Requirements For Discharge Of Trade Effluent Into Public Sewer

"Trade effluent" means any liquid, including particles of matter and other substances in suspension in the liquid, which is the outflow from any trade, business or manufacture or of any works of engineering or building construction.

All trade effluent to be discharged into the public sewerage system must be done so with the written consent of the Public Utilities Board. The requirements for trade effluent discharge are spelt out in the Sewerage and Drainage Act, Chapter 294 and the Sewerage and Drainage (Trade Effluent) Regulations.

The physical and chemical characteristics of the trade effluent to be discharged into the public sewer shall not exceed the following limits:

1. The temperature of the trade effluent shall not exceed 45o Celsius at the point of its entry into any public sewer.

2. The pH value of the trade effluent shall not be less than 6 nor more than 9 at the point of its entry into any public sewer.

3. The caustic alkalinity of the trade effluent shall not be more than 2,000 milligrams of calcium carbonate per litre at the point of its entry into any public sewer.

4. Maximum concentrations of certain substances in trade effluent:

   S/No	List of Substances	Limit in milligrams per litre of trade effluent (or otherwise stated)
   1	5 Day Biochemical Oxygen Demand (BOD) at 20°C	400
   2	Chemical Oxygen Demand	600
   3	Total Suspended Solids	400
   4	Total Dissolved Solids	3,000
   5	Chloride (as chloride ion)	1,000
   6	Sulphate (as SO4)	1,000
   7	Sulphide (as sulphur)	1
   8	Cyanide (as CN)	2
   9	Detergents (linear alkylate sulphonate as methylene blue active substances)	30
   10	Grease and Oil (Hydrocarbon)	60
   11	Grease and Oil (Non-hydrocarbon)	100
   12	Arsenic	5
   13	Barium	10
   14	Tin	10
   15	Iron (as Fe)	50
   16	Beryllium	5
   17	Boron	5
   18	Manganese	10
   19	Phenolic Compounds (expressed as phenol)	0.5
   20	Fluoride (expressed as fluoride ion)	15

5. Maximum concentrations of metals in trade effluent:

   S/No	List of Metals	Limit in milligrams per litre of trade effluent (or otherwise stated)
   1	Cadmium	1
   2	Chromium (trivalent and hexavalent)	5
   3	Copper	5
   4	Lead	5
   5	Mercury	0.5

   S/No	List of Substances	Limit in milligrams per litre of trade effluent (or otherwise stated)
   6	Nickel	10
   7	Selenium	10
   8	Silver	5
   9	Zinc	10

Note: Where 2 or more of the metals listed in the table are present in the trade effluent, the total concentration of the metals shall not exceed 10 milligrams per litre.

1. any toxic industrial waste specified in the first column of the Schedule to the Environmental Public Health (Toxic Industrial Waste) Regulations (Cap. 95, Rg 11);

2. calcium carbide;

3. petroleum spirit or other inflammable substance;

4. any organic compound specified in First Schedule as follows:

5. any substance that either by itself or in combination or by reaction with other waste or refuse may give rise to any gas, fume, odour or substance which is or is likely to be a hazard to human life, a public nuisance, injurious or otherwise objectionable, or which prevents or is likely to prevent entry into the public sewer by workmen maintaining or repairing it;

6. yeast, spent or unspent molasses, crude tar, tar oil, crude oil, carbon disulphide, hydro-sulphide and poly-sulphide;

7. any radioactive material;

8. any waste or refuse liable to form a viscous or solid coating or deposit on any part of the public sewer or sewerage system;

9. any excessively discolouring substance;

10. any pesticide, fungicide, herbicide, insecticide, rodenticide or fumigant ;

11. blood waste;

12. infectious waste.

1. Applicant may, notwithstanding item 4, with the prior permission of PUB, discharge into any public sewer trade effluent containing trace amounts of any substance specified in item 4.

2. PUB may refuse or revoke any permission under (I) if it considers that the discharge is likely to be a hazard to the safety or health of any person at work in the public sewer or the sewerage system to which the public sewer is connected, or interfere with –

   1. the proper working of a sewerage system to which the public sewer is connected, or any facility, machinery or equipment related or connected to the sewerage system;

   2. the proper working of any facility, machinery or equipment which treats sewage from the public sewer for reuse;

   3. any process of treating trade effluent or other waste or refuse from the public sewer; or

   4. any process of treating sewage from the public sewer for reuse.

Applicant may with the prior permission of the Board discharge into any public sewer trade effluent containing BOD or TSS greater than 400 milligrams per litre but not exceeding 6000 milligrams per litre of the trade effluent with payment of Trade Effluent Fee. However, the corresponding COD shall not be greater than 10,000 milligrams per litre of the trade effluent or 3 times the concentration of BOD in the trade effluent, whichever is the lower. The fees to be levied are computed in accordance with the scale set out in the following Schedule:

Note : BOD = Biochemical Oxygen Demand (5 day at 20oC)

TSS = Total Suspended Solids

1. The discharger shall maintain any trade effluent treatment facilities in good order to ensure that the trade effluent complies with the Regulations.

2. The discharger shall submit in writing to the Water Reclamation (Network) Department, PUB within 14 days of any change or addition to the following:

   • Name of company and address; and

   • Process or operation used in the trade, manufacture, business or building construction.