Antioch Brackish Water Desal Project

Antioch’s Need for Desalination

The City of Antioch’s current water supply system serves over 112,000 people within a 28.8 square-mile service area. The main sources of water for the City include water pumped from the San Joaquin River under the City’s senior (pre-1914) water right, and purchases from the Contra Costa Water District. The amount used from each source depends on the time of year and the type of year (dry or wet). The City uses river water as much as possible because it is less expensive than water purchased from CCWD. However, over the years the salinity of river water has increased steadily and forced the City to purchase more water from CCWD. The graph (below) shows the water supply trend.

Calendar of Events

Upcoming Events
There are no upcoming events at this time.

Past Events

To improve water supply reliability and operational flexibility while saving costs, especially during droughts and future changes in Delta water management, the City is implementing the Brackish Water Desalination Project. The Project will allow the City to use water from the river year-round, even when the salinity is above levels normally treated at the existing conventional Water Treatment Plant.

The main Project objectives include:

  • Improve water supply reliability and water quality for customers.
  • Develop a reliable, and drought-resistant water source to reduce dependency on purchased water supplies by maximizing the use and preserving the value of the City’s pre-1914 water rights.
  • Maximize the use of existing infrastructure to minimize capital costs .
  • Provide cost effective operational flexibility to allow the City to respond to changes in source water quality, emergencies, and changes in climate and California Bay-Delta conditions.

What is Brackish Water Desalination?

Desalination is the process of removing minerals and salts from water to produce a purified water. This is achieved by pushing water at a high pressure through reverse osmosis (RO) membranes (semipermeable membrane) to remove salt and other minerals.

The source water for desalination can come from a variety of sources including seawater, agricultural run-off, salty groundwater, or other brackish water sources. Brackish water refers to water that has higher concentrations of chlorides (salinity) and total dissolved solids (TDS) than freshwater, but is not as salty as ocean water. Ocean water has approximately 35,000 mg/L of TDS, while brackish water can range from 1,000 to 10,000 mg/L of TDS.

At certain times of year, the waters near the City of Antioch are considered brackish when San Joaquin River flows decrease and the salty Bay waters reach further upstream. Because brackish water has lower concentrations of TDS and nitrates, less energy is needed to push the water through the RO membranes. Brackish water desalination can produce potable water supply at less than half the energy usage of seawater desalination.

Before the finished water is ready to be pumped into the water system and distributed to customers, minerals are reintroduced into the water to make it compatible with other water supplies.

Project Description

The Antioch Brackish Water Desalination Project utilizes existing infrastructure to the degree possible and also includes new facilities and infrastructure to improve the City’s water supply reliability and operational flexibility. The completed desalination facility will have a capacity of 6 million gallons per day, producing up to 5,500 acre feet per year (ac-ft/yr) which will offset purchases of more expensive CCWD water.

City of Antioch’s Brackish Water Desalination – Project Components

The Antioch Brackish Water Desalination Project consists of the following components:

  • New river intake pump station to replace the existing San Joaquin River intake pump station. The pump station will consist of three 8 mgd pumps (16 mgd firm capacity) each with a fish screen that meets the protective criteria of the California Department of Fish and Wildlife and National Marine Fisheries Service.
  • New 3,000 foot pipeline connecting the City’s existing raw water pipeline to the City’s Water Treatment Plant to allow a direct connection and maximize the use of existing infrastructure
  • New 6 mgd desalination facility (reverse osmosis, post-treatment systems, chemical feed and storage facilities, brine conveyance facilities, and other associated non-process facilities).
  • Approximately 4.3 miles of a new brine disposal pipeline to convey discharge brine the Delta Diablo Wastewater Treatment Plant for disposal into the San Joaquin River through an existing outfall. Discharge of brine water into the San Joaquin River will result in minor local increases in salinities that are within the tolerance range of native species.

Existing facilities that are utilized in this project include the:

  • Existing raw water pipeline – to convey river water to the treatment plant.
  • Existing Water Treatment Plant – to provide pretreatment of the raw water before reverse osmosis instead of constructing a new microfiltration facility.
  • Existing Wastewater Treatment Plant effluent water – will be blended with discharge brine to reduce the salinity and meet river discharge requirements.
  • Existing Wastewater Treatment Plant Outfall – used to convey brine water to the San Joaquin River.

Location

The Project facilities will predominately be located in the City of Antioch, California. The desalination facility will be located within the fence line of the City’s existing water treatment plant at 401 Putnam Street, Antioch and the pipeline routes will follow road right-of-ways. The brine will be conveyed to the Delta Diablo Wastewater Treatment Plant in Pittsburg, CA and then discharged to the San Joaquin River west of the Dow Wetlands Preserve using the existing WWTP outfall.

Customers

Water treated at the City of Antioch’s Brackish Water Desalination Facility will enter the City’s drinking water distribution system and benefit all residents who receive water from the City of Antioch, approximately 112,000 people.

Project Cost and Financing

The total capital cost of the Project is approximately $63 million which will be financed through a variety of sources. Potential sources include the EPA Water Infrastructure Finance and Innovation Act (WIFIA) loan, the Department of Water Resources Proposition 1 Desalination Grant, a State Revolving Fund loan, and the City of Antioch’s Capital Improvement Budget.

Project Timeline

Project and Related Documents

Contact Us

If you have any questions or comments, please contact: