2.5 Calculation
The VS reduction percentage was calculated based on the inlet and outlet VS concentration of the two-stage anaerobic digester based on the following equation
\(\text{Volatile\ solids\ }\left(\text{VS}\right)reduction\%=\frac{\text{VS}\text{inlet}-\text{VS}\text{outlet}}{\text{VS}\text{inlet}}\times 100\)equation (1)
The specific intracellular concentration of superoxide radicals is calculated based on the following equation.
\(Specific\ intracellular\ superoxide\ radical,\ s[O_{2}^{-}]\ (umoles/gTS)=\frac{\text{Superoxide}\ (umoles/l)}{\text{Total\ solids}\ (\frac{g}{l})}\)equation (2)
The process stability of anaerobic digestion was measured by FOS/TAC ratio, as per the following equation.
\(FOS/TAC=\frac{Volatile\ fatty\ acids\ (\frac{\text{mg}}{l})}{Alkalinity\ (\frac{\text{mg}}{l})}\)equation (3)