|M.Sc Student||Penn Roni|
|Subject||Quantification of the Influence of On-Site Urban Greywater|
Reuse on Sewer Systems
|Department||Department of Civil and Environmental Engineering||Supervisor||Professor Eran Friedler|
|Full Thesis text|
On-site greywater reuse (GWR), in the urban sector, reduces urban demand of fresh water resources. In recent years research on GWR has focused mainly on the single-house scale, paying much attention to different treatment systems and their performances. However the effects of GWR practice on domestic wastewater quantity and quality, and the consequent effects on urban wastewater conveyance systems were generally overlooked. This study discusses and quantifies these effects.
The first step towards quantifying the influence of GWR on the municipal wastewater section of the urban water cycle is quantification of the influences of GWR on domestic wastewater quality and quantity. For this three scenarios were studied referring to the sub-daily diurnal flow patterns, rather than to the average daily flows. The reason for that is twofold, the first being the fact that the sewer system operates under unsteady flow conditions and the second being the fact that the sub-daily instantaneous flows are responsible for transport (or precipitation) of solids in sewers.
Then the effects of GWR on the municipal sewer system, positive and negative, were studied by modeling a representative urban sewer system. Different GWR scenarios were modeled and analyzed using the SIMBA simulation system.
The results show that, as expected, as GWR increases, the flow, velocity and proportional depth decrease. Nevertheless, the reduction is not evenly distributed but mainly occurs during the morning and evening peaks flow periods. Further, it is indicated that as a result of the GWR, blockages rate of sewers is not expected to increase. The results support the possibility to construct new sewer systems with smaller pipe diameters. The analysis shows that as the penetration of GWR system increases, concentrations of pollutants increase too, but at a rate lower than proportional reduction of sewage flow. The results, further show that the spatial distribution of the houses reusing GW does not have much effect on the parameters examined. Having more effect on upstream nodes of the sewer system than on downstream ones.