TOTAL VIABLE COUNTS AT 22°C 48 HOURS
A mandatory water treatment process used by the company is disinfection. This processes is not sterilisation and hence it is not surprising to find colony numbers below the alert value in routine samples taken from the final tap on the works and in the distribution system.

The "plate count" at 22 and 37 degrees centigrade does not culture all the bacteria present, however providing the analytical method remains consistent there is value in using the results in conjunction with other microbiological determinations. 

The use of these analyses is as a comparative one. When figures rise by an order of magnitude from the previous recording then it must be concluded that a deterioration in quality may have taken place. When a value above alert is detected at a random or customer complaint tap then comparason is not possible in most cases.

Health Implications
None.

COLIFORMS, E.COLI, CLOSTRIDIA & FAECAL STREPTOCOCCI
Coliform microorganisms are a group of different bacterial species which share certain biochemical properties with Escherichia coli, an inhabitant of the gut of mammals and birds. Not all coliforms occur in sewage or faeces. Some survive and grow in environments that are free from contamination with sewage or faecal matter. For this reason judging the sanitary significance of any coliform(s) found in a sample of drinking water is far from straightforward.

Escherichia coli is used as the primary indicator of faecal pollution. 
Secondary faecal indicators

Faecal streptococci are less abundant than E.coli in human faeces, but may be more numerous in the gut flora of other animals. They are used as a confirmatory test of faecal pollution after the isolation of coliforms or E.coli in a routine sample as they can survive longer out of the gut than E.coli. 

Clostridia perfingens is also a secondary indicator of faecal pollution but is used less frequently than faecal streptococci. It can form resistant spores which survive longer out of the gut than both other faecal indicators and is usually present in much lower numbers in faeces.

Its use is routinely restricted to specialist applications e.g., for new ground water source assessments.

Health Implications
These tests offer the most sensitive test for the detection of faecal and hence potentially serious pollution. Faecal pollution is likely to carry pathogenic organisms with it and this is a serious risk to public health.

CRYPTOSPORIDIUM
Cryposporidium and Giardia are enteric protozoan parasites found in many vertebrates including man. 
The faeces of an infected animal contains oocysts (a spore like stage in the parasite's life cycle), which are resistant to the disinfectant action of chlorine. 

The analysis for cryptosporidia and giardia is not routine except at the raw and treated waters derived wholly or in part from river sources.

In exceptional cases (suspected outbreak conditions) analysis will be carried out in the distribution system at the discretion of the event scientist. 

Health implications
Ingestion of viable oocysts can cause gastro-intestinal and "flu-like" symptoms in the host after an incubation period of 2-14 days. Sometimes symptoms do not appear. 

Those most at risk are the young the old and the immuno-compromised. No effective drug has so far been found to counteract the diseases.

GIARDIA LLAMBLIA
Cryposporidium and Giardia are enteric protozoan parasites found in many vertebrates including man. 
The faeces of an infected animal contains oocysts (a spore like stage in the parasite's life cycle), which are resistant to the disinfectant action of chlorine. 

The analysis for cryptosporidia and giardia is not routine except at the raw and treated waters derived wholly or in part from river sources.

In exceptional cases (suspected outbreak conditions) analysis will be carried out in the distribution system at the discretion of the event scientist. 

Health implications
Ingestion of viable oocysts can cause gastro-intestinal and "flu-like" symptoms in the host after an incubation period of 2-14 days. Sometimes symptoms do not appear. 

Those most at risk are the young the old and the immuno-compromised. No effective drug has so far been found to counteract the diseases.

ENTEROVIRUS
The majority of viruses enter water courses from sewage treatment works and agricultural run off. River derived water treatment works are most at risk from a challenge by these entities. 

Viruses which multiply in the intestine are of most concern as they are able to survive and remain viable (but not multiply) outside of the host organism in some cases for several months. 

Analysis is only undertaken in treated water when it is suspected that faecal contamination has taken place. Therefore an INCIDENT or an Infringement trigger for coliforms or faecal indicators will already have been passed and the first response model or QSD emergency procedures been enacted.

Health implications
Enteric viruses are capable of great variety of symptoms in their hosts, e.g., fevers, gastroenteritis, hepatitis, meningitis, myocarditis, rashes and respiratory conditions.

The most important of these as far as water is concerned are infectious hepatitis and gastroenteritis. The young, old and immuno- compromised are most at risk from these conditions, healthier individuals often show no symptoms from imbibing the same infective dose.

SALMONELLA
The majority of viruses enter water courses from sewage treatment works and agricultural run off. River derived water treatment works are most at risk from a challenge by these entities. 

Viruses which multiply in the intestine are of most concern as they are able to survive and remain viable (but not multiply) outside of the host organism in some cases for several months. 

Analysis is only undertaken in treated water when it is suspected that faecal contamination has taken place. Therefore an INCIDENT or an Infringement trigger for coliforms or faecal indicators will already have been passed and the first response model or QSD emergency procedures been enacted.

Health implications
Enteric viruses are capable of great variety of symptoms in their hosts, e.g., fevers, gastroenteritis, hepatitis, meningitis, myocarditis, rashes and respiratory conditions.

The most important of these as far as water is concerned are infectious hepatitis and gastroenteritis. The young, old and immuno-compromised are most at risk from these conditions, healthier individuals often show no symptoms from imbibing the same infective dose.

FUNGI
The only routine analyses performed for fungi are on customer complaints and commissioning samples as they may be useful in investigating biofilm formation problems. e.g., localised warming of unlagged pipes in a domestic premises, aerial fungal spores contaminating a service reservoir. In cases of ingress fungal spores may also gain entry into the distribution from soil.

Health implications
None. 

PSEUDOMONADS
Pseudomonas aeruginosa is often but not always associated with faecal contamination. It is also able to multiply within the distribution system when suitable nutrients are available to it. These can be derived from unsuitable materials used in the distribution system or from the any organic nitrogen derived after the treatment process itself. 

Health implications
Members of the genus Pseudomonas are opportunist pathogens of the young, infirm and immuno-compromised. They are generally undesirable in potable water, and can create problems in particular circumstance where the degree of water purity required should be high.

microbiology  |  chemistry  |  metals