Two Birds with One Stone: Addressing Off-Season Woes and Producing a Class A Product at SHVUA

Located about 20-min south of Detroit, the South Huron Valley Utility Authority (SHVUA) operates a 24 mgd Wastewater Treatment Plant (WWTP) that treats an average of 10 mgd. The SHVUA WWTP treats wastewater from 7 communities: Brownstown Township, Woodhaven, Gibraltar, Van Buren Township, Huron Township, and South Rockwood which is comprised of approximately 90,000 residents. Due to the rural nature around Michigan, many facilities land apply biosolids. Prior to 2020, SHUVA would combine gravity thickened primary sludge and WAS and then lime stabilize to create a liquid-lime product which would be Class B land applied during the summer and stored during the winter. Since 2014, the facility struggled to store all the material over the winter, especially if the fall or spring was particularly wet thereby limiting the ability to liquid land apply. Historically, the facility would have to 'store' solids in the primary clarifiers and bioreactors which put the facility at risk of permit compliance. In fall 2018, Jacobs was selected to contract operate the SHVUA WWTP. Part of the first step of taking over was to 'un-constipate' the plant using mobile dewatering which cost nearly half a million dollars to dispose at the landfill. At WEFTEC 2018, knowing that biosolids hauling was a systemic issue during the winter, Jacobs conducted an informal technology review. Among those technologies reviewed, Lystek appeared to be viable option by being capable of increasing the available detention time from 180 days at 6-7% total solids (%TS) to approximately 326 days of storage due to a higher concentration (14-16%TS). In addition, the process also created a Class A product, although this was not a major driver given that there was generally sufficient land available for Class B land application. In spring 2019, Hubble, Roth & Clark (HRC), SHUVA's resident engineer, evaluated multiple biosolids technologies to address the off-season woes as part of a 20-yr capital improvement plan. The evaluated alternatives included: -Installing additional winter storage -Ship excess biosolids to a regional facility for process -Install a new sludge stabilization system consisting of Thermal hydrolysis and anaerobic digestion and a combined heat and power system. -Installing a permanent dewatering facility to dewater excess solids and dispose to the landfill -Continue emergency mobile dewatering and landfill disposal The results of the HRC evaluation proposed installing a permanent dewatering facility. However, in Fall 2019, Jacobs augmented that evaluation by including the Lystek process alongside the prior evaluated alternatives. The Lystek process was found to be the most cost effective on a unit cost per dry ton basis and could utilize an existing building (see Table 1). In addition, it would maximize the beneficial reuse of biosolids. The new Lystek facility, Michigan's first, was constructed using a design-build contract and is operational today, producing a Class A product. This presentation will provide the background how SHVUA, Jacobs, and HRC worked together to address the on-going plant issues and develop a cost effective, environmentally friendly solution that was constructed and operates successfully today.