Water Significance and Contamination

Water is essential for all forms of life and certain human activities.

In the course of survival, certain living organisms may contaminate water required for use by others.

Human activities may also lead to contamination of water sources with toxic substances.

Why control water standards?

Health and survival of man and other organisms depends on the purity of the water they use.

Different measures are used to access and control water quality with varying degrees of relevance and acceptability.

Hence the need to adopt generalized methods of assessment and arbitrary standards for water quality.

Water Quality Assessment

Water Quality

Physical Chemical Microbial

Water Quality Parameters• Turbidity

• Palatability

• Conductivity

• Total Dissolved Solutes

• Organoleptic Properties

• etc

Physical

• pH

• Dissolved Oxygen Concentration

• Residual Free Chlorine

• Radionuclides

• Organic/ inorganic Chemical Contents

• etc

Chemical

• Faecal Coliform Count

• Total Coliform Count

• Faecal Streptococci

• Cysts/ Ova of Parasites

Microbial

Microbiological Analysis

Offers the most sensitive test for the detection of recent and potentially dangerous faecal pollution

Provides a hygienic assessment of water quality with high sensitivity and

specificity

It is important to examine water sources frequently by simple tests rather than infrequently by more complicated test or series of tests

Indicator OrganismsInvestigation for individual specific

pathogens is rarely practical since they are fewer in numbers than the non-pathogenic organisms and their detection methods are too demanding.

Therefore, indicators of human/animal pollution e.g. coliforms are used to access water quality.

Indicators

E. coli

Faecal Coliforms

Total Coliforms

Faecal Streptococci

Indicator Organisms Cont’d

•Found in human and animal faeces; in sewage, treated

effluents, and natural waters subjected to

faecal contamination•Up to 109 per gram in

fresh faeces. •Routine identification is complex, but tests are

available for rapid reliable identification.

Escherichia coli

•Genus Escherichia and some spp of Klebsiella, Enterobacter and Citrobacter•May originate from organically enriched water or from decaying matter.•Rarely regrow in the distribution system

Faecal coliforms

Indicator Organisms Cont’d

•Gram-ve, bacilli tolerant to bile salts.

•Not necessarily faecal bacteria.

•Should not be detected in treated water and, if found,

suggest inadequate treatment, post treatment

contamination, or excessive nutrients.

• Test used as an indicator both of treatment efficiency

and of the integrity of the distribution system.

Total Coliforms

• Present in the faeces human and animal faeces.

•Belong to the genera Enterococcus and

Streptococcus•Most spp are of faecal origin

and indicate faecal contamination.

•Rarely multiply in polluted water, and are more

persistent than the coliforms. •Indicators of treatment

efficiency.

Faecal streptococci

SamplingSampling from a tap or pump outlet

Remove any attachments from tap that may cause splashing.

Wipe off the dirt from outside the tap.

Turn on the tap at maximum flow rate and let the water flow for 1-2 minutes.

Sterilize it for a minute with flame using gas burner, lighter or ignited cotton wool soaked in spirit.

Open the tap and allow water to flow at medium rate for 1-2 minutes.

Open the container for collecting the sample and fill the water by holding the bottle under the water jet. Leave a small airspace to facilitate shaking at thetime of inoculation prior to analysis.

Stopper the cap and label the container.

Sampling from reservoir Submerge the bottle in the

water. Open the bottle inside of the

water. Fill it by holding it by the lower

part, submerging it to a depth of about 30 centimetres, with the mouth facing slightly upwards. If there is a current, the bottle should face the current.

Pull it out when the bottle is filled.

Discard a little water to provide airspace

Stopper the bottle and label it.

Methods for Microbial Analysis

Microbial Analysis

Membrane filtration method

Multiple-tube method

Sampling cont’dSampling from a dug well

Attach a stone of suitable size to the sampling bottle with a piece of string.

Tie a 20 meter length of clean string on the bottle and to a stick.

Open the bottle as described above and lower into the well. Immerse the bottle completely in water without touching

the sides of the well and lower it down to the bottom of the well.

Pull it out when the bottle is filled. 6. Discard a little water to provide airspace. 7. Stopper and label the bottle.

Membrane Filtration MethodAseptically introduce sample into sterile membrane filter assembly ( 0.2 or 0.45 μm)

Filter retains indicator organisms

Transfer to a suitable culture medium and incubate

Count colonies and report results in CFU /100 ml

Membrane filtration machine

Multiple-tube methodAdd different measured sample volumes of to tubes containing a suitable culture medium

Organisms reproduce and produce acid with or without gas

Statistically determine MPN of organisms in the original sample

Principle

Separate analyses are usually conducted on five portions of each of three serial dilutions of a water sample.

The individual portions are used to inoculate tubes of culture medium that are then incubated at a standard temperature for a standard period of time.

The presence of coliforms is indicated by turbidity in the culture medium, by a pH change and/or by the presence of gas.

The MPN index is determined by comparing the pattern of positive results (the number of tubes showing growth at each dilution) with statistical tables.

The tabulated value is reported as MPN per 100 ml of sample.

Culture media

Isolation media

Double strength broth: Dissolve 71.2 g of lauryl sulphate broth in 1 litre distilled water.

