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Frequently Asked Questions about our services

What are the main sources of Water Pollution?
What are the main sources of pollutants?
What are the main diseases caused by waterborne pathogenic microorganisms?
What are the limits of detection for methods used?

What are the main sources of Water Pollution?


Potential Effects

Trace elements

Health, aquatic biota

Heavy Metals

Health, aquatic biota

Metal-organic compounds

Metal Transport



Inorganic pollutants

Toxicity, aquatic biota



Acidity, alkalinity, salinity

Water quality, aquatic life



Organic pollutants


Polychlorinated biphenyls (PCB's)

Possible biological effects


Toxicity, aquatic biota, wildlife


Petroleum wastes

Wildlife, aesthetics

Sewage wastes resulting in increased

Water quality, oxygen level

Biochemical oxygen demand

Water quality, oxygen level




Eutrophication, wildlife, aesthetics



Deterioration in Taste, odour and colour


Increased Sediment

Water quality, aquatic biota, wildlife

What are the main sources of pollutants?

There are several points within the water cycle where water may become polluted. The most significant is the point at which the water is abstracted from rivers, lakes and wells and used by humans for drinking, cooking, cleaning and industrial processes. During use, water is converted to wastewater and what happens this, largely determines the extent of water pollution. The options available range from pumping it back to source or treating it to a very high standard (i.e. restoring it to its former condition). Sources of pollution fall into two main categories point and non-point sources. Point sources are defined as the point of entry of polluting material into a watercourse e.g. effluent discharge pipe, storm water overflow or a known point where waste is habitually dumped into the water. Pollution from non-point sources tends to enter the water cycle during precipitation or overland flow. The actual point where the pollutants enter depends on the type of source, its location and on the physical form of the pollutants. If the pollutants are gasses or fine airborne particles, they can fall to the ground directly as rain. The rain can also wash particles which have been deposited on surfaces into nearby watercourses. If pollutants are soluble they can be transported long distances in the water. During storms, quite large particles, including soil, can be washed down from the land into water bodies. These can sometimes have pollutants such as pesticides attached to them.


Non-point sources of pollution transport processes in urban areas are likely to be different from those in rural areas. There are several reasons for this:


Impenetrable materials cover quite a large part of urban areas. Thus, quite a lot of rainwater will become runoff and eventually enters drains and sewers.


In urban areas, less soil is exposed and so less erosion and hence transport of soil particles into surface waters can be expected.


In urban areas, pollutant loadings are mainly affected by the accumulation of litter, fallout and road traffic. In rural areas most of the pollution is due to erosion of soils.


In the long term, almost all of the pollutants deposited on impermeable surfaces in urban areas that are not removed by external processes (e.g. street cleaning), will eventually end up as surface runoff. In rural areas, deposits can be incorporated into the soil where their removal rate can be reduced.


Seepage of landfill leachate to underground strata and rivers


Point sources

Non-point sources

Discharge from sewage treatment works to river

Runoff and under-drainage from agricultural land into rivers

Discharges of industrial wastewaters to rivers

General contamination of recharge rainfall to outcropping aquifers

Discharge of farm effluents to rivers not underground strata

Septic tank soakaways into permeable strata

Discharges of collected landfill leachate to rivers

Wash-off litter, dust and dry fallout, from urban roads to rivers


What are the main diseases caused by waterborne pathogenic microorganisms?

The majority of waterborne diseases arise as a result of the contamination of water used for drinking with human or animal faeces. The pathogens contained in the faeces of a diseased human or animal are distributed within the water body and may be ingested by others, either directly by drinking or by consuming crops irrigated or washed with the same water. In addition to sewage, pathogens that infect humans have been identified in livestock, fowl, wildlife pets and even fish in contaminated water. This highlights the range of mobility that exists for enteric pathogens and explains the level of concern over faecal pollution.

Portal of entry

Pathogenic organism


Gastro-intestinal tract

Salmonella typhi   Vibrio  cholerae

Typhoid fever   


Shigella dysenteriae



Legionella pneumophilia



Salmonella spp.


Campylobacter spp.





Hepatitis A virus



Entamoeba histolytica

Amoebic dysentery

Viral Infections -

Viral infections are caused either by enteroviruses which live and reproduce within the gastro-intestinal tract, for example coxsackieviruses, echoviruses and polioviruses, or those which only occasionally infest the gastro-intestinal tract such as rotaviruses, reoviruses, adenoviruses and the hepatitis A virus. Although the last are not strictly enteric viruses, they are found in the faeces of infected individuals and may be transmitted via the faecal contamination of water. Enteric viruses are small, with diameters typically of

Parasitic protozoan infections -

Flagellate diarrhoea is caused by the intestinal flagellated protozoan Giardia lamblia. Contamination of drinking water by sewage provides one of the main transmission routes of this cyst-forming organism. On ingestion, G. lamblia attaches itself to the intestinal wall of the host by means of a suction disc. In severe infections, the resultant coverage of the intestinal surface restricts absorption of, for example, fats into the body. A variety of symptoms are produced, the most frequent being that of protracted, intermittent diarrhoea.


By the mid 1980's, waterborne outbreaks due to Cryptosporidium parvum began to appear in the US, and in 1993 this organism was responsible for the largest waterborne outbreak in US history. Recreational waterborne outbreaks have also been reported. Cryptosporidium can cause severs a diarrhoea that is self-limiting in immunocompetent individuals but may be prolonged and life threatening in the immunocompromised. 


Surveys have demonstrated the wide distribution and occurrence of Giardia cysts and Cryptosporidium oocysts in raw and treated water supplies and are known to be somewhat resistant to normal chlorination regimes. Ingestion of water containing these organisms may cause disease. Giardia and Cryptosporidium occur in domestic and feral animals as well as in humans. The environment may become contaminated through direct deposit of human or animal faeces or through sewage and wastewater discharges to receiving water.


What are the limits of detection for methods used?

We at City Analysts Ltd tailor our services to clients in order to minimize the burden associated with achieving compliance with directives and licenses. Our validation of methods and determining limits of detection for chemical and microbial contaminants and /or additives, are guided both by EU directives and client requirements. If clients have specific requirements for target levels e.g. achieving Dutch Directive limits, we attempt to meet their requests for all parameters and matrices. If specifically required, limits of detection may be included on reports.

Water Testing
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