Representative Projects

Representative Project Summaries

The following are a series of relevant industrial wastewater treatment engineering, operations, and management projects.


Wastewater Treatment Facility

Salty Snack Food Manufacturing Plant

This international salty snack food manufacturer constructed a new manufacturing operation in Orizaba, Mexico that was required to provide pretreatment of its 1.5 MGD process wastewater stream. Conceptual and detailed design services were performed on a fast track schedule (45 days) to meet the clients accelerated construction schedule. The treatment system was designed to provide full secondary treatment, although the initial phase of construction included only the primary treatment system. The primary treatment system consisted of screening, flow equalization, pH adjustment, chemical conditioning, dissolved air flotation, and sludge dewatering facilities to handle approximately 25,000 lbs/day dry solids. Construction of the facility was completed in October 1999 at a cost of approximately US$2.3 million.

Sludge Treatment Facility

Baby Food Manufacturing Plant

This international baby food manufacturing plant operates an on-site pretreatment plant that was plagued with problems related to deficient sludge storage/digestion facilities. Engineering and economic analyses determined that the existing aerobic digester tank could be utilized for a new autoheating thermophilic aerobic digestion process for stabilization and mass/volume reduction of the waste biological solids. Preliminary studies were performed on site using a trailer mounted pilot plant to confirm the applicability of the process and develop the design parameters for the full-scale system. Based on the results of the study, the client elected to implement the project using a design/build project delivery method. Preliminary design documents were developed and used for price negotiations with construction contractors. Other services provided under the design/build contract include start-up assistance and training of the client’s treatment plant operations staff.

Wastewater Pretreatment Facility

Snack Food (Bakery) Manufacturing Plant

This large snack food manufacturing plant operated a biological wastewater treatment plant to provide pretreatment of its process wastewater prior to discharge to the municipal sewer system. The existing plant was in poor condition and required a major expansion to handle planned production increases. Engineering and economic evaluations determined that the lowest cost alternative was to abandon the existing treatment plant and construct a new treatment system to serve the industries long term needs. The economic evaluation also determined that the additional capital and operating cost to provide secondary treatment was greater than the cost of the municipality’s sewer surcharges. The decision was made to construct only primary treatment with the option of upgrading the system to full secondary treatment in the future. The primary treatment system consists of screening, flow equalization, dissolved air flotation, sludge dewatering and pH adjustment to treat an average daily flow of approximately 300,000 gpd. The client requested a design/build project delivery method, and preliminary design documents were used to select a contractor and establish a guaranteed maximum price.

Wastewater Pretreatment Facility

Salty Snack Food Manufacturing Plant

This international snack food manufacturer operates a large manufacturing plant in the border town of Mexicali, Baja Mexico. The industry recently completed construction of a physical/chemical pretreatment plant, but new federal regulations required the plant to meet more stringent discharge limits. Conceptual engineering evaluations determined that a coupled biotower fixed-film/activated sludge treatment process was the most cost effective solution for this particular installation. Services included detail design for the treatment process and preparation of detailed equipment specifications for direct purchase by the client.

Wastewater Pretreatment Facility Upgrade

Candy Manufacturing Plant

This international candy manufacturing firm operates a two-stage activated sludge treatment plant for pretreatment of process wastewater prior to discharge to the municipal sewer system. The industry had been hauling away sweetwater from the manufacturing process at high cost, and requested an evaluation of the treatment system to determine the modifications required to enable the wastewater plant to treat the 50,000 mg/L to 100,000 mg/L COD sweetwater. An engineering and operational evaluation of the existing treatment plant determined that it was already operating near maximum capacity. Conceptual engineering evaluations of several alternatives determined that a new thermophilic activated sludge process could replace the existing 1st stage activated sludge tank and effectively double the treatment plant capacity in a much smaller tank volume and without increasing the aeration horsepower requirements. Extensive pilot studies using a trailer mounted pilot plant confirmed the suitability of the thermophilic activated sludge process and provided the necessary engineering design parameters for design of the full-scale system. The process consists of flow equalization, a new 225,000 gallon insulated grade steel tank, jet aeration system, effluent cooling system, liquid/solid separation and sophisticated automated control system.

Wastewater Pretreatment Facility

Salty Snack Food Manufacturing Plant

This international snack food manufacturer operated a manufacturing plant in western Venezuela. The original manufacturing plant was equipped with a simple activated sludge pretreatment plant that was inadequate to handle the flow and organic loading from the existing production lines. The industry desired to further expand production and requested an evaluation of the wastewater treatment plant to determine the improvements necessary to accommodate the additional flow. Engineering evaluations determined that a primary treatment system would be required, and that addition conversion of the biological process to a two-stage activated sludge system was most economical. Primary treatment consists of screening, flow equalization, dissolved air flotation, chemical conditioning and pH adjustment. Improvements to the biological system include a new activated sludge tank with coarse bubble diffused aeration, and a new clarifier. Primary and biological sludge is dewatered with a belt filter press. Services included detail design, preparation of detailed equipment specifications for direct purchase by the owner, start-up assistance and operator training.

Wastewater Pretreatment Facility

Salty Snack Food Manufacturing Plant

This international snack food manufacturer is planning construction of a new manufacturing plant in central Venezuela. The facility will be required to provide treatment of its process wastewater prior to direct discharge to a receiving stream. The industry desired to construct the treatment plant in multiple phases to match the Economic evaluations. The Stover Group determined that a conventional activated sludge treatment plant would be the most cost effective process for this location. Services included detail design, preparation of detailed equipment specifications for direct purchase by the owner, start-up assistance and operator training

Wastewater Treatment Facility

Juice and Baby Food Manufacturing Plant

This major U.S. based baby food manufacturer operates a juice and baby food manufacturing plant in Poland. When the production facility was initially purchased it was a juice processing plant. With the significant increase in production (juice and baby food) and associated wastewater discharges, the facility was required to implement wastewater pretreatment. The decision was made to develop wastewater treatment capabilities for either pretreatment or direct discharge alternatives. The first activities included developing a process design basis and performing concept engineering analyses for the new wastewater treatment facilities. The selected alternative consisted of biological treatment using sequencing batch reactors (SBRs). The overall treatment process consisted of raw wastewater pretreatment by screening biological treatment and sludge processing. Process engineering details were finalized and requests for proposals were prepared for detail design and construction. The Stover Group from the beginning of the project through design, construction, and operations start-up and training provided total wastewater program oversight.

Wastewater Pretreatment Facility

Candy Manufacturing Plant

This major U. S. based candy manufacturer operates a manufacturing plant in the southeastern U. S. The wastewater pretreatment facilities were suffering from process overloading, design deficiencies, equipment problems, and lack of a proper operational process control and management program. The Stover Group was requested to take over operations of the pretreatment facility through a contract operations and management program, develop a program for repair/replacement of equipment, evaluate upgrade/improvement alternatives, and select the best method for increasing treatment plant capacity. The wastewater pretreatment facilities consist of equalization, chemical conditioning, dissolved air flotation, biological/activated sludge treatment, and effluent polishing by constructed wetlands.

