What Goes Into Treating Drinking Water
Paul M. Neal Water Treatment Plant
A conventional treatment plant capable of treating 50 million gallons per day
After traveling through two miles of transmission pipeline that transports Lake Michigan water from the RWPS to a state-of-the-art water treatment facility, the real magic begins. Using a conventional treatment process, CLCJAWA is capable of purifying 50 million gallons of water per day.
Ozonation
Removes Taste and Odor
The first treatment process encountered in the plant is ozonation. As one of the most powerful oxidants available, ozone provides many benefits such as disinfection, taste and odor control, and enhancement of particulate removal.
Due to its high reactivity, ozone must be generated onsite. Ambient air is filtered to create 94% oxygen which is then pumped into our ozone generators. Ozone is generated by applying electricity to the oxygen. The resulting ozone is bubbled into the water, where it lasts for less than 20 minutes.
Rapid Mixing
Uniformly disperses coagulant into water
After ozonation, the water enters the rapid mix basins where a coagulant is added to facilitate the removal of suspended particulate matter. The rapid mix basins provide quick and uniform dispersion of the coagulant. Coagulants react with particulates in the raw water to enhance their ability to bind together.
Flocculation
Coagulates and flocculates particles in water
Following the rapid mix basins, the water is gently stirred in a three-stage flocculation process. As the water slowly travels through the flocculation basins, the particulate matter continually collides and sticks together into progressively larger particles called floc. The multi-staged basins along with variable speed mixers allow for optimized treatment as water quality, flow rate and temperature vary.
Sedimentation
The workhorse of the plant, removes 95% of dirt from water
Following flocculation, the floc particles are large and heavy enough to settle within the sedimentation basins. The sedimentation basins are equipped with a series of parallel inclined plates to enhance the settling process.
As an innovative technology, the use of inclined plates substantially reduces the basin surface area requirements, accomplishing equivalent solids removal in a much smaller floor area than in a conventional sedimentation process.
In the sedimentation basin, as the flocculated water travels upward between the plates, the heavy floc particles naturally fall by gravity. Once a floc particle lands on a plate surface, it slides down the plate to the bottom of the basin for removal.
From there, the solids are sent to the residual solids processing facility.
Filtration
Polishes the water to the high level expected at CLCJAWA
Fine particulate matter that escapes the sedimentation process is removed by the filtration process. In addition to trapping solids, the filters provide the capacity to remove dissolved organic compounds through the process of biological degradation.
The plant is equipped with 12 filters, each consisting of a large concrete box containing four feet of biologically active carbon over sand and gravel. Water quality is continuously monitored to meet turbidity standards.
The filters must be periodically backwashed, or cleaned, by reversing the direction of flow of water. During the backwash cycle, compressed air followed by clean water is forced backwards through the filter bed, thereby removing the particles that have been trapped in the media. The backwash water with the removed particles is sent to the residual solids processing facility.
Ultraviolet Disinfection
Inactivation of bacteria and viruses
Following the filtration process, filtered water is subjected to ultraviolet light. The ultraviolet light process, added in 2005, inactivates bacteria and viruses in the filtered water without the use of any chemicals. From the ultraviolet reactors, the filtered water proceeds to the finished water clearwells.
Clearwell Chlorination
Chlorine is the water's backup defense as it travels to customers
Prior to entering the clearwells, chlorine is added to maintain a residual disinfectant throughout the distribution system. The filtered water is stored in two clearwells with a total capacity of 5.4 million gallons.
The Final Touches
A corrosion inhibitor is added to the water to control lead and copper.
Fluoride is added to the water for the prevention of cavities.
After chlorination, the water benefits from the addition of phophoric acid, a corrosion control inhibitor. Although CLCJAWA has no lead and copper in the system, some communities that we serve may have older homes that have lead or copper. A consistant dose of phosphoric acid forms a scale on the pipe that reduces the leaching of lead and copper into the water. CLCJAWA adds 0.35 PPM of phosphoric acid to the drinking water.
Fluoride is then added to the drinking water to aid in the prevention of tooth decay. The State of Illinois requires that all public drinking water utilities add 0.7 PPM of fluoride to the water to help decrease dental carries.
Moving the Finished Product
Finished water pumps draw water from the clearwell to send out to all the CLCJAWA communities. Six pumps move the treated drinking water out into our water pipeline and on to the towns and villages that deliver water to our customers.
