Chapter:	358AK	Title:	TECHNICAL MEMORANDUM STANDARDS FOR EFFLUENTS DISCHARGED INTO DRAINAGE AND SEWERAGE SYSTEMS, INLAND AND COASTAL WATERS	Gazette Number:
Part:	2	Heading:	EFFLUENT STANDARDS	Version Date:	30/06/1997

PART II	EFFLUENT STANDARDS
6.	Discharges to foul sewers
6.1	Table 1 lists the standards for effluents to foul sewers leading to Government sewage disposal works. If the works include microbial treatment, there are extra requirements. Table 2 lists them. Information on the catchments of sewage disposal works is available for inspection in the Drainage Services Department.
6.2	In addition to the effluent standards, there are some substances that are harmful to the sewers, or resistant to removal by treatment processes. The Authority will not permit them to be discharged into foul sewers. They are listed below.
	Prohibited substances-FOUL SEWERS polychlorinated biphenyls (PCB) polyaromatic hydrocarbon (PAH) fumigant or pesticide radioactive substances chlorinated hydrocarbons flammable or toxic solvents petroleum oil or tar calcium carbide wastes liable to form scum or deposits in any part of the public sewer any substance of a nature and quantity likely to damage the sewer or to interfere with any of the treatment processes
6.3	The Authority will not normally allow sludge discharges to sewers. To avoid overloading the foul sewers, the Authority will not allow unpolluted water to be discharged into them.
6.4	The Authority will not allow dilution as a means of meeting effluent standards. This would cause excessive hydraulic loading on the disposal system. For this purpose the licence may specify an instantaneous peak flow. This does not necessarily prohibit mixing different effluent streams within the premises.
7.	Discharges to storm water drains
7.1	The Authority will not normally allow effluent to storm water drains. In exceptional circumstances, he may do so, in which case the effluent standards will be as for the downstream environmental waters. This may be inland waters or inshore waters. The Authority will also take the advice of the Director of Drainage Services on the available capacity of the storm water drain.
7.2	In a few areas, the foul sewerage is not adequate for existing sewage flows, and storm water drains may serve as combined sewers. The Authority will, after consulting the Director of Drainage Services, declare these combined sewers to be foul sewers for the purpose of fixing effluent standards. This will continue until the effluents can be diverted to separate foul sewers. The Government is working on a territory wide sewerage improvement programme to make this possible.
8.	Discharges to inland waters
8.1	Tables 3, 4, 5 and 6 list the standards for effluents to Group A, B, Group C and Group D inland waters respectively. The standards apply to groundwater as to other inland waters.
8.2	For general guidance, Group A inland waters include all waters in water gathering grounds and within the boundaries of country parks. Group B waters are mainly those draining agricultural areas in the New Territories. Group C waters are those running through areas where there are large numbers of fish ponds, mostly in the Yuen Long area. Group D waters are those large enough to permit secondary contact recreation and those draining urban and semi-urban areas.
8.3	The Authority will not allow new effluents to rivers, streams or storm water drains that are within 100m of a gazetted bathing beach and flow through the beach area. This is to protect the health and comfort of bathers.
8.4	They are some substances that the Authority will not allow in effluents to inland waters. They are listed below.
	Prohibited substances-INLAND WATERS polychlorinated biphenyls (PCB) polyaromatic hydrocarbon (PAH) fumigant, pesticide or toxicant radioactive substances chlorinated hydrocarbons flammable or toxic solvents petroleum oil or tar calcium carbide wastes liable to form scum, deposits or discoloration sludge or solid refuse of any kind detergents in Group A inland waters only
8.5	The Authority will not allow dilution as a means of meeting effluent standards. This would cause excessive loading on the receiving waters and their biota. For this purpose the licence may specify an instantaneous peak flow. This does not necessarily prohibit mixing different effluent streams within the premises.
8.6	The effluent standards in the tables do not apply to household septic tanks that discharge to the ground. The Authority will control them by design and maintenance standards. The general prohibitions still apply.
9.	Discharges to coastal waters
9.1	Tables 7, 8, 9a and 9b, and 10a and 10b list the standards for effluents in the various groups of coastal waters. Regardless of these standards, the Authority will not allow new effluents in certain areas. They are listed below.
	Prohibited Effluents-COASTAL WATERS No new effluent will be allowed: £»within 100m of the boundaries of a gazetted beach in any direction, including rivers, streams and storm water drains; £»within 200m of the seaward boundaries of a marine fish culture zone or a site of special scientific interest, and within 100m of the landward boundaries; £»in any typhoon shelter; £»in any marina; £»within 100m of a seawater intake point.
9.2	There are some substances that the Authority will not allow in effluents to coastal waters. They are listed below.
	Prohibited substances-COASTAL WATERS polychlorinated biphenyls (PCB) polyaromatic hydrocarbon (PAH) fumigant, pesticide or toxicant radioactive substances chlorinated hydrocarbons flammable or toxic solvents petroleum oil or tar calcium carbide wastes liable to form scum, deposits or discoloration sludge, floatable substances or solids larger than 10 mm
9.3	The Authority will not allow dilution as a means of meeting effluent standards. This would cause excessive loading on the receiving waters and their biological systems. For this purpose the licence may specify and instantaneous peak flow. This does not necessarily prohibit mixing different effluent streams within the premises.