Ph.D Thesis

Ph.D StudentPenn Roni
SubjectImpacts of On-Site Greywater Reuse on Urban Wastewater
Systems - an Integrated Simulation Approach
DepartmentDepartment of Civil and Environmental Engineering
Supervisor PROF. Eran Friedler
Full Thesis textFull thesis text - English Version


Following ever increasing shortage of freshwater around the world, efficient tools for the reduction of water consumption are being developed, of these, onsite greywater reuse (GWR) is considered to be a highly efficient one. Reducing domestic water demand by GWR for toilet flushing and garden irrigation has the potential to contribute to alleviating the stress on precious water resources. Studies on GWR to date focused mainly on the household scale, the performance of greywater (GW) treatment systems and possible environmental and health effects of GWR. On the other hand, hardly any attention has been given to the effects of GWR on domestic wastewater quantity and quality, on urban sewer systems and wastewater treatment plants (WWTPs) performance. Therefore, this research aimed at substantiating conclusions on the extent of the effects that on-site GWR systems, if implemented on a large scale, may have on the urban wastewater system. This will better allow to set up and to promote GWR schemes, which are expected to provide significant water saving and increase the sustainability of urban water use.

The research is combining experimental field work with development of an integrated stochastic simulation system for GWR in urban areas. Several simulation models were developed and integrated into one model. Adaptation and combining of earlier modeling approaches into a current state of the art modeling system was included. The simulation models include stochastic generator of domestic wastewater streams and municipal sewer network model which includes hydrodynamic simulation, gross solids and pollutant transport, and simulation of processes occurring within sewers. The simulation system that served as a basis for the research was SIMBA (originally developed by ifak, Magdeburg). The integrated model is validated by field experiments in real sewers. Fieldwork included design and manufacturing of artificial gross solids and developing a tracking methodology of their transport in sewers. In the experiments the movement of gross solids along the sewer reaches was traced as well as flow characteristics in the sewer segments (discharge, velocity and depth of flow). Further, the developed model was used for assessing the impacts of GWR for various future scenarios. 

An impress of this research is a stochastic, complex modeling of the entire sewer system, considering both flow quantity and quality, under evolving future alternatives of operational conditions. Currently this information is not available in the scientific and engineering literature. The integrated model can potentially serve as a tool for analysing any new sewer system or existing sewer systems subject to changes in flows, as with result of GWR just as presented in this thesis or other water saving measures. The research results are further expected to assist in long term planning of introducing on-site GW treatment systems to the urban sector and of designing and managing the urban wastewater system that is influenced by these systems or any other measure that will alter domestic wastewater flows. This will better allow to set up and to promote on-site GWR or any other measures and will increase water system efficiency and sustainability.