Greywater treatment and reuse results from a 50-person trial

Abstract

The paper describes a seven year project to develop a greywater treatment plant for lavatory flushing. Site surveys and laboratory research was used to produce a design for a 50-person residential University hall. The final design included a balancing tank (13:1 peak to average capacity) screening (5 mm), a moving bed bioreactor and alternating deep bed double filtration (reticulated foam). The plant achieved a recycled water quality of 3 mg/l biochemical oxygen demand (BOD) (used as an indicator of odour potential and regrowth) a water clarity of 2 nephelometric turbidity units (NTU) and 2 mg/l suspended solids. Ultra violet (UV) disinfection was added to meet the UK guidelines of zero microbial indicator organisms. The demonstration trial lasted 5 years and users were unable to differentiate between the recycled water and mains water in the blind trial.

Keywords:

• water use and reclamation patterns
• submerged aerated biological filters
• greywater recycling
• cost benefit of package plant UV disinfection

Acknowledgements

The authors gratefully acknowledge the financial support given to the research by Titan tanks and Anglian and Yorkshire Water.