Wastewater Treatment Facility

Snack Food Manufacturing Plant

This major U. S. based salty snack food manufacturer operates a manufacturing plant in Turkey. A wastewater treatment plant had been designed and built for treatment of all the process wastewaters prior to direct discharge. The treatment facilities consisted of screening, equalization, dissolved air flotation, biological sequencing batch reactors, and sludge handling and processing facilities. After start-up, the treatment plant was not capable of achieving the direct discharge standards or handling the waste sludges produced. The Stover Group was retained to perform a detailed plant evaluation, perform operator training, develop an operational process control program, and oversee plant operations until the plant came into compliance. The plant was brought into compliance and a resolution to the sludge handling problems was developed. Additional sludge handling facilities were designed and installed to provide adequate capacity. Additional wastewater concept engineering studies have been completed for future production plant expansions.

Wastewater Pretreatment Facilities

Snack Food Manufacturing Plants

This major U. S. based salty snack food manufacturer operates manufacturing plants in South Africa. Wastewater pretreatment plants had been provided at these production facilities. The existing treatment processes were preliminary treatment by screening, solids/liquid separation, and solids handling facilities. Design, operational, and performance problems existed at these facilities. The Stover Group was retained to perform process engineering and functional operational evaluations of these facilities along with operational advice/assistance. Concept engineering studies were performed for plant improvements along with increased treatment capacity.

Wastewater Treatment Facility

Soy Protein Plant

This large soy flake processing plant produces various soy protein products. Process wastewater was treated in anaerobic lagoons followed by activated sludge treatment. Various biological process problems, including anaerobic upsets, filamentous growth problems, and pH control problems, along with aquatic toxicity test failures, and plans for future production expansions required process engineering evaluations, toxicity identification/toxicity reduction evaluations, pilot studies, concept engineering analyses, and operating assistance. The Stover Group was retained to provide all of these services over the last several years. Significant operational process changes have been implemented, additional anaerobic treatment capacity has been built, additional aerobic capacity has been built, an anoxic denitrification step has been installed, and an operational process control program has been developed. The Stover Group continues to provide operational advice/assistance oversight to this complex wastewater treatment program for anaerobic, anoxic and aerobic biological treatment including biological nutrient removal.

Wastewater Treatment Facility

Soy Protein Plant

This major U. S. based soy protein processing manufacturer operates a plant in Belgium. Process wastewater is treated by anaerobic lagoons followed by an activated sludge biological nutrient removal system. Stricter regulatory requirements and the desire for production expansion necessitated the development of an overall master plan for improved and expanded wastewater treatment facilities. The Stover Group was retained to provide overall wastewater program technical management and planning assistance. Activities have included wastewater characterization studies, process engineering and functional operational evaluations, concept engineering studies, operational advice/assistance, as well as technical oversight of all aspects of the wastewater treatment plant evaluations.

Wastewater Treatment Facility

Baby Food Manufacturing Plant

This major U. S. based baby food manufacturer operates a baby food manufacturing plant in Mexico. Regulatory requirements dictated that the facility build a new wastewater treatment plant. Unfortunately, after the plant was designed, built, and started up, the client learned that the new plant could not achieve the required discharge limitation. The plant consisted of screening, primary clarification, rock trickling filter activated sludge processing, and sludge handling and dewatering facilities. The Stover Group was initially retained to perform a process engineering and functional operational evaluation. This evaluation determined that there were major capacity deficiency problems in the biological treatment process. The Stover Group then performed concept engineering analyses, and developed upgrade/expansion alternatives for the plant. The rock trickling filter was converted to a plastic media biotower with forced air ventilation, the primary clarifier was converted to an aeration basin and additional aeration horsepower was supplied to the existing aeration basin. An operational process control program was developed, operator training was performed, and total wastewater program oversight was provided until all the problems had been resolved.

Wastewater Treatment Facility

Poultry Processing Plant

This large poultry processing plant operates a direct discharging treatment plant which was operating near design capacity. The facility was constructed new in 1992 as a turn-key project, and the facility was plagued by a number of design and operating problems and was frequently out of compliance with its discharge permit limits. The treatment plant utilized dissolved air floatation for primary treatment followed by a biological tower and clarifier for secondary treatment.

The Stover Group’s initial services were operations consulting and process optimization. Subsequently, the client desired an evaluation of the treatment facility to determine if the facility was capable of meeting the discharge limits. A detailed process analysis based on the plant’s operating records was used to predict the likely effluent quality at design loading conditions. It was determined that the biotower process would be inadequate to meet the discharge requirements. A concept design was performed to define a cost effective alternative for upgrading the facility. The recommended upgrade included construction of a new larger clarifier and retrofitting the existing clarifier to serve as an activated sludge nitrification process. Thus, the biological treatment system was converted to a coupled biotower/activated sludge process. It was also recommended to construct a centrifugal grit removal system between the biotower and activated sludge tank to remove the large amount of snails entrained in the biotower effluent.

Based on these recommendations, detailed construction plans and specifications were prepared. The facility was constructed and started up in 1996/97. The modifications were constructed without having to shut down the existing treatment plant and with no major interruptions to the manufacturing process. Engineering services also included construction phase engineering assistance and preparation of an operational process control manual. A computerized data management program was prepared to assist with data analysis and daily operational/process control decisions. The modified system quickly achieved, and has consistently maintained, full compliance with the requirements of the discharge permit. The coupled biotower/activated sludge process has proven to be easy to operated, and has been highly resistant to shock loadings. Effluent quality has been very consistent, even at flow and loading conditions greater than the design basis.

Wastewater Treatment Facility

Poultry Processing Plant

This large wastewater treatment plant is owned and operated by a small municipality to treat process wastewater from a large poultry processing plant under an unusual industrial development agreement. The wastewater treatment plant was plagued by persistent operational problems, and even though it was operating well below its design flow and loading conditions, the plant was frequently out of compliance with the requirements of the discharge permit. Problems consisted of poorly conceived chemical conditioning systems prior to the dissolved air floatation units, hydraulic bottlenecks, and inadequate oxygen transfer capacity.

Because the municipality was in danger of sanctions by EPA, the municipality and the poultry processing company jointly requested an expedited engineering assessment of the treatment plant, as well as recommendations and cost estimates for a program to upgrade the plant to enable it to meet the requirements of the discharge permit at design flow and loading conditions. The recommendations presented in the evaluation report were adopted by the municipality and poultry processing company. The report was also submitted to the regulatory agency and served as a basis for consent agreements with the regulatory agencies to delay sanctions, and to secure emergency funding from the industrial development authority. An interim operational program was developed to help maintain the best effluent quality possible during the design and construction phases of the project.

Based on the recommended program, construction plans and specifications were prepared on an expedited schedule. The modifications included a new flow equalization basin, additional aeration equipment, and modifications to the chemical conditioning systems. The project was implemented without having to shut down the existing facility and with no major interruptions to the manufacturing operations. Engineering services also included construction phase engineering assistance and preparation of an operations manual.

