California water supplies are stressed as a result of decreasing supply and increasing demand. While conservation and efficiency are the most cost effective solutions, they may not completely solve the problem. Water recycling is an additional solution that is applicable across the entire state and can produce a relatively consistent resource regardless of the season or weather. Wherever there is a wastewater treatment plant there is an opportunity to generate a local, sustainable supply of recycled water. Indeed, generating recycled water is not a challenge, distributing it is. A major barrier to implementing a successful regional recycled water system is the cost of distribution pipelines.
Recycled water can be implemented on a smaller scale; generating water in the same location as its demand eliminates the need for expensive distribution systems. Similarly, rainwater harvesting can also provide a local, low-cost supply of water. On-site water generation (both recycling and rainwater harvesting) has the potential to not only conserve water but save energy used by supply and distribution infrastructure.
In December 2012, the Alliance completed a study entitled On-Site Water Generation: An Analysis of Options and Case Study that documents the characteristics of the on-site water generation systems and also conducts a detailed cost benefit analysis for a representative case study on the City of Huntington Beach. The study sought to understand:
- Types of technologies available to provide on-site water generation.
- Costs and benefit analysis of the on-site water generation options.
- Primary market barriers to technology adoption.
Key study conclusions include:
- On-site recycled water systems can supply water at lower energy intensity than imported water and desalination in Southern California.
- On-site recycled water systems are most cost-effective in larger capacities.
- On-site water recycling can provide more water than rainwater harvesting.
- Rainwater harvesting systems are more cost effective in areas with a good balance of supply (rain) and demand throughout the year.
The study also discusses a number of recommendations for California policy-makers to stimulate the production and use of on-site water generation. Download the full report for more details.