Greenhouse Gas Emission Reductions from Improved Anaerobic Digestion and Methanol Replacement Via Focused Pulsed Treatment of Wastewater Sludge

We used Focused Pulsed (FP) technology to enhance solubilization of organic material in primary and waste activated sludge (WAS), with the goal of making it more bioavailable for methane production during subsequent anaerobic digestion and for use as a replacement for external carbon sources used to drive denitrification. After a more than a year of steady-state operation at the Mesa, AZ Northwest Water Reclamation Plant (NWWRP), digester performance improved considerably: In 2008, 17% less biosolids were trucked from the plant, biogas production increased by 32%, natural gas consumption decreased by 58%, and the use of an external carbon source was discontinued. During this period, 53% of the sludge feed to the digesters was treated by FP. The performance improvements expected with treatment of the full sludge volume, coupled with beneficial use of the biogas produced from anaerobic digestion, will drive a significant decrease in the calculated GHG emissions from the Mesa NWWRP. With full FP treatment, the overall non-biogenic GHG emissions from the NWWRP are estimated to decrease by 13%.