Wastewater Pretreatment Facility

Corn Wet Milling Plant

This large corn wet milling facility produces corn sweetener and modified cornstarch products. Process wastewater is pretreated in a coupled biotower/activated sludge process prior to discharge to the municipal sewer system. The client had constructed the biotower as a replacement to a large trickling filter which had been abandoned. The biotower had become a source of significant odors and the initial engineering services involved a review of the treatment facility to help troubleshoot and identify the cause of the odors. A detailed process evaluation revealed that the biotower was significantly overloaded, and that design problems limited the ability to mitigate problems with operational changes. The overloaded biotower was populated with nuisance organisms which seeded the activated sludge system with filamentous bacteria and caused process problems to the extent that the plant was out of compliance with the industrial discharge permit. The client was also anticipating an expansion in the production plant and requested a conceptual engineering design for an upgrade/expansion program. Alternatives for upgrading the facility were evaluated and the recommendation was made to implement the expansion/upgrade in two phases. The first phase of the program was a new clarifier and process piping modifications which enabled a portion of the influent wastewater to be diverted around the biotower to the activated sludge system. This initial phase was implemented on a fast track basis to alleviate the odor problems and improve effluent quality. Engineering services included detailed design, permitting assistance, construction phase engineering and start-up assistance and operational consulting. Construction of the initial phase was completed in 1996.

The second phase of the improvements will include new aeration tanks, two new clarifiers, a sludge pumping station, chemical feed systems, aeration blowers, and blower/control building. The detailed design for the second phase of the program was completed in 1996.

Wastewater Pretreatment Facility

Milk Processing Plant

This facility receives and processes raw milk to produce a variety of intermediate and final products. Process wastewater was treated in an activated sludge pretreatment plant prior to discharge to the municipal sewer system. The existing process was significantly overloaded and lacked adequate oxygen transfer and clarification capacity. In addition, highly variable influent water quality made the process nearly impossible to operate. The treatment plant was frequently in violation of its industrial discharge permit limit, and there was considerable political pressure to remedy the situation. The client requested a conceptual engineering evaluation to define the best alternatives for upgrading the facility. A detailed analysis of plant operating records was used to develop a design basis. The recommended program included a new equalization basin, a new clarifier and abandonment of the existing floating aeration equipment in favor of a new retrievable fine bubble diffused aeration system.

Detailed construction plans and specifications were prepared for the improvements. Additional engineering services included construction phase engineering, preparation of a process control manual, and start-up assistance and operator training.

Wastewater Pretreatment Facility

Baby Food Manufacturing Plant

This major U. S. based baby food manufacturer operated a baby food manufacturing plant in Venezuela which was housed in leased factory space. When the lease expired, the client was forced to relocate its manufacturing line. An abandoned manufacturing facility was purchased in another city and converted to house the relocated manufacturing line. The client requested a conceptual design for a new wastewater pretreatment facility that would make the best use of existing facilities at the abandoned manufacturing site. A treatment process consisting of flow equalization and a biotower was developed which made use of a number of existing tanks in an abandoned tank farm. The regulatory agency required that the wastewater pretreatment plant be operational prior to the start of manufacturing operations at the new site which necessitated an expedited design and construction schedule. Detailed process drawings were prepared, including P&IDs, piping plans, and conceptual design details for the structural and electrical work. The detailed structural and electrical design drawings were prepared by local engineers based on the conceptual design documents. The facility was constructed and started up in advance of the start of manufacturing operations. The system was placed in service in August 1997.

Wastewater Treatment Facility

Candy Manufacturing Plant

This major U. S. based candy manufacturer operates a manufacturing plant in Brazil. The regulatory agency required that a treatment plant be constructed to treat process and sanitary wastewater prior to direct discharge. The client requested a conceptual engineering evaluation to define the best alternative for a secondary treatment process to precede a constructed wetlands tertiary treatment process. A high rate, upflow hybrid anaerobic treatment process was recommended. Detailed design was performed for the process related aspects of the project, as well as conceptual level designs for the structural, electrical and instrumentation/controls. The detailed structural and electrical designs were performed by local Brazilian engineers based on the conceptual designs. The system was constructed and started up in June 1997 and has met all the performance requirements required prior to the application to the constructed wetlands.

Wastewater Treatment Facility

Snack Food and Pet Food Manufacturing Plant

This major U. S. based manufacturer operates a manufacturing plant near Beijing, China. The manufacturing complex contained separate facilities for snack (candy) manufacturing and pet food manufacturing. A small package treatment plant was being used to treat the process wastewater from the pet food manufacturing operation, but it was heavily overloaded and unable to meet the regulatory requirements for direct discharge. Also, the regulatory agency was requiring that the process wastewater from the snack food manufacturing operation be treated before discharge. The regulatory agency was threatening to force the manufacturing operations to cease until the wastewater treatment facilities were in place. The client requested an expedited evaluation of the existing system and recommendations for a program for expanding/upgrading the system to treat the combined pet food and snack food wastewater to meet the stringent direct discharge requirements. A program of short term improvements and operational changes was developed and implemented which drastically improved the quality of the effluent from the package plant and satisfied the regulatory agency while the major expansion/upgrade was designed and constructed. The recommended expansion/upgrade improvements included new aeration basin, clarifier, effluent polishing and chemical treatment process for color removal and COD reduction.

Wastewater Equalization/Neutralization Facility

Sugar Refinery

This large sugar refinery was discharging process wastewater to a regional publicly owned treatment plant (POTW) without treatment. Slug loadings were causing process upsets at the POTW as well as low pH in the collection system. The regional sewerage authority was demanding that the refinery install a flow equalization/neutralization system to help mitigate the problems. The client requested an evaluation to determine the potential benefits of a flow equalization/neutralization system. A bench scale treatability/equalization simulation study was recommended to determine the likely changes in wastewater quality due to equalization. The bench scale study revealed that equalization and neutralization using sodium hydroxide, followed by aeration, produced an effluent with a very stable pH, and also provided significant BOD reduction. Recommendations were made for a two-stage system consisting of a first stage equalization/neutralization tank, in which equalization, neutralization and fermentation will take place. The second stage of the process will be an aeration tank in which BOD removal will take place as well as generation of sodium bicarbonate alkalinity as a by product of the biological treatment process. The recommended program was presented in a concept engineering report which was used to gain approval of the regional sewerage authority. The detailed design was implemented on a fast track approach to enable construction to begin as soon as possible.

Wastewater Treatment Facility

Pharmaceutical Manufacturing Plant

This large bulk pharmaceutical manufacturer operates an activated sludge direct discharging treatment plant which is operating at close to design capacity. Previous work included operations consulting and plant evaluation services including process optimization, rerating studies, impact assessments of new discharge criteria, volatile emissions control system evaluations, and alternative disinfection studies.

The client initially desired an evaluation of the impact of production expansion on the wastewater treatment facility, and it was determined that the additional high strength flow from the new production facility would overload both the existing aeration and solids handling systems. An extensive treatability study was next performed in order to determine the suitability of anaerobic treatment of the process wastewater from the new production facilities as a side stream, with the pretreated wastewater then discharged to the existing treatment plant. Having determined anaerobic to be a suitable treatment process alternative, a detailed analysis was performed which evaluated the cost, technical, and operational aspects of utilizing an anaerobic process for “point source” treatment of this stream versus expansion of the existing activated sludge system and sludge handling facilities. Based on the lower capital costs, operating (energy) costs, reduced sludge production aspects and smaller space requirements associated with the anaerobic alternative, a detailed design was completed.

Wastewater Pretreatment Facility

Pharmaceutical Manufacturing Plant

This industrial client has an existing aerobic pretreatment plant which was operating near design conditions. In anticipation of major production increases, an in-depth evaluation of treatment alternatives was performed in order to accept the increased flow and loadings.

