Integrated Vertical-flow Constructed Wetland Research Articles

Performance of the combined SMBR–IVCW system for wastewater treatment

A new SMBR–IVCW system, which combined a submerged MBR (SMBR) unit and an integrated vertical-flow constructed wetland (IVCW) unit, was applied to treat the high strength integrated wastewater. The study showed that this system of biological and ecological combination was stable and good at improving the quality and efficiency of polishing wastewater. Six runs under different HRT combinations were carried out in order to obtain the better purification performance of the SMBR–IVCW system. The results indicated that the better HRT combination was 7.7 h for SMBR and 11.52 h for IVCW. In such condition, the concentrations of COD, ammonia and TP in the final effluent were 11.0, 0.086 and 0.44 mg L − 1 , respectively, which reached the Class III of the national environmental quality standards for surface water in China. In fact, the HRT of the two units had great effect on the purification efficiency and investment cost. By regulating the ratio of HRT between these two units, the optimum operation conditions could be obtained to reach the double wins of high purification and low costs. In the SMBR–IVCW system, the SMBR unit acted as the secondary treatment, contributing to removing the organics and nitrification. While the IVCW unit was more like as the tertiary treatment, contributing to the denitrification and further dephosphorization.

Advanced wastewater treatment by integrated vertical flow constructed wetland with vetiveria zizanioides in north China

The use of tail water for irrigation is becoming increasingly common. However, raw tail water is often contaminated and can cause environmental harm and pose health risks. Nevertheless, it is often used without any significant pre-treatment, a practice mistakenly considered safe. The aim of this study is to explore the removal efficiency of Integrated Vertical Flow Constructed Wetland (IVFCW) with Vetiveria zizanioides, an economically sound, low-tech and easily maintainable treatment system that would allow safe and sustainable use of tail water for landscape irrigation for COD, NH3-N, TN at different hydraulic retention time and different temperature in north China. The IVFCW can remove about 71% of the chemical oxygen demand, 67% of NH3-N and 80% of TN after five days at the hydraulic load of 0.6~0.8m3/m2.d in summer; But at low temperature, all kinds of pollutants has a lower removal efficiency compared with summer. At 10°C, the highest removal ratio of CODCr, NH3-N, TN are only 51.71%, 19.87%, and 29.76%, respectively.

Characteristics of the microbial communities in the integrated vertical-flow constructed wetlands

Microorganisms play an important role in removing pollutants from constructed wetlands. We investigated the microbial characteristics in a novel integrated vertical-flow constructed wetland (IVCW), which has been in operation in Wuhan, China since 1998. We used phospholipid fatty acid (PLFA) and amoA gene to analyze the structure and diversity of the microbial community within the IVCW. PLFA results suggested that the amount of bacterial PLFA was significantly higher than that of fungal PLFA, but the total microbial biomass represented by PLFA index was low in the system. Microbial spatial distribution showed significantly higher bacterial (both G+ and G-) and fungal biomass in the surface than in the subsurface layers. The ratios of monounsaturated to branched PLFA demonstrated that an anaerobic layer sandwiched by two aerobic layers existed in the IVCW, consistent with the redox potential results. Analysis of the amoA revealed the presence of Nitrosomonas-like sequences in the surface substrate of the downflow chamber and apparent diversities of ammonia-oxidizing bacteria in the system. These results suggest that microorganisms, despite their relatively low biomass, have inhabited the IVCW, and the results will offer some valuable information on microbe to system designers and managers.

Effects of Cd2+ and Pb2+ on the substrate bioflms in the integrated vertical-flow constructed wetland

The effects of single Cd2+ and Pb2+, and combined Cd2+ and Pb2+ on dehydrogenase activity and polysaccharide content of the substrate biofilms in the integrated vertical-flow constructed wetland (IVCW) were studied. Dehydrogenase activities decreased linearly with the increasing concentrations of Cd2+ and Pb2+ at different times (6, 24, 72, and 120 h). The activities at both 6 and 24 h were significantly higher than that at 72 and 120 h in the case of single and combined treatments. The single Cd2+ and Pb2+ treatments significantly inhibited dehydrogenase activities at concentrations in excess of 20 micromol/L Cd2+ and 80 micromol/L Pb2+, respectively. The inhibitory effect of Cd2+ was much greater than that of Pb2+. At the same time, the combined treatment of Cd2+ and Pb2+ significantly inhibited dehydrogenase activities at all five concentrations studied and the lowest combined concentration was 1.25 micromol/L Cd2+ and 5 micromol/L Pb2+. A synergistic effect of Cd2+ and Pb2+ was observed. On the other hand, polysaccharide contents varied unpredictably with the increasing concentrations of Cd2+ and Pb2+ and extended experimental time. There were no significant statistical differences within the range of concentration and time studied, whether singly or in combination. These results implied that the effects of heavy metals on biofilms should be a concern for the operation and maintenance of constructed wetlands.

Efficiency and mechanism of treating the polluted river water with constructed wetland

针对采用人工湿地系统净化镇江市内污染较为严重的古运河河水中遇到的问题, 采用复合垂直流人工湿地小试装置, 研究人工湿地系统对污染河水的净化效果及净化机理.镇江古运河水质调查结果表明, 河水中悬浮态污染物质含量较高, 为劣Ⅴ类水体;当水力负荷为750mm/d时, 人工湿地系统对COD_Mn去除率约为50%-60%, TN去除率约为40%-50%, TP去除率约为30%-40%, 能够将劣Ⅴ类水处理为Ⅳ类水甚至Ⅲ类水, 表明其对污染河水处理的有效性.研究人工湿地内部污染物浓度的沿程变化规律, 可以发现河水中污染物质的去除主要发生在湿地下行池, 尤其是表层30cm处, 而上行池未能发挥应有的作用, 分析表明与可能与污染河水中的碳氮比有一定的关系.通过本次实验发现湿地表层对污染物的去除表现为滤料及植物根系的过滤、吸附、截留以及微生物的降解、植物吸收等综合作用.;Aiming at the problem which was faced at the time of treating the seriously polluted water in the Old Canal of Zhenjiang by the constructed wetland, the removal efficiency and the mechanism of treating the polluted river water by the integrated vertical-flow constructed wetland were studied.The investigation of the water quality of the Old Canal showed that the suspended pollutant concentrations was higher and the water quality was worse than Grade V;When the hydraulic loading of the integrated vertical-flow constructed wetland (IVCW) was about 750 mm/d, the removal rates of the COD_Mn, TN and TP were respectively from 50% to 60%, from 40% to 50%, and from 30% to 40% and the effluent quality can reach the Grade Ⅳ even Ⅲ.it showed that the IVCW was a valid method to the treatment of the polluted river water.The variation of the pollutant concentration along the flow showed that the pollutant was removed mainly by the down-flow chamber, especial the surface layer (0-30 cm), while the function of the up-flow chamber was little which may have relation to C/N.The removal function of the surface layer was mainly by the filtration of the medium and plant roots, the degradation of the microorganism, and the absorption of the plants.