microbiology of water supply

8/6/2019 Microbiology of Water Supply

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By

Dr Emmanuel Odjadjare


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MICROBIOLOGY OF WATER SUPPLY


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INTRODUCTION W

ater supply in the context of this course is any waterresource that is useful to man

This will imply that almost all aspects of the water cycle

may form part of the water supply (Fig. 1)

The focus of this class however is the microbiology ofwater supply

First lets take a look at the water supply


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The Water Supply

Reservoir

2

Aquifers

WaterTreat.

3

Ind.

Use

6

Dom

. Use5

Effl.

Treat

8

Water

reclam

Sew.

Treat10

Water

reclam

.

Land

1

4 7

7

4

9

11

Sewers

12Rivers

Disposal of sludges15

14

SeaEstuary

Evaporation

Further

dischargesFurther abstraction

Repeat some

items from 2 to 11

1213

Rain


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Microorganisms exert influence at almost all phases of thewater cycle

Broadly these influences can be distinguished in terms of:

Aggravation of pollution problems by microbial release

Release of pollutants that encourages microbial proliferation

Microbial activities beneficial to the water supply


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Microbiology of WS as rain water

goes through land, streams, rivers Percolation of rain water enhances microbial activities

such as:

Decomposition of organic matter

Nitrification Denitrification etc

This results in the availability of nutrients for soil biotaincluding plants

Rain water runoff could also erode top soil microflora and

nutrients into surface water bodies


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This may result in the introduction of pathogens into thewater supply at the river level

Pathogens may find their way into municipal supplies ifnot well treated

The introduction of nutrients & other suspensions intothe river may result in high turbidity of the water supply

This may result in high cost of treatment & reducedtreatment efficiency

In case of agricultural catchments, water runoff mayintroduce inorganic nutrients that cause eutrophication


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Microbiology of the Water Reservoir Microflora in water reservoir depends on the source of the

stored water

If the water is from land runoff, soil microflora will beexpected to form a significant part of the population

Where river water is the source, microflora indigenous tothe river and sometimes to the watershed are expected

In any case reservoir waters are usually allowed to stand

And this generally affects the microbial population therein


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Allowing the water to stand results in the settling out ofmicrobes attached to suspended materials

This results in the reduction of microbial populationincluding pathogens

Settling out of suspended materials also results in reductionof turbidity

UV rays kills a portion of the microflora during holdingperiods; especially in the tropics

Predation may also result in reduction in microbialpopulation during holding periods


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Predation could be of positive or negative consequence:

Where pathogens are preyed upon - +ve effect

Where biodegrading microbes are preyed upon - -ve effect

On the whole water leaving the reservoir is of better qualitycompared to the reservoir influent

Holding water in reservoir prior to treatment is thus a formof primary treatment


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Microbiology of WS at the level of

Water Treatment At this level, Microbes are removed from the water supply by

sand filters through adsorption or direct filtration

Microbes attached to sand filters remove contaminants fromcirculation by biodegradation

W

ater treatment also involves disinfection by chlorination,UV irradiation or Ozonation


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Microbiology of Water Supply in

the Distribution System Water entering the distribution system is assumed to be

clean, safe and free of contaminants

The water may however, be recontaminated on transit tothe end user

Sources of recontamination include:

Faulty, leaky, or broken pipes

Residual chlorine and pathogens in distribution system


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Microbiology of Water Supply at

the Level of Domestic Use Domestic activities will add contaminants (pathogens &

nutrients) into the water supply

Such activities include:

washing (of hands, clothes, food materials, kitchen waresetc); talking, sneezing, spitting, coughing etc

Washing may also introduce inorganic nutrients fromdetergents into the water supply


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Microbiology of WS at the Level of

Industrial Use of Water The type of industry will determine the kind of

contaminants contributed to WS by the industrial process

Effluent from the food/beverage industry is expected to behigh in BOD & may introduce microbes into water supply

Effluent from meat processing industry are expected to

contain some pathogens in addition to high BOD

Chemical/Pharmaceutical industry may introducesubstances that inhibits microbial growth &/or conferresistance on water supply microflora


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Microbiology of WS: Ind/Sewage

Effluent in Drainage System The microbial activity at this level is similar to thosedescribed under MCB of Industrial Water Use

Except that when the anaerobic content of the drainagesystem is released into aerobic zones (e.g. rivers), thesulphides (e.g. H2S) formed under anaerobic conditionmay be converted to sulphoric acid.

