Xianghua Wen

Microbial community structures in different wastewater treatment plants as revealed by 454-pyrosequencing analysis

In this study, 454-pyrosequencing technology was employed to investigate the microbial communities in 12 municipal wastewater treatment plants (WWPTs) with different treatment processes. In total, 202,968 effective sequences of the 16S rRNA gene were generated from 16 samples that widely represented the diversity of the microbial communities. While Proteobacteria was found to be the dominant phylum in some samples, in other samples it was Bacteroidetes. The Simpsons diversity index and evenness index were lowest in samples from membrane bioreactors (MBRs), possibly due to the long sludge retention time (SRT) and low food/microorganism ratio (F/M). For one WWTP which had two disparate treatment processes operating in parallel, the structures of microbial communities in the two systems were compared. The differences found between the two indicated that the treatment process likely had effects on the structure of microbial communities.

Pyrosequencing Analysis of Bacterial Diversity in 14 Wastewater Treatment Systems in China

ABSTRACT To determine if there is a core microbial community in the microbial populations of different wastewater treatment plants (WWTPs) and to investigate the effects of wastewater characteristics, operational parameters, and geographic locations on microbial communities, activated sludge samples were collected from 14 wastewater treatment systems located in 4 cities in China. High-throughput pyrosequencing was used to examine the 16S rRNA genes of bacteria in the wastewater treatment systems. Our results showed that there were 60 genera of bacterial populations commonly shared by all 14 samples, including Ferruginibacter, Prosthecobacter, Zoogloea, Subdivision 3 genera incertae sedis, Gp4, Gp6, etc., indicating that there is a core microbial community in the microbial populations of WWTPs at different geographic locations. The canonical correspondence analysis (CCA) results showed that the bacterial community variance correlated most strongly with water temperature, conductivity, pH, and dissolved oxygen (DO) content. Variance partitioning analyses suggested that wastewater characteristics had the greatest contribution to the bacterial community variance, explaining 25.7% of the variance of bacterial communities independently, followed by operational parameters (23.9%) and geographic location (14.7%). Results of this study provided insights into the bacterial community structure and diversity in geographically distributed WWTPs and discerned the relationships between bacterial community and environmental variables in WWTPs.

Ultrafiltration membrane bioreactor for urban wastewater reclamation

A 162-day pilot-scale operation for reclamation of urban wastewater was studied by using an ultrafiltration membrane bioreactor (UMBR). Performance of the UMBR was investigated with a sludge retention time (SRT) of 5, 15, and 30 days, a hydraulic retention time (HRT) of 5 h, and membrane flux between 75 and 150 l m 2 h 1 , respectively. It was observed that the highest sludge concentration in the reactor viz. a suspended solids (SS’s) concentration of 23.1 g l 1 and a volatile suspended solids (VSS’s) concentration of 13.5 g l 1 , respectively, could be reached. The ratio of sludge VSS to sludge chemical oxygen demand (COD) was 1.428 in the study, which approximated to the theoretical value of 1.415. Mass loading rates of the UMBR were close to those of conventional activated sludge processes (CASP’s), while the volumetric loading rates were two to five times those of CASP. Averaged 97% of COD, 96.2% of ammonia nitrogen (NH 3-N), and 100% of SS’s were removed. It was found that the bioreactor was responsible for 85% of COD removal, while 12% was due to separation of the membrane module. The reclaimed water could be reused directly for municipal purposes or indirectly for industrial uses after additional treatment.

Bacterial community dynamics in a functionally stable pilot-scale wastewater treatment plant.

To determine whether functional stability was correlated with a stable microbial community structure in a functionally stable pilot-scale wastewater treatment plant, bacterial communities in the system were monitored over a one-year period. Bacterial community dynamics was characterized by the terminal restriction fragment length polymorphism (T-RFLP) of 16S rRNA genes. During the study period, the effluent BOD concentrations were very stable, with the average BOD concentration below 10 mg/L. The effluent TN concentrations were always below 20 mg/L, except for the first 40 days. T-RFLP results showed that, during the test period, the bacterial community structures were not stable, with an average change rate (every 15 days) of 20.4%±11.2%. Based on Lorenz distribution curves, it was observed that 20% of the species corresponded with 40-77% of cumulative relative abundances. Results clearly revealed that, in the pilot-scale wastewater treatment plant, functional stability did not correlate with stable bacterial communities.

Degradation of tetracycline and oxytetracycline by crude lignin peroxidase prepared from Phanerochaete chrysosporium - a white rot fungus.

Pharmaceuticals are becoming an emerging environmental issue that attracts increasing attention in recent years. This study chose tetracycline (TC) and oxytetracycline (OTC) as examples of pharmaceuticals. Crude lignin peroxidase (LiP) produced by Phanerochaete chrysosporium were used to degrade TC and OTC in vitro. The results illustrated that LiP has a strong degrading ability towards TC and OTC. At 50 mgL(-1) of TC and OTC and 40 UL(-1) of the enzyme activity, the degradation of TC and OTC reached to about 95% in 5 min. The degradation of TC and OTC by LiP was dependent on pH and temperature and was largely enhanced by increasing the concentrations of veratryl alcohol (VA) and initial hydrogen peroxide (H2O2). The optimized degradation conditions were determined as pH 4.2, 37 degrees C, 2 mM VA, 0.4 mM H2O2.

