Dive into the Wondrous World of Water


Three large white tanks holding liquid oxygen

The world of water quality is often filled with complex terms and scientific language – from parts per trillion to turbidity. Luckily the technicians at Zone 7’s state-of-the-art lab conduct the science to ensure customers have safe and clean water. In order to provide full transparency, the Wondrous World of Water campaign helps answer the question, “what in the world does all this mean?”

Learn all about how water treatment works, the difference between ozone disinfection and chlorine disinfection, and how groundwater is treated differently than surface water through these animated videos, GIFs and infographics.

Where in the world do we start?

The world of water treatment is complex! There is a great deal of work that goes into preparing the water that originates as rain, snowmelt or from underground aquifers to meet the Zone 7 water quality goals before it can be delivered to homes and businesses.

Our water treatment process is carefully designed and managed to take water from different sources through multiple treatment steps before it reaches you. Thanks to best-in-class systems and a highly skilled team of experts, customers can be confident in drinking Zone 7 water straight from the tap.

Zone 7 Water Agency applies a multi-barrier approach from source to tap to safeguard water supplies and achieve high quality drinking water.

Our approach to water treatment includes the following multi-step process:

Source water protection

Source water protection simply means we help prevent contaminants from entering our water supply as much as possible. We use different forms of best management practices to protect our surface water and groundwater.

Infographic of Source Water Protection. Reduce the amount of untreated sewer spills into surface waters. Restrict direct runoff from cattle ranching operations near surface water sources
Infographic of Source Water Protection, Limit pesticides and fertilizers and avoid excess irrigation to reduce runoff. Ensure chemicals are stored and disposed of properly. Ensure proper construction and destruction of wells and septic tanks

Ozone Treatment

Ozone treatment uses liquid oxygen and electricity to destroy contaminants with fewer byproducts.

Infographic of first step of Ozonation, Ozone Molecules. Adding an electric spark to Oxygen creates supercharged ozone molecules
Infographic of reasoning behind ozonation. Contaminants in water may include bacteria, viruses, and algal byproducts that impact taste and odor
Infographic of third step of Ozonation. Ozone is injected into the water as a gas at our new ozonation site in the Del Valle Water Treatment Plant. Ozone seeks out and destroys contaminants in water
Infographic of final step of Ozonation. Ozonation leaves behind pure, high-quality water, without the byproducts left behind by other disinfectants

Conventional dual-media filtration

Surface water is filtered at our state-of-the-art plant using a multi-step filtration process. This conventional filtration process removes particles and more than 99% of waterborne pathogens, including viruses.

 Infographic of water undergoing the first step of Surface Water Filtration, Add Minerals. Iron or aluminum salts called coagulants are added to water containing unwanted particles
Infographic of water undergoing the second step of Surface Water Filtration, Cooagulation. The particles then bind together or coagulate
Infographic of water undergoing the third step of Surface Water Filtration, Flocculation. Gentle mixing helps create larger particle groups called flocs
Infographic of water undergoing the fourth step of Surface Water Filtration, Sedimentation. The heavy flocs settle, leaving clarified water
Infographic of water undergoing the fifth step of Surface Water Filtration, Filtration. Clarified water is pushed through sand and gravel to remove remaining sediment
Infographic of water undergoing the final step of Surface Water Filtration, Purified Water. These treatment processes remove at least 90% of viruses and at least 99.7% of larger pathogens

Blending and/or filtration

Groundwater is filtered naturally over time removing pathogens, however it picks up minerals in the process. We treat groundwater through a process of blending and/or reverse osmosis as needed to reduce the concentration of minerals and other types of contaminants in the water.

Infographic of first step of blending filtration, Reverse Osmosis. Some of our groundwater is pushed through a semi-permeable membrane by applying pressure to reduce the amount of minerals
Infographic of second step of Blending filtration, Blending. Some contaminants cannot be removed naturally, so the water is blended with other sources to reduce the amount of unwanted particles to a safe level
Infographic of third step of Blending filtration, Chloramines. Chloramines are added to our groundwater to keep a consistent level of disinfectant residual in our system. keeping it safe as it travels to your home


We disinfect our surface water using the scientifically proven method of chlorination to deactivate or kill remaining pathogens, aka germs!

Infographic of first step of Disinfection of Surface water, Chlorine. A powerful disinfectant called chlorine is added to water to kill bacteria and viruses
Infographic of second step of Disinfection of Surface water, Ammonia. Adding ammonia converts chlorine to chloramines and reduces the formation of chlorination byproducts
Infographic of third step of Disinfection of Surface water, Chloramines. Chloramines provide a disinfectant residual to keep water clean throughout the distribution system

Safe storage and distribution

Finally, a consistent level of disinfectant residual is maintained in our distribution system to prevent bacterial growth as water travels to your tap.

Infographic of water droplet going through a pipe system
Infographic showing the four retailers serviced by Zone 7 Water Agency: Livermore, Pleasanton, Dublin-San Ramon Services District and CalWater
Infographic of a pipe leading to customers serviced by Zone 7 Water Agency

Ozonation: A whole new world of water treatment

Ozonation is a proven, successful water treatment method that uses ozone gas to effectively disinfect water. Ozone can replace chlorine as our main disinfectant, resulting in a higher quality finished water product. An ozone facility is currently online at Del Valle Water Treatment Plant and another is being added to Patterson Pass Water Treatment Plant, which is due to be completed in 2022.

This investment in ozonation will improve water by treating taste and odor impacts from algae growth, reducing chlorine-related byproducts and killing even more pathogens than chlorine.

Learn more about how in the world it works in our animated video!