Spatiotemporal correlations between water quality and microbial community of typical inflow river into Taihu Lake, China.

Changxing River, which is a typical inflow river into Taihu Lake and occurs severe algae invasion, is selected to study the effect of different pollution sources on the water quality and ecological system. Four types of pollution sources, including the estuary of Taihu Lake, discharge outlets of urban wastewater treatment plants, stormwater outlets, and nonpoint source agricultural drainage areas, were chosen, and next-generation sequencing and multivariate statistical analyses were used to characterize the microbial communities and reveal their relationship with water physicochemical properties. The results showed that ammonia nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) were the main pollutants in Changxing River, especially at stormwater outlets. At the same time, the diversity of microbial communities was the highest in the summer, and dominant microbes included Proteobacteria (40.9%), Bacteroidetes (21.0%), and Euryarchaeota (6.1%). The results of BIOENV analysis showed that the major seasonal differences in the diversity of microbial community of Changxing river were explained by the combination of water temperature (T), air pressure (P), TP, and CODMn. From the perspective of different pollution types, relative abundances of Microcystis and Nostocaceae at the estuary of Taihu Lake were correlated positively with dissolved oxygen (DO) and pH, and relative abundances of Pseudomonas and Arcobacter were correlated positively with concentrations of TN and nitrate nitrogen (NO3--N) at stormwater outlets. This study provided a reference for the impact of pollution types on river microbial ecosystem under complex hydrological conditions and guidance for the selection of restoration techniques for polluted rivers entering the important lake.

Diatomite-enhanced coagulation for algal removal in polluted raw water: performance optimization and pilot-scale study.

Algae blooms have seriously threatened the health of aquatic ecosystems and the safety of drinking water. In this study, diatomite-enhanced coagulation technology was developed to improve the removal of algae and other pollutants. The dosage and ratio of diatomite and aluminum salts were optimized to 40mg/L and 1:1 which achieved algal removal efficiency of 98.8±0.65%. The effect of environmental factors was studied and it shows that cell density, pH, and temperature had a significant impact on algal removal. The mechanism of diatomite-enhanced coagulation was speculated to be adsorption bridging and sweep flocculation. Pilot-scale equipment was set up to verify the performance of diatomite-enhanced coagulation in engineering applications on algae polluted raw water. Results showed a better removal efficiency of algae, NH4+-N, NO2--N, and CODMn and lower operation cost than the actual operation in the Waterwork Corporation were achieved with good application prospects and promotion value.

The regulation of N-acyl-homoserine lactones (AHLs)-based quorum sensing on EPS secretion via ATP synthetic for the stability of aerobic granular sludge.

According to the relationship among microbial activity, quorum sensing (QS) and structural stability of aerobic granular sludge, the mechanism of QS regulation for microbial activity and granular stability was investigated in AGS process. Results showed that ATP content decreased sharply from 1.8 µmol/gVSS of stable granules to 0.8 µmol/gVSS of disintegrating granules, and the relative abundance of QS-activity microbes, Rhodobacter spp. and Xanthomonadaceae decreased in initially unstable granules compared with stable granules. The main AHLs were detected in this study, and C8-HSL, 3OHC8-HSL and 3OHC12-HSL decreased significantly when structure of granules changed from stability to disintegration. Accompanying with the decrease of AHLs level, the extracellular polymeric substances (EPS) content in initially unstable granules decreased sharply from 226.8 to 163.6 mg/gVSS with the ratio of extracellular protein to exopolysaccharide (PN/PS) decreasing from 3.6 to 2.2, despite EPS-secretion microbes enriched. The effect of QS on microbial activity was proved by AHL add-back study, results indicated that ATP and EPS content in sludge increased significantly (p < 0.05) with AHLs added, but EPS production was limited when ATP synthesis was disrupted. It was concluded that the AHLs-based QS favored the granular stability via the enhancement of ATP synthesis in microbes. This study provides a new perspective for QS regulation in aerobic granular sludge system, because the ATP regulated by QS could be the energy currency for cellular metabolism, such as nutrient removal, degradation of emerging pollutants, microbial growth and other aspects.

Response of syntrophic aggregates to the magnetite loss in continuous anaerobic bioreactor.

Increasing studies indicate that magnetite addition could accelerate the methanogenesis via enhancing direct interspecies electron transfer (DIET)-based anaerobic syntrophy. However, magnetite is found to run off in continuous bioreactor, and the effect of magnetite loss on syntrophic aggregates is still underreported. In this study, two EGSB reactors (RM with magnetite-enhanced sludge, and RB as a control) were operated to investigate the magnetite behavior in continuous bioreactor and the corresponding response of syntrophic aggregates. Results showed that magnetite in RM was washed out gradually in form of iron ions, and a slightly acidic niche was supposed to be the major cause. Nevertheless, candidate DIET partners like Geobacter and Methanothrix along with syntrophic volatile fatty acids (VFAs)-degrading microbes were enriched in RM. In addition, the improved redox activity of extracellular polymeric substance (EPS), higher sludge conductivity and electron transport activity suggested that the DIET ability of sludge in RM was still enhanced, which favors the syntrophic metabolism of VFAs. Interestingly, syntrophic partners were loosely combined under the condition of high organic loading rate (OLR) in the presence of magnetite, but with gradual loss of magnetite, dense and active anaerobic granular sludge (AGS) was formed in RM. This study provided a comprehensive understanding of magnetite behavior in continuous bioreactor and the response of syntrophic aggregates. The robust DIET-based syntrophy after magnetite adding could favor the high-efficient anaerobic wastewater treatment and resource recovery in the future, and further investigations on magnetite resupply and the mechanism of magnetite enriching candidate DIET partners are recommended.