[Effect of substrate concentration on pathogen indicators inactivation during thermophilic anaerobic digestion].

Because excess sludge contains high density of pathogens, it has to be treated to reduce pathogens before being disposed for land application. In this study, the effect of substrate concentration on pathogen inactivation during thermophilic anaerobic digestion was investigated. The results show that, with the increase of substrate concentration, VFAs and cumulative methane production increased. The density of total coliforms in the suspension liquid has a 2.0-3.0 orders of magnitude decline and fecal coliforms has 1.8-3.3 orders of magnitude decline after 28 days thermophilic anaerobic digestion at substrate concentration of 28-84 g x L(-1) and temperature of 55 degrees C. More than 99% of total coliforms and fecal coliforms have been killed after 28 days digestion. Salmonella spp. was not detected in the suspension and solid after anaerobic digestion. When substrate concentration was higher than 45 g x L(-1), the inactivation of total coliforms and fecal coliforms declined.

[Anaerobic digestion of animal manure contaminated by tetracyclines].

Anaerobic digestion of pig manure spiked with tetracycline (TC) and chlortetracycline (CTC) and the degradation of the two antibiotics during the anaerobic digestion at 35 degrees C were investigated. The results indicate that propionate was the main volatile fatty acid produced during the anaerobic digestion followed by acetate. Compared with the CTC addition, TC + CTC addition showed obvious inhibitory effect on the hydrolysis and acidification of easily digestible organic components of pig manure. The cumulative methane production of TC, CTC, TC + CTC and CK2 during anaerobic digestion was 386.4 mL, 406.0 mL, 412.1 mL and 464.6 mL, respectively. Degradation of TC and CTC followed the first-order kinetic equation. The half-life of TC and CTC was 14-18 days and 10 days, respectively. After the treatment of 45-day anaerobic digestion, the degradation efficiency of TC was 88.6%-91.6% with 97.7%-98.2% of CTC. Therefore, anaerobic digestion shows the benefit on the management of animal manures contaminated by tetracyclines.