Simulation method for stochastic generation of domestic wastewater discharges and the effect of greywater reuse on gross solid transport

Abstract

Together with significant water saving, due to lower wastewater discharges, greywater reuse (GWR) may also increase the impacts of faecal matter and other gross solids (GS) on sewer systems (sedimentation, blocking). Modelling and assessments of these effects require detailed descriptions of individual domestic wastewater streams. A novel stochastic methodology to generate such streams was developed and validated. The generator was developed while considering dependencies between in-house water-use events, and their varying degree of elasticity. These generated streams served as input to a sewer model, where scenarios of GWR were simulated and their effects on GS transport were examined. Extensive GWR decreases GS movement mostly in upstream links. Nevertheless, transient high flows, characterising these links, may move stationary GS and prevent blockages. The developed generator can be adopted to other sewer-related studies. Intelligent implementation of the results can assist in introducing GWR, or other water saving measures to the urban sector.

Keywords:

• Diurnal patterns
• greywater reuse
• gross solids
• sewers
• stochastic generator

Acknowledgements

The authors wish to thank Netanya Water Corporation for providing data on the sewer system and for permitting and supporting the in-sewer flow measurements. Flow data were obtained from R.Z.E.E Ltd. (Roberto Zimmerman Environmental Engineering).