Sewers - they bring it to Terminal Island

Force main sewers (sewers under pressure) carry wastewater to Terminal Island for treatment from the industries and residences of the Harbor area. About 60% of the flow comes from industry and 40% from residences. The average daily flow into the plant is about 16 million gallons. The plant can treat up to 45 million gallons per day in wet weather.


At the headworks, bars and screens remove the largest solids - things as big as branches, plastics, and rags - and as small as sand and other gritty solids. This is called preliminary treatment. After leaving the headworks, the wastewater the wastewater moves by gravity to primary treatment.

Primary treatment – taking out the sludge

Most of the solids are removed here after they sink to the bottom of covered, underground tanks and are pumped to the digesters. The tanks are covered to reduce odors. Other wastes are skimmed from the surface. The liquid is then pumped to the secondary treatment system for further treatment.

Secondary Treatment – nature's way

In covered, oxygen rich aeration tanks, bacteria living in the wastewater consume most of the remaining solids. The bacteria and solids are separated from the wastewater in clarifiers. Some of the biomass is sent back to the aeration tanks to perform additional Secondary Treatment and some is thickened and then sent to the anaerobic digesters. The treated wastewater is then sent to the tertiary treatment process.

Tertiary Treatment - coagulation and sand bed filtration

The secondary effluent is further treated to remove the very smallest solid particles.  First, a coagulant is added to help the solids settle from the wastewater.  Then the wastewater passes through sand filters where remaining solids are removed. Most of the tertiary product is discharged into the Los Angeles Harbor. A portion is sent to the Advanced Water Treatment Facilities.

Advanced Water Treatment Facilities - making it really clean

The AWTF contain a two-stage process that produces water that is cleaner than your drinking water. This water meets or exceeds the water quality requirements of the state and federal agencies and provides a beneficial resource to Harbor area industrial users which saves many million gallons of potable water each year.

First, water is pumped through a microfiltration unit where membranes remove minute particles that remain in the tertiary effluent. In the second stage, the microfiltration effluent is pumped through reverse osmosis membranes that filter pollutants as small as water molecules. This water is chlorinated to destroy any viruses or other remaining organisms, then dechlorinated to make it compatible with disposal in the Los Angeles Harbor for reuse applications.

Digesters - egg shaped

Solids removed during primary and secondary treatment are pumped to these huge, egg shaped vessels. Terminal Island digesters were the first ever egg-shaped - built in 1985. The shape is particularly efficient for the digestion process and creating a large capacity on a small footprint. Bacteria living in this warm, oxygen-free space digest the solids. The bacteria, along with the heat, destroy virtually all pathogens and release a biogas (methane) that is processed for energy recovery. The biosolids that are processed here are considered Exceptional Quality, which is a pathogen-free Class A organic product, suitable for many landscaping and agricultural applications.

Centrifuges - spin cycle

The biosolids that come out of the digesters are very wet - about the consistency of toothpaste. Much of the water is removed in large centrifuges. The drier product is much less costly to transport to the sites where beneficial reuse occurs.

Beneficial Use Sites - putting it back into the ground

Biosolids are nutrient-rich organic materials that are very valuable to farmers and others who need amendments and composts to improve their soil. The City owns a 4,688-acre farm site, Green Acres Farm in Kern County, where 99.9% of the biosolids are applied. Non-food crops such as corn, wheat, and alfalfa are grown on the farm. Class A is the required standard for applying biosolids in Kern County and Terminal Island 's product exceeds that quality level. Other biosolids are mixed with green waste and zoo wastes and used as landscape compost or for non-food agricultural applications.