| 摘要 |
The process comprises adding a coagulant to sewage, adjusting the pH to obtain optimum coagulation, adding a conditioning agent to the sewage, passing the sewage seriatim through beds each comprising a layer of coarse filter media and a layer of fine filter media (flow direction from coarse to fine in each case) and then passing the sewage through a bed of activated carbon. From 5 to 300 p.p.m. (preferably from 150 to 278 p.p.m.) of alum may be added as coagulant. Alternative coagulants are copper, ferric or ferrous sulphate or ferric chloride. The pH adjustment may be to between 4 and 6.5 (preferably between 4 and 5). The conditioning agent is preferably a polyacrylamide, e.g. one having carboxylic groups substituted for a few of the amide groups; alternatively it may be a polysaccharide, an acrylamide polymer hydrolyte, a seaweed derivative, guar gum or an ammonium lignosulphonate derived from wood. 0.5 to 24 p.p.m. of conditioning agent may be added, but preferably it is added in two portions (each preferably of 0.6 to 12 p.p.m.), one before passage through each of two filter beds.ALSO:The process comprises adding a coagulant to the sewage, adjusting the pH to obtain optimium coagulation, adding a conditioning agent to the sewage, passing the sewage seriatim through beds each comprising a layer of coarse filter media and a layer of fine filter media, the beds being arranged so that the flow in each is in the direction from coarse to fine, and then passing the sewage through a bed of activated carbon. The coagulant may be aluminium, copper, ferric or ferrous sulphate or ferric chloride. The conditioning agent is preferably a polyacrylamide, e.g., one having carboxylic groups substituted for a few of the amide groups; alternatively it may be a polysaccharide, an acrylamide polymer hydrolyte, a seaweed derivative, guar gum or an ammonium lignosulphonate derived from wood. Preferably the polyelectrolyte dosage is divided, a portion being added to the sewage just before entry into each bed. Preferably two beds are provided, each consisting of anthracite (coarse layer) and sand (fine layer). Preferably two beds of activated carbon are provided. |
