Utilizing Recovered Heat to Economically Produce Class A Biosolids

The Clark County Department of Public Works (County) in Vancouver, Washington, evaluated alternatives for supplementing or upgrading an existing Class B biosolids land application program at the Salmon Creek Treatment Plant (SCTP). In the course of planning improvements, other alternatives for biosolids processing including thermal drying were considered. Economics were unattractive due to the high cost of fuel for evaporating water. However, the County observed that the fluidized bed incinerator (FBI) at the nearby City of Vancouver (City) Westside Water Reclamation Facility had potential for heat recovery. The concept of using recovered heat was subsequently explored jointly with the City.The study concluded that goals for both agencies could be met by using an integrated approach. For the County, drying biosolids with recovered heat had the potential to produce a Class A product with annual costs competitive to the current Class B land application program. For the City, biosolids drying was more cost effective than electric power generation considering low power rates in the Pacific Northwest and potential tipping fee revenue from the County.