THREE DIMENSIONAL SIMULATION OF CONTAMINANT TRANSPORT OF INDUSTRIAL WASTE PRODUCED WATER AND RELATED ENVIRONMENTAL HAZARDS

Abstract

A three dimensional numerical flow and contaminant model (Proce .G-!HLModFl2f~:.tas CJf. fe •• ·~~·# been used to simulate groundwater flow of the underlying aquifet""'regTrfies and contaminant transport dispersion plumes of the Kahota Industrial Triangle and an urban settlement area adjacent to the Soan River, Islamabad-Pakistan. A systematic approach has been adopted to accomplish the task in two phases. First phase is related to data acquisition. Comprehensive field survey was carried out to collect required field specific data. In addition to this, required information about the hydrogeology of the area and about the parameters used in the study was obtained through literature survey and from various agencies. In the second phase data obtained during the initial phase was compiled in the modeling format. Initially, a groundwater three dimensional steady state flow model has been developed, calibrated to the known observed heads of 24 water wells, verified, and confirmed that convergence has actually arrived. Later, the non steady state simulations were carried out by assigning storage factor and pumping 54 water wells with constant discharge rates and variable recharge rate determined from the observed historical precipitation data so that observed drawdown matched with the simulated drawdown that appears to fall in close agreement with a difference of O.25m. As such, the developed groundwater flow model has facilitated to understand, evaluate, and to predict regional trends of groundwater and has been used to simulate Selenium contamination present in the groundwaters of the area. Chemical parameters related to selenium characteristics including horizontal and vertical transverse dispersivityllongitudinal dispersivity, effective molecular diffusion coefficient and bulk density of the porous medium of aquifers have been used in MT3D contaminant transport model. The contaminant transport model is again calibrated against the 32 values of observed selenium concentrations. The final calibration has been achieved with residual value of 3.88 x 10-05 Kg/m3 . Seven hypothetical observation wells are used to monitor the selenium concentrations over a long-term period of time. It is apparent from the results of simulation that the Selenium concentration is decreasing with time however it will take long time to come at below pollution level.