Understanding Water Quality Standards: Parameters and Permissible Limits

Water is a vital resource for life, and ensuring its quality is crucial for the well-being of both ecosystems and human communities. To assess and regulate the quality of water, various parameters are measured against established standards. These standards set permissible limits for specific indicators, guiding efforts to maintain safe and healthy water sources.

1. pH (Hydrogen Ion Concentration):

Parameter: pH measures the acidity or alkalinity of water on a scale from 0 to 14, with 7 considered neutral.
Permissible Limit: The standard permissible range for pH in drinking water is typically between 6.5 and 8.5. Extreme pH levels can impact aquatic life and indicate potential issues with water treatment.

2. Dissolved Oxygen (DO):

Parameter: DO represents the amount of oxygen dissolved in water, crucial for the survival of aquatic organisms.
Permissible Limit: For healthy aquatic ecosystems, DO levels should ideally be above 5 mg/L. Low DO levels can harm fish and other aquatic life.

3. Turbidity:

Parameter: Turbidity measures the cloudiness or haziness of water caused by suspended particles.
Permissible Limit: The standard permissible limit for turbidity is often below 5 NTU (Nephelometric Turbidity Units) for drinking water. Higher turbidity can impact water aesthetics and treatment processes.

4. Total Dissolved Solids (TDS):

Parameter: TDS measures the total concentration of dissolved substances in water, including minerals and salts.
Permissible Limit: While TDS itself doesn’t have a specific health-based limit, elevated levels can affect taste and indicate the presence of contaminants. Guidelines may vary based on regional standards.

5. Total Coliforms and E. coli:

Parameter: These are indicators of bacterial contamination in water, suggesting the possible presence of harmful pathogens.
Permissible Limit: Drinking water should be free of total coliforms, and E. coli should be absent in a 100 mL sample. Their presence indicates potential fecal contamination and the risk of waterborne diseases.

6. Nitrate and Nitrite:

Parameter: Nitrate and nitrite levels in water primarily result from agricultural runoff and wastewater discharges.
Permissible Limit: The permissible limit for nitrate in drinking water is often set at 10 mg/L. High nitrate levels, especially in infant formula, can pose health risks, such as methemoglobinemia or “blue baby syndrome.”

7. Heavy Metals (e.g., Lead, Mercury, Arsenic):

Parameter: Heavy metals can enter water sources through industrial discharges and natural processes.
Permissible Limit: Strict limits are set for heavy metals due to their toxicity. For example, the permissible limit for lead in drinking water is often below 15 µg/L.

8. Chlorine Residual:

Parameter: Chlorine is commonly used to disinfect water supplies, and residual chlorine levels indicate the effectiveness of water treatment.
Permissible Limit: Residual chlorine levels should be maintained within a specified range to ensure disinfection without causing taste and odor issues.

9. Conductivity:

Parameter: Conductivity measures the ability of water to conduct an electric current, indicating the presence of dissolved ions.
Permissible Limit: While there’s no direct health-based limit, high conductivity may suggest elevated levels of dissolved solids, affecting taste and potentially indicating contamination.

10. Phosphates:

Parameter: Phosphates in water can result from agricultural runoff and wastewater discharges, contributing to nutrient pollution.
Permissible Limit: Permissible limits for phosphates aim to control nutrient levels and prevent issues like algal blooms. Guidelines may vary based on the specific water body and its use.

11. Biological Oxygen Demand (BOD):

Parameter: BOD measures the amount of dissolved oxygen consumed by microorganisms during the decomposition of organic matter.
Permissible Limit: Permissible BOD levels in water vary depending on the specific water body and its designated use. Lower BOD values indicate healthier water ecosystems.

12. Chemical Oxygen Demand (COD):

Parameter: COD measures the amount of oxygen required to chemically oxidize organic and inorganic matter in water.
Permissible Limit: Similar to BOD, permissible COD levels vary based on water body and use. Elevated COD levels can indicate increased pollution and potential harm to aquatic life.

These parameters are among the many assessed to determine water quality. Permissible limits are established based on scientific research and considerations for both environmental health and human well-being. Regular monitoring and adherence to these standards are essential for safeguarding water resources and ensuring access to clean and safe water for all.