Annacis Island WWTP Codigestion Facility

Design and construction for major treatment plant

Annacis Island Wastewater Treatment Plant (AIWWTP) is the largest secondary treatment plant in British Columbia and serves about a million people.

This is a full scale pilot facility to allow Metro Vancouver to receive and test a variety of digestible organic wastes, monitor the feed rates and measure the effects of these feedstocks on the performance of the digesters.

Feed stocks include:

  • Fats, oil, greases (FOG) from West Cost Reduction (WCR)
  • Dissolved air flotation thickener (DAFT) float
  • Thickened primary sludge (TPS) from the other WWTPs of Metro Vancouver
  • Off-spec milk
  • Glycerol from biodiesel production and spent de-icing fluid

The facility is also capable of receiving and screening thickened sludge hauled from other wastewater treatment plants, providing relief to manage digester upsets at other sites.

We designed the codigestion facility to handle average delivery of five truckloads per day; unload truckloads of 5000 L each, with occasional 20,000 L TPS truckloads; and with pumping capacity of 3 L/s (260m3/d) to feed the digesters.

The key process elements and flow rates for the facility are:

  • One unloading pump station capable of unloading incoming trucks up to 10 L/s, including rock trap, screening and heat traced codigestion storage tank (35m3)
  • A system feed pump capacity of 3 L/s for pumping the ‘feedstock’ to the digesters, and a VFD on this pump to test various feed rates
  • Flushing systems utilizing hot water and hot digested sludge from digesters circulation line
  • System automation for tie-in to the corporation’s CDAC system