modeling of fecal coliform bacteria in surface drip irrigationin clay loam soil

water for agriculture is one of the most important factors in arid and semi-arid areas and municipal wastewater treatment is an important resource for this purpose. therefore, potential of transfer contaminations is a serious problem regarding use of treated wastewater for agriculture. due to the risk of transfer contaminations through the use of wastewater, the study of transfer microbes in soil in recent decades has been of interest to researchers. in the present study, the transfer of bacteria fecal coliform was investigated in a lysimeter and the hydrus-1d model was used to simulate water flow and the fecal coliform in the soil. for calibration of the model and estimating the model input parameters, soil hydraulic and transport parameters, were inversely estimated. results represented that the hydrus-1d with reasonably accurately simulated the outlet flow. to simulate the transfer of the bacteria in the soil, one site sorption model, two kinetic sites model (particle transport using attachment/detachment) and one kinetic site model were used. in the simulation of bacterial transfer, one site sorption model was selected as the proper model for this study. one site sorption model estimated solid-phase growth coefficient ( ) about sextuple more than liquid-phase. it showed that deposited cells had a higher division rate compared with the cell in liquid-phase. the calibrated model was used for surveying the effect various irrigation intervals and irrigation times on bacterial transfer. the results showed that by increasing irrigation times, more bacteria leached out from the soil. also by increasing irrigation intervals, more bacteria observed in the soil profile, due to favorable environmental conditions and food for the bacteria growth. according to the results, the best interval and irrigation times were one day and four hours, respectively.