California's water supplies are derived from a variety of sources, including local and imported surface water, groundwater, desalinated seawater, and recycled water. Water resources are becoming limited due to population increases, droughts, and reductions in imported water allocations. Furthermore, global climate change may exacerbate the problem in the future. Water recycling for nonpotable and indirect potable applications has played an integral role in helping to meet the state's water demands. California's water needs will continue to increase in future years, and new sources of supply are needed to satisfy future water demands.
Planned 1PR via the augmentation of groundwater supplies by either surface spreading basins or direct injection has been practiced in California since 1962, and there are several such projects in the state. As indicated in Table 1, the number of 1PR projects has increased substantially in the last five years.
CDPH has published draft IPR regulations related to groundwater recharge [California Department of Public Health, 2008]. While the draft groundwater recharge regulations do not address direct potable reuse, several requirements in the draft regulations may be applicable to direct potable reuse as well, although it is likely that some requirements would be modified to be more restrictive.
For IPR via augmentation of water supply reservoirs, it is stated in the California Health and Safety Code (Section 116551) that CDPH shall not issue a permit to a public water system or amend a valid existing permit for the use of a reservoir as a source of supply that is directly augmented with recycled water unless CDPH performs an engineering evaluation of the proposed treatment technology and finds that the proposed technology will ensure that the recycled water meets all applicable primary and secondary drinking water standards and poses no significant threat to public health [State of California, 2009]. Although there currently are no existing planned IPR projects in California involving surface water augmentation and no draft regulations have been developed by CDPH to date, this type of potable reuse is currently being evaluated.
The potential of using recycled water for direct potable reuse is being raised in California in response to the need for new water supplies in water-scarce areas. Direct potable reuse would provide greater flexibility to augment potable water supplies without the need for underground or surface environmental buffers and could result in significant environmental benefits (e.g., reduced discharge of wastewater to the ocean or surface waters and reduced extractions of water from underground aquifers and surface waters). However, direct potable reuse raises a number of issues and requires a careful examination of treatment technology, regulatory requirements, health concerns, project management and operation, and public perception and acceptance. To date, no regulations or criteria have been developed for direct potable reuse anywhere in the U.S.
The purpose of this white paper is to identify specific issues associated with direct potable reuse that would need to be addressed by regulatory agencies (and utilities interested in pursuing direct potable reuse projects) in California if direct potable reuse is to be considered for implementation in the future. This white paper is particularly focused on identifying measures and information needed to ensure public health protection. It is not intended to identify or recommend specific regulatory requirements that may be imposed on direct potable reuse projects. While it is recognized that public acceptance is a significant concern that would have to be addressed, this white paper does not examine the issue of public acceptance. A separate white paper sponsored by WateReuse California is being prepared to address this issue.