Raw water for the Howell Water Treatment Plant is drawn from six wells. The water is pumped to the water plant through an 18-inch transmission line. The water enters the plant and goes into a Head Tank equipped with a multiple tray aerator. Aeration is necessary for the removal of taste and odor causing substances such as carbon dioxide and hydrogen sulfide gases, which might interfere with the softening and treatment processes. The Head Tank is positioned higher than the cone to supply pressure to lift the lime blanket inside the cone.
Water is directed from the Head Tank to the Claricone clarifier. Water enters the clarifier at the mixing zone located in the bottom of the Claricone. Lime is added to the water in this zone where it reacts with the calcium and the magnesium in the water to form precipitates.
The water plant incorporates a single stage lime softening operation to remove hardness. Hardness is caused by the presence of dissolved bivalent and polyvalent metal ions, predominantly calcium and magnesium. The water plant utilizes conventional lime softening treatment where raw water passing through the Claricone, is subjected to lime addition, mixing, and clarification.
Filtration is a process which water is passed through a porous medium to remove suspended matter present in the water or generated from the chemical reactions occuring in the softening process. The suspended matter consists of silt, clay, colloids, and micro-organisms ranging in size from one millimicron to fifty microns.
Pre-chlorination and post-chlorination are used to insure the safety of the water supply. Pre-chlorination yeilds benefits by improving coagulation in the Claricone treatment process, suppressing decomposition of organic matter in the sludge, and aiding filter operation by controlling slime formation in the filters. Post-chlorination is used primarily for disinfection of the water. This is added both in the clearwell and the high service discharge as water enters the distribution system.
Hydrofluosilicic acid provides the source of fluoride, which is beneficial in the prevention of tooth decay in children. A fluoride concentration of 1.1-1.2 mg/l is usually desirable in the plant tap. The City of Howell's groundwater does have some natural fluoride in it. Generally, it measures about 0.42 mg/l in the raw water before the addition of hydrofluosilicic acid.
Lime sludge is drawn from the Claricone as a by product of the softening process. This sludge is pumped to the sludge dewatering beds located at the wastewater treatment plant via sludge pumps and forced main. Dewatered lime sludge is annually removed from the beds for application to agricultural land for pH control.
From the clearwell inside the water plant, water flows into a 620,000 gallon ground storage tank as a reserve for city consumption and fire control.
Treated water is pumped to the distribution system by high service pumps. There are four pumps available for this, each with the ability to pump 1100 gallons of water per minute. These pumps also fill the north tower storage tank. The cycle throughout the day as demand dictates. When these pumps are on they maintain system pressure. Average system pressure is 50-55 psi.
This 300,000 gallon elevated tank is located at the entrance to the City Park. This tower was constructed in 1959. The tank supplies system pressure when the high service pumps are off.
The water plant can be run in emergency situations due to a loss of electricity. A 250kW diesel generator can run the entire water plant, Department of Public Works compound, and the high service pumps the fill the north tower and maintains system pressure.