Xinshan Song

High-effective denitrification of low C/N wastewater by combined constructed wetland and biofilm-electrode reactor (CW–BER)

The low denitrification effect on constructed wetlands (CWs) treating low carbon to nitrogen ratio (C/N) wastewater was a problem. In this study, a novel coupled system by installing CW and biofilm-electrode reactor (CW-BER) was developed. In this system, the heterotrophic and autotrophic denitrifying bacteria all played their roles in denitrification process. The system was investigated systematically with simulated wastewater at different C/Ns, electric current intensities (I), hydraulic retention times (HRTs), and pH. Results showed that the optimum running conditions were C/N=0.75-1, I=15 mA, HRT=12 h, and pH=7.5. The highest removal efficiency of NO3-N and TN at the best conditions was respectively 63.03% and 98.11% for CW-BER. Also, the TN and NO3-N enhancive removal efficiency of CW-BER was 23.26% and 24.20%, respectively. No residual organic carbon source was detected in final effluent at the best parameters.

Nitrate removal and bioenergy production in constructed wetland coupled with microbial fuel cell: Establishment of electrochemically active bacteria community on anode.

The constructed wetland coupled with microbial fuel cell (CW-MFC) systems operated at different substrate concentration and pH influents were evaluated for bioelectricity generation, contaminant removal and microbial community structure. Performance of CW-MFC was evaluated at organic loading rate of 75.3gCODm-3d-1 and pH gradients of (5.18±0.14, 7.31±0.13, and 8.75±0.12) using carbon fiber felt as electrodes. Peak power density was observed at slightly neutral influent condition. Compared with the open circuit CW-MFC, average COD and NO3-N removal efficiency in CW-MFC increased by 8.3% and 40.2% respectively under slightly neutral pH of influents. However, the removal efficiency and bioenergy production have been inhibited with acidic influents. The relative abundance of beta-Proteobacteria, nitrobacteria and denitrifying bacteria was significantly promoted in closed-circuit CW-MFC. Using of CW-MFC as a biochemical method for nitrate removal and bioelectricity generation under slightly neutral and alkaline influent conditions was a promising technology.

Microbial community structure of different electrode materials in constructed wetland incorporating microbial fuel cell

The microbial fuel cell coupled with constructed wetland (CW-MFC) microcosms were operated under fed-batch mode for evaluating the effect of electrode materials on bioelectricity generation and microbial community composition. Experimental results indicated that the bioenergy output in CW-MFC increased with the substrate concentration; maximum average voltage (177mV) was observed in CW-MFC with carbon fiber felt (CFF). In addition, the four different materials resulted in the formation of significantly different microbial community distribution around the anode electrode. The relative abundance of Proteobacteria in CFF and foamed nickel (FN) was significantly higher than that in stainless steel mesh (SSM) and graphite rod (GR) samples. Notably, the findings indicate that CW-MFC utilizing FN anode electrode could apparently improve relative abundance of Dechloromonas, which has been regarded as a denitrifying and phosphate accumulating microorganism.

The inhibition and adaptability of four wetland plant species to high concentration of ammonia wastewater and nitrogen removal efficiency in constructed wetlands

Four plant species, Typha orientalis, Scirpus validus, Canna indica and Iris tectorum were selected to assess their physiological response and effects on nitrogen and COD removal to high total ammoniacal nitrogen (TAN) in constructed wetlands. Results showed that high TAN caused decreased relative growth rate, net photosynthetic rate, and leaf transpiration. C. indica and T. orientalis showed higher TAN adaptability than S. validus and I. tectorum. Below TAN of 200 mg L(-1), growth of C. indica and T. orientalis was less affected or even stimulated at TAN range 100-200 mg L(-1). However, S. validus and I. tectorum was obviously suppressed when TAN was above 100 mg L(-1). High TAN generated obvious oxidative stress showing increased proline and malondialdehyde contents, and superoxide dismutase was inhibited. It indicated that the threshold for plant self-bioremediation against high TAN was 200 mg L(-1). Whats more, planted CWs showed higher nitrogen and COD removal. Removal rate of C. indica and T. orientalis was higher than S. validus and I. tectorum.

High efficiency of inorganic nitrogen removal by integrating biofilm-electrode with constructed wetland: Autotrophic denitrifying bacteria analysis

The constructed wetland coupled with biofilm-electrode reactor (CW-BER) is a novel technology to treat wastewater with a relatively high level of total inorganic nitrogen (TIN) concentration. The main objective of this study is to investigate the effects of C/Ns, TIN concentrations, current intensities, and pH on the removal of nitrogen in CW-BER; a control system (CW) was also constructed and operated with similar influent conditions. Results indicated that the current, inorganic carbon source and hydrogen generated by the micro-electric field could significantly improve the inorganic nitrogen removal with in CW-BER, and the enhancement of average removal rate on NH3-N, NO3-N, and TIN was approximately maintained at 5-28%, 5-26%, and 3-24%, respectively. The appropriate operation conditions were I=10mA and pH=7.5 in CW-BER. In addition, high-throughput sequencing analysis implied that the CW-BER reactor has been improved with the relative abundance of autotrophic denitrifying bacteria (Thiobacillus sp.).

