Effects of chlortetracycline,Cu and their combination on the performance and microbial community dynamics in swine manure anaerobic digestion

Swine manure was typical for the combined pollution of heavy metals and antibiotics. The effects of widely used veterinary antibiotic chlortetracycline（CTC）, Cu and their combination on swine manure anaerobic digestion performance and microbial community have never been investigated. Thus, four 2 L anaerobic digestion reactors were established including reactor A（control）, B（CTC spiked by 0.5 g/kg dry weight, dw）, C（Cu spiked by 5 g/kg dw） and D（combination of CTC, 0.5 g/kg dw, and Cu, 5 g/kg dw）, and dynamics of bacterial and archaeal community structure was investigated using high throughput sequencing method. Results showed that addition of CTC and Cu separately could increase the total biogas production by21.6% and 15.8%, respectively, while combination of CTC and Cu severely inhibited anaerobic digestion（by 30.3%）. Furthermore, corresponding to different stages and reactors, four kinds of microbes including bacteria and archaea were described in detail, and the effects of CTC, Cu and their combination mainly occurred at hydrolysis and acidification phases. The addition of Cu alone changed the dynamics of archaeal community significantly. It was genus Methanomassiliicoccus that dominated at the active methane production for A, B and D, while it was genus Methanobrevibacter and Methanoculleus for C.

Advanced treatment of municipal wastewater by nanofiltration： Operational optimization and membrane fouling analysis

Municipal sewage from an oxidation ditch was treated for reuse by nanofiltration（NF） in this study. The NF performance was optimized, and its fouling characteristics after different operational durations（i.e., 48 and 169 hr） were analyzed to investigate the applicability of nanofiltration for water reuse. The optimum performance was achieved when transmembrane pressure = 12 bar, p H = 4 and flow rate = 8 L/min using a GE membrane. The permeate water quality could satisfy the requirements of water reclamation for different uses and local standards for water reuse in Beijing. Flux decline in the fouling experiments could be divided into a rapid flux decline and a quasi-steady state. The boundary flux theory was used to predict the evolution of permeate flux. The expected operational duration based on the 169-hr experiment was 392.6 hr which is 175% longer than that of the 48-hr one. High molecular weight（MW） protein-like substances were suggested to be the dominant foulants after an extended period based on the MW distribution and the fluorescence characteristics. The analyses of infrared spectra and extracellular polymeric substances revealed that the roles of both humic- and polysaccharide-like substances were diminished, while that of protein-like substances were strengthened in the contribution of membrane fouling with time prolonged. Inorganic salts were found to have marginally influence on membrane fouling. Additionally, alkali washing was more efficient at removing organic foulants in the long term, and a combination of water flushing and alkali washing was appropriate for NF fouling control in municipal sewage treatment.

Water environment protection and sustainable development in townlet of China: A case study in Taicang

The Environmental Kuznets Curve(EKC) model was applied to investigate the relationship between economic growth and water environment quality based on panel data of Taicang during 2010–2017. The typical inversed-U shaped relationship has been obtained between GDP(gross domestic product) and indicators of ammonia, total nitrogen(TN) and total phosphorus(TP), respectively. The EKC turning point appeared when the GDP per capita was around US$2270, which was much lower than those in some developed countries(US$11,200). However, the decoupling between chemical oxygen demand(COD) and GDP per capita occurred even before this period, which should be attributed to the strict COD emission regulation being implemented since 2010. Further, analysis based on the Tapio decoupling coefficient elasticity model analyzed the ammonia nitrogen and economic development of each industry. We found that the agriculture no-point was strong decoupling in 2011–2014, then came to Recessive decoupling. The domestic wastewater had been in a strong decoupling state;Both urban non-point and industry experienced expansive negative decoupling, due to strict policy that prioritizes the environment over development and the investment in improvement of environment and techniques, both of them gradually came to strong decoupling. The result demonstrated that the EKC turning point could be appear in earlier economic stage and the decoupling coefficient elasticity could be improved through taking strong regulation measures.

New concept of contaminant removal from swine wastewater by a biological treatment process

Pollution from concentrated animal feeding operations(CAFOs)are the most serious pollution source in China now,and swine wastewater contains high concentrations of nutrients such as chemical oxygen demand(COD),biochemical oxygen demand 5(BOD 5),ammonium,and emergent contaminants related to public health.Biological processes are the most popular treatment methods for COD and ammonium removal.Considering the low operation cost,easy maintenance and high removal rate of contaminants in recent years,nitrogen removal via nitrite and real-time control processes using oxidation-reduction potential(ORP)and/or pH as parameters to control the aerobic and anaerobic cycles of a system has received much attention for animal wastewater treatment.During the biological treatment process,the emergent contaminants such as estrogen,antibiotics,and disinfec-tion reagents have been the focus of research recently,and degradation bacteria and resistance bacteria have also been extracted from activated sludge.The microbial analysis technique is also advancement in the field of biodegrada-tion bacteria and resistance bacteria.All of these advance-ments in research serve to improve wastewater treatment and decrease environmental hazards,especially for using manure as a fertilizer source for crop production.