There are numerous routine indicators for tap water drinking water testing that are set to ensure the safety and suitability of the water for human consumption.The following are some of the main routine indicators and their criteria:
Total colony count: The standard stipulates that the total colony count in every 1ml of drinking water should not exceed 100CFU (colony forming unit).This can be used as an indicator for evaluating the degree of water cleanliness and assessing the purification effect.
Total coliforms: The standard stipulates that total coliforms shall not be detected in every 100ml of drinking water.Total coliform is one of the important microbiological indicators for evaluating the hygienic quality of drinking water, which can indicate the possibility of transmission of intestinal infectious diseases.
Arsenic: Standard limit of 0.01 mg/litre (or 50 ug/litre).Arsenic is an important contaminant in drinking water and is one of the few substances that can cause cancer through drinking water.
Cadmium: Standard limit of 0.005 mg per litre.Cadmium is a cumulative poison that accumulates in the soft cell tissues of the body, causing health problems such as kidney lesions.
Chromium (hexavalent): Standard limit is 0.05 mg per litre.Hexavalent chromium has a great irritating and corrosive effect and is one of the main toxic substances in water.
Lead: Standard limit of 0.01 mg per litre.Lead often enters the human body with drinking water and food, and excessive intake can cause cumulative poisoning, with the main toxicity manifestations being anaemia, neurological disorders and kidney damage.
Mercury: Standard limit of 0.001 mg per litre.
Cyanide: Standard limit of 0.05 mg per litre.Cyanide, which comes mainly from industrial wastewater, is highly toxic and can cause rapid death when it enters the body.
Chromaticity: The standard specifies that the chromaticity should not be greater than 15 degrees.Colour is an important indicator for evaluating sensory quality.
Turbidity: The standard shall not exceed 1 NTU (Scattering Turbidity Unit).Turbidity is an important indicator of water clarity or turbidity.
Odour and taste: The standard specifies that there should be no strange odour or taste.Polluted waters often have unusual odours.
Visible to the naked eye: the standard specifies that visible to the naked eye should be none.The presence of visible substances in water can affect the appearance and safety of drinking water.
pH: The standard specifies that the pH should be between 6.5 and 8.5.This range of pH is more suitable for human body, too low will corrode the pipeline, too high will reduce the effect of chlorination disinfection.
Free residual chlorine: The amount of chlorine or chlorine compounds added during disinfection that remains in the water and is used to evaluate the effectiveness of disinfection.
Iron: Standard limit of 0.3 mg per litre.When water contains high levels of iron, it can affect the taste and colour of the water and may damage pipes and equipment.
Manganese: Standard limit of 0.1 mg per litre.High concentrations of manganese are toxic, mainly to the central nervous system.
Copper: Standard limit of 1 mg per litre.Copper is one of the main trace elements needed by the body, but excessive intake can cause health problems.
Zinc: Standard limit of 1 mg per litre.Excessive intake of zinc can irritate the gastrointestinal tract and produce symptoms such as nausea.
Chloride: Standard limit of 250 mg per litre.Excessive chloride increases the rate of corrosion of metal pipes and produces a salty odour.
Sulphate: Standard limit of 250 mg per litre.Physiological reactions such as diarrhoea, dehydration and gastrointestinal disturbances may occur after high intake of sulphate.
Total dissolved solids: Standard limit is 1000 mg per litre.It is an important basis for evaluating the degree of mineralisation of the water, and high concentrations are unpleasant to the taste and may damage pipes and equipment.
Total hardness: The standard limit is 450 mg per litre (as calcium carbonate).Total hardness reflects the amount of calcium and magnesium ions in the water, which may be too high or too low for human health.
The above indicators and standards are based on authoritative documents such as the Hygienic Standard for Drinking Water for Domestic Purposes, which aims to ensure the safety and suitability of drinking water from the tap.In actual testing, appropriate testing items and frequency should be selected according to specific circumstances to ensure that the water quality meets the standards.