Mobilization of heavy metals from Le An River sediment

The release of sediment-bound heavy metals can have a significant influence on river water quality. Generally speaking, variations of pH and oxygen are among the most important chemical factors that affect the mobility of sediment-bound metals. Recent research has indicated that sulfide, measured as acid-volatile sulfide (AVS), is an important partitioning component of heavy metals. We determined the metal release potential of sediments from the Le An River which receives drainage from a major copper mining operation. We found that the in-situ Cu, Pb, Zn, Cd and As concentrations of the Le An River sediments below the mine are much higher than are the global background values, but that Ni was not elevated. There is potential for mobilization of bound metals to the overlying water, the order of metal release ratio in terms of pH dependencies is Zn > Cu > Cd approximately Pb. Sulfide is not a major binding component for metals in Le An River sediment. It is more likely that the iron and manganese oxides are the most important metal binding components in the sediments of the Le An River.

TREATMENT OF HOSPITAL WASTEWATER USING A SUBMERGED MEMBRANE BIOREACTOR

Abstract Performance of a submerged hollow fiber membrane bioreactor (MBR) for treatment of hospital wastewater was investigated. The removal efficiency for COD, NH 4 + –N, and turbidity was 80, 93 and 83% respectively with the average effluent quality of COD 4 + –N Escherichia coli removal was over 98%. The effluent had no colour and no odour. The transmembrane pressure increased slowly during 6 months operation. No membrane cleaning operation was used and no sludge was discharged during the 6-month operation period.

Enzymatic degradation of tetracycline and oxytetracycline by crude manganese peroxidase prepared from Phanerochaete chrysosporium

Pharmaceuticals have been attracting increasing attention in recent years as emerging contaminants, of which the most frequently detected kind in various environments are antibiotics. In this study, crude manganese peroxidase (MnP) prepared from the Phanerochaete chrysosporium, a white rot fungi, was taken as a highly efficient biocatalyst to degrade tetracycline (TC) and oxytetracycline (OTC) which are widely used antibiotics. The results show that 72.5% of 50mg/L of TC was degraded when added 40 U/L of MnP, while 84.3% of 50mg/L of OTC was degraded with the same amount of the catalyst added, both within 4h. The degradation rate was dependant on the pH and the temperature of the reaction system, and was likely sensitive to the concentration of H(2)O(2). With the pH at 2.96-4.80, the temperature at 37-40 degrees C, the Mn(2+) concentration higher than 0.1mM and up to 0.4mM, the H(2)O(2) concentration of 0.2mM, and the enzyme-substrate ratio above 2.0 U/mg, the degradation rate reached the highest. In addition, a separate series of experiments also show that the compensation of H(2)O(2) during the reaction process could improve the degradation of TC by MnP.

Community analysis of ammonia-oxidizing bacteria in activated sludge of eight wastewater treatment systems

We investigated the communities of ammonia-oxidizing bacteria (AOB) in activated sludge collected from eight wastewater treatment systems using polymerase chain reaction (PCR) followed by terminal restriction fragment length polymorphism (T-RFLP), cloning, and sequencing of the alpha-subunit of the ammonia monooxygenase gene (amoA). The T-RFLP fingerprint analyses showed that different wastewater treatment systems harbored distinct AOB communities. However, there was no remarkable difference among the AOB T-RFLP profiles from different parts of the same system. The T-RFLP fingerprints showed that a full-scale wastewater treatment plant (WWTP) contained a larger number of dominant AOB species than a pilot-scale reactor. The source of influent affected the AOB community, and the WWTPs treating domestic wastewater contained a higher AOB diversity than those receiving mixed domestic and industrial wastewater. However, the AOB community structure was little affected by the treatment process in this study. Phylogenetic analysis of the cloned amoA genes clearly indicated that all the dominant AOB in the systems was closely related to Nitrosomonas spp. not to Nitrosospira spp. Members of the Nitrosomonas oligotropha and Nitrosomonas communis clusters were found in all samples, while members of Nitrosomonas europaea cluster occurred in some systems.

Occurrence of selected pharmaceuticals and caffeine in sewage treatment plants and receiving rivers in Beijing, China.

The occurrence of nine different types of pharmaceuticals and caffeine were analyzed in various units of three wastewater treatment plants (WWTPs) and their receiving rivers in Beijing, China. Analyte concentrations were determined using ultra performance liquid chromatograph-tandem quadruple mass spectrometers (UPLC-MS/MS) and multiple-reaction monitoring. The studied pharmaceuticals and caffeine were found in all the WWTPs and receiving rivers. Their concentrations in the WWTP influents varied from 38 ng/L of sulpiride to 89.5 microg/L of caffeine, and those in the effluents ranged from 27 ng/L of sulpiride to 2.7 microg/L of erythromycin. Typically, the biological treatment appeared more effective in the removal of pharmaceuticals and caffeine than primary treatment in a WWTP. For an individual compound, the overall removal efficiency varied from one WWTP to the next. Mean values ranged from no removal of carbamazepine to 99.8% removal of caffeine. Most of the compounds in the receiving rivers were present at similar or higher concentrations compared to those in the WWTP effluents. The data set for this study does not include variations in concentrations along receiving waters because there were other point and nonpoint sources discharging to these rivers. The preliminary aquatic environmental risk assessment showed that carbamazepine, erythromycin, and trimethoprim is a potential chronic environmental risk in water bodies in Beijing, China, and is worth further investigation.