The Loma Prietan - November/December 2009

Recycled greywater for irrigation is coming to the San Mateo coast. Here, George Long, John Wade, and John Malard monitor the equipment at the Sewer Authority Mid-Coastside Plant. Photo: Tony Pullin, SAM Technical Services Supervisor

Recycled water prepares to debut on the San Mateo coastline as the Sewer Authority Mid- Coastside (SAM) wastewater treatment plant in Half Moon Bay starts a pilot project. Producing recycled water for the San Mateo County Coastside has been long in the making, with discussions going on for over a decade. A preliminary study was done as long ago as 2002.

SAM can potentially produce recycled water to serve irrigation customers' needs in its service area, stretching from Half Moon Bay to Montara, Moss Beach, and El Granada and looping out to parts of unincorporated San Mateo County. The area currently consumes over 1.2 million gallons per day of potable water for irrigation, including water for farms, nurseries, and families. The majority is purchased from the Coastside County Water District; other supplies are drawn from wells and creeks in the region.

The scope and cost of a complete Coastside recycled water project have been daunting. In an effort to get started, SAM Directors proposed a pilot study to verify the feasibility of producing water that complies with California's Title 22 laws concerning recycled water. SAM had a willing buyer for the recycled water: The Ocean Colony Partner Golf Course (OCP). Producing water for OCP meets the following goals:

1) Proving the viability of recycled water in real-life situations.

2) Shutting down a group of wells near Pilarcitos Creek as part of a major creek and lagoon restoration project.

3) Reducing discharges to the ocean.

Several technologies were studied, including sand filtration with chlorination, microfiltration with UV disinfection, and reverse osmosis. A modular low-pressure microfiltration system, provided by a joint venture of Dow Water and Process Solutions, Applied Membranes, and Clean Filtration Technologies, was chosen for the initial tests. This unit combined newer technology, reasonable costs, and modular expansion capability. A small unit is undergoing a three-month trial of the technology. After the trial, a unit that can produce 600,000 gallons/day for the entire golf course will be chosen. The eventual goal? Expand up to 1.65 million gallons a day to treat the total average dry weather flow of the plant and eliminate all discharges into the ocean. What a challenge!

SAM began producing water for tests in mid- September. Duties during the pilot will be:

1) SAM's responsibility for pilot plant operation, including treatment, all water quality sampling, day-to-day operation, and maintenance.

2) The Coastside County Water District's responsibility for transporting recycled water from the pilot plant to Ocean Colony Partner.

3) OCP's responsibility for the application of the recycled water to a specified small golf course area.

Ric Lohman is current President of the Granada Sanitary District and co-author of the Pilot Recycled Water Plan.