The Treatment Of Phenolic Wastewater Using High-efficiency Moving Bed Biofilm Reactor

Phenol, which is a kind of important industrial material, is common constituent in many industial wastewaters. As phenol is toxic to most of organisms, it may cause adverse effects on both human health and aquatic ecosystems. Therefore, phenolic wastewaters need to be well purified to eliminate the phenolic compounds before discharged into receiving water bodies. Moving bed biofilm reactor, short for MBBR, is a new concept in some degree, and is thought to occupy lots of advantages, such as easy operation and effective management. The objective of the present investigation was to determine the capacity of MBBR to eliminate high-strength phenol from artificial wastewater. Furthermore, a series of biochemical indicators were determined to deep understand the phenol biodegradation.(1) At the beginning of the start-up, the MBBR was inoculated with activated sludge (MLSS:3500mg/L) for24h, and then all the sludge was drained and replaced with synthetic wastewater containing glucose as the sole carbon source and additional nutrients to make biofilm grow fast. Until the COD and ammonia removal efficiency reached as high as90%and80%respectively and the biofilm was thick enough, biofilm colonization was thought to be finished. The analysis of fluorescence in situ hybridization (short for FISH) showed the rare existence of yeast and the majority of eubacteria in MBBR. Then, the reactor was fed with the wastewater containing glucose and phenol as the carbon source. After six days operation, phenol, concentration of400mg/L, was used as the sole carbon source, while HRT was12h. When phenol removal efficiency reached nearly100%, the biomass had been acclimated well enough.(2) In order to investigate the capacity of phenol biodegradation by MBBR, the phenol concentration in the influent was increased stepwise from200mg/L to1600mg/L at a fixed HRT of24h. When the inlet concentration ranged between200mg/L and1400mg/L, the reactor performed well with the phenol removal efficiency of nearly100%and COD removal efficiency of about98%. When the influent concentration reached as high as1600mg/L, the performance of reactor began to become worse. Nonetheless, as the phenol concentration decreased back to1000mg/L, the reactor quickly recovered to the previous level. Biochemical indicators at representative spots, such as, evolutions of extracellular polymeric substances, corresponding enzyme activities, quantities of biomass, et al, was checked and the results showed the profile of initial increase and latter decrease. HRT could also influence the performance of MBBR. In this study, different HRTs at the constant influent phenol concentration of1000mg/L were chosen to determine the effect. The result demonstrated that MBBR had the capacity of handling as high as1.5g/(L·d) phenol loading rate. It was necessary to study the ability of resistance to shock loading. The tests including concentration shock and hydraulic shock were conducted, and the evolutions of effluent phenol concentration show that the performance of reactor could recover back in two shock periods.(3) At the end of the experiment, FISH was applied to analyze the special microbial composition of suspended sludge and attached biofilm from the reactor. The relative abundance of bacteria (the ratio of bacteria to the entire microbe) referring to attached biofilm and suspended sludge was larger than that of yeast.