Advanced Water Management Centre

AWMC Seminar Program: Liguo Zhang

Increasing capacity of an anaerobic sludge digester through free nitrous acid pretreatment of waste activated sludge

Abstract: Free nitrous acid (FNA) pretreatment has been demonstrated to be effective in enhancing methane production from waste activated sludge (WAS) with biochemical methane production (BMP) tests, suggesting FNA-based pretreatment would enhance the destruction of volatile solids (VS) in an anaerobic sludge digester. However, previous studies usually adopt pH of 5.5 as pretreatment condition, anaerobic digestion (AD) process usually need long hydraulic retention time (HRT) to improve methane yield. Based on the lower pH (5.0) FNA pretreatment of feeding WAS, this study experimentally evaluates the possibility of shortening HRT to achieve the same level of VS destruction using continuously operated bench-scale anaerobic digesters. It was confirmed that the pretreatment with pH 5.0 did not affect the pH of the AD process. The results showed that FNA pretreatment enabled the gradual decreasing of HRT of AD from 15 d to 7.5 while still attaning a higher VS destruction level (39.0% ±1.1%) than that (30.0% ±0.7%) of the control reactor with HRT of 15 d. The average improvement of methane production by VS added was 35.7%, although a shock did shortly occur at the beginning of the pretreatment. The solids content of digested sludge in the experimental and control reactors were comparable during the long-term experiments (p>0.05). The results demonstrated the potential application of FNA pretreatment to upgrade AD digesters in WWTPs without significant capital cost.

Event Details
Date & Time: 
Friday, 01 September 2017
9am - 10am
Venue: AIBN Building 75, Level 1 Seminar Room

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