Key Parameters Checked in Treated Water Testing as per Indian Standards
With India’s growing industrialization and increasing emphasis on sustainable water management, treated water testing has become an essential practice. Proper testing of treated water—whether it is industrial effluent, municipal wastewater, or recycled water—ensures compliance with regulatory norms and protects public health and the environment. Indian regulatory bodies such as the Central Pollution Control Board (CPCB) and the Bureau of Indian Standards (BIS) have laid down specific standards and guidelines for treated water quality.
This blog explores the key parameters that are routinely tested in treated water in India, why these parameters matter, and the Indian standards governing them.
Why Treated Water Testing is Important
Treated water testing is crucial for several reasons:
Ensures compliance with environmental regulations.
Prevents contamination of natural water bodies.
Supports safe water reuse in agriculture, industry, or domestic use.
Protects ecosystems from harmful pollutants.
Helps industries maintain operational efficiency in their wastewater treatment plants.
Indian Regulatory Framework for Treated Water
Central Pollution Control Board (CPCB)
The CPCB prescribes effluent discharge standards for various parameters to regulate treated wastewater discharge from industries and sewage treatment plants.
Bureau of Indian Standards (BIS)
BIS issues relevant standards such as:
IS 10500 – Drinking water specifications.
IS 11624 – Wastewater for irrigation.
Various other standards specifying limits for chemical, physical, and microbiological contaminants.
Together, these guidelines define acceptable levels of contaminants in treated water.
Key Parameters Checked in Treated Water Testing
1. pH
Why it matters: pH indicates the acidity or alkalinity of water. Extreme pH can harm aquatic life and corrode infrastructure.
Indian standard: Typically, treated water pH should be between 6.5 and 8.5 as per CPCB norms.
Testing method: pH meter or colorimetric methods.
2. Biochemical Oxygen Demand (BOD)
Why it matters: BOD measures the amount of oxygen required by microbes to decompose organic matter. High BOD indicates high pollution.
Indian standard: Generally, BOD must be below 30 mg/L for treated effluent discharge.
Testing method: Dilution and incubation method over 5 days (BOD5 test).
3. Chemical Oxygen Demand (COD)
Why it matters: COD measures total quantity of oxygen required to oxidize both biodegradable and non-biodegradable organic matter.
Indian standard: COD limit is usually 250 mg/L or less.
Testing method: Potassium dichromate oxidation.
4. Total Suspended Solids (TSS)
Why it matters: TSS includes particles suspended in water that affect clarity and may carry pollutants.
Indian standard: Treated water should have TSS less than 100 mg/L.
Testing method: Gravimetric analysis.
5. Total Dissolved Solids (TDS)
Why it matters: TDS includes dissolved salts and minerals; high levels affect water taste and suitability for reuse.
Indian standard: TDS for treated water used in irrigation typically should be below 2100 mg/L.
Testing method: Conductivity meters or gravimetric evaporation.
6. Oil and Grease
Why it matters: Presence of oil can harm aquatic life and interfere with treatment processes.
Indian standard: CPCB limits oil and grease to below 10 mg/L.
Testing method: Extraction and gravimetric or infrared spectrometry.
7. Heavy Metals
Why it matters: Heavy metals like lead, mercury, chromium, and cadmium are toxic even at low concentrations.
Indian standards: Limits vary, but often in the range of micrograms per liter; e.g., Lead below 0.1 mg/L.
Testing method: Atomic absorption spectroscopy (AAS), Inductively Coupled Plasma (ICP).
8. Coliform Bacteria
Why it matters: Coliforms indicate fecal contamination and potential pathogens.
Indian standard: For safe reuse or discharge, fecal coliform should be less than 1000 MPN/100 ml (Most Probable Number).
Testing method: Membrane filtration or multiple tube fermentation.
9. Nutrients (Nitrogen and Phosphorus)
Why it matters: Excessive nitrogen and phosphorus cause eutrophication in water bodies.
Indian standards: Limits vary based on discharge location; generally nitrates below 10 mg/L.
Testing method: Colorimetric and spectrophotometric methods.
10. Chlorides and Sulphates
Why it matters: High chloride or sulfate content can affect taste, corrosion, and soil health.
Indian standard: Chlorides and sulfates usually should be below 600 mg/L and 400 mg/L respectively.
Testing method: Titration or ion chromatography.
Sampling and Frequency of Testing
Proper sampling techniques are critical for accurate results.
Frequency depends on industry type, regulatory requirements, and treatment process stability.
Most industries test treated water weekly or monthly, with more frequent sampling if required.
Role of NABL Accredited Labs in Testing
Testing must be performed in NABL accredited laboratories to ensure data integrity and acceptance by regulators like CPCB and State Pollution Control Boards.
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