Evaluating impacts of recharging partially treated wastewater on groundwater aquifer in semi-arid region by integration of monitoring program and GIS technique.

The current study investigates the impact of recharging of partially treated wastewater through an infiltration basin on the groundwater aquifer quality parameters. A monitoring program supported by a geographic information analysis (GIS) tool was used to conduct this study. Groundwater samples from the entire surrounding boreholes located downstream the infiltration basin, in addition to samples from the recharged wastewater coming from the Beit Lahia wastewater treatment (BLWWTP), were monitored and analysed between 2011 and 2014. The analysis was then compared with the available historical data since 2008. Results revealed a groundwater replenishment with the groundwater level increased by 1.0-2.0 m during the study period. It also showed a slight improvement in the groundwater quality parameters, mainly a decrease in TDS, Cl- and NO3- levels by 5.5, 17.1 and 20%, respectively, resulting from the relatively better quality of the recharged wastewater. Nevertheless, the level of boron and ammonium in the groundwater wells showed a significant increase over time by 96 and 100%, respectively. Moreover, the infiltration rate was slowed down in time due to the relatively high level of total suspended solid (TSS) in the infiltrated wastewater.