The Lakeway Municipal Utility District’s water treatment is a conventional surface water treatment with a capacity of 6 million gallons per day (MGD). The plant was originally constructed in 1988 and expanded in 1997, 2000 and 2002.

As the raw water enters the plant site, venturi meters measure the flow. When appropriate, the backwash recycle is returned to the head of the plant and the resultant flow is split between Plant A and B/C through the use of set point controllers, flow meters and flow control valves. Next is chemical injection. Alum, the primary coagulant; a cationic polymer, as a coagulant aid; chlorine, as the primary disinfectant; (and atypically, caustic soda, if required for pH adjustment); are injected into static in-line mixers downstream of the flow split. The nominal flow rating for each Plant A, B and C is 2 MGD. The operator selects the desired treatment flow rate set point to each plant and the Supervisory Control and Data Acquisition (SCADA) system will vary the raw water pumping accordingly, automatically taking into account the return of recycled water.

Plant A:  Plant A consists of a reactor (solids contact) clarifier and three dual media filters that are operated in parallel. The nominal capacity of Plant A is 2 MGD, but is reduced by 1/3 during backwash of one of the three filters. This keeps the flow rate to the filters constant to improve performance. During peak summer demand, this plant is operated continuously, while plants B and C cycle on and off as required. This also improves performance. The clarifier has a recirculating pump within the centerwell, reaction chamber, and sludge collection mechanism. The effluent from the clarifier is collected in V-notch radial launderers. Sludge is withdrawn on a periodic basis to the lift station, which pumps the sludge to the S-5 wastewater plant.

The settled water from the clarifier flows through a stilling well before the filters. The three filters are operated in parallel as down flow, constant rate, variable head design. Each filter consists of 103.8 square feet of area, dual media (30 inches of anthracite and sand), and perforated stainless steel plate underdrain. The flow into the filters is limited to 5 gpm per square foot by orifices, and by the SCADA system. Each filter is equipped with loss-of-head instrumentation and an on-line turbidimeter. The filtered water is metered in route to the clearwell. Fluoridation occurs just before the clearwell, as does post chlorination, as a secondary disinfectant.

The backwash of the filters is normally done automatically based on filter run length in hours. Six feet filter loss of head can also initiate backwash. The backwash sequence starts with surface scour, concurrent scour and filter backwash, and ends with backwash only. After a backwash, water is filtered to waste for 30 minutes to allow the filter to "ripen" before placing it into production service.

Plant B/C:  Plant B/C consists of two "Microfloc" modular treatment units having a nominal capacity of 4 MGD. The unit includes an adsorption clarifier, tri-media filter, and controls. The coagulated flow from the static mixers flows up through the adsorption clarifier media. In the adsorption clarifier, the rough filtering effect removes most turbidity. The clarified water flows from the adsorption clarifier to the filter through a distribution trough. The filter is a constant head, variable flow rate design with 280 square feet filter area, mixed media, and well screen underdrains. The mixed media consists of anthracite, sand, and garnet with no support gravel. From the treatment unit, the filtered water flows to the clearwell, where it is metered and fluoride and chlorine are added.

The backwash of the filters is normally done automatically based on operating time, although filter loss of head will also initiate. The backwash sequence starts with air scour, concurrent scour and filter backwash, and ends with backwash only. After a backwash, the filter effluent is wasted to drain for 30 minutes to allow the filter to "ripen" before placing it into service.

Filtered water flows into the 275,000-gallon clearwell. Clearwell levels control the raw water pump operation, based on lead, lag and 2^nd lag levels selected by the operator. A venturi meter totalizes the finished water flow while an on-line chlorine analyzer and turbidity meter continuously monitor finished water quality.

The high service pump station delivers water to the Lakeway lower pressure plane using one 500, two 1400, and/or two 2800 gpm pumps. The pumps all have smart motor controllers for soft starts and stops to eliminate pressure surges. The station also has two backwash and one surface wash water pumps.

Operators do not continuously man this plant, but there is always an "On Call" operator available. The very sophisticated Supervisory Control and Data Acquisition system (SCADA) enables this. Through a graphic Human Machine Interface (HMI), the system allows the operator to observe and control every aspect of the plant operation. The control network includes raw water supply systems, the plant site, as well as the complete Lakeway water distribution system of booster pump stations and elevated storage. The network allows operator access remotely by laptop from anywhere. There are 32 separate water quality, tank level, and equipment alarms that call an operator via cell phone. Often, the operator can respond via remote connection and resolve the alarm. If not, the operator has the information to mobilize the proper response.