Effluent, ETP and STP water testing
Discharge compliance is assessed against the limit for your discharge route — inland surface water, public sewer, land for irrigation or marine disposal each have different limits. The core panel is pH, BOD, COD, TSS and oil and grease; your process decides which metals and specific pollutants get added.
General discharge limits — inland surface water
CPCB general standards for discharge into inland surface water. Your consent conditions may be stricter or add process-specific parameters; send us the consent letter and we will match the scope to it.
| Parameter | Unit | Limit | Note |
|---|---|---|---|
| pH value | — | 5.5 – 9.0 | Controlling parameter |
| BOD (3 days at 27 °C) | mg/L | 30 | Biodegradable load |
| COD | mg/L | 250 | Total oxidisable load |
| Total suspended solids | mg/L | 100 | Settling performance |
| Oil and grease | mg/L | 10 | Needs a separate sample bottle |
| Total residual chlorine | mg/L | 1.0 | Over-chlorination of treated sewage |
| Ammoniacal nitrogen (as N) | mg/L | 50 | Nitrification performance |
| Sulphide (as S) | mg/L | 2.0 | Anaerobic conditions |
| Phenolic compounds | mg/L | 1.0 | Process specific |
| Hexavalent chromium | mg/L | 0.1 | Plating, tanning, dyeing |
| Total chromium | mg/L | 2.0 | Plating, tanning |
| Lead (as Pb) | mg/L | 0.1 | Process specific |
| Copper (as Cu) | mg/L | 3.0 | Process specific |
| Zinc (as Zn) | mg/L | 5.0 | Process specific |
| Cyanide (as CN) | mg/L | 0.2 | Plating, heat treatment |
| Fluoride (as F) | mg/L | 2.0 | Process specific |
What to send us
Grab sample or composite?
A single grab sample tells you about one minute of the day. If your process is batch-based, a grab taken during a clean cycle can pass while the plant is non-compliant on average. For consent monitoring, a time-proportional composite over the shift is far more defensible — and if the board samples independently, it is closer to what they will find.
Questions about this test
Which limits apply to me?
It depends on your discharge route and your industry category. Discharge to a public sewer is generally less strict than to inland surface water, but your consent letter overrides the general table. Send it with the enquiry.
Why is COD high when BOD is fine?
It usually means the load is chemically oxidisable but not readily biodegradable — solvents, dyes or surfactants passing through a biological plant untreated. The BOD:COD ratio is the diagnostic, not either number alone.
Do you test STP water for reuse?
Yes. Reuse for flushing, gardening or cooling has its own quality expectations — typically tighter on TSS, BOD and residual chlorine, plus bacteriological indicators for any use where people may contact the water.