Key Water Quality Parameters for Daily Drinking Water

Access to safe drinking water is a fundamental requirement for public health. In China, the primary standard governing drinking water safety is the Standards for Drinking Water Quality (GB 5749-2022), which took effect on April 1, 2023. This standard classifies water quality indicators into two broad categories: routine indicators (43 parameters) and expanded indicators (54 parameters). 

Routine indicators reflect the basic condition of drinking water and are mandatory for daily testing, while expanded indicators address regional, seasonal, or situational pollution risks that require selective monitoring.

Microbiological Indicators

Microbiological safety is the top priority for drinking water. Three routine microbiological parameters are specified. Total coliforms serve as an indicator of fecal contamination; their presence signals potential contamination by sewage or animal waste and the possible existence of enteric pathogens.

 Escherichia coli is a direct and definitive marker of fecal pollution — if detected, the water is considered unsafe regardless of other test results. Heterotrophic plate count measures the total number of culturable bacteria in water; while not directly indicating pathogens, it reflects overall cleanliness and treatment efficiency.

Toxicological Indicators

Toxicological parameters address chemical contaminants that may cause chronic health effects even at low concentrations over long-term exposure. The routine toxicological list includes 18 parameters. These include heavy metals (arsenic, cadmium, hexavalent chromium, lead, and mercury) as well as non-metallic elements (cyanide, fluoride). 

Nitrate is also regulated because it can be reduced to nitrite in the human body, leading to methemoglobinemia — the “blue baby syndrome” in infants. The standard also regulates disinfection by-products, including trihalomethanes (chloroform, bromodichloromethane, dibromochloromethane, and bromoform) and haloacetic acids (dichloroacetic acid, trichloroacetic acid), because these compounds are potentially carcinogenic.

Sensory and General Chemical Indicators

This group comprises 16 routine parameters that collectively assess the physical acceptability and chemical balance of drinking water. Color and turbidity measure clarity and suspended particles, directly affecting user acceptance. Odor and flavor, as well as visible particles, are immediate indicators of aesthetic quality. pH is monitored to ensure water is neither too acidic nor too alkaline, which could affect corrosion of pipes or taste. Iron, manganese, copper, and zinc are essential trace elements but must be kept within appropriate ranges to avoid staining or unpleasant taste. Chloride and sulfate affect taste and may cause corrosion. 

Total dissolved solids indicates the total mineral content; water with either very low or very high TDS may be less desirable for drinking. Total hardness (measured as calcium carbonate equivalent) influences scale formation and soap consumption. The permanganate index reflects organic pollution, while ammonia indicates the presence of recent organic contamination.