An extensive treatability study was performed which included bench-scale studies of various anaerobic processes (fixed-film suspended growth) as well a conventional activated sludge and activated sludge with powdered activated carbon (PACT). Based on the treatability studies it was determined that conventional activated sludge with provisions for isolating and treating high strength and high TKN spike loads provided the best treatment strategy.

A concept design and detailed evaluation of various aeration systems was then performed including evaluation of mechanical surface aerators, jet aeration and several coarse bubble diffuser systems. A number of other issues were also addressed including sludge handling and control of volatile emissions in anticipation of future regulations.

Based on recommendations, the client is implementing the program in phases over the next three years. The first phase is liquid treatment including a new aeration system which will serve as the first stage of a two-stage activated sludge process and will use the existing aeration system as the second stage. The project also includes extensive modifications to chemical addition and pH adjustment systems, a new influent pumping system, flow measurement and a PLC based distributed control system. The design provided for future construction of aerobic digestion facilities followed by sludge dewatering facilities and finally a system for recovery of off-gases from the first stage aeration system and utilizing the off-gases as the air supply for the second stage aeration system. The upgraded facility will have a design capacity of 210,000 gpd, and 9,840 lbs/day BOD. The project budget for the Phase One construction is $3.7 million. Construction, start-up, and operations have been completed.

Wastewater Treatment Process Engineering and Operations Assistance

Pharmaceutical Manufacturing Plant

Biological kinetic studies were used to perform full-scale plant evaluations, provide operations advice and evaluate upgrading and expansion requirements. Plant capacity, equalization requirements, variability in wastewater loadings and operating methodologies were determined. Off-gas emission studies and gas chromatograph analysis were conducted to determine the fate of specific chemicals like toluene, chloroform, acetone, mesityl oxide, ethyl acetate, ethanol and methanol during activated sludge treatment. Methodologies and concepts were developed for enhanced biodegradation of these compounds to minimize and control atmospheric fugitive emissions. The full-scale plant was modified for volatile emission control using these concepts of enclosed tanks and enhanced biodegradation of the volatile compounds. The plant is now successfully operating in this modified mode with successful odorous volatile compound emission controls.

Anaerobic Treatability Study

Pharmaceutical Manufacturing Plant

Three reactors were utilized during the study: Two suspended growth and one fixed-film anaerobic reactor. The investigative program provided the following information:

  1. Organic loading rates
  2. Hydraulic loading rates and the associated reactor retention time
  3. Organic treatment performance capabilities
  4. Handling requirements of the two major waste streams
  5. Sludge production rates
  6. Process engineering design
  7. Cost estimates.

Process Engineering and Operations Assistance

Pharmaceutical Wastewater Plant

Biological kinetic studies were used to perform full-scale plant evaluations, provide operations advice and evaluate upgrading and expansion requirements. Plant capacity, equalization requirements, variability in wastewater loadings and operating methodologies were determined. Off-gas emission studies and gas chromatograph analysis were conducted to determine the fate of specific chemicals like toluene, chloroform, acetone, mesityl oxide, ethyl acetate, ethanol and methanol during activated sludge treatment. Methodologies and concepts were developed for enhanced biodegradation of these compounds to minimize and control atmospheric fugitive emissions. The full-scale plant was modified for volatile emission control using these concepts of enclosed tanks and enhanced biodegradation of the volatile compounds. The plant is now successfully operating in this modified mode with successful odorous volatile compound emission controls.

Wastewater Pretreatment Facility

Candy Manufacturing Plant

This large candy manufacturing facility operated a two-stage activated sludge pretreatment plant. The plant was operating near design capacity and changes in the manufacturing process caused variability in the loadings which resulted in unstable operations at the wastewater treatment plant and frequent process upsets.

A treatability study was first conducted to determine the suitability of an anaerobic treatment process as a first stage of a two-stage biological process in which the existing aerobic system would serve as the second stage. Subsequently, a concept design and detailed cost estimate were prepared for an extensive upgrade including the anaerobic process, new sludge dewatering system, and added clarification capacity.

The detailed design and construction of this project has been completed. The project included several interesting aspects, including a heat recovery system on the anaerobic biogas burner that satisfy the heating requirements of the anaerobic system and a virtually complete on-line replacement of the existing equipment control instrumentation with a PLC-based distributed control system that would automate most of the process control operations. Total project costs exceeded $4.0 million. Successful start-up and operation of the facility occurred in 1993.

Wastewater Treatment Evaluation

Brewery Complex

This large brewery complex required preparation of an operational assessment and evaluation of its new anaerobic pretreatment plant along with the municipal plant it discharges to. Both plants were experiencing operational difficulties during the transitional start-up period. Proper changes in the operational process control program at the municipal plant had not been implemented to deal with the lower loadings from the brewery. The brewery was the major contributor of flows and organic loadings to the municipal plant.

Wastewater Pretreatment Facility

Alcoholic Beverage Processing and Bottling Plant

This facility processes and bottles a variety of alcoholic beverages and discharges its process wastewaters directly to the City of Fort Smith’s sewer system. Due to anticipated changes in discharge criteria and to reduce their costs from sewer surcharges, the client retained The Stover Group to perform an engineering evaluation of alternatives for on-site pretreatment facilities to reduce the effluent wastewater strength below surcharge levels. The Stover Group investigated a number of alternatives including anaerobic, coupled anaerobic/aerobic, biological tower, and sequencing batch reactors before recommending biological tower technology. Subsequently, the client retained The Stover Group to perform detailed engineering design of the selected alternative which included flow equalization, biological tower, clarification, sludge digestion, flow measurement, neutralization and nutrient feed systems. Construction was completed and successful start-up and operation occurred in 1996. Services also included start-up, and operator training. The total project budget was approximately $1.0 million.

Wastewater Treatment Facility

Food Flavoring Manufacturing Plant

This facility processes a variety of foods flavorings for soft drink and food ingredients. Process wastewaters were treated on-site in a submerged fixed-film reactor prior to final disposal by land applications. The treatment system did not function as intended by the designer and suffered complete process failure. Firmenich retained The Stover Group to perform operations troubleshooting, treatability studies, and conceptual engineering design of the selected upgrade alternative, which included conversion of unused existing tankage to serve as additional aeration tanks, an aeration system upgrade, a new clarifier and rapid sand filtration system, new flow measurement and neutralization facilities, and ultra-violet effluent disinfection facilities. Services also included start-up, and operator training. The total project budget was approximately $1.0 million. Construction was completed and successful plant start-up and operation ensued.

Wastewater Pretreatment Facility

Baby Food Manufacturing Plant

This client experienced persistent process and operational problems from the time of start-up of a new facility. A number of significant problems were identified including a lack of nutrient addition facilities, flow splitting problems, and most importantly, inadequate solids handling facilities. A mobile sludge thickening system was provided in order to relieve the solids handling problem, and provide valuable process information for the design of permanent facilities.

The most recent phase of the program was a treatability and concept design for an upgrade to the plant to increase solids removal efficiencies and enable the plant to discharge directly to a local river. Detail design services were performed for the new effluent polishing system which included chemical addition systems, flocculating clarifier and re-aeration. This design work was performed concurrently with the detail design for the permanent sludge thickening system which utilizes gravity belt thickeners with provisions for future addition of sludge dewatering equipment.

