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Posted on: July 3, 2019

Water Treatment Plant

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The City of Liberty Hill prioritizes timely and transparent communication with our residents. This webpage has been created to ensure everyone is informed about the operations of the Liberty Hill Regional Wastewater Treatment Plant (WWTP), including any issues or updates.

Please check back for regular updates or subscribe to our email list.

Plant Background and Operation

Liberty Hill’s current WWTP began operating in January 2018, providing additional capacity to support the city’s growing population and replacing an older Sequence Batch Reactor (SBR) wastewater treatment plant. The new plant processes approximately 800,000 gallons of influent per day, with a total permitted capacity of four million gallons per day.

The City is committed to ensuring its systems operate at the highest level, and the new plant uses Membrane Batch Reactor (MBR) technology with an ultraviolet (UV) disinfection process rather than chlorination. MBR is the leading industry practice for municipal and industrial wastewater treatment.

Wastewater enters the influent collection structure and is then sent through the MBR headworks and treatment train of the plant. The headworks consists of an automatic rotary bar screen and degritter, an aerobic sludge basin and a sludge belt press to remove wastes. Wastewater then passes into a basin where it receives an initial UV disinfection treatment and then is filtered before being released to an effluent outfall. The treated and disinfected water is then discharged into the San Gabriel River.

Due to the volume of wastewater that area residents generate, the MBR is reaching its capacity. For that reason, the City is upgrading and putting the SBR back into service.

Environmental Impact and Protection The City’s WWTP is regulated by the Texas Commission on Environmental Quality(TCEQ). As part of TCEQ’s protocol, regular inspections are conducted and the City is responsible for reporting any issues or violations that may occur.

The operation of a wastewater treatment plant, especially the MBR, is complex, and mechanical issues sometimes occur unexpectedly. The City uses a SCADA control system for the treatment plant, which allows the City to monitor and run the plant remotely. Various data points come into a central hub, and the system will provide an alarm if there is an issue.

Recent News and Updates

In March 2019, the City initiated the process of bringing the SBR back into service to handle the additional flow from area residents. This required additional construction on site. Unfortunately, as happens in construction and start-ups, there were some unintended and unforeseen events. Here, wires to the SCADA (alarm) system were cut during some excavation. In the meantime, a filter became clogged and wastewater levels rose to the point where the wastewater bypassed the separation barrier and it entered the effluent outfall without filtration. This prevented the alarm from notifying the operators of the issue. The result was that from March 16 to 17, 2019, approximately 3,000 gallons of partially treated wastewater was released to an effluent outfall. After reporting the spill to TCEQ and investigating the issue, the City removed the partially treated solid and properly disposed of them. The City has since replaced all necessary components to ensure the alarm works properly moving forward.

Resulting TCEQ inspections resulted in the City being cited on May 7, 2019, for one violation: failure to prevent that unauthorized discharge. The City worked quickly to bring its operations into compliance with TCEQ’s standards ahead of the June 6, 2019 deadline. Even this small amount of discharge – less than one percent of the influent the plant treats on a daily basis – is too much. This situation provided an opportunity for City staff to evaluate protocols and improve processes to prevent this type of occurrence in the future.

Actions City staff have taken to address this situation and prevent future issues include:

  • Updating the WWTP control system to ensure everything is working properly;
  • Enhancing the cleaning process for the filters used at the WWTP;
  • Proactively cleaning the outfall, removing any vegetation that might impede flow;
  • Sending out a vacuum truck on a weekly basis to maintain a clean outfall; and,
  • Taking samples upstream, near the outfall and downstream, multiple times per week, to monitor the water and ensure the WWTP is not affecting the river.

As a City, we will continue to use this situation as a learning opportunity as we strive to improve daily. If you ever have questions about the City’s operations of the WWTP, please contact us.

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