Evaluation of Long Term Biosolids Management Alternatives for the Detroit WWTP

The Detroit Wastewater Treatment Plant (WWTP) is one of the largest capacity WWTPs in the United States, with an average flow of about 650 mgd and peak wet weather flows up to 1,700 mgd. Average biosolids production is about 450 dry tons per day (dtpd) and peak production up to about 2,000 dtpd during wet weather treatment periods. Historically, the Detroit WWTP has utilized multiple hearth incineration for processing the majority of biosolids produced at the treatment plant and landfilling of peak solids quantities. There have been a number of issues that have recently caused the Detroit Water and Sewerage Department (DWSD) to re-evaluate the method of long-term biosolids disposal, including 1) Aging incinerator facilities (six of the incinerators were constructed in 1940 and eight were constructed in 1970); 2) Increasing energy costs; 3) DWSD's desire to optimize energy recovery and beneficial reuse of biosolids; 4)potentially more stringent future regulations for incineration and landfill disposal; and, 5) the termination of a private biosolids disposal contract.Because of these issues, DWSD recognized the need to update their long-term biosolids management plan for the Detroit WWTP. As such, DWSD requested Malcolm Pirnie, Inc. and Tucker, Young, Jackson and Tull to evaluate and recommend long-term disposal alternatives at the Detroit WWTP. This paper presents the methodology which was used to develop DWSD's recommended long term biosolids disposal plan and will discuss recent developments that have required modifications to the initial plan.