Wastewater Treatment Facility Consulting

Yeast Manufacturing Plant

This large yeast production facility required preparation of a detailed operational evaluation, assessment, and troubleshooting for its new anaerobic treatment plant that was experiencing start-up problems. The wastewater was complex in nature, with high sulfate concentrations. Use of ferric chloride for control of bulk liquid sulfide and biogas sulfide concentrations complicated plant operations. Specific conclusions and recommendations were developed along with operations assistance to resolve the problems.

Wastewater Pretreatment Facility

Candy Manufacturing Plant

This client has an existing activated sludge pretreatment system that was experiencing operational process problems due to their high strength waste loading variabilities. There were plans to expand the candy production facility with an anticipated hydraulic and organic load increase being placed on the existing wastewater pretreatment system. Since the existing plant was already at its design capacity, options had to be evaluated to define the best technical and economical expansion alternative.

A phased approach was recommended to provide the best treatment strategy fro this industrial client. The first phase involved immediate/interim modifications to the existing aerobic system by upgrading and expanding for anticipated production expansions. The second phase involved the installation of an intermediate anaerobic pretreatment process upstream from the aerobic system to provide for further BOD reduction. Treatability studies, concept designs and cost estimates were completed for the addition of a new anaerobic system along with sludge thickening and dewatering.

Wastewater Treatment Facility

Brewery

A detailed wastewater treatment plant (activated sludge) evaluation was first performed including engineering design and operations evaluation. The primary purpose of the initial evaluations was to define plant capacities, capabilities, and limitations along with evaluating the operations process control programs. This detailed evaluation developed specific recommendations for operational process control, “fine tuning” and optimization of operations, and plant staffing needs in order to resolve the problems and difficulties the plant was experiencing in reliably meeting its direct (NPDES) discharge requirements.

The problems have been resolved, and the plant has achieved reliable, stable operations. The brewery had already completed a detailed design for upgrading the wastewater treatment plant by adding an anaerobic treatment step ahead of the activated sludge process. We were then asked to provide a detailed process design review of the anaerobic process. The plant construction has been completed and the transition start-up period has been completed without any adverse effects. The plant upgrade also increased plant capacity to 5.5 MGD at 88,500 pounds per day of BOD loading.

Wastewater Treatment Consulting Services

Snack Foods Manufacturer

This industrial client requested an evaluation of the capacity of municipal wastewater treatment systems in targeted cities where they were considering locating new food processing plants. For each location, evaluation reports, site surveys, concept designs and cost estimates were developed for upgrading the POTW at the client’s expense versus on-site pretreatment at the client’s proposed plants. These projects were highly confidential and had to be performed in very short time frames to assist management with site location decisions. Detailed POTW plant performance evaluations required definition of capacities, capabilities, limitations, and bottlenecks along with operational evaluations. Critical issues such as sludge handling and hydraulic and organic loading status had to be defined in great detail in order to prevent future operational problems with increased flows and loading rates.

Wastewater Pretreatment Facility

Rice Processing Plant

A large rice production facility was required to resolve a complex situation that developed between the local municipal POTW and the rice production plant which discharged pretreated wastewater to the POTW. The rice production wastewater was discharged to the municipal POTW following screening, flow equalization, and pH adjustment. Severe operational problems at the POTW including flow and organic overloading, nutrient deficiency, oxygen transfer limitations, and inadequate sludge handling capacity were restricting the rice production facility. The first objective was to perform a detailed evaluation of the POTW capacities, capabilities, limitations and bottlenecks along with an in-depth operations program evaluation to define an interim solution to the POTW problems while the best technical and economical long term solution could be developed. As a result of this evaluation a complete modification of POTW was performed including modification from contact stabilization to conventional activated sludge operations, piping modifications, addition of nutrients, replacement of the existing diffused aeration system with a different type of diffusers, and complete modification of the operational process control program. An Operations Supervision/Management Program was provided to implement the new operational concepts and train the operators. The POTW leased a mobile belt filter press to resolve its sludge handling problems. A detailed study was performed to define the best technical and economical long-term solution for both the rice plant and the POTW. These studies included pilot anaerobic treatability studies, concept design, and a detailed design evaluation to develop refined capital and operating cost estimates. Through all the detailed evaluations, with the significant improvement in POTW performance along with a significant increase in treatment capacity, the decision was made to perform in-plant production modifications to reduce flows and loadings from the rice plant. These measures with the improved process performance have provided a significant relief to serve as an intermediate long-term solution.

Toxicity Reduction Evaluation

Large Aerospace Maintenance Facility

The Stover Group was retained to develop and implement an extensive Toxicity Identification Evaluation (TIE) program for a large aerospace manufacturing facility. The facility had a prior history of Whole Effluent Toxicity test failures using Ceriodaphnia dubia and Pimephales promelas. A multi-phase TIE plan was prepared for each of four effluent outfalls which were discharging treated wastewater and/or cooling water. The phases consisted of acute toxicity assessment and identification, transient toxicity assessment and identification, and chronic toxicity assessment and identification.

Toxicity Characterization/Identification Evaluation studies determined that the primary toxicants were elevated levels of heavy metals and residual chlorine. Methods of toxicity reduction were recommended including source reduction/elimination pretreatment facilities for metals removal and dechlorination. For the chlorine-induced toxicity, dechlorination was recommended for consideration as a toxicity reduction option in addition to source reduction and pretreatment.

Toxicity Reduction Evaluation

Large Electric Generating Station

The Environmental Protection Agency directed this utility client to submit a plan for a Toxicity Reduction Evaluation (TRE) program. The Stover Group was retained to develop and implement the plan, which proposed a two-phased approach, including seven tiers of effort, to successfully identify and confirm the toxicant(s) and/or practices responsible for inducing effluent toxicity. Three Toxicity Characterization/Identification Evaluation (TIE) studies were conducted during the program. These studies produced similar characterization profiles, suggesting that cationic metals may have been primary causative toxicants. Analytical analyses revealed elevated levels of copper, zinc, aluminum, and manganese. Two of the TIE studies included an effluent simulation study in which the receiving stream make-up water was cycled up at bench scale, thereby simulating the discharged effluent. In addition, MINTEQ geochemical equilibrium computer modeling was utilized to evaluate potential toxicant sources, predict chemical speculation of the suspected toxicants, and determine the effect of the effluent matrix on toxicity. Results of these preliminary studies suggested that copper, and possibly zinc, may have been products of corrosion from within the circulating cooling water system. Aluminum and manganese, however, appeared to have been simply concentrated from the river make-up water during cooling water circulation. Suspected toxicant(s) Whole Effluent Toxicity correlation studies indicated that a fairly strong correlation existed between the concentration of soluble copper and the toxicity observed in the effluent.

To further confirm the findings and to determine whether the toxicants were produced from within the cooling system, an on-site source identification study was implemented. Preliminary results indicated that the river water corrosiveness varied with time and that the cooling system was losing a substantial amount of copper.

A pilot-scale study indicated that corrosion-inhibiting chemicals were capable of reducing toxicity of the cooling water sample by chelating soluble copper ions. A five (5) month full-scale test confirmed the effectiveness of the toxicity reduction method.

