Water Quality

Allowable Limits for Trade Effluent Discharge to Watercourse or Controlled Watercourse

Discharge of trade effluent

Under the Environmental Protection and Management (Trade Effluent) regulations, no trade effluent can be discharged into a watercourse, or on land, without written permission.

Substances in trade effluent

The trade effluent discharged into any watercourse, or on land, must not include any of the following substances:

  • radioactive material;
  • any pesticide, fungicide, herbicide, insecticide, rodenticide or fumigant;
  • refuse, garbage, sawdust, timber, human or animal waste or solid matter;
  • petroleum or other inflammable solvent; or
  • a 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.

Allowable limits for trade effluent discharge


Items of Analysis Watercourse Controlled Watercourse
(Units in milligram per litre or otherwise stated)
1 Temperature of discharge 45ºC 45ºC
2 Colour 7 Lovibond Units 7 Lovibond Units
3 pH Value 6- 9 6- 9
4 BOD (5 days at 20°C) 50 20
5 COD 100 60
6 Total Suspended Solids 50 30
7 Total Dissolved Solids- 1000
8 Chloride
(as chloride ion)
- 250
9 Sulphate
(as SO4)
- 200
10 Sulphide
(as sulphur)
0.2 0.2
11 Cyanide
(as CN)
0.1 0.1
12 Detergents (linear alkylate sulphonate as methylene blue active substances) 15 5
13 Grease and Oil  10 (Total)
10 (Hydrocarbons)
1 (Total) 
14 Arsenic 0.1 0.01
15Barium 2 1
16 Tin - 5
17 Iron (as Fe) 10 1
18 Beryllium - 0.5
19 Boron 5 0.5
20 Manganese 5 0.5
21 Phenolic Compounds
(expressed as phenol)
0.2 Nil
22 *Cadmium 0.1 0.003
23 *Chromium (trivalent and hexavalent) 1 0.05
24 *Copper 0.1 0.1
25 *Lead 0.1 0.1
26 *Mercury 0.05 0.001
27 *Nickel 1 0.1
28 *Selenium 0.5 0.01
29 *Silver 0.1 0.1
30 *Zinc 1 0.5
31 *Metals in Total 1 0.5
32 Chlorine (Free) 1 1
33 Phosphate
(as PO4)
5 2
34 Calcium
(as Ca)
- 150
35 Magnesium (as Mg) - 150
36 Nitrate
(as NO3)
- 20


The trade effluent shall be analysed in accordance with the latest edition of Standard Methods for the Examination of Water and Wastewater published jointly by the American Water Works Association and the Water Pollution Control Federation of the United States.   

Note:

1 Controlled Watercourse refers to a watercourse from which water supplied by PUB under the Public Utilities Act is obtained but does not include a watercourse from which water is pumped into a main of the PUB.

2 Where two or more of the metals listed in the table are present in the trade effluent, the total concentration of the metals shall not exceed: (i) 1 milligram per litre, if discharged into watercourse other than controlled watercourse; and (ii) 0.5 milligrams per litre, if discharged into controlled watercourse.

3 “- ” No specified maximum concentrations under the Regulations. 

4 More information on the EPM (Trade Effluent) Regulations can be found here.