Sewage Effluent

EFFLUENT STANDARDS

Effluent standards are the values for each parameter fixed by the BIS as the upper limit in the effluent to be discharged in to various environments such as land, water bodies etc. The tolerance limits fixed by the BIS for discharge of industrial effluent into various environments are furnished in Table 1. The tolerance limits of discharge of wastewater effluent into the water bodies are furnished in Table 2.

Table 1 Tolerance limits for discharge of Industrial effluent

Sl. No.	Characteristics	Tolerance limits for discharge of trade effluent into
		Inland surface waters a	PublicSewers b	On land forirrigation c	Marine /coastal areas d
1.	Suspended Solids, mg/L	100	600	200	100
2.	Total dissolved solids, mg/L	2100	2100	2100	-
3.	pH value	5.5 to 9.0	5.5 to 9.0	5.5 to 9.0	5.5 to 9.0
4.	Temperature, °C	40	40	-	40
5.	BOD (3days 27°C), mg/L	30	350	100	100
6.	COD, mg/ L	250	-	-	250
7.	Hexavalent Chromium, mg/L	0.1	2.0	2.0	1.0
8.	Chloride, mg/ L	1000	1000	600	-
9.	Sulphate, mg/L	1000	1000	1000	-

 

“as per IS 2490 – 1974 pt I
as per IS 3306 – 1974

as per IS 3307 – 1977

^d as per 7968 – 1976

Table 2 Tolerance limits for discharge of domestic wastewater effluent into surface waters

SI. No.	Characteristics	Tolerance limits
1.	pH	5.5 to 9.0
2.	Total Suspended Solids, mg/L	30
3.	BOD (3 days at 27°C), mg/L	20

 

Example

For the BOD test of a sample the dilution factor for the mixture of wastewater and dilution water is 0.03. The DO of the mixture is initially 8.0 mg/L and five days of incubation depeleted DO to 2.0 mg/ L. What is the five day BOD of the waste?

• Solution

Initial DO of sample before incubation,         DO. 8.00 mg/L

Final DO of sample after incubation,               DOf = 2.00 mg/L

Dilution factor,                                                    p     = 0.03

BOD5 of the wastewater	DO, — DO,

8.00 — 2.00

= 200 mg I L

0.03

Result: BOD₅ of the wastewater = 200 mg/L