The Rancho Murieta Community Services District's wastewater treatment plant is unique. It utilizes a number of basic and proven processes to produce a very high quality effluent. Normally, golf course type development projects are limited in space and, therefore, employ treatment concepts that are less area intensive than those used at Rancho Murieta.
Wastewater is received at the treatment plant from various pumping stations. The influent enters aeration pond #1 and flows successively through the other four aeration ponds. Wastewater is treated naturally through bacteriological action and supplemented with mechanical aeration. After this process, the effluent water quality is similar to the one obtained by secondary treatment.
Secondary effluent is then stored in two large reservoirs. Within these reservoirs, additional natural treatment occurs. These reservoirs allow storage of the secondary treatment wastewater until the need arises for irrigation of the golf courses. They have the capacity to store wastewater for almost half a year.
When the need arises, typically in late April, stored secondary effluent is further treated in the tertiary plant. It is operated until the supply from the reservoirs is exhausted or the irrigation season ends, about the end of October.
Secondary effluent is withdrawn from the reservoir through a tertiary pumping station and sent for further processing in the tertiary plant.
The tertiary treatment plant consists of a DAF (dissolved air flotation), filtration and disinfection. These processes remove algae and fine solids contained in the secondary effluent. The effluent from the filter is discharged to the chlorination contact chamber for disinfection. Two (2) parallel process trains exist.
Disinfected wastewater enters the 1.8 million gallons equalization basin. It serves as a flow equalizer, as the demand from the golf courses varies, while it is desirable to maintain a fixed flow through the tertiary process.
Final tertiary effluent, meeting Title 22 quality requirements, as prescribed by the California Department of Public Health and enforced by the California Regional Water Quality Control Board (CRWQCB), is pumped to the North Course or flows by gravity to Lake 16 located within the South Course. To assure the effluent quality at all times, he turbidity and chlorine are monitored continuously after filtration. Historically, this effluent quality, as measured by the turbidity, has approached the quality of drinking water.
Solids accumulated in the DAF are discharged to sludge drying beds for natural drying. Dried solids are used as top soil within the District's treatment plant perimeter. Backwash water from the filter contains a minute amount of solids. Because sludge drying beds are sensitive to large amounts of water, the backwash water from the filter is returned to the ponds. Periodically, these ponds have to be taken out of service and the solids removed. These solids can then be transferred to the sludge drying beds for drying and proper disposal.