Quantifying the Cost-Effectiveness of Nutrient-Removal Strategies for a Lowland Rural Watershed: Insights from Process-Based Modeling

Abstract

Several management strategies, such as wastewater treatment plants (WWTPs), have been increasingly used to mitigate nutrient pollution at watershed scale during the past few years. However, their cost-efficiency in controlling nutrient load is still debatable. This study quantified the annual cost of WWTP and constructed wetland based on process-based modeling of nutrient dynamics within a typical lowland rural watershed in Eastern China. The evaluation results revealed that constructed wetland with macrophyte coverage increased by 10% and 15% can result in an identical reduction of nitrogen and phosphorus load by WWTP. However, a cost analysis revealed that the strategy of WWTP had a higher annual cost (65,538 Yuan/yr) compared with the strategy of constructed wetland with an annual cost of 24,012 Yuan/yr. The case study revealed that WWTPs are not necessarily cost-effective for controlling nutrient load from China’s lowland rural areas. This is because WWTP is costly, while constructed wetland based on the widely-distributed pond ecosystems in lowland areas can save considerable investments. We concluded that an adequate cost-effectiveness evaluation for management strategies in nutrient removal will benefit our decision-making.