A treatment pond at the Community Services District wastewater treatment plant is believed to be the source of odors that have prompted recent complaints from South residents, CSD General Manager Ed Crouse said Tuesday.
The plant is located across Highway 16 from Murieta South and the treatment pond that's closest to the highway is the first step in the treatment of the community's raw sewage.
"That's where all the raw sewage goes in and that's where all or most of the biological activity takes place," Crouse said. The biological activity consists of "natural bacteria-eating organisms" that consume nutrients in the sewage. Mechanical aeration in the ponds contributes to the process.
Biological treatment is about 90 percent complete by the time the wastewater goes through the reclamation process to produce recycled water, highly treated, chlorinated water used to irrigate the golf courses.
During the initial biological treatment process, odors are "not totally out of the norm, but it is something we are very concerned about," Crouse said, adding, "It's never been so bad that we've had residents complain."
The complaints haven't come directly to the CSD, Crouse said. Some complaints have been "anecdotal," he said, one has appeared as an e-mail on RanchoMurieta.com, and "a couple" were reported to government agencies that then contacted the district.
"We're concerned that they're not calling us," Crouse said. "We'd like to be informed of when and where they experience the odors so we can track the progress of anything we do to reduce it, given the time of day, the location, the prevailing winds, and build a data base ...
"We do have a requirement that says the plant should be free of odors. But, again, it's part of a natural process. Sometimes odors are beyond what is acceptable. Right now those odors are causing some of the residents concern. We just want the residents to know we are aware of it (and) taking steps to mitigate it. It's not an automatic on/off type of activity because it's a biological process."
Crouse said warmer daytime temperatures increase the biological activity that breaks down the raw sewage and prevailing winds carry the odor across the highway to settle in lower-lying areas. In the absence of wind, the odors stay at the plant, which is located next to the CSD Building. Cooler night temperatures also keep odor levels down.
To deal with the odor problem, pond levels are being lowered and chlorine is being added the the ponds, Crouse said.
Other short-term fixes that are being considered include adding aromatics to mask odors, fogging the pond with reclaimed water to produce a mist that attaches to the odor and contains it, and removing sludge or "floatables" that appear on the surface of the ponds.
"We're making changes and we're pursuing things on a daily basis," Crouse said.
Long-term solutions may involve changes in the operation of the plant, he said. "Everything's designed for full build-out but we have to go back in and take a look operationally to see if we're doing everything we can ..."
Odors can be reported to Crouse or Paul Siebensohn, acting director of field operations, by calling the CSD offices at 354-3700.