Effluent Discharge Standards (effluent standards)

Effluent discharge standards are the numerical limits that treated liquid waste (effluent) must satisfy before it can be released into the environment. In India they are notified by the CPCB under the Environment (Protection) Rules 1986 (the General Standards in Schedule VI) and made enforceable through each unit's Consent to Operate under the Water (Prevention and Control of Pollution) Act 1974. They cover parameters such as pH, BOD, COD, total suspended solids, oil and grease, heavy metals (lead, chromium, cadmium, copper, zinc, nickel, arsenic), cyanide, phenols, sulphide, ammoniacal nitrogen and more.

The defining feature is that the standards vary by the mode of disposal — the same plant faces different limits depending on whether it discharges into inland surface water, public sewers, land for irrigation, or marine coastal areas. For example, suspended solids are capped at 100 mg/L for inland surface water but 600 mg/L for public sewers and 200 mg/L for irrigation; BOD is 30 mg/L for inland surface water but higher for sewers leading to a treatment plant. The receiving environment determines which column of the standard applies.

For recyclers, effluent discharge standards bite wherever a wet process generates liquid waste: hydrometallurgical metal recovery (acid leach liquors heavy in metals), plastic washing lines (high suspended solids and detergent load), battery recycling (acidic, lead-bearing effluent), tannery and similar pre-processing, and the digestate liquor of CBG plants. Each must be treated to the standard for its chosen discharge mode before release.

The practical approach is to design the effluent treatment plant (ETP) to meet the standards for the intended discharge mode, with margin, and to know that the cheapest compliance is often reducing effluent volume and recycling water rather than treating ever-larger flows. Many SPCBs now push recyclers toward zero liquid discharge, especially in water-stressed states, which removes the discharge-standard question entirely by eliminating discharge. Routine NABL-lab analysis of treated effluent against the applicable column is the evidence the board checks.