Storm Water Pollution Prevention Plans

Fixture Manufacturing Facility

The client has three manufacturing facilities which produce both plated and painted store fixtures. Each facility is required to report chemical inventories and releases under the Section 312 and Toxic Release Inventory Regulations. Storm water pollution prevention plans were prepared as per federal and state general storm water permit requirements following seasonal evaluation of the facilities.

Preliminary drafts were delivered to the client and discussions were held with the storm water pollution prevention team to ensure accuracy and completeness. Final drafts were developed which included innovative methods for record keeping and pollution prevention. The completed plans were prepared in hard copy and on magnetic media, thereby facilitating possible updating requirements in the future as regulations and/or plant processes change.

Feasibility Assessment for Evaluating Ozone as a Disinfection/Decolorization Alternative for Industrial Effluent Treatment

The Stover Group was retained to perform a feasibility study by providing the pilot plant ozonation equipment, supervision, oversight, and management of the study along with development of the experimental program, data analysis, and report preparation. The Stover Group trained the client personnel to operate the pilot plant equipment and to perform all the water quality (chemical and biological) testing on-site.

The pilot plant study confirmed that ozonation would be an effective disinfection alternative to chlorination as well as an effective color removal process. Ozone transferred doses of around 40 mg/L were found to be required to achieve the effluent disinfection criteria of 200 fecal coliforms per 100 mL. At this transferred ozone dose, significant positive benefits of color removal and lack of formation of THMs were observed. The only negative impact of ozonation was an increase in BOD that would start approaching the discharge effluent limit.

The study confirmed that ozone offers significant advantages as a disinfection and decolorization alternative to chlorination relative to regulatory compliance issues such as effluent residual chlorine limits, color removal, and THM formation potential reduction.

Treatability Study of a Complex Petrochemical Wastewater

Petrochemical Company

The Stover Group was retained by a major national consulting engineering firm to assist in a treatability study of a complex petrochemical wastewater for a confidential client to develop a preliminary conceptual design. The major objective of the study was to define a feasible treatment alternative to deep well injection. The extensive pilot plant program involved a matrix of 12 biological reactors treating complex wastewaters which included compounds. The key emphasis of the treatability studies was to achieve specific organic compounds removal to allow surface discharge. This complex wastewater included biorefractory organics which were inhibitory and/or toxic, and therefore present biodegradation rate limiting problems for activated sludge treatment. Specific organics included, among others, 2,4-dinitrophenol, 2,4-dinitrotoluene, 2,6-dinitrotoluene, and nitrobenzene. During the 18-month study, The Stover Group provided:

  1. Overall program consultation.
  2. On-site personnel for overall project coordination, database management, data analysis, and technical assistance.
  3. A bench-scale physical/chemical pretreatment study of raw and biotreated wastewaters using ozone, hydrogen peroxide, and acidification/crystallization.
  4. Analytical support: BOD, TSS, VSS, and long-term BOD.

The reactor configurations included single and two-stage activated sludge, with and without powdered activated carbon treatment (PACT), and with pretreatment with hydrogen peroxide.

Without powdered activated carbon addition, specific compound biodegradation was limited due to the inhibition/toxicity problems noted, and the pilot treatability system did not achieve nitrification. The treatment trains which included PACT were the most effective process alternatives. Upon development of the optimum PAC doses and attainment of optimal process operational control, these systems achieved adequate organics removal and nitrification.

Organic Phosphorus Wastewater Characterization; Treatability and Process Definition

Confidential Industrial

The Stover Group was retained to perform an in-plant sampling survey, wastewater characterization, conduct pretreatment study with three chemical oxidants, perform biological treatability studies, and develop the necessary data and information for upgrading the wastewater treatment facility at an organic phosphorus chemical plant. An in-depth water balance and wastewater characterization program was conducted to define major water sources and quantities discharged to the process wastewater system. Pretreatment studies were conducted using ozone, hydrogen peroxide, and permanganate, with the primary objective of enhancing biodegradation. Three bench-scale activated sludge systems were operated over a wide range of operating conditions in order to evaluate the treatability of the raw wastewater, the pretreated wastewater, and the treatment of a high salt stream. The laboratory and bench-scale biokinetic data was used to develop a process design basis, conceptual design and preliminary cost estimates.

Wastewater Treatment Plant Process Evaluation and Treatability Studies on Chemical Plant Wastewater

Petrochemical Company

This Company retained The Stover Group to perform a detailed process engineering and functional evaluation of the wastewater treatment plant to determine capabilities and limitations to meet effluent criteria. Additionally, bench-scale treatability studies were performed to determine the treatability characteristics of the wastewater generated at the Santa Rita production plant using activated sludge treatment technology. The main components present in the wastewater were glycols, which yield high COD concentrations in the wastewater. The bench-scale biological reactors were operated at different organic loading conditions to determine the biological kinetic constants, representative of the treatment system performance. An evaluation of powder activated carbon addition to the activated sludge systems to lower the COD was also performed. The use of ozone followed by biological treatment was investigated as part of the treatability studies. The results of the treatability studies indicated that the high COD wastewater generated at the company’s facility could be successfully treated in an activated sludge system to comply with the final effluent limits.

Bench-Scale Treatability Study for API/DAF Separation on an Industrial Wastewater

U.S. Navy Facility

A bench-scale treatability study was performed on two industrial wastewaters to verify the technical feasibility of API separation and Dissolved Air Flotation (DAF) treatment process. The sources of one of the wastewaters included submarines and surface vessels, typically from domestic sources, cleaning wastewater, cooking grease, and salt water. The other wastewater was a saline wastewater generated aboard ships that contains percent levels of various types of petroleum products. The pretreatment effluent requirements to be met were: oil and grease between 10 mg/L and 50 mg/L, total suspended solids between 10 mg/L and 50 mg/L, and pH of around 8.0.

Both industrial wastewaters were treated in bench-scale setups to simulate the API and DAF processes. At the API unit, the free oil and grease is separated by gravity, while at the DAF unit the emulsified oil and grease are separated by addition of a gas phase, usually air, in fine bubbles to the liquid phase. It was necessary to use chemical aids to enhance oil and grease separation prior to the DAF unit. Jar tests were run for breaking the oil/water emulsion using ferric chloride, aluminum sulfate, and polymers.

The successful treatment scheme for both wastewaters was API separation followed by DAF separation with chemicals addition (ferric chloride and anionic polymer). The proposed pretreatment process for both wastewaters was: equalization, API separation, DAF separation with chemical addition, and pH adjustment. The pretreated effluents were to be pumped to a centralized biological treatment process for final treatment.

On-Site Technical Assistance in Petrochemical Complex

Petrochemical Company

The Stover Group was retained by this company to provide on-site technical assistance during approximately two months (400 manhours) at a site in Venezuela. The on-site technical assistance consisted in performing a series of activities related to the environmental engineering field, with the most important activities being the following:

  1. Review and analysis of the local environmental regulations in order to propose a plan of action to comply with the regulations.
  2. Development/updating of procedures for solid and hazardous waste handling, including identification, segregation, recycling and reuse, temporary storage, and treatment.
  3. Development of an air quality and point source sampling program.
  4. Process engineering and functional evaluation of the wastewater treatment plant (activated sludge system).

