Wastewater Treatment Plant Design and Rehabilitation

Regional Treatment Plant Hydraulic Improvements

PECI 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.

Plant Rehabilitation

PECI has designed multiple improvements to a 10 MGD plant serving two cities in north Texas. PECI specified a biological odor control system (bioscrubber) with organic media for the influent lift station. This allowed the owner to reduce the usage of the existing chemical scrubber located at the solids handling building and resulted in substantial chemical and energy costs. To reduce corrosion in the existing electrical room, PECI specified a positive pressurization unit to pressurize the room with scrubbed air. In addition PECI redesigned the existing chemical storage area with new bulk tanks to accommodate full truckloads of sodium hydroxide and sodium hypochlorite.

Primary and Secondary Clarifier Rehabilitation

PECI served as prime consultant responsible for design of major corrosion repairs to four large primary clarifiers and four secondary clarifiers at a 48 MGD regional wastewater system serving multiple north Texas cities. The project involved assessment and repair of corrosion damage to concrete structures, rehabilitation of four 135-foot aluminum low-profile basin covers, weir and baffle replacements and skimming system rehabilitation. An assessment of the effectiveness of the scrubbing and ventilation systems serving the primary clarifier was also included.

Blower and Aeration System Upgrade

PECI served as prime design consultant assisting a major north Texas city with an update of the activated sludge process in its 24 MGD wastewater treatment plant. The project included installation of new high speed turbo aeration blowers, air piping, and fine bubble membrane diffusers. The existing aeration system included four multistage centrifugal blowers. The project was placed in service at a cost of $2.6 million.

Snail Collection and Slurry Pumping System

As part of a larger plant rehabilitation project, PECI designed a special settling basin to capture snails from a trickling filter process. A pumping system was designed to move the snail-laden slurry into a classifier so that snails could be deposited in a roll-off container for hauling off-site. The project significantly reduced snail accumulation in downstream basins.

Screen and Conveyor System Replacement

PECI assisted the City of Garland with replacement of screening and conveyor equipment in the headworks building at the City’s 24-MGD Rowlett Creek Wastewater Treatment Plant. Equipment installation was performed by City personnel.

Plant-Wide Rehabilitation Improvements

PECI was retained by to assess and prioritize rehabilitation needs throughout a 24 MGD  wastewater treatment plant serving multiple cities. The treatment facilities had been constructed and expanded under numerous contracts, with many facilities over 40 years of age. Corrosion and structural deterioration was a concern in a number of areas.

​

PECI served as prime consultant responsible for detailed design of the highest priority improvements under two construction projects.  These projects included extensive corrosion repairs to a number of covered concrete structures within the plant, drainage improvements inside the plant’s dewatering building, addition of a 5,000 CFM bioscrubber for odor control, replacement of the plant’s aging return and waste activated sludge piping and distribution system, rehabilitation of approximately 3,500 square yards of in-plant paving surfaces, and addition of access and security improvements. Full-span truss supported aluminum covers were added to the plant's primary clarifiers, screens were replaced, and major electrical gear was rehabilitated.

Plant Rehabilitation Needs Assessment

PECI served as prime consultant responsible for a plant-wide assessment and prioritization of rehabilitation needs for this 152 MGD regional wastewater treatment facility. The effort included review of the age, criticality, and condition of dozens of major process units, along with development of projected costs for rehabilitation. Coordination with multiple consultant teams was required. The evaluation identified recommended in-plant rehabilitation totaling approximately sixty million over a span of six to ten years.

Wastewater Treatment Plant Domes and Mixing System Addition

Perkins Engineering Consultants, Inc. assisted the City of Sherman with addition of domes to cover three 90-foot final clarifiers for algae control. The project also included addition of a jet mixing system for the plant’s wet weather storage facility. The project was placed in service at a cost of $1.4 million.