A systematic analytical artifact that significantly influences anaerobic digestion efficiency measurement

Volatile solids reduction efficiency is widely used to assess the efficiency of anaerobic digestion of municipal wastewater sludge. When calculation methods that rely on the assumption that the nonvolatile or fixed solids are unaltered by anaerobic digestion have been used, it has been observed that higher volatile solids reduction efficiencies are typically obtained with primary sludge digestion than when waste biological sludges are digested. The research reported in this paper demonstrates that this difference in efficiency largely results from an artifact caused by the decomposition of ammonium bicarbonate during the total solids analysis.