Shiyu Fu

Enhancing biodegradation of wastewater by microbial consortia with fractional factorial design

Batch experiments were conducted on the degradation of synthetic and municipal wastewater by six different strains, i.e., Agrobacterium sp., Bacillus sp., Enterobacter cloacae, Gordonia, Pseudomonas stutzeri, Pseudomonas putida. By applying a fractional factorial design (FFD) of experiments, the influence of each strain and their interactions were quantified. An empirical model predicting the treatment efficiency was built based on the results of the FFD experiments with an R(2) value of 99.39%. For single strain, Enterobacter cloacae, Gordonia and P. putida (p=0.008, 0.009 and 0.023, respectively) showed significant enhancement on organic removal in the synthetic wastewater. Positive interaction from Enterobacter cloacae, Gordonia (p=0.046) was found, indicating that syntrophic interaction existed, and their coexistence can improve total organic carbon (TOC) degradation. Verification experiments were performed to evaluate the effect of bioaugmentation by introducing three selected strains into an activated sludge reactor for treating municipal wastewater. The removal efficiency of TOC with the bioaugmentation was increased from 67-72% to 80-84% at an influent TOC concentration of 200mg/L. The results derived from this study indicate that the FFD is a useful screening tool for optimizing the microbial community to enhance treatment efficiency.

Study on the treatment of the sulfite pulp CEH bleaching effluents with the coagulation–anaerobic acidification–aeration package reactor

The coagulation-anaerobic acidification-aeration package reactor was designed for the treatment of pulp CEH bleaching effluents, the efficiencies in CODcr, BOD(5), AOX and toxicity removal achieved were 88.1%, 81.0%, 98.4% and 92.0%, respectively, with 15 h HRT. The toxicity and AOX were removed mainly through coagulation and anaerobic process, while the COD and BOD(5) were removed mainly through coagulation and aerobic process. The pretreatment of coagulation precipitation decreased the following organic load, which decreased the following treatment retention time and increased the stability of the system. The results of GC-MS showed: pollutants of wastewater were mainly chlorinated organics, most of AOX and the toxicity were removed by reductive dechlorination and acidified hydrolysis in anaerobic unit, the high COD removal in aerobic unit showed further degradation of pollutants. Chlorine atoms in the ortho position were preferentially dechlorination, that in para position were difficult to remove from chlorinated phenols during biological treatment.

Effect of oxygen availability on the removal efficiency and sludge characteristics during pentachlorophenol (PCP) biodegradation in a coupled granular sludge system.

This study systematically investigated the metabolism of pentachlorophenol (PCP) in batch experiments using coupled sludge granules under various dissolved oxygen concentrations. Results indicated that the oxygen condition in serum bottles has a significant effect on the microorganism metabolism. A greater degree of mineralization of PCP was achieved under oxygen-limited conditions (e.g., 40 and 60 initial headspace oxygen percentage (IHOP)), producing trichlorophenol (TCP), dichlorophenol (DCP) and monochlorophenol (MCP) as intermediates and chloride as one of the final products. Reductive dechlorination was identified as the primary pathway for the PCP degradation. Under strictly anaerobic or slightly oxidative conditions (0 and 20 IHOP), the reductive dechlorination of PCP led to an accumulation of TCP. Under aerobic conditions (80 and 100 IHOP), PCP degradation was less significant due to the hindered reductive chlorination in the presence of oxygen. It is also observed that cell hydrophobicity, protein (PN) concentration, settling velocity and specific gravity of the sludge granules decreased with IHOP from 0 to 60, and then increased with IHOP from 60 to 100. Specific methanogenic activity (SMA) and specific oxygen uptake rate (SOUR) confirmed that degradation of PCP was achieved by methanogenic and methanotrophic populations coexisting in a single granule. Because of a combination of reductive and oxidative degradation mechanisms, aerobic or facultative bacteria were found to oxidize the intermediates of PCP degradation products produced by methanogens and strict anaerobes during fermentation.

Optimized Biodegradation of Pulping Effluent by Microbial Combination with Statistical Experimental Design

Statistics based experimental designs were used to construct a mixed-culture community for maximal chemical oxygen demand (COD) degradation of pulping effluents. By applying a fractional factorial design (FFD) of experiments, the significant effect of each strain on COD degradation was first quantified. Then steepest ascent method was employed to approach the experimental design space, followed by an application of response surface methodology (RSM) for further optimization. A quadratic model was found to be fit COD removal efficiency. Response surface analysis revealed that the optimum levels of the tested variables for the degradation of COD. A COD removal efficiency of (65.3 ±± 0.5) % was observed in verification experiment, which was close to the predicted value.