International discharge norms compared

Treated sewage limits from India, IFC, the EU and the US side by side, and how to decide which one governs your project.

Treated sewage limits compared

Limits for treated sanitary sewage from each source. They are not like-for-like: each source uses its own basis, as explained below the table.

Parameter	India (new STP, tighter set)	IFC EHS (2007)	EU UWWTD	US EPA secondary
pH	6.5 to 9.0	6 to 9	not set in Annex I	6.0 to 9.0
BOD (mg/L)	10	30	25 (or 70 to 90% reduction)	30 (30-day avg), 45 (7-day avg), 85% removal
COD (mg/L)	50	125	125 (or 75% reduction)	not set
TSS (mg/L)	20	50	35 (optional requirement)	30 (30-day avg), 45 (7-day avg), 85% removal
Total nitrogen (mg/L)	10	10	15 or 10 in sensitive areas (by size)	not set
Total phosphorus (mg/L)	not set	2	2 or 1 in sensitive areas (by size)	not set
Oil and grease (mg/L)	not set in table	10	not set	not set
Coliform	Faecal coliform 230 MPN/100 mL permissible	Total coliform 400 MPN/100 mL	not set in Annex I	not set

Sources: Indian values as on our India discharge norms page; IFC General EHS Guidelines (2007) indicative values for treated sanitary sewage, as reproduced in a JICA report; EU Directive 91/271/EEC Annex I; US 40 CFR 133.102.

Why the columns are not directly comparable

Different bases: EU limits can be met by concentration or by percentage reduction. US limits are 30-day and 7-day averages with a percentage removal. IFC values are indicative guideline values. Indian limits are set in the consent and notifications, and many states enforce the tighter set for new STPs.
Different purposes: EU and US values define treatment standards for public plants. IFC values are used by lenders and international projects. India sets limits by discharge mode and state.
Sensitive areas: EU nitrogen and phosphorus limits apply only to discharges into areas sensitive to eutrophication, and depend on plant size.

Which limit governs your project

The authority comes first: The consent, permit or licence from the local authority is the legal limit. It can be tighter than any table here.
Lender or client standard: Projects funded by international lenders usually require IFC guideline values, or the local limit if stricter. Check the loan or tender document.
No local limit given: Agree a reference standard with the client in writing before design. We usually propose the stricter of the local and IFC values.
Reuse: Reuse needs tighter quality than discharge, including disinfection. See the reuse standards and design standards pages.

Check before you design

Standards are amended. Verify every value against the current official text and your authority notification before you finalise a design. We can do this check as part of a proposal: send your RFQ details and any specification.

Common questions

Which standard should I design a plant to if the country has no clear limit?

Agree a reference with the client in writing. A common approach is the stricter of the local limit and the IFC indicative values. It also depends on the receiving water and any reuse.

Are the EU and US values the same as the Indian ones?

No. They differ in values and in how they are expressed, as percentages or averages. Compare them using the table and the notes, not number against number.

Do you design plants to meet these limits?

Yes. Each plant is designed backwards from the limit that binds. Send the limit with your water data and we tell you which stages it needs.