The data on microbial community structure in constructed wetlands enable biological indicators of wastewater treatment efficiency to be revealed
Constructed wetlands (CW) are often used for wastewater treatment in many European and Asian countries. This technology is environmentally friendly, easy to maintain, and effectively removes pollutants and xenobiotics. Most of the removal processes in CW are regulated by microorganisms which make up their microbial community. In addition, the removal efficiency of a particular pollutant is correlated with the size of a certain functional group which requires individual living conditions. For example, the mineralization of organic pollutants is mainly performed by fungi and bacteria both under aerobic and anaerobic conditions. Nitrogen removal (N) from wastewater in CW is achieved primarily by means of the microbial activity associated with nitrification, denitrification and anaerobic oxidation of ammonium (anammox). Microorganisms also play a considerable role in phosphorus removal (P) serving as biological mineralizers of organic P (release of the mineral P during the decomposition of organic matter inside the cells) and biochemical mineralization (release of the mineral P by enzymatic hydrolysis by extracellular enzymes). Identification of the taxonomic and functional structure of the microbial community provides new insights into biological processes of CW, which has a great potential for planning the design and maintenance of such facilities. The structure and diversity of the microbial community can be studied using various approaches, for example, polymerase chain reaction – denaturing gradient gel electrophoresis (PCR-DGGE) or high-performance 16S rRNA sequencing. Using these and some other methods enables us not only to describe the taxonomic structure of a particular community, but also to evaluate important parameters, such as the Shannon diversity index (SDI) or microbial biomass carbon (MBC) which are useful for assessing and predicting the quality of pollutant removal in CW. However, information on the relationship between the structure of the microbial community and the removal efficiency of pollutants is still limited. Industrial environmental monitoring of biological wastewater treatment systems, such as CW, is based on the assessment of the removal of organic substances, nutrients and pathogenic microorganisms. Indicators that primarily characterize and quantify these processes include suspended materials, ash content of suspended materials, chemical oxygen demand (COD), biochemical oxygen demand (BOD), organic nitrogen, ammonium, nitrites, nitrates, and phosphates. Thus, the rate of wastewater treatment can be estimated by the difference of these parameters at the inlet and outlet of the installation. The widespread and widely used chemical analyses make it possible to assess the overall efficiency of the installation, but in case of any malfunction, it is impossible to understand which process does not work properly and where the failure is. However, the analysis of the microbial community structure at certain points of CW can determine the state of all the main biochemical processes at these points. Subsequently, it can become a useful tool to identify problems and monitor CW.
Our team has collected extensive data on the taxonomic and functional composition of the CW microbiota. Significant correlations have been found between the presence of a number of pathogenic microorganisms in the community and the overall treatment efficiency. A number of functional groups have also been identified which characterize the removal processes of nutrients and decomposition of complex organic pollutants, xenobiotics.
Shchegolkova N.M. et. al. Taxonomic and Functional Diversity of Microbial Communities as an Indicator of the Effectiveness of Water Treatment in Constructed Wetlands