Our Water Treatment Process

San Diego uses a water treatment process similar to many other large water utilities throughout the country. The process produces safe drinking water by removing and inactivating potentially harmful substances and organisms.

Raw water is treated using a multi-barrier approach to ensure our water meets federal and state drinking water quality regulations. Each treatment barrier provides an additional step to give added safety to the drinking water. The barriers include coagulation, flocculation/sedimentation, filtration and disinfection.

• The coagulation process uses ferric chloride and organic polymers to neutralize particles in the water to allow them to combine.

• Flocculation is the process in which the neutralized particles combine to form larger clumps of particles. These larger clumps of particles are then allowed to settle out of the water in the sedimentation process. Any remaining particles are then removed through the filtration process.

• Chlorine is added to the water as the primary disinfectant to prevent illness due to water-borne pathogens. The final barrier is the addition of ammonia to the water to react with chlorine and form chloramines. Cloramines are used to maintain a residual disinfectant throughout the water distribution system to ensure water quality to the consumer’s tap.

Also, as part of the water treatment process, potassium permanganate and chlorine are used to remove taste and odor compounds, and sodium hydroxide is used to adjust the pH making the water non-corrosive and to protect the pipes, plumbing fixtures and appliances from corrosion (rust)

Each year the Water Department publishes an Annual Drinking Water Quality Report, also known as the Consumer Confidence Report (CCR) that includes details about the source of our water, what it contains, and other important information about the water we provide to our customers.