Effect of antibiotics on psychrophilic anaerobic digestion of swine manureslurry in sequencing batch reactors

The effect of antibiotics on the psychrophilic anaerobic digestion (PAD) of swine manure slurry in sequencing batch reactors (SBRs) was investigated. Six antibiotics, tylosin, lyncomycin, tetracycline, sulphamethazine, penici llin and carbadox, were individually added to the pig diet at their maximum prescribed level. Manure slurries collected from pigs receiving control an d medicated diets were individually fed to pairs of SBRs at organic loading rates (OLRs) ranging from 2.2 to 3.5 g total chemical oxygen demand (TCOD) per litre of bioreactor initial sludge volume per day. Three mixtures of s lurries from pigs fed on individual, antibiotics were also tested at OLRs v arying between 2.5 and 3.2 g TCOD/l/d. The presence of penicillin and tetra cycline in manure slurries reduced methane production by 35% and 25%, respe ctively. However, the slurries from pigs receiving the other antibiotics an d the slurry mixtures did not significantly affect (P > 0.05) methane produ ction. In addition, the presence of individual and combined antibiotics did not have noticeable adverse effects on process stability and treatment eff iciency. Total and soluble COD (TCOD and SCOD) reduction, total and volatil e solids (TS and VS) removal, pH and volatile fatty acid (VFA) concentratio ns in experimental units were not statistically different (P > 0.05) than i n the controls. In all bioreactors, the TCOD, SCOD, TS and VS removal excee ded 62%, 76%, 65% and 75%, respectively. Crown Copyright (C) 2000 Published by Elsevier Science Ltd. All rights reserved.