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Constructed wetlands have been recognized as a removal treatment option for high concentrations of contaminants in agricultural waste before land application. The goal of this study was to characterize microbial composition in two constructed wetlands designed to remove contaminants from dairy washwater. Water samples were collected weekly for 11 months from two wetlands to determine the efficiency of the treatment system in removal of chemical contaminants and total and fecal coliforms. The reduction by the treatment was greatest for biological oxygen demand, suspended solids, chemical oxygen demand, nitrate, and coliforms. There was only moderate removal of total nitrogen and phosphorus. Changes in the total bacterial community and ammonia-oxidizing bacterial composition were examined by using denaturing gradient gel electrophoresis (DGGE) and sequencing of PCR-amplified fragments of the gene carrying the ␣ subunit of the ammonia monooxygenase gene (amoA) recovered from soil samples and DGGE bands. DGGE analysis of wetlands and manure samples revealed that the total bacterial community composition was dominated by bacteria from phylogenetic clusters related to Bacillus, Clostridium, Mycoplasma, Eubacterium, and Proteobacteria originally retrieved from the gastrointestinal tracts of mammals. The population of ammonia-oxidizing bacteria showed a higher percentage of Nitrosospira-like sequences from the wetland samples, while a higher percentage of Nitrosomonas-like sequences from manure, feces, raw washwater, and facultative pond was found. These results show that the wetland system is a natural process dependent upon the development of healthy microbial communities for optimal wastewater treatment.Although natural wetlands have existed for ages across the globe, the use of constructed or artificial wetlands built for the improvement of water quality is a relatively new concept of the last two decades. Wastewater from intensive agricultural activities (cattle feedlots and dairies) typically have significantly higher concentrations of organic matter and nutrients than treated municipal effluent. The high pollutant loads being generated pose particular problems and challenges for the dairy industry, since high concentrations of nutrients can contribute to water management problems if wastes are allowed to discharge directly into receiving waters. For this reason agricultural wastes must be treated prior to disposal. Constructed wetlands in association with stabilization ponds have been suggested as a potential treatment option prior to land application. The extent of water treatment in natural or constructed wetlands depends upon the wetland design, microbial community, and types of plants involved. The bulk of the water quality improvement in natural and constructed wetlands is due to bacteria (2).It has long been recognized that certain microbial groups in animal waste are responsible for breaking down various organic compounds and for the suppression of pathogens in waste. However, very little work has been don...

Production and emission of CO2 from different sources have caused significant changes in the climate, which is the major concern related to global warming. Among other CO2 removal approaches, microalgae can efficiently remove CO2 through the rapid production of algal biomass. In addition, microalgae have the potential to be used in wastewater treatment. Although, wastewater treatment and CO2 removal by microalgae have been studied separately for a long time, there is no detailed information available on combining both processes. In this review article, microalgae-based CO2 biofixation, various microalgae cultivation systems,¯ and microalgae-derived wastewater treatment are separately discussed, followed by the concept of integration of CO2 biofixation process and wastewater treatment. In each section, details of energy efficiency and differences across microalgae species are also given.

Aims:  To correlate microbial community composition and water quality changes within wetland cells containing varying plant densities and composition in a free water surface (FWS) constructed wetland. Methods and Results:  Water chemistry was monitored weekly for nitrate, orthophosphate, and suspended solids, at various sites throughout the wetland for 6 months. Treatment ponds with 50% plant cover had about a 96·3% nitrate removal. The average change between the influent and effluent was 50–60% nitrate removal and 40–50% orthophosphate removal. Community profile of total DNA, generated by using denaturing gradient gel electrophoresis (DGGE), was used to determine the major microbial composition associated with the wetland sediment, rhizosphere, and surface water. Bacterial cloned libraries were constructed, and 300 clones were analysed by amplified ribosomal DNA restriction analysis (ARDRA) and grouped into operational taxonomic units (OTUs). A total of 35, 31, and 36 different OTU were obtained from sediment, rhizosphere, and surface water, respectively. The bacterial members within the dominant group of our clone library belonged to unclassified taxa, while the second predominant group consisted of members of the phylum Proteobacteria. The dominant organisms within the class were in the γ, β, and δ classes. Conclusion:  Microbial diversity as determined by Shannon‐Weaver index (H) was higher in the wetland cells with 50% plant density than the 100%. This was in agreement with the most efficient wetland contaminant removal units. Significance and Impact of the Study:  This study provides evidence that wetlands with 50% plant cover may promote the growth of diverse microbial communities that facilitate decomposition of chemical pollutants in surface water, and improve water quality.

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