Liquid stream secondary process design at the Annacis Island wastewater treatment plant of the Greater Vancouver sewerage drainage district

The upgrading of the largest wastewater treatment plant in Greater Vancouver from primary to secondary treatment is described. The selection of the trickling filter/solids contact process and its design are explained, with details of the trickling filters, the solids contact tank and secondary clarifiers. The phasing of the project is outlined. Odour treatment by caustic scrubber and biofilter is discussed. Finally, influent pumping and improvements to primary treatment are briefly considered. The whole project cost 470 million Canadian dollars. An interim phase 1 process used the aerated solids contact tanks and secondary clarifiers to provide full activated sludge secondary treatment to a portion of the flow for 1 year prior to the commissioning of the filters in late 1998. The whole plant would be completed in the year 2000.