 d. The
reactor was operated at 23 C, almost equal to the annual average temperature in
the influent. The bioreactor was fed with wastewater pre-treated in a filter with a 3
mm-pore size diameter. The sludge was pumped through a filter o f 0.5 mm
diameter prior to entering the membrane, and the filtrate was a utomatically
returned to the bioreactor. The membrane unit consisted of a VS EP containing 15
double membrane plates with a total area of 1.20 m2. Before the trial period, an
extensive membrane experiment was performed in order to obtain the maximum
hydraulic capacity. The membrane chosen for the period of evalu ation was a
PTFE Teflon membrane, with a pore size of 0.45 mm. Diaphragm cl ogging is
prevented by the shear forces which are induced near the surfac e of the vibration
membrane VSEP unit, allowing the hydraulic capacity to be maint ained during a
relatively long period. Hydraulic capacity of the membrane is a ffected by the
characteristics of the feed, the amplitude of the vibration mem brane pore size and
type of membrane [4-6]. System components are shown in Figure 1 . RO unit
consisted of a feed pump, a reverse-osmosis, an open feed tank (0.5 m3) and a
closed permeation tank (1.0 m3), a cross-flow spiral membrane with a surface area
of 2 m2 and a saline reduction capacity of 99%. Mainly, there were app lied two
phases of operation: recirculation and concentration. During th e concentration
phase, the permeate was collected in the permeate container and in the phase of
recycling both concentrate and permeate were directed to the fe ed tank.

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Number: 1 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 10:17:50 AM
By default, using domestic wastewater means very low content of heavy metals, which renders redundant your claim.

Number: 2 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 10:22:05 AM
You should provide a table with the main geometric characteristics of the bioreactor and RO unit, together with the operating parameters.

Number: 3 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 10:24:20 AM
It is hard to believe that this is an annual averaged temperature. Provide the source of this data.

Number: 4 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 10:25:45 AM
The merits of each of these citations.

Number: 5 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 10:22:53 AM
This should appear after the first sentence.

Number: 6 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 10:27:37 AM
You should explain better how did you kept the process continuous.

New trends in wastewaters treatment – MBR technology

Fig. 1. Schematic representation of the system

The reverse osmosis was used four times in four different exper iments.
Acid was added to the feed to prevent fouling and evaporation o f ammonia. The
temperature in the feed tank of the RO was kept constant at 23 C with a water
cooling system. In order to evaluate the fouling of the membran e caused by
precipitation, the first experiments was conducted without addi ng any acid. The
second and third experiments were conducted with hydrochloric a cid. A mixture
of nitric and phosphoric acids wer e used in the fourth experime nt. The use of
nitric acid and phosphoric acid increases the nutrient concentr ations in the
concentrate and makes it more attractive as a fertilizer, where a s t h e u s e o f
hydrochloric acid might generate a concentrate that could be un suitable for some
crops [6-8].
Wastewater was sampled every day and then mixed into a composit e
sample at the end of each week. This method was used for influe nt and effluent
from the AMBR. The RO experiments were analyzed separately.

3. Results and discussion
3.1 AMBR operation
The bioreactor was fed with wastewater pre-treated in a filter with a 3 mm-
pore size diameter, the characteristics of the wastewater being presented in table
1. In the round brackets there are presented the annual mean va lues.

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Number: 1 Author: Reviewer #1 Subject: Sticky Note Date: 10/4/2016 10:37:29 AM
What are these two? What is their role in the process?

Number: 2 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 10:30:41 AM
All these has to be part of the aforementioned table, or a new one.

Number: 3 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 10:31:53 AM
What about the costs?

Number: 4 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 10:29:12 AM
The merits of each of these citations.

Number: 5 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 10:32:37 AM
Not clear, should be better explained.

Number: 6 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 10:33:41 AM
The right way is: mean+-standard deviation.

