THE EFFECT OF SEPTIC TA KS EFFLUE T O GROU D WATER QUALITY I KHARTOUM CITY

Abstract

Groundwater in Sudan is the main water supply source for drinking water and domestic use for more than 80% of the human population and is found under about 50% of the country's area. Khartoum state the capital of Sudan is not covered with sewerage system except for a small area at Khartoum centre and industrial areas in Khartoum North covering only 25% of the area. The main sewage treatment system in the other areas of the state is septic tanks and disposal wells. This study seeks to estimate the extent of ground water contamination due to septic tanks in Khartoum city, it presents a case study in which a contaminant transport model, (MT3D) is used to so predict the level of contamination of groundwater due to septic tank effluent (Ammonia was considered to be the major output contaminant from septic tanks). The model results show that an increase in the ammonia concentration was projected in the vertical directions through the ground layers and horizontal directions to the point source areas. Considering a threshold value of ammonia concentration of (1.5 ppm) according to the Sudanese Drinking Water Standards, the study shows that the contamination front emanating from the use of septic tanks travels horizontally at a rate of (500 m/year) reaching to the depths of (75 m) below the water table after 60 years from the beginning of simulation period (time zero).