Expanded wastewater plant coming online



Nestled quietly between two new subdivisions, a short way down a small road off US Highway 183, sits a technologically advanced new addition to the Liberty Hill landscape that will not be found anywhere in Texas.

The City’s new $10 million wastewater treatment plant is being brought online, and those who know the business, know this plant is economically and environmentally different than anything Central Texas has ever seen.

“The capabilities of the new plant are so far beyond the capabilities of the existing plant that you can’t really compare them,” said Superintendent Vince Perkins. “Other than the fact that they both treat wastewater, there’s no comparison between them. They both have their advantages and disadvantages, but it’s just that the new plant is so far ahead of what we had, that the quality of the effluence leaving the plant is light years from what we had.”

The differences begin with capacity and treatment method. The old plant, a sequential batch reactor, brings in wastewater, treats it, then sends out the effluence before bringing in a new batch of water, similar to how a traditional water heater operates.

“The new plant is a constant flow plant, so it will constantly be bringing new flow in while flow goes out,” Perkins said.

In addition, the new plant can process 800,000 gallons per day, compared to the old plant’s 400,000 gallon capacity.

With both plants online, the city has tripled its daily capacity, but the hope is to bring the old plant offline for maintenance and perhaps mothball it until it is needed at a later date.

“The plan is to shut down the SBR as soon as the other comes online, to do maintenance and make sure everything is good to go on it before we bring it back online,” said Liberty Hill Public Works Director Wayne Bonnet. “That’s if we bring it back online.”

Less maintenance and operating costs are the driving factor in the desire to shut down the old plant.

“The new plant has so much less maintenance requirement that the treatment cost per gallon is going to be a lot less, therefore we would rather try to stay with the new technology, use the old one if we have to in the interim, but try to help the city to move with the newer technology and more efficient cost,” Perkins said. “This plant has far less valves and gizmos and gadgets that you have to do maintenance on than the old plant does.”

The pace of growth will dictate the future use of the old plant, and how quickly the City moves into planning for another addition.

“We feel like we probably have the capacity for somewhere around 5,000 homes,” said City Administrator Greg Boatright. “We’re probably serving between 3,800 and 4,000 now, so we need to move into the planning phase for our next expansion.”

The next expansion, when it comes, will be a mirror image of the new plant, designed to be built at less cost thanks to shared infrastructure on the site.

“Our engineers added a lot of things with this stage that we will be able to adapt the next stage a little more easily,” Bonnet said. “Trying to predict the future as to how the growth is coming, and accommodate that, is very important. We’re all the time looking for ideas for new lift stations, increasing capacity of water lines, things of that nature in town, that we as operators can look at and know we need to get ahead of.”

The City is permitted to handle 4 million gallons per day on the site, but the current expansion was a 14-month process itself, so future expansions will take time and funds.

“It’s a challenge on both ends, just from the timing, because you don’t want to build too soon to where you have that capacity sitting there, but that’s why it is critical for us to be in tune with the development community and our engineers, as to where we need to be in our planning for expansion,” Boatright said.

While efficiency and capacity are important facets of the new plant, for the handful of city employees who are working to get the new plant online and understand how it operates, the science is the thrill.

City employees – part chemist, part biologist, part computer tech and part mechanic – know they are dealing with the top of the line in water treatment, helping Liberty Hill, but also the local environment for all Central Texans.

“As we look at it, we’re trying to do the best we can for the next community,” Bonnet said. “It’s not only for Liberty Hill, it’s for the next community downstream.”

What makes this plant special, is it sends out effluence that meets drinking water standards. The plant tracks the turbidity of the water that has been treated, a key measure used to test water quality.

“It is normally a term only associated with drinking water plants,” Perkins said. “Turbidity is not something you normally measure in wastewater effluence because it’s not that clean. This plant, the effluent coming out is so clean it has turbidimeters to measure the turbidity.”

Drinking water must measure below one to meet turbidity standards. The effluence coming out of the new plant is measuring half that or less.

“The effect that will have on the receiving stream, down here in the river, is incredible,” Perkins said. “We’re going to be putting water in that receiving stream that is well above drinking water standards as far as cleanliness.”

The treatment process is biological, using the same bacteria found in the human digestive system. Keeping them healthy, efficient and the right balance of bacteria is key.

“There are a lot of impacts such as biological factors, weather,” Perkins said. “These bugs are like us, they’d much rather work when it is nice and warm. If you get a big shock load of cold rainwater that comes in from somewhere, they don’t like that. When someone dumps old paint in the system, that creates a chemical shock load, the bugs can’t deal with it. We do a lot of testing on a daily basis to know exactly what’s going on biologically.”

The department takes great pride in using this new technology and hopes to be a great example for other communities.

“We’re licensed by the State of Texas to do what we do,” Perkins said. “They consider us stewards of the environment, so in addition to everything else we do, we’re expected to do our part to protect the environment. This is the only membrane plant, in this part of the United States, with this type of membrane. I fully expect to have people come visit from all over.”