Ramona Zgavarogea, Violeta Niculescu, Marius Miricioiu, Andreea Iordache, Marin Neacsa
Table 1
The average concentrations in wastewater
Parameter Average
Temperature C 22 (19.5-22.8)
TOC, mg/L 210 (190-240)
COD-tot, mg/L 650 (630-700)
NH 4-N, mg/L 65 (60-70)
Kj-N, mg/L 85 (80-90)
Tot-P, mg/L 12 (10-14)
Ni, g/L 6.5
Ni, g/L 6.5
Cu, g/L 40
Zn, g/L 70
Cd, g/L 0.1
Hg, g/L 0.04
Pb, g/L 3.5

Membrane and VSEP unit required frequent cleaning. The cleaning
process required hot water tap, a commercial liquid detergent t o dissolve organic
matter and sodium hydroxide to improve the dissolution of organic matter or
hydrochloric acid to solve the clogging due to chemical precipi tation. Each
cleaning cycle last 30 minutes at temperatures above 23 C and it was followed by
a wash cycle, in which VSEP unit was supplied with clean water.

3.2 RO-unit operation
The highest volume reduction factor (VRF) reached was 50, which means
>90% reduction of the volume. The procedure of RO cleaning was similar to the
procedure used for the VSEP. However, other chemicals were used : liquid
detergent and citric acid – to resolve chemical precipitation.
There is a reduction of suspended solids in the pre-filter of o nly about 2%
for chemical oxygen demand (COD) and probably even smaller for phosphorus
and nitrogen. The organic load on the bioreactor has been relat ively constant,
around 0.6 kg COD/day. The membrane unit contributed to the red uction of
organic matter by filtration of suspended solids, a relative co nstant accumulation
of organic matter (about 0.10 kg COD/day) in the reactor being observed. No
excess sludge has been withdrawn from the reactor, except a sma ll insignificant
amount due to sampling. The anaerobic process was stable and a continuous
production of methane gas amounting to 0.2–0.6 m3 /week being achieved. The
experiments showed a good anaerobic activity in the sludge at a temperature of
23C. The low gas production is explained by the accumulation of C OD in the
reactor (17% of the influent) and by methane dissolved in the p ermeate. The
dissolved methane is potentially an environmental problem, but suitable systems
to recover dissolved methane [9-17].
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Number: 1 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 10:34:39 AM
Redundancy

Number: 2 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 10:39:47 AM
How much wastewater is generated each cleaning period, as compared with the treated domestic water? 1(former) to 1 (latter)? 2(former) to
1 (latter)?

Number: 3 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 10:40:28 AM
See the previous comment.

Number: 4 Author: Reviewer #1 Subject: Comment on Text Date: 10/4/2016 10:41:37 AM
Better to say "not measured" or "not available".

Number: 5 Author: Reviewer #1 Subject: Comment on Text Date: 10/13/2016 9:31:57 AM
Makes no sense; no more that 2 citations in a row. Otherwise, please put some words justifying why you cite this particular paper.

Number: 6 Author: Reviewer #1 Subject: Comment on Text Date: 10/13/2016 9:30:40 AM
Here, you have to provide the solubility of methane in permeate (at least, in water, to justify this assumption – not sustainable.

New trends in wastewaters treatment – MBR technology
Table 2 describes the average change in concentrations over the s y s t e m
throughout the period of investigation and also the reduction o ver the AMBR and
RO. Organic matter was mainly reduced in the AMBR, whereas nutr ient reduction
mainly was achieved in the RO.
Table 3 shows the change in concentrations of the nutrients and orga nic
matter over the RO for each experiments. In the first experiment, no acid was
added and only VRF of 10 was reached. The membrane was fouled, probably due
t o p r e c i p i t a t i o n , t o t h e p o i n t w h e r e t h e p e r m e a t e f l o w r e a c h e d zero. For the
second, third and fourth experiments, the specific flow decreas ed relatively
linearly with increasing VRF as an effect of increased salinity ( m e a s u r e d a s
conductivity). Thus, the reduction in specific flow for experim ents 2–4 was
probably due to increased osmotic pressure and not due to fouli ng and/or
precipitation. In the experiment 4, the concentrations of nitro gen and phosphorus
in the concentrate are relatively high because of the added aci d. It could be
estimated that the effluent concentration of nitrogen would be about 10 mg /L N,
resulting in an overall nitrogen removal efficiency of 86%. Thu s, the addition of
acids such as HNO 3 will result in a concentrate, with a relatively high
concentration of nutrient, which would probably be suitable for agricultural use.
However, the addition of acids containing nitrogen and phosphor us will reduce
the overall removal efficiency. There could be an accumulation of nutrients,
mainly phosphorus, in the RO due to precipitation. At higher pH , there is also a
risk of ammonia gas evaporation.

