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Surface Water and Treatment System

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The Brazos Regional Public Utility Agency water treatment facility has a total rated production capacity of 13 million gallons a day. The plant consists of a traditional filtered water operation and an Ultra Filtration and Reverse Osmosis operation. The plant receives raw water through one intake located on Lake Granbury, which is fed by the Brazos River.

The treatment plant construction began in 1988. The plant consists of a raw water intake structure located ¼ mile from the plant site. Initially the intake structure was comprised of 3 vertical pumps, two rated at 3,500 gpm and one rated at 3000 gpm. Water was pumped through a 24” line to a two-stage rapid mix basin.   Water flowed from the rapid mix to (2) two 60’ diameter upflow (solids-contact) clarifiers for flocculation and clarification.   Sludge was blown down manually to sludge lagoons. Chlorine dioxide was added as a pre-disinfectant for the raw water. A generator at the plant mixes sodium chlorite and chlorine gas and forms chlorine dioxide, which is pumped from the plant to the intake and injected in the raw water header. Chlorine dioxide provides the contact time needed for disinfection credit and does not react with organics in the water. The Brazos River water contains bromide.

In 2000, the plant was expanded from 5.04 MGD to 13 MGD. In addition to high chloride and sulfate content, the Brazos River also has elevated barium levels. The expansion included construction of a new treatment train, which consisted of: a parallel 30” raw water line, a new clarifier initially rated at 6.2 MGD dedicated to the membrane system train; a lime/soda ash slaking system; an Ultra-Filtration membrane system; an RO membrane system; a recarbonation system; and a sludge press system.   For additional storage to the original 1 MG tank, a baffled 3 MG finished water storage tank was constructed during Phase I of this expansion, and the dual media conventional filters were rehabilitated with Leopold underdrains. The new clarifier was added for the membrane system, although water can be routed to the dual-media filters. The (2) two original clarifiers are dedicated to the conventional filters.

Membranes cannot tolerate polymer, thus the system is restricted on the amount of aluminum residual that can remain in the feed water to the membranes. As a result, ferric chloride is used as the coagulant in addition to the lime and soda ash. A lot of sludge is generated with the lime process, so a J-Press is used to process the sludge for landfill disposal.

The treatment process schematic is as follows. Raw water is pumped from the intake to the plant through both the 24” and 30” parallel raw water lines. Chlorine dioxide is injected in the raw water header at the intake. Ferric chloride is injected in the raw water line after the meter and prior to the clarifiers. Lime is fed on top of each clarifier center well. The plant previously used soda ash, but soda ash was not completely going into solution, and was fouling the strainers on the UF feed system. Soda ash was discontinued in 2003 and is not in service. Carbon dioxide is injected in a recarbonation basin prior to the UF membrane system and conventional filters to bring the pH back down to a range between 7.5-7.8. Chlorine gas and LAS (liquid ammonium sulfate) is also introduced into this basin to form chloramines ahead of the membrane treatment facility and conventional filters. Due to our high TTHM potential, free chlorine is not used, so chloramines are added. After the recarbonation basin, water can be pumped to the UF system or gravity flow to the conventional filters. The UF permeate flows to a 500,000 gallon tank, where water is pumped to the RO membrane system or can overflow to the conventional filtered water storage tank. The RO permeate is then blended with the conventional filtered water, disinfected with chloramines, and pH adjusted with caustic (sodium hydroxide) prior to entering the 3 MG finished water. Water flows from the 3 MG tank to the 1 MG tank before it is sent out to distribution.   The plant is permitted through the state to send the RO concentrate water back to Lake Granbury. The plant was divided into 2 trains: a conventional plant and a membrane plant. Monthly operating reports include the conventional plant, the membrane plant, a Chlorine Dioxide MOR, and a TPDES report for the RO concentrate reject water.

In 2007, the Ultra-Filtration system was expanded by adding a 5th train and retrofitting the older trains to fit the new membranes (Norit). The UF capacity is 9.125 MGD, and in 2009, the RO trains were retrofitted to bring the capacity to 7.5 MGD.

All of the sludge from the clarifiers is now blown down to the sludge thickener. From there, it is pumped to the dewatering building where the sludge is pressed by the J-Press into cakes and is hauled off to landfill. The plant has a septic tank system and drain field for wastewater. The plant recycles as much process water as is possible. Waste materials are hauled from the plant by commercial waste haulers.

In 2012, AMUD and JCSUD purchased the plant and formed a new entity called Brazos Regional Public Utility Agency which took over the operations of the facility in June 2012.