After solubilisation, dispense 10 ml into each test tube containing inverted Durhan-tubes.

Sterilise by autoclaving at 121°C for 15 minutes. Cool down slowly to prevent bubbles in Durhan-tubes.

Single strength broth: Dissolve 35.6 g of lauryl sulphate broth in 1 litre distilled water.

After solubilisation, dispense 10 ml into each test tube containing inverted Durhan-tubes.

Sterilise by autoclaving at 121°C for 15 minutes. Cool down slowly to prevent bubbles in Durhan-tubes.

Medium uses Incubation periods

Lactose broth Total or thermotolerantcoliforms

48 hours at 35 ± 0.5 °C or 37± 0.5 °C for total coliformsand 24 hours at 44 ± 0.25 °Cor 44.5 ± 0.25 °C forthermotolerant coliforms

MacConkeyBroth & Lauryl tryptose(lactose) broth

Total orthermotolerantcoliforms

48 hours at 35 ± 0.5 °C or 37± 0.5 °C for total coliformsand 24 hours at 44 ± 0.25 °Cor 44.5 ± 0.25 °C forthermotolerant coliforms

Prepare the required number of tubes of culture medium. The volume and strength (single or double) of medium in the tubes will vary depending on the expected bacteriological density in the water and the dilution series planned.

Select and prepare a range of sample dilutions

Pipette the appropriate volumes of sample and diluted sample into the tubes of medium

Label the tubes with the sample reference number, the dilution and the volume of sample (or dilution) added to the tube.

Shake gently to mix the sample with the medium. Place the rack in an incubator or water-bath for 48 hours at 35 ± 0.5 ºC or 37 ± 0.5 ºC.

Procedure cont’d After 18 or 24 hours, note which tubes show growth. Tubes that show turbidity and gas production, or a colour change

indicating the production of acid (if the medium contains a pH indicator), are regarded as positive

Return the tubes to the incubator and re-examine after a total of 48 hours of incubation. Continue with the next step of the procedure.

Confirmatory test Prepare the required number of tubes of confirmation culture medium

(BGLB broth for total coliforms and E. coli medium for faecalcoliforms).

Using a sterile wire loop, transfer inocula from positive tubes into the confirmation medium

Incubate them for 48 hours at 35 ± 0.5 °C or 37 ± 0.5 °C for total coliforms (BGLB broth) or for 24 hours at 44 ± 0.5 °C for faecalcoliforms (E. coli medium)

Procedure cont’d

After the prescribed incubation time, note which tubes show growth with the production of gas,

and record the number of positives for each sample dilution

The test organism is cultured in a

medium which contains

tryptophane, kovac’s reagent

added to confirm indole

production

Compare the pattern of positive results with a most probable number table such as one of those given in Tables

Sample 50ml 10ml 1ml 0.1 0.01ml

Treated drinking-water 1

1 5

Partially treateddrinking water

5 5 5

Recreational water

5 5 5

Protected source water

5 5 5

Typical sample volumes and number of tubes for multiple fermentation tube analysis

Membrane Filtration...Method involves

comparatively simpler procedures.

Technique is inappropriate for highly turbid waters.

Filters may be expensive in some countries.

MPN statistical table Combination of positive

MPN index /100ml 95% confidence levelUpper lower

0 0 0 < 2 - -

0 0 1 2 1 10

1 1 0 4 1 15

2 1 0 7 2 20

Multiple-tube method...Method is applicable

to all kinds of water:

clear, coloured, or turbid

containing sewage, sludge,

mud or soil particles,

provided the contaminants

in the prepared test samples

are homogeneously

Distributed.

Method is comparatively complex.

Water Quality StandardsRegulations on the purity of water used for various purposes.

Mandatory limits concerning constituents and contaminants of water known to be hazardous and/or cause inconveniencies.

Sets of procedures and practices required to meet the mandatory limits.

Water Quality Standards

Water Quality Standards

Surface Water Quality

Standards

Drinking Water Quality

Standards

Water Quality Parameters

Physical properties

Chemical / Inorganic Substances

Organic Constituents

Disinfectants and their by-products

Radionuclides

Microbiological Parameters.

ISO Drinking Water Quality Standard

Quality Standards of Water( Summary)

Physical parameter

Fresh water Communal water

Trout water High quality water

Turbidity 50/25 NTU 10 NTU < 10 NTU

Temperature RT RT RT RT

Hardness 100mg/l cacO3

Chemical parameter

Fresh water Communal water

Trout water High quality water

pH 6-9 6.8-8.5 7

Salinity N N N N

Chlorine 230mg/l 250mg/l N

Alluminum 87ug/l 6500ug/l

Dessolvedoxygen

Not less than 5.mg/l

Not less than 6mg/l

Not less than 6mg/l

Quality Standards of Water cont’dBacteriological parameter

Fresh water Communal water High quality water

Enterococcus 35org. /100ml

Feacal coliforms 200org. /100ml

Key: NTU- Neplelometric Tubidity UnitRT- Room TemperatureN- Normal

Refer to Table 1. Microbial Examination of Water and Water Quality Standards (group 2) for more detail