Numerical Modeling of the Effects of Municipal Wastewater Treatment Plant Construction on Quantity and Quality of Groundwater Resources in Ardakan City

Ardakan Wastewater Treatment Plant with biological sludge treatment system of activated sludge and total nominal capacity of 23328 cubic meters per day and an area of 14 hectares, is responsible for wastewater treatment in the entire city of Ardakan, which can have significant effects on the environment and water resources. The purpose of this study is to investigate the effects of constructing a complete municipal wastewater collection network and implementing the complete phase of the treatment plant on quantity and quality groundwater resources in Ardakan using the MODFLOW numerical model. The conceptual model prepared using observatory wells, aqueducts, aqueducts, absorption wells, hydraulic conductivity, aquifer boundary layers and surface feeding. All layers were defined in different formats including polygon, linear and raster and point in ArcGIS and then inserted to GMS. The modeling results showed that the use of treated effluents to improve and compensate for the drop in water levels in groundwater resources in the Yazd-Ardakan plain can be very effective and prevent at least 23% reduction in groundwater levels. The RMSE values obtained from the model calibration in steady and unstable states were 0.41 and 0.42, respectively. The results showed that in the defined scenarios, in exchange for removing the municipal wastewater collection network from the hydrological cycle in general, we will encounter the largest drop in water level, which is equivalent to 35%, which from the management perspective for the underground aquifer in the direction Reducing the trend of water level drop in this scenario can be considered as the most inappropriate scenario. Also, from the point of view, the effect of the sewerage network on the water level, there is the least negative effect on the aquifer.