San Juan picks system to treat high nitrate levels in water

A farm worker moves a sprinkler in a field in San Juan Bautista.

San Juan Bautista officials picked a treatment option for high nitrate levels in the local water supply that involves removing the substance before the waste is hauled away and dumped in the ocean.
San Juan council members Tuesday unanimously supported the installation of an ion exchange system over four other choices, including reverse osmosis and tapping into the school district’s well supply, as city officials prepare a report due to the state by the end of June.
The ion exchange system would cost $726,000 in up-front capital and another $110,000 annually for operations of the plant with capacity to handle 400 gallons per minute of demand, comfortably above the city’s normal levels of about 300 gallons per minute. Council members gave preliminary approval so that City Manager Roger Grimsley can take the strategy to the California Department of Public Health to get its blessing.
“My feeling is, we need to go with some sort of long-term solution instead of short term,” said Councilman Rick Edge, arguing in support of an ion exchange system before the approval.
In early May, the quaint mission city off Highway 156 announced that nitrate levels in one of its three wells, No. 2, exceeded the state’s safe standards. Nitrates can come from natural, industrial or agricultural sources such as septic systems, stormwater run-off or fertilizers. They can pose a serious health risk to young children, according to the city in its May alert released to residents.
Water samples from April and May showed nitrate levels of 29 to 48 milligrams per liter, above the maximum contaminant level of 45 milligrams per liter.
San Juan council members Tuesday heard a breakdown of the options to treat nitrate levels before they sided with the ion exchange system, while they also discussed the possibility of pursuing another well option to the north of the city. Officials chose the ion system among the proposals ranging in cost from about $400,000 to $1.5 million.
Most of the $110,000 in operational costs would come from disposing the wastewater after it goes through membranes. A speaker for the company making the ion exchange systems told council members the city would have to transport the wastewater, likely by truck, for dumping into the ocean.
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What is an ion exchange system?
“Ion exchange (IX) processes are reversible chemical reactions for removing dissolved ions from solution and replacing them with other similarly charged ions. In water treatment, it is primarily used for softening where calcium and magnesium ions are removed from water; however, it is being used more frequently for the removal of other dissolved ionic species.”
Source: Environmental Protection Agency

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