Pilot-Scale Chemical and Biochemical Treatability Study for Contaminated Landfill Groundwater Near a Refinery

Petrochemical Company

A pilot-scale chemical/physical treatability study followed by a bench-scale biological treatability study was performed for the removal of sulfonated surfactants and BOD (biochemical oxygen demand) from a contaminated landfill groundwater. The objective of the study was to first neutralize the surfactant molecule with calcium chloride and form an insoluble calcium precipitate. The second objective was to successfully biologically treat the chemically pretreated wastewater creating a good quality effluent. The treatability study was performed in two steps: chemical pretreatment followed by biological treatment. Raw contaminated groundwater was treated chemically using calcium chloride to neutralize the polar end of the surfactant molecule and form an insoluble calcium precipitate. This treatment reduced the organic content of the water as well as the levels of surfactant thus minimizing foaming problems in the biological treatment steps. The biological processes studied were activated sludge, power activated carbon treatment (PACT) with activated sludge, and rotating biological contractors (RBCs). The activated sludge reactors were operated at various food to microorganism (F/M) ratios and sludge retention times (SRTs). The chemical pretreatment step was successful in reducing the surfactant levels and reducing the organic content of the groundwater. Biological bench-scale reactors indicated the feasibility of treating the chemically pretreated groundwater with the activated sludge process performing the best.

Refinery Wastewater Characterization, Treatability and Process Development

Petroleum Company

The Stover Group was retained to perform wastewater characterization, conduct laboratory and bench-scale treatability studies, and develop the necessary data and information required for scale-up design for new wastewater treatment facilities for a large refinery in Ardmore, Oklahoma. An in-depth water balance and wastewater characterization program was performed to define major water sources and quality discharge to the process water sewer systems. Bench-scale activated sludge reactors were operated over a wide range of operating conditions to evaluate treatability for specific compounds with special concern for ammonia and sulfides. The treatability study included investigation of nitrification inhibition to evaluate the feasibility of two-stage, carbonaceous-nitrification biological treatment. Results indicated that an activated sludge system preceded by API separators and induced air flotation would provide adequate treatment necessary to achieve reliable discharge standards. In-plant wastewater flow and mass balance evaluations identified two sources as the major contributors of COD and sulfides. Impacts of storm water discharges were also evaluated. Assistance with existing wastewater treatment facility operations was also provided and operational changes and modifications were made to achieve effluent compliance.

Refinery Wastewater Characterization, Treatability Assessment, Process Engineering and Operations Assistance

Refinery Company

The Stover Group was retained to perform wastewater characterization, treatability assessment screening studies, treatment plant process engineering evaluations, and provide operations advice and assistance with the wastewater treatment program at the UNOCAL refinery. Specific in-plant process streams were characterized and screened for treatability assessment relative to nitrification inhibition/toxicity concerns. The Santa Maria refinery processes high sulfur and nitrogen crude oils, and as such, it produces process streams that can exhibit difficult treatment characteristics relative to maintaining stable, reliable nitrification reactions. Contributions from various process streams, including contaminated storm water, were evaluated for their impact on wastewater treatment. Treatment capacities, capabilities and limitations were defined relative to achieving reliable effluent discharge criteria. Operations monitoring and process control measures were implemented along with operations advice and assistance for improved operations process control.

Evaluation of Alternatives to Use of Supplemental Carbon Source in Refinery Wastewater Treatment Plant

Refinery Company

The Stover Group was retained to perform the necessary engineering evaluations, studies and assessments for the elimination of a supplemental carbon source to the Tulsa refinery wastewater treatment plant (activated sludge system) while maintaining permit compliance. A two-phased approach was developed to achieve the project objective. The primary focus of the Phase I activities was to define the capabilities and limitations of the existing treatment process to successfully treat the wastewaters generated at the refinery at the present operational production scheme without feeding supplemental carbon source. Phase II consisted of bench-scale treatability studies to confirm the treatability of the wastewater streams generated at the refinery without supplemental carbon source addition, using the activated sludge technology. Additionally, the requirements of aeration volume, oxygen, nutrients, sludge handling and disposal previously presented in the Phase I evaluation were confirmed during treatability studies. Both phases of the project indicated that the wastewater streams generated at the refinery could be successfully treated without addition of supplement carbon source.

Permit Application Renewal for Direct Discharge of Wastewater (National Pollutant Discharge Elimination System, NPDES) for Petroleum Refinery

Petroleum Company

The Stover Group was retained to prepare a permit application renewal to discharge wastewater effluents from a large refinery in Tulsa, Oklahoma, to the Arkansas River. In order to prepare this permit application renewal it was necessary to review in detail the wastewater characteristics of all the wastewater streams as well as to do wastewater characterization of some of them. Also, a review of the process flow diagrams, chemical usage, and water usage was necessary. The application package consisted of Form1, ODEQ/U.S. EPA (General Information) and Form 2C, NPDES EPA (Application for Permit to Discharge Wastewater, Existing Manufacturing, Commercial, Mining and Silvicultural Operations).

Oil Field Chemical Manufacturing Wastewater Treatability Studies and Process Development

Petroleum Company

This large petrochemical plant in Conroe, Texas manufactures a number of chemicals that are widely used in the oil field industry. The original wastewater treatment plant consisting of a batch treatment process (physical/chemical treatment) using a number of mixing and holding tanks periodically exceeded its new effluent discharge limits. The Stover Group was contracted to perform a treatability study to evaluate biological treatment of the wastewater to consistently achieve the new effluent discharge criteria. Wastewater characterization was performed along with both continuous flow and batch activated sludge treatability simulation studies. All the effluent discharge criteria were readily achievable with the exception of the high chlorides and sulfates which are not treatable by these treatment processes. Additional study work was required if a waiver could not be attained for chlorides and sulfates.

Refinery Wastewater Treatment Plant Process Evaluation, Operations Assistance, and Operator Training

Petroleum Company

The Stover Group was retained to perform a process engineering evaluation of the wastewater treatment facilities at the Sweeny refinery relative to capacity and capabilities to achieve the required effluent limitations. Capacity and capability limitation problems were defined especially relative to the biological part of the process, the Rotating Biological Contactors (RBCs). Operations troubleshooting, advice, and assistance were also provided along with operational process control and monitoring recommendations. Operator training was also provided for additional assistance in attaining the desired treatment objectives.

Refinery Wastewater Treatment Process Engineering Evaluation

Petroleum Company

This large refinery in Tulsa was experiencing problems with their Rotating Biological Contactors (RBCs) relative to specific compounds performance and plant stability. The Stover Group was retained to perform process engineering evaluations of the RBC process to define problems and limitations. A problem definition phase including wastewater characterization and plant performance evaluations was performed. Specific conclusions and recommendations were made including operations advice and assistance to improve overall plant performance.

Treatability Studies, Pilot Studies, and Process Design of Two Contaminated Groundwater Treatment Systems

Petroleum Company

The Stover Group was contracted to conduct process treatability studies, prepare a concept design, and develop capital and operations costs estimates for treatment of complex groundwaters. This project included an evaluation of the PACT process for removal of specific organics.

