Wastewater reclamation at Rancho Murieta, California; golf course irrigation with upgraded pond effluent meeting California's strictest requirements for wastewater reuse

Abstract

Rancho Murieta is an exclusive 1,400 ha (3,500 acre) master-planned golf-course-oriented community and is located approximately 39 km (24 miles) southeast of Sacramento, the capital of California. The community located along the banks of the Cosumnes River, one of the last pristine rivers in California, is situated in the great Central Valley of California which enjoys a Mediterranean-like semi-arid climate. The community has a present population of 3,500 people and is projected to have an ultimate population of 15,600. The Rancho Murieta Community Services District provides wastewater collection treatment and disposal services, among others within the community. In the early 1980s, the District obtained 55 ha (135 acres) of land for a wastewater treatment facility from the original developer of the community. Despite the immediate proximity of the plant to the Cosumnes River, the District was not allowed to discharge any plant effluent to the river. In favor of preserving the pristine qualities of the river, a “zero discharge” was required. Therefore, the District had to provide for some form of reuse of its effluent, a land disposal alternative. After considerable study, a plan was developed to integrate the community's two proposed championship golf courses into a comprehensive wastewater reclamation program. In addition to significantly decreasing the demand for treated domestic water within the community, a comprehensive program to irrigate the golf courses with reclaimed wastewater would also significantly lower the summertime demand for water from the river, thereby providing increased flows to downstream agricultural users along the river, a true “win-win” situation for all parties concerned. In order to provide treatment to an acceptable level for irrigation of golf courses surrounded by dwellings, it was decided that a tertiary treatment plant would be designed to meet California's wastewater reclamation requirements. The current treatment plant was constructed in three phases. California has very strict standards for effluent reuse and they are described in Title 22 of the California Code of Regulations. Use of reclaimed wastewater for most golf courses requires oxidation, coagulation, filtration and disinfection. The effluent has to meet a 2 NTU turbidity and 2.2 MPN/100 coliform standard. To comply with these standards, the District developed a unique treatment process that has allowed the District to be in full compliance since start-up without a single violation of the plant's discharge requirements. The initial treatment process consists of oxidation ponds. Mechanical aerators are located on the ponds to ensure that sufficient oxygen is provided at all times for treatment and most importantly for odor control. The pond effluent is discharged into two large reservoirs. These two reservoirs are sized to store wastewater for up to 150 days during periods of non-irrigation. When irrigation can be performed on the golf course, the tertiary treatment process is activated. It consists of dissolved air flotation for algae removal, filtration for polishing, and disinfection. Treatment design parameters, effluent quality results and capital and operating costs are presented.