Table 2
Reduction over the AMBR and RO
Analysis TOC (mg/L) K j-N (mg/L) Tot-P (mg/L)
Influent 210 85 12
AMBR permeate 20 55 8
RO permeate <5 ≤5 ≤0.5
Reduction, AMBR 95% 6.5% 6.66%
Reduction, Total >98% >90% >99%

Table 3
Results from RO experiments
Exp 1 Exp 2 Exp 3 Exp 4
VRF 10 30 60 60
Acid used No acid used HCl HCl H 3PO 4+HNO 3
T O C ( m g / L )
AMBR permeate 20 20 20 20
Concentrate 150 300 500 600
Permeate <5 <5 <5 <5
T o t – P ( m g / L )

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Ramona Zgavarogea, Violeta Niculescu, Marius Miricioiu, Andreea Iordache, Marin Neacsa
AMBR permeate 12 12 12 12
Concentrate 50 250 400 1200
Permeate ≤0.5 ≤0.5 ≤0.5 ≤0.5
Kj-N (mg/L)
AMBR permeate 55 55 55 55
Concentrate(tot-N) 550 1500 2500 10000
Permeate ≤5 ≤5 ≤5 ≤5

Table 4
Metal content in RO concentrates
mg/kg P Cu Zn Ni Cr Cd Hg Pb
Exp 1 (VRF 10) 50 300 400 40 <0.1 0.6 7
Exp 2 (VRF 30) 250 1800 220 75 0.3 0.2 40
Exp 3 (VRF 60) 400 160 340 55 0.1 0.3 3
Exp 4 (VRF 60) 100 100 170 20 0.3 <0.1 1
Urine 101 45 7 – 0.7 0.8 0.7

Table 4 shows the heavy metal content in the concentrate as mg/ kg P from
four experiments using the RO-unit. For comparison, data for ur ine approved for
agriculture use is listed. Low Me/P ratios for most metals are mainly explained by
a high removal performance of heavy metals in the AMBR. However , they are
also explained by a relative low Me/P ratio in the influent. Th e VSEP-unit
produces a permeate containing no suspended solids, minimizing the
concentration of heavy metals fed into the RO-unit. The electri city consumption is
relatively high. Based on the operational data and experiences from full scale
treatment plants concerning specific energy consumptions, the t otal electricity use
for operation for the entire system, including the energy deman ding RO-unit, is
estimated to be 3–6 kWh/m3. The VSEP-unit has an estimated energy
consumption of 0.5–1.5 kWh/m3. Thus it is important to reduce the amount of
wastewater treated. One way of doing this is to treat only wast ewater from toilets
and possibly kitchen waste disposers.
4. Conclusions

The concept of using AMBR and RO is well suited for the purpose o f
nutrient recovery from domestic wastewater. The end product is water that meets
high effluent requirements and a concentrate ready to be used a s nutrient on
agricultural farmland. The studied system did not require any h eating and the high
temperature of the influent made production of high energy meth ane gas possible.

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Number: 1 Author: Reviewer #1 Subject: Comment on Text Date: 10/13/2016 9:34:46 AM
Explain the source of these heavy metals, prior to justify their level.

Number: 2 Author: Reviewer #1 Subject: Comment on Text Date: 10/13/2016 9:35:42 AM
Please, revise this chapter, emphasizing better your achievements.

New trends in wastewaters treatment – MBR technology
AKNOWLEDGEMENT

The work has been funded by the Romanian Ministry of Education and
Scientific Research, the National Authority for Scientific Rese arch and
Innovation, 34N/2016 NUCLEU Program, under Project PN 16 36 04 03
„Research on the development of new porous materials with high selective and
catalytic properties for the redu ction and stabilization of the pollutant
concentrations in gaseous and liquid backgrounds”.

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Ramona Zgavarogea, Violeta Niculescu, Marius Miricioiu, Andreea Iordache, Marin Neacsa
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