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Treatment Process

RAW WATER STORAGE AND TREATMENT

Surface water is obtained from the Upper Cuyahoga River via three impounding reservoirs. Lake Rockwell, the primary reservoir, is supplemented by Wendell R. Ladue Reservoir and East Branch Reservoir.

ALGAE CONTROL
A copper-based algaecide is used to control problem algae in the reservoir. These algae release chemical compounds responsible for musty, vegetative odor and taste in the water. When their numbers become too great, algaecide is applied to the reservoir.

FINE SCREENING
Within the intake structure of the water treatment facility, fine screens prevents items larger then ½" in size from entering the treatment plant. This would include fish, leaves, and other miscellaneous debris.

POTASSIUM PERMANGANATE
Potassium permanganate (KMnO4), is an oxidant which aids in the removal of iron, manganese, taste, and odor. Iron and manganese metals are dissolved naturally in surface water sources and pose no health risks but can cause staining of plumbing fixtures and laundry. Potassium permanganate also oxidizes organic chemicals that cause taste and odor problems

COAGULATION, FLOCCULATION AND SEDIMENTATION

SETTLING BASINS
Four (4) settling basins of varying size are utilized during the treatment process to treat flows ranging from 4 MGD to 20 MGD.

ALUMINUM SULFATE
Alum is the common name for aluminum sulfate (Al2(SO4)3). Alum is used as a coagulant to bind together fine suspended particles into larger particles. These larger particles, called floc become heavy enough to settle out of the water. This settling removes suspended solids, color, turbidity (cloudiness), and the alum.

ALUMINUM CHLOROHYDRATE
Aluminum Chlorohydrate (ACH) is an alternate coagulant used in the same manner as alum. ACH has the advantage of not lowering the pH (not making the water more acidic) depending on raw water conditions.

CHLORINE DIOXIDE
Chlorine dioxide, ClO2, is a disinfectant and oxidant made on site by mixing sodium hypochlorite, sodium chlorite and hydrochloric acid. Like elemental chlorine, chlorine dioxide destroys bacteria and other pathogens as well as oxidizing iron, manganese and organic chemicals associated with taste and odor problems. The benefit of chlorine dioxide over chlorine is that it does not form harmful trihalomethanes or haloacetic acids when combined with organic chemicals as elemental chlorine can.

POWDERED ACTIVATED CARBON
Powdered activated carbon (PAC) is added to the water to further adsorb organic chemicals that cause taste and odor problems in the water. The surface of the carbon particles attracts these chemicals. The carbon and adsorbed compounds are removed later through filtering, so are the chemicals.

SEDIMENTATION
Sedimentation occurs as the large particles of floc become heavy enough that the water can no longer support their weight and the floc begins to settle out. The water has lost much of its turbidity by the time it has traveled to the end of the sedimentation basin. The accumulated floc is regularly pumped out of the bottom of the basin, dried in drying basins and hauled away to be beneficially reused as topsoil..

FILTRATION

During the filtration process, any particles that were not removed through sedimentation are taken out of the water. The filters are made up of layers of anthracite coal, sand, fine gravel and coarse gravel. Because particles get trapped in the filters, it is necessary to clean, or backwash, them on a regular basis.

RAPID SAND FILTERS
Twenty-five (25) rapid sand filters are utilized during the treatment process and generally filter flows up to 2 MGD each. The media within each rapid sand filter consists of up to 12" of anthracite coal, 12" of silica sand and 12" of gravel. Depending on the water temperature, the filter media is cleaned between 20 to 80 hours of operation by backwashing the filtered particles to the wash water lagoons

FINAL CHEMICAL ADDITION AND PUMPING

During the final stage of the water treatment process, different chemicals additives including Zinc Orthophosphate, Fluoride, Caustic Soda and Sodium Hypochlorite are fed into the filtered water. After final chemical addition, six (6) high lift pumps ranging in size from 15 MGD to 25 MGD are utilized to pump treated finished water to Akron Water Supply customers.

ZINC ORTHOPHOSPHATE
Zinc orthophosphate (Zn(PO4)), is used in small amounts as a corrosion inhibitor. It coats the inside of water mains and prevents corrosion of iron pipes.

FLUORIDE
Fluoride in the form of hydrofluorosilicic acid (H2SiF6), is added to the drinking water to reduce tooth decay.

CAUSTIC SODA
Caustic soda, also known as sodium hydroxide (NaOH), is used to adjust the pH of the water. Adding alum and chlorine tends to lower pH and caustic soda brings the pH back to a near neutral state of 7.3. Neutral pH helps prevent corrosion and scale from forming on pipes.

SODIUM HYPOCHLORITE (Chlorine)
Chlorine (Cl2), is added to the water as a final disinfectant after most of the organic chemicals have been removed through settling and filtering. Enough chlorine is used that excess (residual chlorine) remains in the water throughout the distribution system. This ensures that there will be no re-growth of bacteria or pathogens in the water mains and pipes. Water Supply uses liquid sodium hypochlorite as the source of chlorine.

 

SOLIDS HANDLING

COAGULANT RESIDUALS DRYING BASINS
The settled solids collected during the sedimentation phase of treatment are pumped to drying basins located on Akron Water Supply property. The drying basins are utilized to dewater the collected material. After drying, a private entity is contracted to haul the dry material off-site and utilize the material for beneficial reuse as a topsoil.

WASH WATER LAGOONS 
The filter backwash water is collected and pumped to lagoons located on Akron Water Supply property. These lagoons provide an opportunity for solids in the backwash water to settle out. The settled solids are then periodically dredged from the lagoons and transferred to the drying basins for drying and beneficial reuse removal.

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Mayor Don  Plusquellic

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