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Nutrient and Solids Separation of Digested Dairy Manure with Bench-Scale Polymer Treatment

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Applied Engineering in Agriculture. 28(5): 665-673. (doi: 10.13031/2013.42430) @2012
Authors:   J. F. Katers, A. M. Pelegrin
Keywords:   Anaerobic digestion, Dairy manure, Solid-liquid separation, Nutrient removal, Polymer

Dairy farms with anaerobic digesters can improve manure management if solids and nutrients are more effectively separated from liquid digestate. The addition of polymers can enhance mechanical separation. In this study, 14 polymers were evaluated to maximize nutrient capture. Cationic polyacrylamide (PAM) with low/medium charge density and low molecular weight achieved the best flocculation. For low total solids (TS) manure, bedding fibers added after PAM treatment greatly enhanced flocculate size to enable effective screening. Capture efficiencies for TS, total phosphorus (P), dissolved P, total Kjeldahl nitrogen, ammonia nitrogen, and total potassium were approximately 86%, 95%, 92%, 50%, 45%, and 41%, respectively. The optimum solids level to the separator was 4.6% TS, with PAM S1100AL applied at 325 mg/L. With chemical costs ranging from $0.134 to $0.168 per cow per day, this technology could provide an economical option for farm nutrient management.

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