Microbiome Wetlands in Nutrient and Contaminant Removal

Purpose of Review

Constructed wetlands (CWs) are engineered systems that have been proven as an alternative option to traditional wastewater treatment technologies because of their ability to provide cost-effective and energy-efficient solutions. This technology depends on natural microbial/biological, physical, and chemical processes to treat wastewater. Processes removing impurities in constructed wetlands are based on the combination of interactive systems such as selected plant species, the nature of substrate used for constructed wetlands, biofilm growth, microbial diversity, and several biogeochemically affected reaction cycles in wetland systems. Microorganisms play a vital role in these processes such as the degradation of pollutants and the transformation of nutrients. Microorganisms remove the pollutants from CWs by catalyzing chemical reactions, biodegrading, biosorbing, and supporting plant growth. An in-depth analysis of the function of microorganisms in CWs is important to understand. This review deals with the recent developments in constructed wetland systems from a microbiological perspective to treat impurities present in wastewater. It focuses on the studies of microbial diversity in CWs and the role of enzymes produced by microbes, the influence of the substrates of CWs on microbial diversity, the influence of the hydraulic design of CWs on the growth of microorganisms, the role of specific microbes in the removal of pollutants and the different software, analytical equipment, tools, and techniques used to measure/quantify the parameters of interest or to design and operate a wetland.

Recent Findings

The combination of different types of substrates in constructed wetlands can form different types of zones such as anaerobic and aerobic zones which can allow to form a diversity of microorganisms. In addition, plant diversity plays a vital role in microbial growth by providing O₂ and increasing plant biomass production which influences the soil microbial community. Moreover, the influent carbon source influences the biomass as for example when the COD/N ratio is increased by 80%, the phospholipid fatty acids (PLFA) concentration of microbial biofilm in glucose constructed wetlands is increased by 50%. At the same time, the biomass of aerobic and anaerobic bacteria and fungi increased significantly. In addition, different microorganisms are responsible in removing different types of heavy metals and micropollutants.

Summary

This article provides useful information on the understanding of the diversity of microbes, influencing factors on the growth of microorganisms, and the efficiency of pollutant removal process in CWs. Overall, this review provides new ideas and directions for the improvement of constructed wetlands from a microbiological perspective.