PVA Degradation By A Combined Method Of Advanced Oxidation Pre-Treatment And Bio-Degradation

In recent years, polyvinyl alcohol (PVA) wastewater treatment has attracted extensive interests by domestic and abroad researchers. The current treatment methods of PVA-containing wastewater are classified into two categories, namely, physical-chemical methods and bio-degradation methods. A method called advanced oxidation processing excels with advantages such as short reaction time, easily controlling, non-selective to degrading organic materials, and thorough degradation level, as an internationally hot spot in wastewater treatment research. Whereas, the high cost of using this treatment method alone becomes obstacles to its application in bulk industrial wastewater treatment. To lower the cost while keeping high proficiency of degradation of PVA wastewater is the ultimate goal of many researchers. There are advantages of little operational cost and second-pulution for bio-degrading PVA. In practice, the development trend should be a combined method utilizing advanced oxidation as pretreatment preceding biological treatment on hard-to-degrade organic wastewater. Base on this guideline, the research works in this thesis were carried out. Three advanced oxidation processing ways, including Fenton method, ozone method, ozone plus ultra-violet light were adopted to pre-treat PVA wastewater, which is transformed into a better bio-degradable intermediate product. Comparing three ways metioned above, the processing parameters of UV/O3 pre-treatment were optimized to obtain a maximum degradation level. The separated dominant PVA degrading bacteria were applied to the intermediate products. Through the designed orthogonal experiments, the main factors effecting PVA degradation were found. That is initial pH value for the medium as 8, O3/UV pre-treatment time as 1 hour, cultivating temperature as 25°C, inorganic nitrogen source selected as NH4NO3. Under such conditions, an initial PVA concentration of 1.0% containing wastewater were processed and degraded. Its COD removal ratio could reach as high as 98.9%, qualified to be safely discharged. The variance analysis result was obtained. It illustrated that the importance sequence of various factors effecting degradation in this process was pH value > pre-treatment time > temperature > inorganic nitrogen source. Among the factors, the pH value and pre-treatment time played a significant role in processing.