2. Interpretation
For the purposes of these Regulations—
“activated sludge” means flocculent sludge produced by the growth of bacteria and other organisms in raw or settled sewage when it is continuously aerated;
“activated sludge process” means a biological sewage treatment: process in which a mixture of sewage and activated sludge is agitated and aerated. The activated sludge is subsequently separated from the treated sewage by sedimentation and may be re-used;
“absorption” means the adherence of dissolved, colloidal or finely divided solids on the surface of solid bodies with which they are brought into contact;
“aeration” the bringing about of intimate contact between air and liquid by one of several methods, i.e. spraying the liquid in the air, forcing air through the liquid, agitating the liquid to promote surface absorption of air;
“biochemical oxygen demand (BOD)” means the amount of dissolved oxygen consumed by chemical and micro-biological action when a sample is incubated at 20°C for a period of 5 days;
“biological filter” means an artificial bed or inert material over which sewage is distributed and through which it penetrates to under drains, thus giving an opportunity for the formation of biological slimes which bring about oxidation and clarification of the sewage;
“chemical oxygen demand” (COD) means the amount of oxygen used in the chemical oxidation of the matter present in a sample by a specified oxidising agent under standard conditions;
“collodial material” means finely divided solids which will not settle but which may be removed by coagulation;
“combined sewer” means a sewer designed to carry both sewage and surface water;
“crude sewage” means sewage which has received no treatment;
“datum” means a place of reference for a system of levels;
“detritus tank” means a tank in which sand, grit and other heavy inorganic materials are removed by sedimentation from sewage;
“digestion” means the biochemical decomposition of organic matter using anaerobic bacteria, which results in the formation of simpler and less offensive compounds;
“dilution” means the ration of the volume of a stream to the volume of sewage effluent discharging to it;
“dry weather flow” (d.w.f.) means the daily rate of flow of sewage, together with infiltration if any, in a sewer in dry weather – measured after a period of 7 consecutive days of dry weather during which the rainfall has not exceeded 0.25 mm;
“effluent” means any liquid which flows out of a containing space, but more particularly the sewage or trade waste, partially or completely treated, which flows out of a treatment plant;
“final settlement tank” means a tank through which the effluent from a biological filter, or aeration tank, flows for the purpose of separating settleable solids. When used with a biological filter it is often called a humus tank;
“industrial effluent” means the fluid discharge, with or without matters in suspension, resulting wholly or in part from any manufacturing process, and including farm and research institution effluents;
“outfall sewer” means the final sewer of a system which carries the sewage to a treatment works or to a point of discharge;
“oxidation” means the chemical change which a substance undergoes when it takes up oxygen;
“pumping station” means an installation of pumps to lift sewage from a low level to a higher level;
“Royal Commission Standard” means a suspended solids content of not more than 30 mg/1 and a BOD of not more than 20 mg/1;
“sedimentation tank” means a tank in which water or sewage containing sediment is retained for a sufficient time at a sufficiently low velocity to remove part of the sediment by gravity;
“sewage” means any water contaminated by domestic waste or trade effluents, water-borne human, domestic and farm waste. It may include effluent, subsoil or surface water;
“sewage treatment” means an artificial process to which sewage is subjected to remove or alter its constituents to render it less offensive or dangerous;
“sewer” means a pipeline to carry sewage or other wastes, and not normally flowing full;
“sewerage” means a system of sewers and ancillary works to convey sewage from its point or origin to a treatment works or other place of disposal;
“sludge” means accumulated suspended solids from sewage deposited in pipes or tanks, mixed with water to form a semi-liquid substance;
“surface water” means natural water from the ground surface, paved areas and roofs;
“suspended solids” mean the solids which are suspended in a sewage or effluent.