The Wastewater to Renewable Natural Gas projects are commonly situated alongside municipal wastewater treatment plants. These initiatives make use of primary sludge and waste activated sludge (WAS) as feedstock, sourced from various points such as the primary clarifier, secondary clarifiers, or Dissolved Air Flotation (DAF) system.
The Anaerobic Digester technology for these applications are in a continuous 2-Phase/2-Stage Process, incorporating Gravity Belt and Rotary Drum Thickeners for WAS thickening, alongside 2-Stage Anaerobic Digester Tanks with Recirculation Pumps and Heat Exchangers to ensure the production of high-quality biogas. Given the diverse sludge handling methods and process designs at municipal wastewater treatment plants, we customize technology deployment to suit the unique characteristics of incoming sludge materials on a case-by-case basis.
Retention times for these projects typically align with the standard anaerobic digester projects, resulting in biogas compositions with approximately 65% to 70% Methane (CH4) and 30% to 35% Carbon Dioxide (CO2). The biogas yields from these anaerobic digesters utilizing primary sludge and WAS typically average around 5 cubic feet of biogas per pound of sludge.
The technologies deployed for these projects are akin to biogas processing and conditioning technologies used for other organic feedstocks, albeit with some degree of variability in biogas quality. The spent digestate from these projects exhibits a high degree of sludge stabilization, with smaller amounts of lighter scum solids and supernatant liquids.
