نوع مقاله : یادداشت فنی
نویسندگان
گروه مهندسی عمران و محیط زیست - دانشگاه یاسوج
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Currently, in many parts of the world and even in Iran, the high concentration of nitrate in drinking water has shown to be a serious problem, mainly caused by introduce of agricultural wastewater and home and industrial sewage runoffs to the water resources, and especially in the groundwater. The ultimate goal of the present study is to design and investigate the bio-geo-filters in order to eliminate of nitrate from the runoffs. In this research, alternate layers of non-woven geotextile filters and sawdust with granular soil (PRB) have been used for reduction and removal of pollution. These layers are of paramount importance in terms of their permissibility and absorption capability and are thus used for the reduction of opacity and amount of absorbed pollutants. For
selection of materials some points have been considered, which include the material capability for pollution elimination, their accessibility, and maximal cost-effectiveness. After conduction of permissibility tests and investigation of the results, the ratio of the weight mixture of the applied materials in PRB has been considered as 25\% sand, 20\% zeolite, 20\% iron borings, and 10\% poplar wood sawdust. For determination of the fracture curvature of the filter with artificial backwater injection with preliminary concentration of 100 milligrams per liter of nitrate, the nitrate characterization and break through happens after 25 minutes from the start of test. PRB break through curve can be classified with engineering approximation of pseudo-Gaussian. Break through
curve is considered to be a normal curve and the value of longitudinal diffusion coefficient is \ $1\times10^{-7}m^{2}/s$.
After the growth of biologic mass in its environment, the filter was able to decrease the amount of nitrate up to 99\% after the elapse of 9 days. In the modeling of the prepared filter, the software SEEP/W has calculated the discharge value at each transverse section to be \ $9.0027\times10^{-5}m^{3}/s$.The software CTRAN/W administers a rational, feasible and precise assessment of the moving trend of the pollutant in the filter. The break through curve obtained from the software CTRAN/W cannot afford a proper assessment of the total time of the break through curve formation in the clinical ambience. However, numerical model calculates the nitrate fracture with a very good approximation which is close to laboratory model. The shape of the obtained break through curve from both numerical and clinical models is both rational and feasible with respect to the statistical and physical considerations.
کلیدواژهها [English]
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