Effect of low levels of oxytetracycline on anaerobic digestion of cattle manure.

Cattle manure is rich in organic matter and nutrients, but it may also contain harmful substances such as residual antibiotics and other toxic compounds. Oxytetracycline (OTC) is a widely used veterinary antibiotic and its presence in manure can affect the subsequent anaerobic digestion process. This study evaluated the effect of OTC concentrations viz. 0.12, 0.3, 0.6, 1.2, 3, 6 and 12 mg L on batch mesophilic anaerobic digestion of cattle manure. The results showed that cumulative biogas yield decreased by 25, 29 and 55% at 3, 6 and 12 mg OTC L in contrast to control. Volatile solids removal was 39% for control which reduced to 13% in 12 mg L OTC spiked reactor. Effect on stability parameters was significant at OTC concentrations from 1.2 to 12 mg L. Two different kinetic models were used for biogas data validation and the modified Gompertz model best fitted to the experimental data.