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We tested at full-scale the innovative Focused Pulsed (FP) technology for pre-treating waste sludge in order to improve methane gas production and biosolids reduction in sludge digestion, but without incurring problems of odors, toxicity, and high costs for chemical or energy consumption. FP pre-treatment of a mixture of primary and secondary sludge increased the soluble COD by 160% and DOC 120% over the control. FP pre-treatment of 63% of the input waste sludge increased biogas production by over 40% and reduced biosolids requiring disposal by 30% when compared to the plant baseline. FP pre-treatment also correlated with a shift of the bacterial and archaeal communities. The most significant change was that the acetate-cleaving Methanosaeta became the dominant methanogen. Full FP pre-treatment should increase biogas production and biosolids removal by 60% and 40%, respectively. Full FP pre-treatment should generate energy benefits of at least 2.7 times and as high as 18 times the FP energy input, depending on heat recovery from FP treatment. For a plant treating 76,000 m3/d of wastewater (380 m3-sludge/d), FP treatment should generate an annual economic benefit of approximately $540,000 net of electricity and other operating and maintenance costs. This represents a payback period of three years or less.

We evaluated the feasibility of using waste activated sludge (WAS) from a wastewater treatment plant as an internal electron donor to fuel denitrification, by increasing its bioavailability with Focused-Pulsed (FP) technology. The focused-pulsed treatment of WAS (producing FP-WAS) increased the semi-soluble chemical oxygen demand (SSCOD) by 26 times compared with the control WAS. The maximum denitrification rate of FP-WAS (0.25 g nitrate-nitrogen [NO 3 2 -N]/g volatile suspended solids [VSS]?d) was greater than for untreated WAS (0.05 g NO 3 2 -N/g VSS?d) and methanol (0.15 NO 3 2 -N/g VSS?d).Centrifuging out the larger suspended solids created FP-centrate, which had a rate (0.14 g NO 3 2 -N/g VSS?d) comparable with that of methanol. Thus, FP treatment of WAS created SSCOD, which was an internal electron donor that was able to drive denitrification at a rate similar to or greater than methanol. One trade-off of using FP-WAS for denitrification is an increase in total Kjeldahl nitrogen (TKN) loading. While FP-WAS achieved the lowest total nitrogen and NO 3 2 -N concentrations in the batch denitrification test, its final ammonia-nitrogen (NH 3 -N) concentration was the highest, as a result of the release of organic nitrogen from the FPtreated biomass; FP-centrate had less release of total soluble nitrogen. While the return of total nitrogen (TN) is small compared with the SSCOD, the effects of the added nitrogen loading need to be considered. Water Environ. Res., 82, 2316Res., 82, (2010.

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