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Water QualityOn completion of this segment you should be able to:

• Have some knowledge of the chemical and physical properties of water

• Have an understanding of water microbiology

• Be aware of some disease causing microorganisms

• Be able to describe the microbiological standards of drinking water

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Typical Raw Water

Good Poor Reject

Average BOD5 mg/L 1.5 - 2.5 2.5 – 4 > 4

Max BOD5 mg/L 3 – 4 4 – 6 > 6

Average coliform (MPN) 100 – 5000 5000 – 20000 > 20000

Max coliform <20% > 5000 <5% > 20000

pH 5 – 9 3.8 – 10.3 < 3.8

Chlorides mg/L 50 – 250 250 – 600 > 600

Fluorides mg/L 1.5 – 3.0 > 3

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Drinking Water Quality

• Water for human consumption must be free from pathogenic organisms and from chemicals hazardous to health

• Water must be aesthetically acceptable (odour, colour, taste), and also non-corrosive or scale forming

• Water should conform to some acceptable guidelines e.g. WHO, NHMRC

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Water Quality CharacterisationWe can characterise water quality in terms of the following

• Physical

• Chemical

• Radiological

• Bacteriological

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Physical Properties of Water

• Colour

• Hardness which may be related to total dissolved solids (TDS)

• Odour and taste

• Turbidity or total suspended solids (TSS)

• Temperature

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Chemical Properties of Water

• Dependent on the composition of solutes present

• Solutes are natural or introduced anions and cations in water, which may contribute to taste, odour and hardness

• Concentrations of solutes that are injurious to to health

• Solutes are largely inorganic but some may be organic

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Maximum acceptable values in drinking water

Characteristic WHO guidelinemg/L

Australianguideline mg/L

Arsenic 0.01 0.007

Aluminium 0.2 0.2

Barium 0.7 0.7

Cadmium 0.003 0.002

Chromium 0.05 0.05

Cyanide - 0.08

Fluoride 1.5 1.5

Lead 0.01 0.01

Mercury 0.001 0.001

Nitrate (as N) 50 as NO3- 50

Some Health related Chemical Characteristics

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RadiologicalRadioactivity is the energy released from the breakdown of radionuclides

• Naturally occurring radioactive species in drinking water sources

• Contamination from concentration of natural levels such as mining and processing of minerals

• Artificial radionuclides which may enter drinking water supplies from medical and industrial use of radioactive materials

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Water MicrobiologyOf living organisms (apart from animals and plants) there is a third kingdom of Protisa

• Bacteria (0.5 - 5 micron)

• Algae, fungi, protozoa (> 5 micron)

• Viruses (20 - 100 nm)

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Microorganisms

• Some are pathogenic

• Majority assist in breaking down matter

• The bacteria cell may be viewed as a chemical machine that converts energy from one form to another through a process of metabolism

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A Bacterium CellSize 0.2 – 5 micron

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Bacteria cellsBacteria, blue-green algae (cyano-bacteria)

• Small size with simple organisation

• Nuclear region – single DNA molecule not separated from cytoplasm by any defined structure

• Cytoplasm - a site of protein synthesis (RNA), a colloidal suspension of protein, carbohydrates and complex organic compounds

• Cytoplasm membrane with enzymes for transport of food into cells and removal of wastes

• Cell wall to maintain rigidity and shape of cell

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Bacteria Cells

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Bacteria may be classified as

• Heterotrophic requiring an external organic source for energy and carbon

• Autotrophic that utilises inorganic compounds for energy and uses CO2 as a carbon source

• Aerobic, anaerobic and facultative in relation with O2

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VirusesDo not have the ability to reproduce themselves but replicated only within a host cell

• Small structures of non-living compounds

• Composed of 2 kinds of macromolecules i.e protein and DNA or RNA

• Acellular

• Obligate intracellular parasites

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Algae

• Resembles plants but without roots, stems, leaves

• Photosynthetic, autotrophic microorganism using nutrients and CO2

• Important role of recycling nutrients in the aquatic food chain

• Causes clogging of filters in water treatment, odour & taste in water, and eutrophication

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Fungi (yeast, mould, mushroom)The ability of fungi to survive under low pH and nitrogen limiting conditions, and distinctive degradative ability makes them important in wastewater treatment

• Non-photosynthetic

• Multi/or unicelluar and immotile

• Reproduce sexually or asexually

• Yeasts are unicellular, capable of aerobic and anaerobic growth

• Moulds are strict aerobes

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Protozoa

• Non-photosynthetic

• Single cell eucaryote that obtain energy from metabolising organic matter by feeding on bacteria, fungi and algae

• Important role in the secondary settling of the wastewater treatment process

• Some are a concern in drinking water e.g. cryptosporidium, giardia

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ProtozoaThe discovery of the cryptosporidium parasite in water supplies in Glasgow (Aug 2002) comes a matter of months after an outbreak struck the north east of Scotland. The latest alert has affected about 140,000 people in Glasgow after the infection, which can cause severe diarrhoea, was detected in the Mugdock Reservoir in Milngavie. Those in the affected areas have been urged to boil water before drinking it.

Cryptosporidium is commonly spread by animals

However, Scottish Water said it was safe to use for washing clothes and dishes and for bathing - although not for bathing babies.

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Waterborne Diseases and AgentsDependent on the causal agent

• Bacterial e.g. cholera, typhoid fever

• Viral e.g. hepatitis A, diarrhoea

• Protozoal e.g. amoebic dysentry, giardiasis

• Helminths e.g. schistosomiasis

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Indicator Microorganisms for Drinking WaterColiform group of microorganisms is present in large numbers in animal and human excreta. Why is there a need for such indicators?

• Pathogenic microorganisms are small in numbers

• Routine testing is not practicable and expensive

• Involves skilled labour and specialist equipment

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Indicator Microorganisms PropertiesMicrobial indicators are E.coli and the coliform group

• Always present when pathogens of like origin are present

• Present in large numbers

• Easy and quick to detect

• Equal or greater survival time than pathogens

• Absent from unpolluted waters

• Similar sensitivity to disinfection as pathogens

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Bacterial Standards of Drinking Water

• 98% of samples in any one year should not have any E.coli in 100 mL

• 95% of samples in any one year should not have any coliform organisms in 100 mL

• Max 10 coliform organisms per 100 mL in any one sample

• No coliform organism in 100 mL of any two consecutive samples

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Frequency of SamplingRelated to population size

Population served Minimum number of samples

Above 100 0006 samples per week, plus 1 additional sample per month for each 10 000 above 100 000

5 000 – 100 0001 sample per week, plus 1 additional sample per month for each 5 000 above 5 000

1 000 - 5 000 1 sample per week

Under 1 000 Minimum samples for small water supplies

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Drinking Water Guidelines

• World Health Organisation

• National Health and Medical Research Council

• Australian Drinking Water Guidelines

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End of Water Quality segment