טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentMuklada Hussein
SubjectOn-site Rainwater Harvesting as an Alternative Water Source
for Urban Areas
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Professor Eran Friedler
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

Rainwater harvesting is an ancient method which has been proven as an alternative source of water. This research work studied two aspect of on-site rainwater harvesting: namely the storage needs and quality of collected rainwater. A stochastic model was developed, employing the Monte-Carlo method, for the quantification of storage capacity needed to exploit rainwater for toilet flushing and washing machine use. This was calculated, as a function of rainfall, roof area, number of residents of the building, specific water use and efficiency required from the system. Rainwater utilization efficiency and proportion of domestic water used supplied by the stored rainwater, were also derived as a function of the above factors and the size of the storage tank. In the second part of the research three roofs of different types (concrete, metal and roof tiles) were constructed. Runoff generated from each roof was collected in a controlled manner. Over 50 rain events were sampled during two rainy seasons in the Technion (Haifa, Israel). For every rain event, rain thickness and the amount of runoff generated on each of the roofs was recorded. A sample for laboratory analysis was taken as well. For every roof, rain-runoff ratio equations were derived. In the laboratory, each sample was scanned for the presence of metals, chemical and physical characterization and fecal coliforms concentration. Most parameters examined, stood in Israeli drinking water regulations. Further on, the effects of environmental factors (rain thickness, length of dry period between consecutive rain events, the date from the beginning of season and roof type) and air pollution parameters (ozone, SO2, NO2, NO, small particles, large particles, wind speed and direction) on water quality variables tested in the laboratory were examined. Statistical analysis shows that there is a significant effect of roof type on runoff pollutant concentrations. A significant effect of different parameters of air pollution on the quality of runoff water from roofs was found. Rain thickness affected only four out of twenty-three variables. In contrast the length of dry period between consecutive rain events was found to be a very important factor affecting the runoff quality. Finally, a significant effect of various factors on FC values was found.  Among them, also wind speed and direction which can indicate a specific pollution source transporting bacteria by wind over the large particles from a specific source to the research roofs.