Evaluation of biodegradation of soluble and particulate matter produced during sewage sludge ozonation by a combination of chemical and microbial approaches

Abstract

In this study a batch aerobic reactor fed with the soluble and particulate matter produced during sludge ozonation (reactor 1) is proposed and its performance was evaluated in comparison to a reactor fed with municipal wastewater (reactor 2) to investigate the biodegradation properties of the ozone-treated sludge. During long-term operation of nearly 7 months, the efficiency of reactor 1 was preserved, although there was a 5% decrease in total COD elimination, compared with reactor 2. The released proteins and polysaccharides during sludge ozonation were effectively decomposed. The volatile suspended solid (VSS)/total suspended solid (TSS) ratio and the oxygen uptake rate in reactor 1 were lower than those in reactor 2 by 19% and 27%, respectively. However, the protease activity per gram of volatile suspended solids and the ammonium oxidation rate in reactor 1 were higher. The yields of sludge in reactor 1 fed with ozonated sludge were lower which implied that the cryptic growth using the organic autochthonous substrate might produce reduced biomass yields, which would decrease sludge production. The debris-like substances observed from scanning electron microscope (SEM) images and the functional groups associated with calcite were only found in reactor 1 by FT-IR analysis, which implies that some of the inert or inorganic substances from sludge ozonation were accumulated in the reactor.