Wastewater Treatment Plant Pump Station Improvements

Ferris, Texas

As a subconsultant to a partnered firm we rehabilitated the sludge and thickener make-up water pumping system at the Ten Mile Creek Wastewater Treatment Plant in Ferris, Texas.  Seven vertical end suction centrifugal pumps were replaced, suction and discharge headers were converted from welded steel to ductile iron pipe, and upgrades were made to the electrical and instrumentation systems including adjustable frequency drives for the new pumps. To minimize process downtime, provisions were put in place to allow for temporary pumping diversion – maintaining a minimum of 50% pumping capacity – while portions of the pump and piping system were rehabilitated.  The improvements utilized the available spacing inside the existing pump station and accommodated new equipment with minimal modifications.

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Regional Treatment Plant Hydraulic Improvements

Grand Prairie, Texas

Perkins Engineering Consultants, Inc., serving as a subconsultant to another firm, was responsible for identifying hydraulic relief improvements needed to enable this 152-mgd regional plant to better distribute flows from its 12 secondary clarifiers to its 32 low-head effluent filters, some of which are being abandoned while others are receiving significant capacity upgrades via cloth media retrofits. Two relief tunnels were identified and designed. The first involved a relatively short but complex 84-inch relief tunnel to connect the effluent troughs from two isolated banks of clarifiers. This pipeline was partially installed by open cut, but due to electrical duct banks and other large utilities in the vicinity, specific portions had to be installed by tunneling in tight, confined operating plant areas and beneath roadways. This project was completed in 2016. A second cast-in-place relief tunnel is scheduled for construction in 2017.

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Regional Wastewater Systems Evaluations

Wylie, Texas

When additional customer cities are added to a regional wastewater facility, or when the choice is between a plant expansion or resurrecting a mothballed WWTP, determining the best course of action can be daunting.  We recently helped one client with this decision at two separate regional systems.  In both cases, we coordinated flow and rainfall monitoring and associated inflow/infiltration analysis, Q vs. i analysis and development of future storm and flow projection scenarios.  Population and flow projections were considered as was the cost of returning old facilities to service. At one facility the Owner decided to expand an existing facility from 1.5 MGD to 3.0 MGD; PECI designed the plant expansion.  In another, PECI conducted a subsequent study evaluating adding two new customers in the regional system.

Nutrient Removal Evaluation and Aeration System Improvements

Mesquite, Texas

PECI evaluated biological nutrient removal (BNR) process configurations for a 33 MGD regional wastewater treatment plant. Historical operating and additional sampling data were collected, organized and analyzed to define design conditions, including diurnal fluctuations. Unit processes, equipment sizes and configurations were determined for three BNR processes using BioWin models and preliminary layouts were developed for each configuration.  Life cycle cost comparisons were prepared for each of the three BNR alternatives.

The first 13.9 MGD phase was constructed at a cost $4.5 million. Improvements include replacing three existing multistage centrifugal blowers with high speed turbo blowers (6,000 scfm each), addition of a new CMU electrical building and adding baffle walls, anaerobic and anoxic zone submersible mixers, mixed liquor recycle pumps and piping, and new effluent gates to six existing Aeration Basins.

Doppler Area Velocity Meter Station

Dallas, Texas

Most open channel flow measurement methods require flow to transition from subcritical to supercritical.  In some cases, the flow transition is difficult or impossible to achieve due to conflicts with existing utilities, existing interceptor hydraulics, or downstream connections.  In those cases, alternate methods of flow measurement are needed.  The Trinity River Authority of Texas recently installed an area-velocity meter to measure flow in an interceptor that was not suitable for other types of metering.  Using Doppler radar and an ultrasonic level indicator, the open water surface area and the velocity of the water can be measured.  These two values are used to calculate the flow rate in the interceptor.  This meter station started operation in 2015.

Parshall Flume Meter Stations

Dallas, Texas

Accurate flow measurement is critical for many clients.  Used for billing, flow projection, and capacity evaluation, dedicated meter stations are used at treatment plants and in collection systems.  Designed with careful consideration of the upstream and downstream hydraulic conditions, our engineers are experienced in optimizing the entrance and exit conditions of Parshall Flumes to achieve a distinct, repeatable transition from subcritical to supercritical flow.  PECI recently designed multiple meter stations for the Trinity River Authority of Texas.  One meter station was particularly challenging as it was experiencing hydraulic wave action that interfered with level measurement.  PECI evaluated the installation and determined that the upstream interceptor could not provide the flow conditions needed for accurate measurement.  PECI recommended a vortex-type flow baffle in an upstream manhole and flattening the slope of the interceptor to improve entrance conditions.  The three-foot flume and associated work is under construction and is expected to be in service by the end of 2017.

Collection System Meter Stations

Perkins Engineering Consultants has become a leader in meter station evaluation and design for wastewater collection systems.  From traditional measuring devices, such as Parshall and Palmer-Bowlus Flumes, to cutting edge technology, such as the Hach Flodar® AV sensor, our engineers have evaluated and designed multiple meter stations.  Flow regimes, hydraulic calculations and interpretation of the results all play important roles in the success and accuracy of any meter station.  Our expertise extends to evaluating upstream and downstream conditions, determining the state of flow across the entire range of flows, and setting the appropriate installation conditions for successful operation.

Regional Treatment Plant Clarifier and Thickener Rehabilitation

Grand Prairie, Texas

Perkins Engineering Consultants, Inc. served as the mechanical and process engineer for rehabilitation and improvements to the CRWS plant. This is a multifaceted project involving a large design team, in which PECI led design efforts for:

  • New primary clarifier scum facility;
  • Mechanism replacement on large rectangular clarifiers;
  • Mechanism replacement on circular gravity thickeners:
  • Aluminum truss supported flat covers on the gravity thickeners; and
  • Corrosion and coatings repairs on multiple structures.

The overall project bid at $23 million and is currently under construction.