AWWA WQTC62612

The Baldy Mesa Water District serves water to approximately 15,000 people inCalifornia's High Desert near Victorville. The District currently relies on groundwaterpumped from nine wells. The measured arsenic concentrations in the wells have rangedfrom 5 to 20 parts per billion (ppb), and all of the wells have experienced Asconcentrations higher than the new MCL of 10 ppb. In addition to the water qualitychallenge, the groundwater basin is in a state of overdraft, and a court-approvedadjudication limits the allowable pumping of groundwater by users in the basin. Tofurther stress water supplies, residential development is occurring at an unprecedentedrate in the District's service area.The District embarked on a water supply plan to evaluate their options in the face of thesechallenges. The options included groundwater treatment, blending of treated and rawgroundwater, and the introduction of a new surface water supply from the State WaterProject. As the District continues to grow, a surface water supply will be more feasible toaugment, or even to replace the District's water supply, although this new water sourcebrings its own water quality challenges, including taste and odor and disinfection byproducts.For groundwater arsenic treatment, the District has evaluated various treatment options(including IX, GFH, and coagulation assisted filtration) and treatment facilityconfigurations, including separate well-head treatment, semi-centralized treatment, andcentralized treatment. The selection of SWP treatment process is hinged on Taste & Odorand DBP control. The technologies evaluated include ozonation followed by biologicallyactive filters, ballasted sedimentation (with PAC) followed by media filtration (withoptional GAC cap), and membranes followed by UV/peroxide oxidation.How to combine two distinctively different water sources and provide the optimaltreatment for regulatory compliance as well as for consumer satisfaction is the ultimatechallenge to the District. The District has adopted the concept of a Proactive WaterQuality Management Plan (PWQMP) to ensure that the District's water supply will be infull compliance with both short-term and long-term regulations. The PWQMP takes intoaccount the considerations of SDWA compliance (such as DBPs, Arsenic, Lead &Copper Rule), simultaneous compliance (the impact of various treatment technologiesand various blending ratios between two water sources), aesthetic water quality assurance(such as T&O), and potential future regulations.The water supply plan is being finalized and presented to the District's Board ofDirectors for approval. It lays out the most cost-effective path for the District to meetincreasing demands and more stringent regulations in a water-scarce environment.This paper will present the specific PWQMP used in this project. The evaluations ofvarious treatment technologies and the associated cost for each treatment strategy forboth water sources will also be presented. Includes abstract only.

Product Details

Edition:

Vol. - No.

Published:

11/01/2005

Number of Pages:

1

File Size:

1 file , 43 KB