Flood simulation using parallel genetic algorithm integrated wavelet neural networks

The conventional means of flood simulation and prediction using conceptual hydrological model or artificial neural network (ANN) has provided promising results in recent years. However, it is usually difficult to obtain ideal flood reproducing due to the structure of hydrological model. Back propagation (BP) algorithm of ANN may also reach local optimum when training nodal weights. To improve the mapping capability of neural networks, wavelet function was adopted (WANN) to strengthen the non-linear simulation accuracy and generality. In addition, genetic algorithm is integrated with WANN (GAWANN) to avoid reaching local optimum. Meanwhile, Message Passing Interface (MPI) subroutines are introduced for distributed implement considering the time consumption during nodal weights training. The GAWANN was applied in the flood simulation and prediction in arid area. The test results of 4 independent cases were compared to reveal the relations between historical rainfall and runoff under different time lags. The simulation was also carried out with Xinanjiang model to demonstrate the capability of GAWANN. The numerical experiments in this paper indicated that the parallel GAWANN has strong capability of rain-runoff mapping as well as computational efficiency and is suitable for applications of flood simulation in arid areas.

Influences of iron and calcium carbonate on wastewater treatment performances of algae based reactors.

The influences of iron and calcium carbonate (CaCO3) addition in wastewater treatments reactors performance were investigated. Adding different concentrations of Fe(3+) (5, 10, 30 and 50mmol/m(3)), iron and CaCO3 powder led to changes in algal characteristics and physico-chemical and microbiological properties. According to the investigation results, nutrient removal efficiency in algae based reactors was obviously increased by the addition of 10mmol/m(3) Fe(3+), iron (5mmol/m(3)) and CaCO3 powder (0.2gm(-3)) and the removal efficiencies of BOD5, TN, and TP in Stage 2 were respectively increased by 28%, 8.9%, and 22%. The improvements in physico-chemical performances were verified by microbial community tests (bacteria quantity, activity and community measured in most probable number, extracellular enzymes activity, and Biolog Eco Plates). Microbial variations indicated the coexistence of Fe ions and carbonate-bicarbonate, which triggered the synergistic effect of physico-chemical action and microbial factors in algae based reactors.

Bioenergy generation and rhizodegradation as affected by microbial community distribution in a coupled constructed wetland-microbial fuel cell system associated with three macrophytes

Rhizodeposits excreted by various macrophytes might lead to the potential discrepancy of microbial community distribution in constructed wetland coupled with microbial fuel cell (CW-MFC), which has been considered as main factors for the variations of bioelectricity generation during wastewater treatment. In this study, CW-MFC has been associated with three macrophytes (J. effuses, T. orientalis and S. validus) for domestic sewage treatment, also unplanted CW-MFC was performed as a control system. Macrophyte T. orientalis and S. validus can significantly strengthen the bioenergy output in CW-MFC. Highest current (94.27mAm-2) and power densities (21.53mWm-2) were obtained in CW-MFC planted with T. orientalis. Removal efficiencies of COD, NO3-N and NH3-N in CW-MFC planted with S. validus was respectively 5.8%, 7.2%, and 23.9% higher than that of unplanted system. Notably, the oxygen depletion in S. validus CW-MFC reactor during the dark cycle was higher that of other reactors. Results of high-throughput sequencing analysis showed that higher biodiversity was observed in rhizosphere than that of anode material, and the relative abundance of Desulfobulbus sp. and Geobacter sp. has been apparently promoted in the samples of rhizosphere. However, a higher relative abundance of electrochemically active bacteria (Proteobacteria) was observed on the surface of anode electrode material. In addition, microbes (Cytophagales, Clostridium sp., and Dechloromonas sp., and so forth) found in rhizosphere show a capability to decompose refractory contaminants. These contaminants and death roots in the upper part of wetland could be oxidized to fat acids, which may be used as the electrons acceptors for promoting the bioelectricity generation during wastewater treatment.

Bacterial and archaeal community distribution and stabilization of anaerobic sludge in a strengthen circulation anaerobic (SCA) reactor for municipal wastewater treatment

In this study, a SCA reactor was employed for municipal wastewater treatment at a mesophilic temperature (30°C) under different hydraulic retention times (HRT) and upflow velocities (Vup) to investigate granule sludge stability and spatial microbial distribution. The stable COD removal efficiency readied at HRT of 15, 12, 9 and 6h, and Vup ranging from 0.6 to 5.9mh-1. EPS fraction analysis of granule sludge shows that municipal wastewater was mainly attributed to the enrichment influence of polysaccharide and tightly bound-EPS. SEM images exhibited that the stability and floating of anaerobic granular sludge may be promoted in the primary three-phase separator area because the channels of the granules was clogged by EPS. The SMA and high-throughput sequencing analysis indicated acetoclastic methanogens and hydrogenotrophic methanogens played an important role in formation and maintenance of the anaerobic granule sludge in low and high organic load rate operation conditions.

Bioelectricity generation, contaminant removal and bacterial community distribution as affected by substrate material size and aquatic macrophyte in constructed wetland-microbial fuel cell

Integrating microbial fuel cell with constructed wetland (CW-MFC) is a novel way to harvest bioelectricity during wastewater treatment. In this study, the bioelectricity generation, containment removal and microbial community distribution in CW-MFC as affected by substrate material sizes and aquatic macrophyte were investigated. The planted CW-MFC with larger filler size showed a significant promotion of the relative abundance of electrochemically active bacteria (beta-Proteobacteria), which might result in the increase of bioelectricity generation in CW-MFC (8.91mWm-2). Additionally, a sharp decrease of voltage was observed in unplanted CW-MFC with smaller filler size in Cycle eight. However, the peak COD (86.7%) and NO3-N (87.1%) removal efficiencies were observed in planted CW-MFC with smaller filler size, which was strongly related to the biodiversity of microorganisms. Generally, the acclimation of exoelectrogens as dominant microbes in the anode chamber of planted CW-MFC with larger filler size could promote the bioelectricity generation during wastewater treatment.