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Seasonal Storage of Reclaimed Water

Project: 09-05
Type: White Paper
Year Released: 2012

Program: Principal
Funding Partners: Bureau of Reclamation, Water Research Foundation
Total Investment: $233,733.84 (Cash: $80,000, In-Kind: $143,733.84)

Principal Investigators: Alan E. Rimer, Ph.D., Black & Veatch and Gerard Miller, Ph.D., Black & Veatch


Previous desktop studies have documented water quality issues and water quality and treatment cost trade-offs associated with storage options for reclaimed water.

Goals and Objectives

The project developed a set of case studies on seasonal storage of reclaimed water in surface waters or open storage facilities. This study focuses on the issues associated with utilities’ efforts in maintaining reclaimed water quality during the storage phase. Where applicable, the water quality of stored flows discharged to surface waters and other reuse applications was also addressed.

Research Approach

To gain insight into the common practices of operating seasonal storage reservoirs for reclaimed water, the study approach included an initial literature review. With the exception of the Irvine Ranch Water District and other California locations, the results of the literature review offered few examples of seasonal storage reservoirs in the United States. Most of the literature currently available is from studies on seasonal storage reservoirs in Europe and the Middle East.

Researchers developed an initial list of utilities to be considered for the case study development on seasonal storage reservoirs. Contact with utilities was made by conducting screening telephone interviews to confirm storage capacity and seasonal operations and to obtain utility internal approvals for study participation. Twelve utilities across the United States and in two foreign locations participated in the WateReuse case studies. For each utility, researchers conducted case study interviews and site tours of the open storage facilities. The case studies were developed based solely on the information provided by participating utilities.

Findings and Conclusions

By researching how utilities operate open storage facilities and identifying the issues associated with open storage of reclaimed water, this study provides a present-day compilation of “lessons learned” and information on best practices. The study benefits utilities worldwide that reclaim water and use surface storage to manage seasonal demand.

Study results are presented in this resource guide. Chapter 4 summarizes the individual case studies, and Chapter 5 provides a quick reference matrix of the case study findings and general conclusions

Valuable information about strategies employed by the various utilities to mitigate some of the identified operating issues provide useful “lessons learned” for other utilities as they evaluate alternatives for reclaimed water storage. The following are some of the identified issues and the solutions applied.

  • Reservoir dead spots—mixing systems can be added to minimize such dead spots in the reservoirs.
  • Algal control:
    • Providing an additional level of filtration prior to discharge to the reservoir,
    • Adding sodium hypochlorite to the reservoir, and
    • Adding copper sulfate to the reservoir.
  • Operational control:
    • Establishing a clear operational plan for storage and drawdown of the reclaimed water, which has proven to be a significant benefit to many of the utilities in avoiding problems.
    • Timing storage and drawdown to minimize reservoir odors and nuisance conditions for customers.
    • Ensuring the proper mixing of the reservoir to avoid dead spots.
  • Odor control—odor complaints can be mitigated by increased aeration of the reservoirs, particularly when the reservoirs are turning over:
    • Fish clogging of intake screens—proper initial design of the intake screen can prevent such problems and should be carefully considered for each reservoir.
  • Weed control:
    • Applying appropriate chemicals on a scheduled basis,
    • Limiting drawdown in the reservoir to a set elevation above bottom, and
    • Aerating the reservoir.

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