Extending thermophilic anaerobic digestion for producing class a biosolids at the greater vancouver regional districts annacis island wastewater treatment plant

The Greater Vancouver Regional District (GVRD) is a major regional agency managing wastewater collection and treatment for Vancouver, Canada and surrounding municipalities. As part of their $ 600 million program to upgrade 2 major plants to secondary treatment, the GVRD was faced with the requirement to produce a treated biosolids meeting the equivalent of a U.S. EPA Class A product to assure success of their new biosolids beneficial use program. Various alternatives to achieve a Class A product were evaluated in detail. The GVRD selected a new and innovative process which they termed extended thermophilic anaerobic digestion. The characteristics of this process which help achieve required pathogen kills are the thermophilic operating temperatures and the series operation of reactors, cutting the bleed-through of pathogens observed in conventional complete mix systems. The new thermophilic digesters have been in operation since 1996 and the flow-through vessels required to complete “extended” operation will be complete in late 1998.