The impact of residential septic tanks on soil water infiltration and groundwater contamination in Duhok city

الملخص

This study was conducted to assess the impact of septic water on soil water infiltration in Duhok city potentially contaminating regional groundwater through designing a large-scaled laboratory physical model of vertical flow direction packed homogenously with silt-Clay soil. The designed model was supplied with newly collected septic water. With steady-state flow condition, the model was run, water samples were collected and analyzed weekly. Various parameters and constituents that may influence soil structure and water infiltration were examined including : Electrical conductivity, sodium, calcium, magnesium, carbonate, bicarbonate, residual sodium carbonate (RSC), pHc and adjusted sodium absorption ratio (adj. SAR). For assessing groundwater quality, bacteriological analysis were conducted. Analytical results were used to estimate the examined parameters and predict their future trends. Results revealed that electrical conductivity (EC) was accumulating until it reaches the carrying capacity. Sever hazard of (RSC) was detected within 25 meter depth. Average pHc was 6.74 indicating the tendency of lime (CaCO3) to precipitate from applied septic water. adj. SAR for port A and port B were 11.1 and 8.65 respectively which, caused severe soil deterioration, but on the other hand helped in decreasing the rate of contaminants transport for treatment within the soil before reaching the groundwater. Results of bacteriological analysis indicated that groundwater shallower than 31 meter was contaminated by fecal and total coliform bacteria. This study helped local authorities in establishing precaution strategies of groundwater management to protect public health.