used if the concentration is between 50 and 100 mg/l if the water is microbiologically safe and there is increased vigilance by medical authorities” (WHO 2011). Operational and Acceptability Monitoring: The WHO guidelines include values for certain parameters which may not pose a health hazard, but may pose operational or acceptability concerns. The acceptance or monitoring thresholds for selected parameters, including nitrate, TDS, pH, and turbidity are summarized below. <Selected parameters for operational and acceptability should be described as well.> Total Dissolved Solids (TDS): Total dissolved solids, or TDS, is an important measure of dissolved salts, or conductivity, of the water. High values of TDS may result in taste concerns. According to the WHO, TDS levels below 600 mg/l are generally acceptable to most consumers, while levels above 1000 mg/l appear to result in water that is unpalatable. High levels of TDS may also result in excessive scaling in equipment. Electrical conductivity (EC): Electrical conductivity (EC) in like TDS, is an indicator of conductivity. μS/cm, EC is relatively easy to measure in the field, and is used frequently as a surrogate for TDS. EC in μS/cm is usually 1 to 2 times the TDS in mg/l depending on the dissolved ion content of the water Corrosion and pH: One of the most important operational parameters in systems is pH. According to the WHO, the optimum range for pH for most water systems is 6.5 to 8. Control of pH within this range generally prevents corrosion and ensures proper operation and maintenance of the drinking water system. Turbidity: Turbidity: Turbidity manifests itself as cloudiness in the water, resulting from suspended particles and colloidal material. It is a critical indicator of possible contamination of the water supply, notably in poorly or untreated surface waters, although turbidity itself is not necessarily a health concern. According to the WHO, for small water supplies with limited or no treatment, levels of turbiditly should remain below 5 NTU, and, if possible, below 1 NTU. Additional WHO guidance documents on drinking water quality are widely available and can be accessed at the WHO drinking water quality website at: .
used if the concentration is between 50 and 100 mg/l if the water is microbiologically safe and there is increased vigilance by medical authorities” (WHO 2011). Operational and Acceptability Monitoring: The WHO guidelines include values for certain parameters which may not pose a health hazard, but may pose operational or acceptability concerns. The acceptance or monitoring thresholds for selected parameters, including nitrate, TDS, pH, and turbidity are summarized below. <Selected parameters for operational and acceptability should be described as well.> Total Dissolved Solids (TDS): Total dissolved solids, or TDS, is an important measure of dissolved salts, or conductivity, of the water. High values of TDS may result in taste concerns. According to the WHO, TDS levels below 600 mg/l are generally acceptable to most consumers, while levels above 1000 mg/l appear to result in water that is unpalatable. High levels of TDS may also result in excessive scaling in equipment. Electrical conductivity (EC): Electrical conductivity (EC) in μS/cm, like TDS, is an indicator of conductivity. EC is relatively easy to measure in the field, and is used frequently as a surrogate for TDS. EC in μS/cm is usually 1 to 2 times the TDS in mg/l depending on the dissolved ion content of the water Corrosion and pH: One of the most important operational parameters in systems is pH. According to the WHO, the optimum range for pH for most water systems is 6.5 to 8. Control of pH within this range generally prevents corrosion and ensures proper operation and maintenance of the drinking water system. Turbidity: Turbidity: Turbidity manifests itself as cloudiness in the water, resulting from suspended particles and colloidal material. It is a critical indicator of possible contamination of the water supply, notably in poorly or untreated surface waters, although turbidity itself is not necessarily a health concern. According to the WHO, for small water supplies with limited or no treatment, levels of turbiditly should remain below 5 NTU, and, if possible, below 1 NTU. Additional WHO guidance documents on drinking water quality are widely available and can be accessed at the WHO drinking water quality website at: .
Annex_4_Standard_Text.docx