Water Treatment


Water is found throughout the County in many forms throughout the year. However, water that lands in our yard as rain, or flows by our school in a creek is not fit for human consumption. Surface water acquires its characteristics (taste, odor, temperature, clarity, etc.) from the environment with which it comes into contact. Surface water may contain various contaminants, such as silts and clays, dissolved minerals and salts, organic material from vegetation and wildlife, algae, bacteria, protozoans, viruses and man-made pollutants. In order to remove these contaminants, and to comply with state and federal water quality standards, water is treated before it is distributed for consumption.

Groundwater acquires its characteristics from the quality of the water entering a groundwater basin, the chemical nature of the groundwater basin and the time of residence within the basin. Generally, water taken from groundwater supplies is naturally filtered as it passes through the layers of the earth. Unless the basin is contaminated, groundwater usually does not require the same level of treatment as does surface water. However, groundwater may also require some treatment in order to meet water quality standards.

For more information on water treatment issues in the county, click on the links below.

Water Treatment Process
Water Treatment Plants

Web Links 

Water Treatment Process

There are many methods of treating water so that it is fit for potable uses. The following information outlines several steps that are typically taken to treat water that will be sold for consumption.


Pretreatment is used to kill disease-causing organisms and help control taste and odor causing substances. A pretreatment chemical could be any number of oxidants or disinfectants. Ozone, hydrogen peroxide, potassium permanganate and chlorine are all commonly used in water treatment.


The purpose of Aeration is to "off-gas" taste and odor causing substances by passing large quantities of air through the water. This is accomplished by pumping air through a series of diffusers placed on the bottom of the storage basins, which causes the water to "boil." The resulting air bubbles carry off the most volatile of the taste- and odor-causing organics.

Flash Mixing 

The flash mix, or rapid mix process, occurs just after coagulation chemicals are added to the raw water. Coagulation chemicals are used to attract particles together that will not readily settle or filter out of the water. Some examples of coagulation chemicals include aluminum sulfate and various polymers.


Coagulation starts immediately after flash mixing and is facilitated by the flocculation process. Flocculation is a gentle mixing of coagulated raw water. This mixing allows particles now "sticky" from the addition of coagulant, to gather to form larger, heavier particles called "floc."


The sedimentation process settles out larger suspended particles and the floc created through the coagulation/flocculation process. As the raw water flows very slowly through the sedimentation basin, heavy particles fall to the floor while the water overflows the basin and is channeled into filters. The particles resting on the floor of the basin are moved into a sludge basin for eventual disposal.


Through the filtration process, any remaining particles are removed from the raw water. The water may be filtered through layers of sand, gravel and/or coal. The raw water travels through the various filter materials and out into the treatment plant reservoir. Some examples of filter materials include mixed media (layers of various sizes of gravel, high-density garnet, sand and anthracite coal), diatomaceous earth, and granular activated carbon (GAC).


The finished water from the treatment plant may be disinfected as it leaves the reservoir and enters the distribution system. Disinfection ensures unwanted bacteria and organisms have been eliminated and helps discourage any further growth of disease-causing organisms in the drinking water.

Water Treatment Plants

Communities in Santa Barbara County rely on different types of water supplies. As a result, there is a wide variety of treatment processes in use. The following information provides a description of the treatment processes used in four communities within the county and in the State Water Project.

City of Santa Barbara

William B. Cater Water Treatment Plant  

The City of Santa Barbara constructed the William B. Cater Filtration Plant in 1964. The plant was originally designed as a lime softening plant with a treatment capacity of 10 million gallons per day. The capacity was increased in 1969 to 16 million gallons per day by converting sand filters to dual media (sand and anthracite coal) filters. The "Joint Exercise of Powers Agreement" to expand and operate the Cater Filtration Plant to treat all Cachuma water delivered to the districts was signed in 1978 and is still in effect for the Montecito Water District, the Carpinteria Valley Water District and the City of Santa Barbara.

CaterCaterThe plant was expanded from 16 million gallons per day to the current 37 million gallons per day capacity in 1982. The increase in capacity was the result of the addition of five filters. The water treated at the plant may be drawn directly from the South Coast Conduit (SCC) or from Lauro Reservoir. The water in the SCC comes directly from Lake Cachuma (via the Tecolote Tunnel). The water in Lauro Reservoir is a combination of water from Gibraltar Reservoir (via the Mission Tunnel into the Penstock pipeline) and water from the SCC. Normal operation is for Cater to draw the water from Lauro Reservoir.

The Cater Treatment Plant method of treatment is considered "conventional treatment" using the pretreatment, aeration, flash mix, coagulation/flocculation, sedimentation, filtration and disinfection process. The water treated at this facility is tested extensively to ensure compliance with state and federal water quality standards. The Plant is located at 1150 San Roque Road and is staffed 24 hours a day. The facility is open to the public and tours are offered. For more information contact the City of Santa Barbara at (805) 897-2609.

Goleta Water District

Corona del Mar Water Treatment Plant 
The Corona del Mar Water Treatment Plant began operation in 1974. Due to the plant elevation of 192 meters (630 feet), water can move through the plant by gravity flow and be delivered without pumping to the vast majority of district customers. The design capacity of the plant is one cubic meter per second (about 24 million gallons per day), with a peak capacity of 1.6 cubic meters per second (about 36 million gallons per day). The "raw water" received from Lake Cachuma is directed to the plant for removal of suspended matter, such as clay particles and algae, in order to meet state health standards. The stages of treatment completed at this plant include pretreatment, flash mixing, coagulation/flocculation, sedimentation, filtration, and disinfection. These processes are precisely controlled and carefully monitored around the clock. For more information about the plant and treatment process, call the Goleta Water District at (805) 964-6761.

City of Lompoc

The City of Lompoc Water Treatment Plant 
For information about the City of Lompoc's water supplies and treatment processes, please call (805) 736-1617.

City of Santa Maria 

The City of Santa Maria relies mostly on State Water Project water for its water supplies. This water is of sufficient quality that it requires little treatment beyond addition of chlorine and ammonia (see below for information on SWP water treatment). For more information contact the City of Santa Maria at (805) 928-5022.

State Water Project Polonio

Polonio Pass Water Treatment Plant  
State Water Project water begins as rain and snow melt from the Sierra Nevada Mountain Range. It passes through both natural streams and rivers and man-made conveyance structures on its way to the Polonio Pass Water Treatment Plant in San Luis Obispo County. At this treatment plant, water is sent through the flash mixing, coagulation/flocculation, sedimentation, filtration and disinfection processes. For more detailed information on the treatment process, please call the Central Coast Water Authority at (805) 688-2292.

Web Links

EPA: Drinking Water Kid's Stuff
EPA: Office of Groundwater & Drinking Water
Local Water Treatment Plants
National Drinking Water Standards