Huazhang Zhao

A novel UASB–MFC–BAF integrated system for high strength molasses wastewater treatment and bioelectricity generation

An up-flow anaerobic sludge blanket reactor-microbial fuel cell-biological aerated filter (UASB-MFC-BAF) system was developed for simultaneous bioelectricity generation and molasses wastewater treatment in this study. The maximum power density of 1410.2 mW/m(2) was obtained with a current density of 4947.9 mA/m(2) when the high strength molasses wastewater with chemical oxygen demand (COD) of 127,500 mg/l was employed as the influent. The total COD, sulfate and color removal efficiencies of the proposed system were achieved of 53.2%, 52.7% and 41.1%, respectively. Each unit of this system had respective function and performed well when integrated together. The UASB reactor unit was mainly responsible for COD removal and sulfate reduction, while the MFC unit was used for the oxidation of generated sulfide with electricity generation. The BAF unit dominated color removal and phenol derivatives degradation. This study is a beneficial attempt to combine MFC technology with conventional anaerobic-aerobic processes for actual wastewater treatment.

Study on treatment of coking wastewater by biofilm reactors combined with zero-valent iron process.

Experiments were conducted to investigate the behavior of the integrated system with biofilm reactors and zero-valent iron (ZVI) process for coking wastewater treatment. Particular attention was paid to the performance of the integrated system for removal of organic and inorganic nitrogen compounds. Maximal removal efficiencies of chemical oxygen demand (COD), ammonia nitrogen (NH(3)-N) and total inorganic nitrogen (TIN) were up to 96.1, 99.2 and 92.3%, respectively. Moreover, it was found that some phenolic compounds were effectively removed. The refractory organic compounds were primarily removed in ZVI process of the integrated system. These compounds, with molecular weights either ranged 10,000-30,000 Da or 0-2000 Da, were mainly the humic acid (HA) and hydrophilic (HyI) compounds. Oxidation-reduction and coagulation were the main removal mechanisms in ZVI process, which could enhance the biodegradability of the system effluent. Furthermore, the integrated system showed a rapid recovery performance against the sudden loading shock and remained high efficiencies for pollutants removal. Overall, the integrated system was proved feasible for coking wastewater treatment in practical applications.

Pilot treatment of wastewater from Dioscorea zingiberensis C.H. Wright production by anaerobic digestion combined with a biological aerated filter

An efficient combined system based on modified two-phase anaerobic digestion (MTPAD) combined with a biological aerated filter (BAF) is proposed to treat wastewater generated in the production of Dioscorea zingiberensis C.H. Wright (DZW). The pilot-scale experiments showed that both organics and sulfates at high concentrations could be removed satisfactorily due to the advantages of the MTPAD in eliminating the negative effects of sulfide inhibition to methanogens. Simultaneous nitrification and denitrification (SND) in the BAF resulted in efficient removal of COD and NH(4)(+)-N. UV-vis analysis showed that the organic compounds with aromatic structures were biodegraded effectively in the anaerobic process. GC-MS analysis revealed that furfural compounds in the influent were also biodegraded, leaving fewer compounds remaining in the final biological effluent. High efficiencies of COD removal (99.3%) and NH(4)(+)-N removal (93.7%) were achieved, and the quality of the final effluent met the National Discharge Standards of China for DZW wastewater.

The best utilization of D. zingiberensis C.H. Wright by an eco-friendly process.

An eco-friendly process for the best utilization of D. zingiberensis C.H. Wright tubers was developed. In the first stage, cellulose and ethanol were recovered by physical separation, multi-enzymes hydrolysis with yeast fermentation, and in the second stage diosgenin was separated using ethanol-modified supercritical carbon dioxide extraction. The new approach could not only recover 95% of diosgenin production, 95% of ethanol and 75% of cellulose, but also efficiently reduce 88% of COD in wastewater compared with the conventional method, which only extract diosgenin with discharging 80,000mg/l of COD into public sewers. The research indicates that the proposed system could be a clean and technological-efficient alternative to conventional processing of D. zingiberensis C.H. Wright tubers in industry.

Arsenite removal from aqueous solution by a microbial fuel cell–zerovalent iron hybrid process

Conventional zerovalent iron (ZVI) technology has low arsenic removal efficiency because of the slow ZVI corrosion rate. In this study, microbial fuel cell (MFC)-zerovalent iron (MFC-ZVI) hybrid process has been constructed and used to remove arsenite (As(III)) from aqueous solutions. Our results indicate that the ZVI corrosion directly utilizes the low-voltage electricity generated by MFC in the hybrid process and both the ZVI corrosion rate and arsenic removal efficiency are therefore substantially increased. The resultant water qualities are compliant with the recommended standards of EPA and WHO. Compared to the ZVI process alone, the H2O2 generation rate and output are dramatically improved in MFC-ZVI hybrid process. Strong oxidants derived from H2O2 can rapidly oxidize As(III) into arsenate (As(V)), which helps to improve the As(III) removal efficiency. The distribution analysis of As and Fe indicates that the As/Fe molar ratio of the flocs in solution is much higher in the MFC-ZVI hybrid process. This phenomenon results from the different arsenic species and hydrous ferric oxides species in these two processes. In addition, the electrosorption effect in the MFC-ZVI hybrid process also contributed to the arsenic removal by concentrating As(V) in the vicinity of the iron electrode.

