THE PROCESS

 

At the District’s request, the Corps of Engineers releases water from Lake Grapevine Dam into Denton Creek.

The water flows down Denton Creek and joins the Elm Fork of the Trinity River to flow into Ski Lake near Hwy. 114 and N.W. Highway.

Water then flows down a pipeline to the District’s’ plant on Regal Row near Harry Hines Blvd. where it is screened and lifted (pumped) up the plant’s elevation.

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Lime slurry, ferric sulfate, and cationic polymer are added to the rapid mix. During times of taste/odor problems in the raw water, powdered activated carbon is also added. The rapid mixer provides mixing of these chemicals with the raw water, causing coagulation or clotting of impurities in the water.

PARK-CITIES-WATER-MAY2015-29The water then goes to the flocculators, where the coagulation continues, creating a floc particle that becomes heavier than water.

From the flocculators, the water enters clarifiers (setting tanks) where the floc settles out of the water. This settle floc or sludge is pumped out to the sludge lagoons for future disposal.

The clarified water then has chlorine and ammonia added to it to form chloramines for disinfection. Chloramines are used to cut down on the formation of trihalomethanes (THMs) or disinfection byproducts caused by the addition of the chlorine above. This disinfected water is run through filters for final removal of remaining particles from the water. This clear, clean water is then stored in a 10-million gallon clean well (underground concrete tank) for pumping to the town and the city.

New Process
With the completion of the District’s new membrane filter facility and plant improvements, the existing process will be greatly enhanced. The existing multimedia filters will be replaced with the new granular activated carbon filters (GAC) to remove taste and odor occurrences. From the new GAC filters, the water will be pumped to the new ultra membrane filters for further filtration. These filters will filter out all the particles, 0.1 microns and larger. This will be a physical barrier to Crytosporidium oocysts and Giardia cysts, cysts that cause intestinal, digestive upsets. Chlorine and ammonia addition will be moved to after the membrane filters prior to entering our 10 million gallon underground clear well (storage tank). The new facility will also enable the District to eliminate two chemicals – cationic polymer and powder activated carbon.