The Marion R. Walker Filtration Plant and our aeration/oxygenation systems are responsible for treating water before it reaches our customers. All Casitas customers receive treated surface water from Lake Casitas at some point during any given year and the water may be blended with treated groundwater from our Mira Monte Well. Ojai Water System customers primarily receive treated groundwater from the San Antonio and Mutual well fields. This is typically supplemented by treated surface water during periods of warm weather and drought, when well production is low and demand is high.
Aeration and oxygenation of Lake Casitas is an important first step in providing pleasant tasting and smelling water by supporting aerobic respiration, and inhibiting nutrient cycling and therefore algae growth. This is particularly important during summer months when algae growth is at its highest. The aeration system releases pumped air at a single elevation, while the oxygenation system diffuses pure oxygen at three distinct depths. The rate and depth of oxygen diffusion is optimized by profiling (measuring dissolved oxygen, temperature, and other water quality parameters throughout the water column) and inputting the data into an oxygen plume model. Oxygenating the deep portions of the lake prevents the release of hydrogen sulfide, phosphorous and other undesirable compounds and nutrients from sediments. When algae levels need to be further reduced, low doses of copper sulfate are used along the shoreline. This chemical is distributed at least 100 feet off the shoreline and away from the bass breeding areas at the north end of the lake in an effort to protect bass fisheries.
Water is released from the lake into the filtration plant through a multi-level, screened intake structure. This allows staff to select the depth water is released at 24 foot intervals. Due to ever-changing lake dynamics, we perform regular water quality profiles and test samples taken from depths corresponding with each available intake gate to select the best available raw, untreated water.
The Marion R. Walker Filtration Plant is a high-rate in-line pressure filtration plant. Features include horizontal pressure filters, continuous real-time monitoring and alarm systems. Chlorine is applied for initial disinfection, and converted to chloramines to provide a protective disinfection residual throughout the distribution system. The filter plant clarifies and reduces turbidity in the water. Silt and other natural materials removed from the water are placed in drying beds and later hauled off for disposal. The filtration plant has a pilot plant attached, which is a small-scale treatment plant that simulates the full-scale treatment plant. It is used to evaluate variations in water quality, and allows testing of different treatment options prior to full scale implementation.
The San Antonio Manganese Filtration Treatment Plant filters groundwater from six groundwater wells located within the San Antonio and Mutual well fields. Chlorine is added to aid in filtration and provide a protective disinfection residual in the distribution system.