Performance Evaluation of Coke Wastewater Treated by Ozone
Date Issued
2006
Date
2006
Author(s)
Chen, Mei-Yin
DOI
zh-TW
Abstract
Abstract
The activated sludge process is the traditional method to treat coke oven wastewater which may have some drawback and inadequate. In order to treat the high pollution strength wastewater, the pre and post -treatment techniques were considered, of which ozonation was focused. According to the highly oxidative nature, ozone can oxidize pollutants without generating hazardous end products, and the surplus ozone gas can self-decompose quickly. Ozonation has been applied in water treatment for decades and the results are demonstrated successfully. Ozone applied in wastewater treatment has shown the feasibility and treatability in recent years. This merging technology may expend from treating textile wastewater to hard-to-degrade wastewater, i.e. coke oven wastewater.
The ozonation experiments are the main focus of this study, some controlling factors are discussed as well. The level of pH would affect the reaction modes of ozonation, direct or free radical reaction mechanism, the treated coke oven wastewater under various pH conditions entering into biological system would have impacts on the microbial system. Therefore, the characters of the ozonation substrate depletion, the relationship between microbial community structure and substrate depletion are investigated. This study also investigated the amount and timing of ozone dose applied into reaction system.
The ozonation experiments were conducted in a semi-batch bubble column reactor. The treated wastewater was discharged into biological system to investigate the biodegradation. The biodegradable index of pre-ozonation combined activated sludge process (O3/ASP) is based on BOD5/TOC, specific oxygen uptake rates, and specific substrate depletion. The index of post-ozonation combined biological activated carbon is based on bioassay, BOD5/TOC and substrate depletion. Meanwhile, by using the molecular biotechnology to explore the microbial community would benefit to understand the process of combination of ozonation and biological treatment.
On the early stage of pre-ozonation, experiments results reveal that the substrate reduction is the major effect factor to the biodegradation; at pH = 4, the combination of ozonations and biological treatment would enhance the biodegradation. An acclimated microbial community from post-ozonation wastewater (O3/ASP) increases degradation of PAH 、 benzaldehyde、aminosalicylate、poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and ammonia. Comparing the different pH operating condition of ozonation, under the conditions of ozonation combined with biological treatment and O3/ASP at pH = 4 could result in various microbial community. Thus, it could be concluded that the combination of pre-ozonation and biological treatments would increase the variety of microbial community.
Taking BOD5/TOC as a biodegradation index, it could be observed from the results that ozonation could enhance biodegradation, and pH=9 is the optimum conditions. In the Daphnia Acute toxicity test, the toxicity reduction was significant under neutral condition. Using microbial community structure to reveal the process of the combination of post-ozonation and biological treatments is still based on the bacteria groups, such as nitrified bacteria and denitrifying bacteria. Although, there is not significant result comes from the combination of post-ozonation and BAC, the rate of biodegradation still can be improved if the nitrifications and amount of bacteria which comes from the acclimated aromatic compound have been enhanced or added in this experiment.
Subjects
臭氧化
煉焦廢水
菌相
生物降解性
coke oven wastewater
ozone
biodegradation
PCR
microbial community
Type
thesis
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