None acidophiles are wiped off, while acidophiles willproliferate

acidic condition may also corrode metal drain pipes


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Industrial Effluent Treatment The main objective for treatment is to remove contaminants

including organic/inorganic materials and pathogens (whereapplicable)

Mixed microbial population of aerobic microbes is usuallyused to treat industrial effluents of several origins

Where strong organic wastes are envisaged in the effluent,

anaerobic processes involving anaerobic microbialpopulations may be used

In all the microbial activities eliminate or reducescontaminants in the effluent before discharge


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Microbiology of Recycled Water

for Industrial Use Microbial communities at this level of the water supply vary

with prevailing environmental conditions

For example, slime forming microbes have been associatedwith surface cooling towers and heat exchangers

Microbial growth inhibitors can be used to control suchnuisance microbes

Disinfection is required in some industries (e.g. food)


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Microbiology of the Water Supply

at the level of sewage treatment

Aerobic processes (e.g. activated sludge) are commonlyused to achieve substantial decontamination

Encouragement of growth of nitrifying or denitrifyingbacteria may eliminate or reduce nitrogenous wastes

Factors that enhance microbial formation of flocculentaggregates are encouraged

Organic matter, Pathogens & other microbes settle out of

the water as flocs


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Recycled Sewage Water The degree of treatment of recycled sewage depends on the

end use of the reclaimed water and available resources

Recycled water for drinking purposes must undergo

stringent treatment Recycled water for irrigation of crops may not undergo very

stringent treatment as in drinking water

Inorganic nutrients (e.g. N & P) may not be eliminated fromrecycled water meant for irrigation

M

icrobial activities at this level also include thosementioned under Sewa e Treatment


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Microbiology of the WS at the

Level of Self-Purification in Rivers The microbial activity at this level include those that

were mentioned in MCB ofWater Reservoirs

The extent and type of microbial activity depends on thecharacteristic features of the river including, depth, rateof flow, turbidity, impact of the catchment, etc

Self-purification is possible in rivers because they areflowing water bodies

provided the source of constant pollution is identified

and stopped on time


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Microbiology of the WS at the

level of Self Purification of Estuary The events here are similar to those described in self-

purification of rivers

Except that a different microbial community highly adaptedto the fluctuating conditions of the estuary environment isinvolved

The estuary environment also have the capacity to handlehigher volumes of pollutants than the river

As in the river, the catchment may affect the microbial

community and hence the microbiology of the estuary


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Self-Purification of the Sea The activities here are similar to those described for estuary Except that the sea is a massive water body that has a higher

capacity of self-purification than the estuary

Of particular interest is the mortality of sewage organisms inthe saline sea water

Biodegradation of recalcitrant substances such as pesticides& PCBs may be quite a challenge for marine microflora

Organic pollutants such as crude oil are relatively slowlyde raded due to cold temperatures & low microbial diversity


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Microbiology of the Water Supply

at the Level of Sludge Disposal Where sludge from sewage treatment is used as manure

in agriculture, steps must be taken to ensure that certainpollutants that could find their way into the food chain

through such plants are removed before application

Little is currently known about the degrading potentialsof microorganisms in sludge discharged into the sea

There will be need to carry out research in this area toelucidate the potentials of microbes in removing suchpollutants in sludge from the marine environment

microbiology of water supply

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