Drinking water is typically sourced from groundwater or surface water supplies, but what with a burgeoning global population and climate change, the world is facing a growing water shortage and scientists are scrabbling for alternate drinking water sources.
One of the new methods of sourcing potable water currently being pursued is planned potable reuse – supplementing potable water supplies with treated wastewater.
Traditionally, treatment for reusable water has been reverse osmosis (RO) which, while effective, demands high energy usage and produces brine reject streams that need to be managed via disposal, volume reduction or further treatment.
The Pure Water San Diego (PWSD) programme in California is, a multiyear program to use proven water purification technology to produce a safe, sustainable, high-quality water supply for San Diego, which currently imports 80% of its water supply. The current project, run in conjunction with the WateReuse Research Foundation (WRRF), is a cost-effective investment for the city’s future water needs and will provide a reliable drinking water supply that is locally controlled and drought-proof.
The Upper San Gabriel Valley Municipal Water District (USGVMWD) is also involved in the project, evaluating alternative treatment trains for potable reuse including the ozone-enhanced biologically active filtration. The project is utilising Xylem’s Leopold Oxelia Ozone-Enhanced Biofiltration System, which combines the treatment synergy of ozone oxidation and biologically active filtration into a single process solution.
Another pilot study is currently being conducted by Trussell Technologies with support from USGVMWD and a consortium of project partners as part of a WRRF study tested the efficacy of several treatment trains for the direct potable reuse of wastewater effluent. In this study, significant water quality and disinfection benefits enabling compliance with public health criteria for chemical and microbiological constituents, was demonstrated. The primary role of ozone was the disinfection of viruses, Cryptosporidium and bacteria, as well as the oxidation of emerging contaminants.
These studies have found that ozone and bio filtration are safe; they also have the potential to significantly contribute to potable reuse treatment and provide an alternative for utilities that want to minimise power consumption and secondary brine management requirements.