Treatment Plant Odor Control and Corrosion Abatement
Odor Control for Large Metropolitan Wastewater Treatment Plant
As part of a larger team, Perkins Engineering Consultants, Inc. (PECI), designed the biofiltration odor control systems for a new 330 MGD screenings and influent pump station. As part of the project, odor control facilities were needed for the lift station, screen channels, and influent junction box. PECI evaluated the proposed design and determined that an organic media biofilter capable of treating 36,900 cfm would be required. This airflow was carefully determined to include capture velocities for the influent area, screening channels, effluent junction, wetwell, and a large junction box upstream of the facility. To provide ease of maintenance the biofilter was constructed with a manufactured plenum system that can be driven on with construction equipment when the organic media needs to be changed.
Evaluation and Design of Odor Abatement Improvements
PECI was retained by the City of Lewisville, Texas to conduct emissions testing and dispersion modeling for prediction of off-site odor impact from major process units at its wastewater treatment plant. The treatment processes found to cause the greatest off-site odor impact include the influent splitter boxes, fine screens and aerated grit basins. PECI provided design services for odor control and other improvements at the headworks. Foul air from the influent splitter boxes, fine screens and grit removal basins is combined and handled by a single bioscrubber. Screenings disposal was simplified with the addition of a dual washer/compactor system. The grit removal system was converted from aerated grit basins to vortex grit removal basins. The project was completed for $3.2 million.
Odor Control Master Planning, Dispersion Modeling and Design
PECI assessed and prioritized odor sources at a 40 MGD wastewater treatment plant. The evaluation included extensive emissions sampling, odor dispersion modeling and a chemical odor control pilot study. The plant’s influent and sludge holding tanks were identified as the most cost effective process units to target for initial odor control efforts. PECI designed odor abatement improvements for these two areas. The construction project also included identified improvements for reducing aeration system pressures, which reduced power consumption for the treatment train by about 50-percent.
Wastewater Treatment Plant Clarifier Equipment Rehabilitation
PECI was retained to evaluate and design improvements for remediation of corrosion on clarifier equipment in four covered 135 foot diameter primary clarifiers in a regional wastewater treatment plant. Scum beaches, center wells, sludge collectors, and concrete received extensive repairs. Corrosion had exposed steel reinforcement in certain places, requiring replacement of reinforcement and concrete rehabilitation prior to coating installation.
Evaluation and Design of Odor Control Improvements
PECI assisted a larger team of consultants with design of a new, state of the art wastewater treatment facility to serve a rapidly-growing central Texas city. PECI modeled odor dispersion from the plant’s major process units and assisted with selection of odor control improvements. PECI personnel participated in a public meeting at the site and assisted in developing odor-related language for incorporation into an agreement with nearby landowners, enabling formal permit protests to be withdrawn. PECI designed an organic media biofilter, ductwork, and a foul air collection system to serve the plant’s headworks structure and dewatering building.
Odor Control Master Plan
PECI served as a subconsultant to another firm, played a lead role in assessing and prioritizing odor sources at a 4 MGD wastewater treatment plant. The city commissioned this evaluation as a proactive step in addressing extensive residential development in areas immediately adjacent to the facility. This evaluation identifies the plant’s headworks facilities, sludge holding tanks, and sludge drying beds as the most cost effective process units to target for initial odor control efforts. The evaluation included training of city personnel for off-site odor monitoring and assessments, and included development of a complaint response protocol for use by city personnel.
Nuisance Odor Prevention Plan Preparation
PECI has prepared nuisance odor prevention plans for numerous clients. These plans are sometimes required due to State setback requirements; some have been a result of enforcement action stemming from nuisance odors. PECI has prepared nuisance odor plans for a food processing facilities, a grease trap waste processing facility, and for numerous domestic wastewater treatment plants.
Odor Dispersion Model and Odor Control Improvements
PECI was retained to conduct dispersion modeling and to recommend and design specific odor abatement improvements for this 4.5 MGD plant near Dallas, Texas. PECI modeled several different dispersion and improvement scenarios. Design of odor control improvements included a full cover on the Plant’s primary clarifier, cover and exhaust improvements to the Plant’s main lift station, and addition of a bioscrubber for treatment of foul air.
Odor Control Planning and Design
PECI was retained by the City of Wichita Falls to perform and odor source assessment and to develop an odor control master plan for the City’s 19.5 MGD River Road Wastewater Treatment Plant. PECI assisted with design of the first phase of odor abatement improvements, which includes primary clarifier weir covers, junction structure covers, corrosion repairs and a 7,500 CFM foul air collection system.
Odor Control Master Plan and Design
PECI served as a subconsultant playing a lead role in assessing and prioritizing odor sources at a 3 MGD wastewater treatment plant in north Texas. The City commissioned this evaluation as a proactive step in addressing extensive lakefront residential development in areas immediately adjacent to the facility. This evaluation identifies the plant’s grit/grease structure and influent lift stations as the most cost effective process units to target for initial odor control efforts. PECI designed odor abatement improvements to these two areas, including an upgrade to the odor control system at the plant’s existing lift station and a new 1,000 CFM system serving the plant's new headworks processes.
Biosolids Odor Evaluation
PECI was retained to assist with an evaluation of the impacts from a number of processes and activities on odor generation potential from the biosolids produced by a 150 MGD Water Reclamation Facility (WRF). The City desired to proactively address odors at remote beneficial use sites. The project targeted identifying management options within the stabilization, dewatering, storage and transportation process to enable the City and/or its biosolids handling contractor to minimize odor emissions at the beneficial use sites.
The evaluation used simplified test methodologies to assess the impact of certain key processes and factors on odor production potential within the dewatered product. The test methodologies were developed to provide guidance with respect to the management options most likely to practically reduce dewatered biosolids odors.
The proposed test protocol addressed the following parameters related to biosolids odor production, with specific tests related to each:
Impact of co-digestion
Impact of lime
Impact of stockpiling, holding and transport practices
Impact of polymer dosing practices
Impact of water plant residuals
Odor Control System Replacement
PECI assisted a major regional system operator with replacement of two chemical scrubber systems using manufactured bioscrubbers at the owner's largest wastewater treatment plant. The new equipment yielded yielded a chemical cost savings resulting in a three to four year return on investment. PECI previously assisted with a major corrosion repair initiative for the plant’s four 135-foot primary clarifiers.
PECI developed an odor dispersion model illustrating intensity, frequency, and spatial extent of nuisance odors generated by the treatment facilities. Both existing conditions and anticipated future conditions with the new primary clarifier bioscrubbers were modeled.
PECI has since assisted with design of multiple additional odor control improvements at this facility.
Odor Control System Replacement
PECI supported a nationally-recognized firm with design of odor abatement features for expansion of this plant to 10 MGD. The plant is uniquely situated in Frisco, Texas, with well over 1,000 existing and planned single family homes less than ½ mile from the treatment units. PECI's design included a 4,200 cfm bioscrubber and tank covers for the plant’s existing primary clarifier and sludge holding tank, a 16,000 cfm bioscrubber, covers and ductwork serving a new headworks structure and primary clarifier, a 2,400 cfm carbon adsorbers serving minor odor sources, a 71,500 cfm packed tower scrubber system serving the plant’s dewatering building, and a 4,200 cfm bioscrubber serving the plant’s influent lift station. Construction was completed in 2020. Odor abatement improvements designed by PECI are estimated at approximately $7 million and were placed in service in 2020.