Potable (Drinking) Water Production
All of our customers’ water comes from the beautiful Lake Travis, where two raw water pump systems are located, right near the iconic “mushroom house” in Old Lakeway off Mariner. To accommodate the lake level variability, the raw water pumps reside on floating barges. The two raw water systems are completely independent but interconnect at our Water Production Plant, located at the end of Lakeway Blvd.
As the raw water enters the plant site, chemicals are injected into raw water line before a static mixer that properly mixes chemicals with water to obtain coagulation. Coagulation is the chemical process of removing suspended and dissolved compounds (turbidity) out of water by forming floc. The floc is where organic and inorganic particles clump together becoming larger and heavier which settle out of the water easier in sedimentation clarifiers or adsorb to pellets in adsorption clarifiers. Various chemicals and techniques are used for coagulation-flocculation in water treatment, but LMUD only uses Chlorine(Cl2) as an oxidizer, Poly Aluminum Chloride(PAC) as primary coagulant and a cationic Polymer(Poly) for coagulation aid.
Plant A is a Solids Contact Clarifier plant consisting of a up-flow clarifier and 3 dual media filters capable of producing 2 million gallons per day (MGD). Plants B and C are two independent Microfloc units consisting of an up-flow adsorption clarifier and tri-media filter capable of producing 2.6 MGD each. Total production is 7.2 MGD.
The settle water flows to the dual media filters for plant A and the tri-media filters for plants B and C. The media filters consist of anthracite coal, sand and garnet that are layered on filter effluent underdrains that collects the filter water uniformly. This stage catches particles that may have pushed through the settling stage.
The individual filtered water from all 3 plants combines in a header pipe where Liquid Ammonia Sulphate(LAS) and Chlorine are added to disinfect the filtered water. With the addition of a 4 to 1 ratio of Cl2 to LAS monochloramines are formed, which kills germs but is still safe to drink. Fluoride is also added at this juncture to help promote healthy teeth.
The disinfected filtered water flows to 3 Clearwells with capacity of just under 2 million gallons. Once travelling through the baffled clearwells the finished water is pumped out to one of the 5 different storage tanks throughout the distribution system. These tanks are called elevated storage. By having the water in a tank high in the air, gravity pulls the water downward, providing pressure so the water will flow when you turn on the faucet.
LMUD’s potable (drinking) water production and wastewater processing never cross paths, with separate facilities and staff handling each process. When wastewater is generated from the homes or businesses we service, the waste enters our system (from sinks, toilets or drains) through pipelines known as the “collection system,” into manholes. Our “lift stations” then pump the waste flow to our treatment plant.
The flow enters the plant through mechanical screens to screen any and every bit of inorganic solids that won’t be processed. The flow then enters what is known as the “aeration basins” for the reaction with diffused air from electrical/mechanical blowers. This helps the bacteria in the sludge process and provides food for the bacteria to continue the growth. In the process, the sludge levels are maintained and controlled from a variety of testing and analysis.
The mixed liquor suspended solids (MLSS) is one the main test performed in the process for the balance of liquid to solids ratio. Through the process the plant is operated to make good, healthy, active sludge. The bad or excessive sludge levels are then wasted to the thickener/digester. This is (was) Waste Activated Sludge for thickening/dewatering. The sludge then gets belt pressed and hauled away to a composting facility.
The good, healthy sludge continues in the process with the multiplying and balance of good bacteria. Through the recirculation of the activated sludge it enters the clarifiers or settling basins then separates solids from liquid. The solids are returned back into the aeration basin process through pumping, this is (RAS) Return Activated Sludge.
The liquid that’s separated and clarified is known as supernatant. The supernatant is flowing out of the clarifiers into the filters for pre-chlorination and filtration. The filters are a 3 layer media level. Large sand, small sand, anthracite media. The filtered water now known as filtered effluent flows out of the filter into the chlorine contact chamber for post-chlorination and contact time. This is now known as wastewater reuse.
Finished water for reuse is transferred to storage in one of our storage ponds. The ponds have pumps that distribute water used for residential, commercial, golf courses, and city medians for landscape irrigation. None of the water is returned to Lake Travis.
Learn more about our conservation efforts through reuse water
Safety, Security, and Consistency Standards
No matter the time or day, there is always an “On Call” operator available. Our sophisticated Supervisory Control and Data Acquisition (SCADA) system enables this for both our potable water and wastewater operations. Through a graphic Human Machine Interface (HMI), the system allows our highly trained operators to observe and control every aspect of our operations. The control network includes raw water supply systems, the plant sites, as well as the complete Lakeway water distribution system of booster pump stations and elevated storage tanks. The network allows our operators 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.