Multi-Pollutant Water Quality Trading: A Conditional Approach for Groundwater Quality Management

Abstract

Groundwater quality management is challenging due to the fate and transport of multiple pollutants in the porous media, extensive polluters, and late aquifer responses to pollution reduction practices. Water quality trading (WQT) is an economically incentive-based policy for waste load allocation (WLA) in water resources. This study evaluates the effectiveness of 12 WLA scenarios on reducing groundwater nitrate and chloride, simultaneously using MODFLOW and MT3DMs. Here, the theoretical efficiencies of multi-pollutant WQT are also testified out of these scenarios by developing environmental, economic and practical conditions. For these purposes, Varamin plain, south-eastern Tehran, Iran, was chosen as the study area where both point and non-point pollution sources were considered in WQT. At first, an allowable quality limit (AQL) for the groundwater was set for pollutants regarding groundwater impairment and simulation outcomes. The AQL violations of WLAs were then calculated in addition to their marginal abatement costs and penalties. Here, nitrate abatement ranges between 3.3–18.3%, while chloride abatement ranges between 4.5–23.6%. Our findings show that, 5 WLA scenarios could pass the conditions of not violating any AQLs, and gaining remarkable benefits (> 25%) for all market attendants. Potential WQT strategies are finally prioritised regarding their viability and marginal costs. According to these conditions, trading discharge permits between wastewater treatment plants (WWTPs) with 50% nitrate removal (sellers) and farmers (buyers) are recommended as the optimal WQT alternative, which imposes no penalties or land-use changes. Here, the overall benefits of sellers and buyers exceed 47% and 81%, respectively, in comparison with not attending any WLA scenario.

Highlights

Varamin aquifer quality is analyzed in 12 WLA scenarios with point and non-point sources.

Wastewater treatment and altering crop pattern can reduce pollutants in 10 years.

Multi-pollutant WQT is theoretically feasible and has economic benefits.

Four conditions are emphasized in order for the feasibility study of potential WQT.

A practical WLA with low benefits has privilege over a highly beneficial WLA without practicability