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Performance and Stability of Two‐Stage Anaerobic Digestion
Author(s) -
Zahller J. D.,
Bucher R. H.,
Ferguson J. F.,
Stensel H. D.
Publication year - 2007
Publication title -
water environment research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.356
H-Index - 73
eISSN - 1554-7531
pISSN - 1061-4303
DOI - 10.2175/106143006x123157
Subject(s) - mesophile , anaerobic digestion , volatile suspended solids , activated sludge , anaerobic exercise , chemistry , pulp and paper industry , waste management , total dissolved solids , single stage , environmental science , environmental engineering , sewage treatment , methane , biology , engineering , organic chemistry , physiology , genetics , bacteria , aerospace engineering
The stability, capacity, and solids destruction efficiency of single versus two‐stage anaerobic digestion was studied in bench‐scale reactors using combined waste activated and primary sludge. Laboratory staged mesophilic digesters showed an improved volatile solids and volatile suspended solids destruction efficiency over a single‐stage system (at the same total solids retention time [SRT]) of approximately 3.2 and 5.8 percentage points, respectively. To quantify stability and capacity, a new digester monitoring method was introduced that measured the digester maximum acetate utilization capacity, V max, ac , and was used to investigate the potential for digester instability at different transient loadings. The ratio of the V max, ac value to the estimated acetate production rate for a given digester loading was termed the acetate capacity numbe r (ACN). Values greater than 1.0 indicate excess acetate utilization capacity. The first stage of the laboratory two‐stage mesophilic system (10‐day SRT for each stage) had an ACN number of 1.3 compared with a value of 1.8 for the single‐stage 20‐day SRT digester. Thus, while a staged mesophilic system can improve solids destruction efficiency, it demonstrates a lower capacity for metabolizing highly variable loads.