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Advanced Water Purification Facilities (AWPF) - TIWRP

LA Sanitation (LASAN) has one of the world's most technologically advanced water reclamation treatment systems at the Terminal Island Water Reclamation Plant (TIWRP) in San Pedro.  


In 2002 TIWRP completed construction of the Advanced Water Purification Facilities (AWPF) which consists of microfiltration (MF), reverse osmosis (RO), and advance oxidation disinfection systems. 


Currently, the facility can produce up to six million gallons per day of highly purified recycled water that is very similar or better than fresh water. The water is injected into the Dominguez Gap Barrier (DGB) to protect groundwater reservoirs from seawater intrusion. This recycled water replaces the use of potable water.


TIWRP is undergoing the AWPF Ultimate Expansion Project; this project aims to double the capacity of the AWPF, doubling the amount of water purified by the end of 2016.

Project Vision

The vision of the AWPF Expansion is to enlarge the facility to twice its current size by the end of 2016, doubling the amount of recycled water that the plant can provide to the Dominguez Gap Barrier from six million gallons per day to 12 million gallons per day. This will be accomplished through the construction of new microfiltration and reverse osmosis systems and the addition of an advanced oxidation process, which uses ultraviolet light and sodium hypochlorite for disinfection.

Project Mission

The mission of the AWPF at TIWRP is to provide reliable and highly-purified recycled water as a potable water replacement to recharge the Dominguez Gap Barrier. After the AWPF Ultimate Expansion is complete, the mission of the AWPF will be to continue supplying a reliable source of recycled water to the DGB, as well as supply recycled water to Harbor Area industrial users and to replenish the evaporation losses at Machado Lake.


As the production of TIWRP effluent improved over the years after the implementation of tertiary treatment facilities in 1997, Terminal Island pursued other avenues for effluent discharge aside from the Harbor. LA Sanitation, the Bureau of Engineering and the Department of Water and Power partnered to form the Harbor Water Recycling Project. The goal of this project is to produce water of such high quality that it can be used as an alternative to the use of potable (drinking) water for indirect potable reuse.

Pilot studies were conducted from 1996 to 2001. Construction was completed in 2002, allowing delivery of water to the Dominguez Gap Barrier to prevent seawater intrusion into the groundwater reservoirs. Seawater intrusion decreases the amount of freshwater stored in coastal aquifers; the recycled water pumped into the DGB keeps the seawater at bay and preserves the freshwater in the aquifer.

As the supply of fresh water reserves has diminished due to drought conditions, recycled water is vital to preserve the remaining fresh water resources. The injection of water from the AWPF into the DGB prevents the intrusion of sea water into drinking water aquifers. There are 94 wells in operation at the DGB, running 24 hours a day.