Drinking Water Contamination And Disinfectiondocx

=== Drinking Water – contamination and disinfection ===

Drinking Water – contamination and disinfection

The water is a fundamental constituent of living matter. It’s the second most indispensable substance for life on Earth. A human can survive without food up to 60 days, but only 3-4 days (1 week at most) without water.

The term ”drinking water” refers to the type of water needed for human use, such as:

Any type of water use for drinking, preparing food or other household purpose, whaterver its origin, whether it’s distributed in bottles or other containers, or it’s provided by the distribution network or by supply tank;

Any type of water used in food industry;

Any type of water provided by local sources like wells, springs, used for cooking, drinking, or other domestic purposes.

Diseases related to contamination of drinking-water constitute a major burden on human health. Interventions to improve the quality of drinking-water provide significant benefits to health.

Drinking water quality must correspond to quality parameters stipulated by the law!

Microbiological parameters for drinking water according to W.H.O.

Parameters of drinking water quality indicators:

Water sampling

The number of water samplings and the frequency that those are collected is established depending on the volume of distributed water or the number of people that use that water. In case of frequently intermitted distribution of water, these samples must be collected from 48 h to 48 h.

Water sampling for microbiological analysis (from 500 ml up to several liters- depending on the complexity of analysis that is being made) is made in sterilized glass bottles, with glass stopper .

In case of tap water sampling, the tap must be previously cleaned (for chemical analysis ) or sterilized (in case of microbiological analysis)

In case of previously disinfected water, the sampling must be made in a sterilized glass bottle where we must add 1 cm3 of 0.5% sodium thiosulfate for each 100 cm3 capacity bottle (to neutralize residual chlorine).

The water quality is adequate when the water quality guidelines are respected for these points of water sampling:

Consumer’s tap water and the entering point into the building

The point where the water is bottled

The poor point of the water in the tank

Monitoring the quality of water

Monitoring the quality of drinking water is made by the manufacturers, distributors, and Local Public Health Department .

Public fountains and springs are surveyed by the Local Public Heath Department at least once a year and the costs are supported by the local authorities.

Individual fountains are surveyed by the Local Public Health Department, when it’s asked by the owner (he will support the costs).

Conditions of building a fountain

When building a fountain you must respect several sanitary regulations such us:

deep soil: choosing a deep aquifer soil (a depth greater than 10 m, and not by any chance smaller than 6 m ). This aquifer soil must provide a constant water flow

location of building: one must place the fountain on the highest point on the land; the area surrounding the fountain must be salubrious – at least 10 m far from any potential sources of pollution (latrine, stables, landfill sites, etc)

the construction:

walls must be made of resistant and water proof materials and high up at least 60 cm above the soil

the fountain is covered with a lid and with a roof on top.

1,5 m around the fountain is being cemented and then surrounded with a fence

Remediation of fountains

It is the process that is being done whenever a fountain no longer meets the qualities parameters, an accidental contamination took place, or in the event of an outbreak.

The remediation of fountains has 4 steps:

Tracing the pollution source: introducing methylene blue or fuscina in possible contamination areas and monitoring water color change in the coming days.

Neutralizing the pollution source

Reconditioning of the fountain: Remove all the water , clean the interior walls of the fountain, remove mud or vegetations.

Water disinfection using chlorite substances (substances that in contact with water, release chlorine ) :

Sodium hypochlorite has 10-14% chlorine

Chloramine has 25% chlorine

Bleach has 30-35% chlorine

For an efficient disinfection a 5-10g chlorine / m3water is needed to be placed in the fountain for at least 24 h.

V=* R2 * h = the water volume

5* V or 10*V = the necessary chlorine quantity

!! Every chlorigene substance has different quantity of chlorine

The determination of residual Cl

It is considered that the disinfection of water by chlorination is efficient if, after 30 minutes, the water has an excess of Cl, called Residual Chlorine. There are two forms:

Free Residual Chlorine ( hypochlorous acid, hypochlorites)

Combined Rresidual Chlorine

This two together form the total residual Chlorine.

The identification or residual cl in the water confirm the efficient disinfection.

Methods of residual cl determination:

Iodometric Method

Total residual Chlorine concentration is equal to the concentration of the free and the combined forms of residual Chlorine. Free residual Chlorine reacts with ammonia to form combined residual Chlorine such as monochloramines. When potassium iodide is added to a sample that has residual Chlorine at an acidic pH, free iodine is released in direct proportion to the amount of total residual Chlorine in the sample. Then, the iodine is titrated with sodium thiosulfate to a colorless endpoint.

Orthotolidine Method

The orthotolidine test will normally gives the total residual chlorine present in water. However, it may be adjusted so as to give separately the quantities of free residual as well as combined residual of chlorine. The free residual chlorine forms the yellow color during the first 5 seconds of the addition of orthotolidine, while the combined residual chlorine goes on forming the color for about 5 minutes. Hence, the color after 5 seconds will give the quantity of free residual chlorine, and the color after 5 minutes will give the free and combined chlorine. The difference in value between the two values is the combined chlorine. The orthotolidine test, however, is not accurate, because the impurities such as iron, manganese, nitrate etc., are likely to cause a false yellow color, and indicating wrong and increased chlorine residual.

Disinfection of small amounts of water

Physical method: boiling water for about 30 min. Although this is an efficient method because it destroys both bacteria and viruses, it also modifies the organoleptic properties of water (the lack of taste )

Chemical methods are used only if the water is clear and is based on using chlorite substances, Iodine or Potassium permanganate.

Chlorite substances: potassium hypochlorite (Javel water), calcium hypochlorite, Chloramine (0.01-0,02 g /l)

Iodine: using the tincture of iodine can cause the medicine taste in water

Potassium permanganate: has a low efficiency