|358AK||Title:||TECHNICAL MEMORANDUM STANDARDS FOR EFFLUENTS DISCHARGED INTO DRAINAGE AND SEWERAGE SYSTEMS, INLAND AND COASTAL WATERS||Gazette Number:|
|1.||Citation and commencement|
|1.1||This technical memorandum is issued under section 21 of the Water Pollution Control Ordinance. It may be cited as the Technical Memorandum on Effluent Standards.|
|2.||Application and scope|
|2.1||The Technical Memorandum on Effluent Standards is a guide to the Authority under the Ordinance. It sets the limits that make effluents acceptable into foul sewers, storm water drains, inland and coastal waters. The limits control the physical, chemical and microbial quality of effluents.|
|2.2||The standards apply to effluents through licences, which the Authority issues under sections 15, 16 and 20 of the Ordinance. The Authority is the Director of Environmental Protection. He will consult this memorandum when fixing the conditions that he will include in a licence. He will not normally impose conditions that are more stringent than those in the memorandum. To do so, he must have good reason.|
|2.3||Where a user takes water from a nature water course or water body, and then returns it after use, different standards may apply. The Authority will not impose standards requiring the effluent to be cleaner than the water that the user takes.|
|2.4||This memorandum does not apply to discharges or deposits of wastes that are controlled by the Waste Disposal (Livestock Waste) Regulations (Cap 354 sub. leg. A). Nor does it apply to dredging, dumping for land formation or solid waste disposal. Other laws and standards control them. The memorandum does apply to all other discharges and deposits.|
|2.5||This memorandum sets standards for effluents that differ in different areas and between surface waters and sewers. The standards also vary with the rate of effluent flow, which the Authority may also limit.|
|2.6||The flow rates the memorandum covers appear in Tables 1 to 10b. The Authority will set standards for effluents outside the listed flow ranges case by case. Standards for effluents above the highest flow band will be more stringent than those in the tables.|
|2.7||Some effluents may have characteristics or components that are not listed and could be harmful. In these cases, the Authority may set limits case by case. There are certain general prohibitions that apply besides the tables, which are listed in paragraphs 6.2, 8.4 and 9.2.|
|2.8||At present, the Government Chemist is the only analyst designated by the Ordinance. He alone certifies the quality of an effluent sample in a prosecution. The effluent standards refer to his analytical methods, which appear for reference only in Annex I.|
|3.1||This memorandum uses standard scientific terms. Where the Ordinance defines a term, that definition applies.|
|3.2||In this memorandum the following definitions also apply.|
"Effluent" (流出物) means any discharge or deposit subject to control under the Ordinance.
"Coastal waters" (海岸水域) means the waters of Hong Kong except inland waters and storm water drains.
"Inshore waters" (沿岸水域) means all coastal waters where the water depth is less than 6m at mean low tide, or that are within 200m of the mean low water mark, whichever position is further from the shore.
"Marine waters" (海洋水域) means all coastal waters except inshore waters.
"Flow rate" (流量率) means the measured volume per unit time of effluent from a premises, averaged over the period of operation in any day accepted by the Authority. Where the flow cannot by measured, it is determined by a method the Authority approves.
"Foul sewer" (髒水渠) means a sewer built for the carriage of foul or waste water or so designated by the Authority.
"Storm water drain" (雨水渠) means a man made conduit built for natural surface drainage or so designated by the Authority.
"Toxic metals" (有毒金屬) includes antimony, arsenic, beryllium, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, thallium, vanadium and any other metals that the Authority specifies.
|4.||Determining the acceptable characteristics of effluents|
|4.1||The Ordinance allows the Government to declare water control zones and to set water quality objectives. The objectives describe the water quality that will promote the conservation and best use of the waters in the public interest.|
|4.2||In deciding whether to grant a licence for an effluent, the Authority's purpose is to meet the relevant objectives. The same purpose governs the conditions that the Authority attaches to the licence. He also must consider the need to protect the drainage or sewerage system, including disposal works, treatment processes, and the health and safety of workers in them.|
|4.3||Each control zone contains four systems into which wastes may be discharged. They are foul sewers, storm water drains, inland waters (which include water in the ground) and coastal waters.|
|4.4||The effluent standards take account of the beneficial uses of the different systems, but the systems and control zones fall into convenient groups. In general terms the standards for each group are as follows.|
Effluent standards for foul sewers leading to similar Government sewage treatment plants do not differ from zone to zone. Effluents into foul sewers leading to a treatment plant with microbial processes must meet more stringent standards for some toxic metals. This is to protect the processes and ensure that they can continue to treat domestic sewage effectively.
|4.4.2||Storm water drains|
Most storm water drains discharge directly into inland or coastal waters. The Authority will not normally allow effluents to them. If, exceptionally, he does so, effluents to them must meet the standards for the next receiving waters downstream.
The beneficial use of inland waters is the only factor governing the effluent quality and quantity that the Authority will license. There is no distinction between zones. There are four groups of inland waters.
|Inland water grouping Beneficial use|
Group A abstraction for potable water supply
Group B irrigation
Group C pond fish culture
Group D general amenity and secondary
|There are four sets of effluent standards corresponding to these groups. Streams which enter the sea at gazetted beaches need special attention; they belong to Group D.|
|220.127.116.11||The water quality and beneficial uses of coastal waters vary in different water control zones. They need separate effluent standards. In practice this memorandum groups together zones with similar objectives.|
|18.104.22.168||The memorandum makes a distinction between inshore and marine waters, except in Tolo Harbour, Port Shelter and Deep Bay where tidal flow is restricted. This results in six sets of standards.|
|Coastal water group Control Zones|
Group I Tolo Harbour, Port Shelter
Group II Deep Bay
Group IIIa Victoria Harbour inshore
Group IIIb Victoria Harbour marine
Group IVa Southern, Mirs Bay, Western Buffer,
Eastern Buffer, Junk Bay, North Western inshore
Group IVb Southern, Mirs Bay, Western Buffer,
Eastern Buffer, Junk Bay, North Western marine
|22.214.171.124||Within the coastal waters are special areas that need specific restrictions. These areas include bathing beaches, sites of special scientific interest, marinas and mariculture sites. Paragraph 9.1 lists the restrictions.|
|5.||Charges for effluent disposal|
|5.1||Some effluent components can be treated much more efficiently in big communal treatment plants than in individual premises. In some cases, factories do not have the space to treat their own effluents properly.|
|5.2||The components that can be treated in this way are measured as biochemical oxygen demand, chemical oxygen demand, and suspended solids. The allowable levels of these determinands in effluents to foul sewers are high; this reflects their treatability in the public sewage disposal system.|
|5.3||All other effluent components have stricter standards. Those who produce effluents must control these other components in their own premises.|
|5.4||A charge will be levied to pay for the safe disposal of the treatable effluent components. It will be the actual extra cost of treating strong industrial and commercial effluents to the same level as domestic sewage. This charge will be independent of any other fees and charges that may be introduced under the Ordinance.|