Advanced Anaerobic Digestion and Biosolids Management Planning

We have performed this work at their 80 MGD Delaware No. 1 Water Pollution Control Facility. A major CCMUA biosolids upgrade completed was an anaerobic sludge digestion and CHP facility to reduce volatile solids and produce electrical and heat energy for use within the plant. Professional services provided by Greeley and Hansen included: feasibility investigation for anaerobic digestion and CHP facility implementation; evaluation of biosolids processes and technologies; evaluation of biogas beneficial use options including power generation, sludge drying and boiler plant utilization; pilot testing of biosolids technologies; evaluation of CHP heat utilization for space heating, digester heating for sludge drying; assistance in developing a public participation program; a biosolids beneficial reuse market study; planning, design, and construction services for CCMUA’s 50 dry ton/day sludge thickening and dewatering facility; evaluation of various procurement strategies for proposed biosolids facility improvements; and value engineering of various biosolids projects. Feasibility Evaluation, Proposal Review, Procurement System Evaluation and Value Engineering for CCMUA’s Anaerobic Digestion/CHP Facility CCMUA’s sludge digestion and CHP project is an integral part of attaining their sustainability and net-zero energy goals.  

Evaluation of process units and pilot studies were planned for and completed to identify appropriate options to move forward with for the County. The unit processes evaluated and investigated included thickening, stabilization, dewatering, conversion and ultimate disposal. Pilot plant tests of vacuum filters, centrifuges, belt filters and plate and frame filter presses were performed on a mixture of primary biosolids and secondary biosolids. The secondary biosolids were generated by an oxygen activated biosolids pilot plant, which was tested on effluent from the Delaware No. 1 Wastewater Treatment Facility. Conversion processes evaluated were thermal reduction by incineration or pyrolysis, co-disposal with solid wastes, co-burning of fossil-fueled power plants, and composting. Landfilling, public distribution, exportation and land spreading were considered for ultimate disposal. 

Alternative sites for biosolids processing and disposal of biosolids residues were evaluated. Detailed cost estimates and environmental impacts were developed for each alternative studied. Based on the results of the cost effectiveness analysis, environmental assessment, and investigations of institutional constraints affecting implementation, a two-staged plan was developed. During the first stage of the plan, biosolids would be dewatered by filter presses and composted at the Delaware No. 1 Facility. The second stage of the plan called for co-incineration with solid waste of the biosolids generated at the treatment facility. Energy would be recovered from the co-incineration facility and used to provide steam and electricity for the plant or for sale to the Utility. 

Greeley and Hansen also performed a biosolids marketing study to investigate markets for the composted biosolids product including markets for end-use as fertilizer, a soil amendment agent, or an energy source. A test marketing program was developed utilizing a pilot plant that will generate samples of the actual product. The pilot plant also permits determined the effect of process and amendment changes on product marketability. The study included identification of potential competing producers and like products and identification and surveys of potential user groups for the produced composted biosolids product. Seasonal variation of usage rates by different categories of users was assessed, as well as optimal distribution and packaging strategies for these identified markets. 

This partnership has led to an ongoing series of successful efforts related to biosolids management that has CCMUA well on its way to achieving its goal of becoming a net-zero energy facility and a national leader in biosolids management. 

Project Highlights: 

• Performed feasibility evaluation for implementation of advanced anaerobic digestion with CHP at CCMUA’s Delaware No. 1 WPCF. 

• Developed strategies for digester gas utilization by the CHP facility, for digester heating, and for use by boiler plants. 

• Created strategies to efficiently utilize heat energy for digester heating, space heating, and sludge drying.