ABSTRACT
58Digestion and co-digestion of faecal matter collected from Urine Diverting Dehydrating Toilet Faeces (UDDT-FS) and mixed Organic Market Waste (OMW) was studied in single stage pilot scale mesophilic plug-flow anaerobic reactors at UDDT-FS:OMW ratios 4:1 and 1:0. Escherichia coli (E. coli) inactivation and Volatile Fatty Acids (VFA) build-up was monitored at sampling points located along the reactor profile. E . coli inactivation achieved in digestion of UDDT-FS: OMW ratio of 4:1, 12% TS was 2.3 log times higher than that achieved in UDDT-FS: OMW ratio of 1:0.
In subsequent trials, a two-stage reactor was studied, applying a UDDT-FS:OMW ratio of 4:1 and 10% or 12% TS slurry concentrations. Highest VFA concentrations of 16.3±1.3 g/l were obtained at a pH of 4.9 in the hydrolysis/acidogenesis reactor, applying a UDDTFS:OMW ratio of 4:1 and 12% TS, corresponding to a non-dissociated (ND)-VFA concentration of 6.9±2.0 g/l. The corresponding decay rate reached a value of 1.6 /d. In the subsequent methanogenic plug-flow reactor, a decay rate of 1.1/d was attained within the first third part of the reactor length, which declined to 0.6/d within the last third part of the reactor length. Results show that a two-stage system is an efficient way to enhance pathogen inactivation during anaerobic digestion.
