A Review on Constructed Treatment Wetlands for Removal of Pollutants in the Agricultural Runoff

Abstract

Constructed wetland (CW) is a popular sustainable best management practice for treating different wastewaters. While there are many articles on the removal of pollutants from different wastewaters, a comprehensive and critical review on the removal of pollutants other than nutrients that occur in agricultural field runoff and wastewater from animal facilities, including pesticides, insecticides, veterinary medicine, and antimicrobial-resistant genes are currently unavailable. Consequently, this paper summarized recent findings on the occurrence of such pollutants in the agricultural runoff water, their removal by different wetlands (surface flow, subsurface horizontal flow, subsurface vertical flow, and hybrid), and removal mechanisms, and analyzed the factors that affect the removal. The information is then used to highlight the current research gaps and needs for resilient and sustainable treatment systems. Factors, including contaminant property, aeration, type, and design of CWs, hydraulic parameters, substrate medium, and vegetation, impact the removal performance of the CWs. Hydraulic loading of 10–30 cm/d and hydraulic retention of 6–8 days were found to be optimal for the removal of agricultural pollutants from wetlands. The pollutants in agricultural wastewater, excluding nutrients and sediment, and their treatment utilizing different nature-based solutions, such as wetlands, are understudied, implying the need for more of such studies. This study reinforced the notion that wetlands are effective for treating agricultural wastewater (removal >90%) but several research questions remain unanswered. More long-term research in the actual field utilizing environmentally relevant concentrations to seek actual impacts of weather, plants, substrates, hydrology, and other design parameters, such as aeration and layout of wetland cells on the removal of pollutants, are needed.

The irrigation suitability potential of an effluent treated by a pseudo‐natural wetland

“…Moreover, this study confirms further that wetlands are considered to be among the most effective approaches for the removal of pollutants in wastewater from different sources. For instance, in the study conducted by Tang et al (2021), removal efficiency of more than 90% was achieved when the wetland was subjected to agricultural wastewater.…”

Study on Water Quality Change Trend and Its Influencing Factors from 2001 to 2021 in Zuli River Basin in the Northwestern Part of the Loess Plateau, China

“…Precipitation and runoff may increase or decrease the level of pollutants in rivers through the transportation of surface pollutants into rivers via surface runoff. Surface pollutants adhere to the soil and enter the river through heavy precipitation and surface runoff [52]; however, increased precipitation can increase runoff, and increased runoff enhances the potency of dilution and reduces the residence time of pollutants in rivers [31,[53][54][55]. Therefore, the quality of water in a river also depends on other environmental factors, such as landscape patterns and land use types [56].…”

Comparison of Contaminants Removal Efficiencies in Wastewater Using Constructed Wetlands of Single and Two Stages

“…Considering previous work, such as that of Zepei Tang et al (2021) on the removal of up to 99% of emerging pollutants from agricultural wastewater, suggests that the efficiency of a constructed wetland does not depend so much on the inlet channel, instead it influences more factors such as primary treatment (use of grease trap, sludge removal, ponds, etc. ), and the level that can affect weather conditions and the maintenance given.…”

“…Requires an impermeable floor basin with a slight slope for continuous flow control. Constructed wetlands and their designs have been used for the removal of both emerging contaminants in agriculture (pesticides, herbicides, pharmaceutical products) with reported efficiencies of up to 100% (Tang et al, 2021).…”