Sanitation in constructed wetlands: A review on the removal of human pathogens and fecal indicators

• Published in: The Science of the total environment 2016-01, Vol.541, p.8-22
• Main Authors: Wu, Shubiao, Carvalho, Pedro N., Müller, Jochen A., Manoj, Valsa Remony, Dong, Renjie
• Format: Article
• Language: English
• Subjects: Bacteria; Biodegradation, Environmental; Constructed wetlands; Construction; Ecosystem; Effluents; Fecal indicators; Feces; Filtration; Humans; Indicators; Mechanisms removal of bacteria; Pathogens; Reduction; Sanitation; Surface chemistry; Waste Disposal, Fluid - methods; Waste Water - microbiology; Wastewater treatment performance; Water Microbiology; Water Pollutants - analysis; Waterborne pathogens; Wetlands
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2015.09.047

Removal of human pathogens from wastewater is a critical factor with linkage to human health. Constructed Wetlands (CWs) are environmental friendly ecosystems that are applicable not only for chemical pollution control, but also for the reduction of pathogens from wastewater. Yet the knowledge on the fate and removal of such indicator bacteria in CWs is still not sufficient due to the complexity of removal mechanisms and influencing factors. This review serves to provide a better understanding of this state-of-the-art technology, which is necessary for further investigations and design development. The fecal indicator bacteria in CWs mainly come from three sources, namely, influent wastewaters, regrowth within the CWs, and animal activities. The properties of microbial contamination vary depending on the different sources. The removal of pathogens is a complex process that is influenced by operational parameters such as hydraulic regime and retention time, vegetation, seasonal fluctuation, and water composition. The most frequent and well-validated removal mechanisms include natural die-off due to starvation or predation, sedimentation and filtration, and adsorption. The concentration of the main fecal indicator bacteria in the effluent was found to be exponentially related to the loading rate. Generally, horizontal subsurface flow CWs have better reduction capacity than free water surface flow CWs, and hybrid wetland systems were found to be the most efficient due to a longer retention time. Further improvement of fecal indicator bacteria removal in CWs is needed, however, levels in CW effluents are still higher than most of the regulation standards for reuse. [Display omitted] •Knowledge on fate and removal of fecal indicator bacteria in CWs is not sufficient.•Three sources of pathogens in CWs were summarized.•Pathogens removal is influenced by hydraulic, vegetation, temperature and so on.•Most frequent and well-validated removal mechanisms were discussed.•Removal of pathogen was found to be exponentially related to the loading rate.