Chlorine and Chemical Treatment

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The Water Division pumps water from deep water wells located throughout the City. These wells are between 500 and 1000 feet deep and pump between 500 and 1800 gallons per minute. The wells contain a deep annular seal to prevent infiltration of surface water, chemicals, or animals.

Well Motor

After the water is pumped from the ground it is injected with sodium hypochlorite. (12.5% bleach) The Reaction Vesselwater then passes through reaction vessels that blend the water and the sodium hypochlorite. The sodium hypochlorite serves two purposes in the treatment process. First the sodium hypochlorite works as a disinfectant for the raw water. Although, there is very rarely a need for disinfection at this point the sodium hypochlorite is available if it is needed to assure the safety of the water. The second purpose for the injection of sodium hypochlorite is for the oxidation of elements (iron and manganese) in the water. Once the elements are oxidized it becomes a precipitant (filterable substance) that can be removed in the filters. 

FiltersAfter the water passes through two reaction vessels and oxidizes the elements and forms a precipitant, it then enters the filters. The filters are made up of several layers of an adsorptive media that filter out the oxidized elements in the water. The media is made up of varying sizes of anthracite coal, garnet, and a proprietary granular media. The filters then run for a specified amount of time or until the pressure differentials is great enough it will cause the filter to go into a backwash to clean the filters.

 The backwash process is achieved by increasing and reversing the flow through the filter. This causes the media in the filter to fluidize and releases or removes the oxidized and collected material. The collected material or backwash water is sent from the filters to a backwash collection tank.

Backwash Tank

Backwash DrainThe backwash water that is collected in the backwash tank is then allowed to settle out the collected material. The water is then be pumped off the top of the tank and sent back through the filter process. The sludge on the bottom is drained to the sanitary sewer.

After treatment the water is pumped into storage reservoirs. The reservoirs are used to store water for use during peak demand and/or for fire protection. The City of Galt has four reservoirs that store a total of 9 million gallons. The reservoirs can be filled two different ways. At some locations the wells supply the water to the reservoirs. At other locations there is control that automatically opens and fills the reservoirs during the off peak times. Maintaining full reservoirs with back up generators assures that the city will have an adequate supply of drinking water as well as backup supply for emergency situations.