Multi-Pollutant Water Quality Trading: An Approach for Groundwater Quality Management in Varamin Plain, Iran

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 a regionally incentive-based strategy for self monitoring and groundwater quality improvement. This study evaluates the effectiveness of 12 waste load allocation (WLA) scenarios on groundwater nitrate and chloride abatement, simultaneously using MODFLOW and MT3D. The theoretical efficiencies of multi-pollutant WQT are also testified out of these WLA policies by considering 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 emission sources were considered in WQT. At first, an allowable groundwater quality limit (AQL) 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 3.3–15.3% while chloride abatement ranges between 4.5–23.6%. However, 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 prioritized regarding their viability and marginal costs. According to these conditions, trading discharge permits between WWTPs with 25% nitrate removal (sellers) and current farmers (buyers) is recommended as the optimal WQT alternative which imposes no penalties or land-use changes. Here, the overall benefits of sellers and buyers exceed 42% and 85%, respectively in comparison with not attending at any WLA scenario.