Arsenate removal from simulated groundwater with a Donnan dialyzer

A simple point of use (POU) device based on the theory of Donnan dialysis was developed for the removal of arsenate (As(V)) in the present study. A commercial anion exchange membrane was used as a semipermeable barrier between the feed and stripping solution (As(V)-spiked groundwater and a 12gL(-1) table salt solution, respectively). The proposed POU device could be operated 26 times before replacing the stripping solution. In each batch, approximately 80% of the arsenate anions were transported across the membrane within 24h, and the arsenic concentration of the stripping solution was finally more than 180 times greater than that of the treated water. Cations were well preserved in treated water; however, a slight increase in the sodium ion concentration was observed due to electrolyte leakage. Alternatively, the chloride ion concentration significantly increased at the expense of a loss of sulfate and bicarbonate. The quality of treated water was in compliance with drinking water standards. Membrane fouling was investigated, and a reduction in the As(V) removal rates was not observed when the membrane was used repeatedly. Our results showed that the proposed Donnan dialysis POU device could effectively remove arsenic from drinking water in rural areas in a sustainable manner.

Denitrification of overlying water by microbial electrochemical snorkel

A novel microbial electrochemical snorkel (MES) bioreactor was constructed by inserting an iron rod into the sediment of a simulated natural water body for the first time. Its nitrate removal performance and mechanism were investigated. The DNA high-throughput sequencing analysis indicates that denitrifying bacteria were grown on the iron rod in the overlying solution. The XRD analysis on the oxides formed on the surface of the iron rod indicates that they are goethite and green rust. In the MES system, the green rust on the iron rod can concentrate nitrate and denitrifying bacteria, forming an anaerobic biocathode. The denitrifying bacteria can reduce the nitrate into nitrogen with the electrons moved from the sediment. The nitrate removal efficiency reached 98% in 16days. This novel MES system showed excellent in-situ nitrate removal performance by moving and concentrating the electrons in sediment and the nitrate in overlying solution in an anaerobic microenvironment.

Enhanced phosphorus flux from overlying water to sediment in a bioelectrochemical system.

This report proposed a novel technique for the regulation of phosphorus flux based on a bioelectrochemical system. In the simulated water system, a simple in situ sediment microbial fuel cell (SMFC) was constructed. SMFC voltage was increased with time until it was 0.23V. The redox potential of the sediment was increased from -220mV to -178mV during the process. Phosphorus concentration in the water system was decreased from 0.1mg/L to 0.01mg/L, compared with 0.09mg/L in the control. The installation of a SMFC produced an external current and internal circuit, which promoted the transfer of phosphate in overlying water to the sediment, enhanced the microbial oxidation of Fe(2+), and increased the formation of stable phosphorus in sediment. In conclusion, phosphorus flux from the overlying water to sediment was enhanced by SMFC, which has the potential to be used for eutrophication control of water bodies.

Water quality assessment and source identification of water pollution in the Banchengzi reservoir, Beijing, China

AbstractWater quality in the Banchengzi reservoir in Beijing has been deteriorating year by year, and it was embodied by increasing concentrations of COD and stable but high levels of total nitrogen. In order to identify the causes and to formulate a strategy for pollution prevention and control, we examined the temporal and spatial variations of water pollution and carried out source identification studies. Routine monthly monitoring data for seven water quality and six hydro-meteorological variables of the Banchengzi reservoir from 2007 to 2012 were analyzed by statistical techniques, including correlation analysis and principle component analysis. In addition, water samples at six different sites in the reservoir were collected and analyzed to investigate the spatial variation of water quality and to further identify the water pollution sources by UV–vis spectroscopy, three-dimensional excitation-emission matrix spectroscopy, and nitrogen stable isotope (δ15N) analysis. The results revealed that dissol...

Characteristics of DBPs reduction of AOM by dissolved air flotation

AbstractAlgae increase the concentration of dissolved organic carbon (DOC), which causes unpleasant tastes and odors in water. This DOC is known as algal organic matter, which comprises extracellular organic matter and intracellular organic matter. Carbonaceous disinfection by-products (C-DBPs) and nitrogenous DBP (N-DBPs) are produced from DOC by disinfection processes, and N-DBPs are about 140 times more toxic than C-DBPs. We compared the levels of N-DBPs when dissolved air flotation (DAF) or conventional gravity sedimentation was used to remove algae before/after chlorination. The degradation of algal cells by chlorine treatment increased the DOC level, which was attributable to DBPs/DBP formation precursors (DBPFPs). The levels of N-DBPs such as dechloroacetonitrile DCAN and C-DBPs such as trihalomethanes increased with the amount of chlorine applied. Haloacetonitriles increased continuously after treatment because the residual chlorine reacted with dissolved organic nitrogen. C-DBPs and N-DBPs were r...