Water Science & Technology—WST Vol 58 No 10 pp 1895–1901 © IWA Publishing 2008 doi:10.2166/wst.2008.547

Full-scale application of focused-pulsed pre-treatment for improving biosolids digestion and conversion to methane

Bruce E. Rittmann, Hyung-sool Lee, Husen Zhang, Jared Alder, James E. Banaszak and Ronald Lopez

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.

Keywords: anaerobic digestion; energy recovery; focused pulse; methane; pulsed electric fields; sludge pre-treatment

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