Pilot project turns drain water into fresh
By Kate Campbell
Betty Hurley Lindeman, Panoche Drainage District treatment plant coordinator, works with researchers and engineers to help integrate new water treatment technology into a cohesive pilot project aimed at reclaiming agricultural drain water for reuse on crops.
Convex mirrors concentrate sunlight to evaporate drain water and separate salts and other minerals.
WaterFX chairman and founder Aaron Mandell, right, says the zero discharge desalination system being tested at Panoche Drainage District near Firebaugh has lower brine disposal costs and higher fresh-water yields than conventional seawater systems.
In the San Joaquin Valley, where water is increasingly precious, technologies are turning irrigation drain water into fresh water that can be reused on crops.
The Panoche Drainage District near Firebaugh is leading the way to a high-quality, reclaimed water source through operation of several promising pilot projects.
If the pilots prove successful, they will help the district clean up salts, selenium, boron and other minerals in tile-drain water coming from irrigated fields and reach its goal of zero agricultural water being discharged into the San Joaquin River by 2019, which is required by an agreement with federal agencies.
"We're in the process of determining if these approaches to treatment are cost-effective and sustainable," said Dennis Falaschi, the district's general manager, adding pilots will continue through the next several years to determine if they are suitable for "scaling up."
The drainage district, which receives subsurface drain water from about 100,000 agricultural acres, is working with WaterFX to demonstrate that solar-concentration desalination can be part of the solution to treat and recover drain water—turning it into water fresher than what's now delivered through the California Aqueduct for farms and cities.
In the 1950s, the federal Central Valley Project began delivering water to farmers in the valley's Grasslands Drainage Area, which includes part of the San Joaquin River Exchange Contractor's service area. The region extends roughly from the City of Mendota northward toward the City of Dos Palos, on the west side of the San Joaquin Valley.
Farmers in the area grow almonds, tomatoes, melons, garlic, asparagus, pistachios, alfalfa and more. Drainage water is collected through a complex tile system installed below irrigated fields and pumped to drainage canals. The district processes it in a number of ways, including filtering and membrane pretreatment.
The overall project, if pilot-testing proves successful, could produce as much as 5,000 acre-feet of fresh water a year. Treated water currently coming from the project is being used on a variety of crops grown on district land, including almonds, pistachios, alfalfa and Jose tall wheatgrass.
The solar-desal demonstration plant, set on about 60 acres of district-owned land, relies on 70 solar collectors to concentrate heat on clear piping to evaporate water, leaving heavy minerals behind. The result is distilled fresh water containing less than 5 parts per million of dissolved salts, which is potable quality, explained plant coordinator Betty Hurley Lindeman.
"Because the process relies on solar energy, and we store heat during the day in thermal storage units, we operate 24-hours a day," Lindeman said. "The plant requires very little commercial power and has very low air emissions."
Irrigation drain water in the San Joaquin Valley can contain salts ranging from 15,000 to over 40,000 parts per million, with salt levels in some areas higher than seawater.
As water supplies become more unreliable, Water FX project engineers said treating waste water using solar desalination technology can help in the development of new freshwater sources throughout the Western U.S.
"We're encouraged by results so far and look forward to scaling up to handle larger water volumes," Falaschi said. "Farmers in this area, working with private technology firms and federal agencies, have invested in this technology with the intention solving drainage issues across the west side."
WaterFX Chairman and founder Aaron Mandell said his company's desalination system differs from traditional seawater desalination, which is performed by a power-intensive reverse-osmosis process that forces salt and other solids through a membrane at high pressure.
The company's system being tested by Panoche Drainage District reclaims water using a "concentrated solar still," a new device with advanced solar absorption technology. The equipment uses minimal electricity and fuel to produce more than 200 acre-feet of freshwater per acre of solar collection area.
Although the concave solar-collection mirrors rising from the surrounding agricultural fields near Firebaugh is the plant's most visually striking feature, the operation includes a solar thermal collector, an absorption heat pump, a multi-stage distillation system and a thermal storage unit to store solar heat and support 24-hour-a-day operation.
The system is modular and moveable, creating a compact footprint and the ability to easily scale the system up or down, unlike heavy, permanent installations, which engineers said adds flexibility for operations like farming.
The system can recover clean water from drainage systems, wastewater, processing water and seawater. The concentrated-solar treatment system gathers extracted metals and salts and makes them available for other commercial uses.
"Panoche is a very forward-thinking water district," Mendall said. "This project represents a dramatic shift in how we use and reuse water in water-scarce regions of California. But, our long-term goal is to chart a new course towards water independence and reduce reliance on imported water."
In its second year of field testing, Falaschi said the WaterFX system's performance is "exciting, intriguing and interesting because it promises to provide solutions for managing and reclaiming problematic wastewater streams."
Other partners include the University of California, Los Angeles and Merced, as well as the U.S. Bureau of Reclamation and local irrigation districts.
"We're working with credible partners, that means scientists and engineers coming together to help resolve long-term water problems," Falaschi said. "This isn't about buying and operating equipment. It's about refining the science and technology that leads to long-term solutions."
(Kate Campbell is an assistant editor of Ag Alert. She may be contacted at email@example.com)
Permission for use is granted, however, credit must be made to the California Farm Bureau Federation when reprinting this item.