You have received a water quality report from your lab. It has twelve parameters, units you do not recognise, and numbers that mean nothing unless you know what they are measuring. This is a frustrating but extremely common situation for factory managers, EHS officers, and plant operators across India. A water quality report is not just a technical document. It is a direct snapshot of how effectively your treatment system is performing and whether your facility is staying compliant with environmental regulations. Understanding what each number means can help you identify treatment issues early, reduce operational risks, and avoid costly penalties. Partnering with a reliable wastewater treatment company in India can also help industries better interpret these reports and improve treatment performance. Why Water Quality Reports Matter A water quality report serves two purposes. The first is regulatory, it documents whether your treated effluent meets CPCB or SPCB discharge standards. The second is operational; it tells you how well your ETP or STP is actually working. A report showing COD near the upper limit is not just a compliance signal; it is an early warning that your biological treatment stage may be under-performing. The Key Parameters Explained pH: Is Your Water Too Acidic or Alkaline? pH measures how acidic or alkaline your water is on a scale from 0 to 14. Neutral is 7. Below 7 is acidic, above 7 is alkaline. CPCB general standard for discharge into inland surface water: pH 6.0 to 8.5. Water that is too acidic or alkaline damages aquatic ecosystems and corrodes pipes and equipment. In an ETP, pH is also critical to biological treatment, as microorganisms have a relatively narrow pH tolerance. If your pH is consistently off, biological treatment is not working at full capacity. BOD: How Much Organic Waste Is in the Water? BOD stands for Biological Oxygen Demand. It measures the dissolved oxygen microorganisms need to break down organic matter over five days at 20°C. The higher the BOD, the more organic pollution in the sample. CPCB limit for inland surface water: 30 mg/L. When high-BOD wastewater enters a river, bacteria depleting oxygen suffocate fish and aquatic life. Rivers with BOD above 8 mg/L are considered polluted under India's water quality classification system. Your ETP's biological treatment stage activated sludge, SBR, MBBR, or MBR exists specifically to reduce BOD. COD: What Organics Can Biology Not Break Down? COD stands for Chemical Oxygen Demand. It measures the total oxygen needed to chemically oxidise all organic compounds including both biodegradable and non-biodegradable substances. CPCB general limit: 250 mg/L for inland water discharge. If your COD-to-BOD ratio is high (above 2.5:1), it signals non-biodegradable compounds that a standard biological ETP cannot handle. Chemical treatment stages Fenton oxidation, activated carbon, or ozone may be needed. This is common in textile dyeing, chemical manufacturing, and pharmaceutical production. TSS: What Solid Particles Are Suspended in the Water? TSS stands for Total Suspended Solids. It measures the weight of solid particles suspended in water that can be filtered out. CPCB limit: 100 mg/L for inland surface water. High TSS clouds water, blocks sunlight in rivers, and can carry heavy metals adsorbed onto particle surfaces. In your ETP, the primary treatment stage coagulation, flocculation, and sedimentation is responsible for reducing TSS. TDS: How Much Is Dissolved in the Water? TDS stands for Total Dissolved Solids. Unlike TSS, TDS measures all dissolved substances salts, minerals, metals, and organic compounds that pass through a filter. CPCB limit for inland water: 2,100 mg/L. For boiler feed water, acceptable TDS is typically below 500 mg/L; for drinking water, BIS standard is 500 mg/L. High TDS causes scaling in pipes, boilers, and heat exchangers increasing energy consumption and reducing equipment life. Reverse osmosis (RO) is the most effective technology for TDS reduction. Oil and Grease CPCB limit: 10 mg/L for inland water discharge. Critical for engineering workshops, vehicle washing, food processing, and refineries. Oil and grease above the limit forms surface films on water bodies, preventing oxygen exchange. Grease traps and dissolved air flotation (DAF) units are common treatment options. Heavy Metals: Chromium, Lead, Mercury, Arsenic Heavy metals carry the strictest limits because they bioaccumulate concentrating up the food chain and not broken down by biological treatment. Total Chromium: 2 mg/L (hexavalent chromium: 0.1 mg/L) Lead: 0.1 mg/L Mercury: 0.01 mg/L Arsenic: 0.2 mg/L Standard biological ETPs do not remove heavy metals. Chemical precipitation and advanced filtration stages are required. Industries at risk: electroplating, leather tanning, battery manufacturing, textile dyeing with chromium-based dyes. How to Read Your Report at a Glance When your lab report arrives, compare each parameter against its CPCB or SPCB-specified limit. Parameters approaching or exceeding limits need immediate attention. The second check is trend analysis three months of readings is a pattern. If your COD is creeping up month on month, something in your process is changing and it is better to investigate before it crosses the limit. The third check is the COD-to-BOD ratio, which tells you whether biological treatment alone is sufficient or whether you need additional chemical stages. Conclusion A water quality report is the most direct feedback available on whether your ETP is doing its job. The teams that read it fluently and act proactively rather than reactively are the ones that avoid compliance surprises and costly violations. At SCT Water, we work with plant managers and EHS teams to interpret reports, diagnose treatment gaps, and design solutions that deliver consistent parameter compliance. If your numbers are not where they need to be, let us take a look. FAQs What is TDS and why does it matter for industry? TDS (Total Dissolved Solids) measures everything dissolved in water salts, minerals, metals. High TDS causes scaling in boilers and heat exchangers, reduces equipment life, and may exceed discharge limits. RO systems are the most effective treatment. What is the difference between BOD and COD? BOD measures what biological organisms can consume. COD measures all organic compounds, including non-biodegradable ones. High COD relative to BOD signals compounds that a standard biological ETP cannot handle alone. What is an acceptable TDS level for industrial water? Boiler feed water typically requires below 500 mg/L. Cooling tower water can tolerate higher. CPCB's general limit for discharge into inland water is 2,100 mg/L. Check your application-specific requirement. How often should I test my water quality? Red category industries with OCEMS must monitor continuously. Others should conduct NABL-accredited lab testing at minimum quarterly, or as specified in their Consent to Operate.
