Initial efforts by Cambria’s services district to limit the amount of nitrates in its wastewater effluent appear to have accomplished their goal, at least in the short term, according to district officials. But they also say the temporary solution is triggering another problem.
The district reduced the nitrate levels by cutting the amount of oxygen injected into the sewage-treatment process. However, having less oxygen in the effluent means the district technically is violating its water-
discharge regulations, which require a certain level of dissolved oxygen in the effluent the district sends to its percolation ponds on San Simeon Creek Road.
That delicate balance affects, in turn, the operation of the district’s percolation ponds, emergency water supply (EWS) project, and a well that feeds it. Those have their own sets of rules about nitrate levels and other elements, levels exceeded during plant operation in mid-April.
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The district shut down the plant and is trying to iron out the issues in the short term and, if needed, a more expensive, complex long term.
The Central Coast Regional Water Quality Control Board sets those oxygen requirements and the ones controlling the nitrate and other levels.
In an April 30 email to the water board and water resources control engineer Jon Rokke, district General Manager Jerry Gruber explained the nitrate-reduction results and the dual-permit conundrum in which the district finds itself.
Gruber reported that nitrate levels in the wastewater-treatment plant’s effluent in March averaged 48.1 Mg/L (milligrams per liter). After plant staff made “a few operational adjustments” and essentially created an anoxic or oxygen-free zone within the treatment plant’s aeration basin, those levels dropped considerably, he wrote.
Levels on April 28 were 7.7 Mg/L, Gruber reported to Rokke.
Gruber wrote that with the district’s existing permit “and the dissolved oxygen requirements (2.0 Mg/L), we cannot denitrify.” He requested that the water board eliminate or “at least significantly reduce” the required dissolved oxygen levels.
District spokesman Tom Gray explained that one possible argument for
allowing the lower oxygen levels to prevail is that the requirements usually apply to effluent being discharged directly into a body of water, such as the ocean or a lake. The district’s effluent flows into percolation ponds on San Simeon Creek Road.
The EWS plant is on the same property.
The EWS plant is designed to operate during declared droughts and extremely dry seasons, when more water is being drawn out of the San Simeon Creek aquifer than is flowing into it from underflow in the creek watershed.
Cambria is under a water-supply emergency declaration, which has been in place since 2001, and a drought-emergency declaration since January 2014. The state and county also are under drought-emergency declarations.
District officials maintained the community could have run out of water during last year’s drought, but ratepayers did a remarkable job of conserving water, reducing their already water-conscious consumption level by nearly 40 percent in 2014.
The project, a water-reclamation plant, filters and treats a brackish blend of fresh and salt water and treated effluent from the district’s wastewater treatment plant. After the water goes through the EWS process, the highly treated liquid is injected back into the ground to recharge the basin and help replenish the aquifer and district source wells.
The project underwent its three-month test run earlier this year, which ended in mid-April.