Preparation of NSC Project Repor ts
Integration of chemical and biological processes for recalcitrant or inhibitory contaminant treatment is an advantageous concept. The aim of chemical oxidation is to partially oxidize the recalcitrant contaminants to more easily biodegradable intermediates since a total mineralization may be not cost effective. However, preoxidation of wastewaters may show some adverse effect on biological processes because some byproducts formed during oxidation appear to be more toxic than the original compound. Therefore, chemical oxidation products play a key role in the total process. In our study, ozonation and a single compound p-nitrophenol were chosen as the model chemical pretreatment and the target compound. First, this study was undertaken to examine the reaction between ozone and p-nitrophenol. The purpose of this part is to develop an understanding of the ozonation process for nitrophenolic compounds. Besides, this research also focuses on the biological process. Sequencing Batch Reactors (SBRs) were chosen to be the subsequent biological system. Different from any previous researches concerning combined processes, a detailed community-level characterization ofmicrobial biomass from SBRs, was carried out using BIOLOG redox-based carbon source utilization assay. Ozonation of p-nitrophenol followed by lab-scale SBRs, rather than biodegradability tests, was conducted in the research. By observing the degradation of intermediates, the elimination of DOC, color and toxicity, and the variation of microbial ecologies, several conclusions can be drawn as followed: Under an ozonation period less than 150 min, ozonation of p-nitrophenol generates nonbiodegradable compounds, and this will bring about some adverse effects to the biological system, such as an increase of the effluent DOC and color, and an less healthy and diverse microbial community. However, under an ozonation period longer than 150 min (>25% TOC reduction), these adverse effects will be eliminated. Therefore, the extent of ozonation plays a key role in the total process, and an improper ozonation time should be prevented.
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