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. Consequently, California water planners are considering multiple alternate water supply options including:
- Brackish water treatment
- Rainwater harvesting (storm water capture)
- Recycled water
Of these, water recycling is the only option that is applicable across the entire state and which 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 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. Typically a network of distribution pipelines and pump stations is needed to connect existing municipal water reclamation plants to potential recycled water customers. Constructing these distribution systems can be expensive ($2-4 million per mile), especially in heavily developed areas such as Southern California. As a result, excess recycled water supply generated by large centralized plants cannot always be used cost-effectively. The Alliance’s 2008 report on recycled water shows that enough existing recycled water supply to meet all of Southern California’s projected increase in water use through 2030 is currently being released to streams and the ocean without benefit.
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. Additionally, water supply and conveyance accounts for the majority of energy use by the state’s water infrastructure - imported water is among the most energy intensive (especially in Southern California). On-site water generation has the potential to not only conserve water also save embedded energy in water.
To better understand the opportunity for on-site water generation, the Alliance has released a new study entitled On-Site Water Generation: An Analysis of Options and Case Study . The study documents the characteristics of on-site water generation systems and also conducts a detailed cost benefit analysis for a representative case study on the City of Huntington Beach, California.Specifically the studyexplores:
- 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 relies on a consistent supply of wastewater and thus can provide more water than rainwater harvesting in Southern California
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.