A detailed groundwater investigative program was performed to define the contamination problems and extent of contamination at an abandoned refinery that had been converted to a hazardous waste treatment facility. The results indicated that groundwater contamination included dissolved petroleum hydrocarbons, chlorinated organics, heavy metals, chlorides, and free floating hydrocarbons. A well recovery system for floating hydrocarbons was designed and installed. The Stover Group was retained to perform bench-scale treatability studies, pilot plant studies, process engineering, and detail engineering designs for the separate groundwater treatment systems to remove both dissolved organics and inorganics. The groundwater treatment technologies considered applicable and tested during the bench-scale and pilot-scale studies included the following:

  1. Metals precipitation with lime, caustic, and potassium permanganate by both gravity settling and dissolve air flotation
  2. Air stripping
  3. High temperature air stripping
  4. Steam stripping
  5. Activated carbon absorption
  6. Reverse osmosis
  7. Evaporation
  8. Biological treatment by activated sludge, aerated lagoon, and powdered activated carbon-activated sludge
  9. Vacuum filtration and plate and frame filter press for sludge dewatering

These studies permitted selection of proper treatment processes and more accurate sizing of treatment units, as well as more effective prediction of treatment efficiencies and performance evaluations. Two separate treatment systems were required due to the high level of inorganics (primarily chlorides) in one of the groundwaters. The two systems designed were as follows:

High Chloride System
  • Rapid Mix (Lime)
  • Flocculation (Polymer)
  • DAF
  • Gravity Filtration
  • Neutralization (HCL)
  • Air Stripping
  • GAC
  • Reverse Osmosis
  • Filter Press
Low Chloride System
  • Rapid Mix (Lime)
  • Flocculation (Polymer)
  • DAF
  • Gravity Filtration
  • Neutralization (HCL)
  • Air Stripping
  • GAC
  • Filter Press

Pilot-Scale Ammonia-Nitrogen Stripping Treatability Study

Film Processing Plant

A pilot-scale treatability study was performed for the removal of ammonia-nitrogen from the wastewater generated at a film processing facility. The objective of the study was to evaluate the feasibility of achieving ammonia-nitrogen concentrations of less that 100 mg/L in the treated effluent from concentrations in the raw wastewater of approximately 200 mg/L. The treatability study was performed in two steps: wastewater sample preparation and air stripping runs. The wastewater preparation consisted of pH adjustment to 11.5 and temperature adjustment to three different conditions: 105°F, 120°F, and 150°F. The pilot-scale treatability unit was operated at three different air to water ratios for each temperature condition. This was achieved by keeping the airflow constant and changing the wastewater flow rate. The wastewater flow rates were 0.5 gpm, 1.0 gpm, and 2.0 gpm.

Sufficient test runs were performed to obtain the critical design information required to select/design a full-scale unit. The results from the different air stripping runs indicated that the concentration of ammonia-nitrogen in the wastewater was reduced from approximately 200 mg/L to the target effluent concentration of less than 100 mg/L when the pilot-scale stripping unit was operated at a wastewater flow rate of 0.5 gpm, a wastewater pH of approximately 11.5, and a wastewater temperature of approximately 153°F.

Pilot-Scale VOCs Stripping Treatability Study

Chemical Plant

A pilot-scale air stripping treatability study was performed on two wastewater samples from a chemical manufacturing facility. The objective of the study was to evaluate the feasibility of achieving the discharge limit level of 196 ppb for 1,3-dichloropropene and 28 ppb for toluene by air stripping. Sufficient air stripping runs were performed to obtain the information needed for designing a full-scale unit. The pilot unit was run at three different air-to-water ratios for each wastewater sample, achieved by keeping the air flow constant and changing the wastewater flow rate. These wastewater flow rates were 0.5 gpm, 1.0 gpm, and 2.0 gpm. During each run, a total of six samples were collected for VOCs analysis. The results from the stripping runs showed that the discharge limit levels of 196 ppb for 1,3-dichloropropene and 28 ppb for toluene were easily achieved by air stripping.

Bench-Scale Treatability Study on an Industrial Wastewater

Metal Finishing Facility

The Stover Group was retained by an industrial client to complete the final phases of an on-going Toxicity Reduction Evaluation (TRE) project. At that time, the activities of the previous TRE phases had identified the toxicants and made preliminary recommendations for treatment processes to remove those toxicants from the waste streams through waste minimization/recycling techniques. A bench-scale treatability study was part of the TRE activities to be performed by The Stover Group.

The main purpose of the treatability study was to verify the degree of the facility’s wastewater treatability for nickel removal. Removal of nickel was associated to toxicity reduction during the preliminary activities of the TRE project. As part of the study, one of the objectives was to develop a physical-chemical treatment scheme that, besides reducing the nickel concentration to the discharge effluent limits, also eliminates whole effluent toxicity. A wastewater treatment plant evaluation was also included as part of the study.

The experimental program to optimize toxicity reduction was planned in two phases: first, optimization of nickel removal and second, toxicity evaluation of each major wastewater source. Since the results obtained from Phase I were successful in optimizing nickel removal and eliminating potential toxicity, Phase II of the study was not necessary. During Phase I of the study, the preliminary screening for polymer doses and optimum pH’s was done by performing jar tests. After optimum pH and polymer doses were found, the treated samples were passed through an ion exchange column for further removal of nickel. Several ion exchange runs were performed in order to define the optimum operating condition. A glass column, 2 cm in diameter with 50 mL of resin (18 cm resin height), was used for the ion exchange tests. After polymer treatment followed by ion exchange, the samples were tested for toxicity. The treatment scheme developed during the treatability study was successful in removing nickel and eliminating whole effluent toxicity.

Evaluation of Treatment Plant Operations and Design

Textile Manufacturing Facility

A textile manufacturer requested assistance in solving serious wastewater treatment problems which were restricting production at the facility. The facility was beset with numerous operational and design problems. During the next four months, the facility was able to develop a reliable water supply, and standard methods of treatment were developed for the physical/chemical system treating the dye waste from the facility. These factors resulted in the facility being able to increase its production through the dye house by at least 33%. An engineering evaluation of the facility was also performed to determine what steps must be undertaken to continue to upgrade the wastewater facility to meet future requirements. This engineering evaluation also included a water balance study of the manufacturing facility.

Detail Engineering Design Physical/Chemical and Activated Sludge

Commercial Airline

The Stover Group was retained on a subcontract basis to perform detailed engineering design services for a combined physical/chemical and biological wastewater pretreatment plant for a major airline carrier maintenance facility in Oklahoma. The pretreatment system was designed to treat high strength industrial wastewater generated by aircraft washing and paint stripping activities. The Stover Group conducted an in-plant water and waste characterization study, and performed treatability studies focusing on various combinations of physical/chemical, aerobic, and powdered activated carbon (PACT) treatment systems. The final design consisted of flow equalization, neutralization, flocculation, solids settling, activated sludge, aerobic sludge digestion, and rapid sand filtration. Sludge handling and dewatering facilities were also designed. The estimated construction costs for the upgraded facilities was approximately $1.2 million.

The design of the facility was performed on a fast-track schedule. Preliminary drawings were provided to the contractor in order to obtain cost estimates. The treatment plant was designed in phased following a predetermined sequence of construction. As phases of the design were completed, they were provided to the construction contractor to obtain final “not-to-exceed” cost figures. A fast-track construction schedule required all preliminary and final engineering designs for the facility to be completed in 120 days.

Detailed Engineering Design for Disinfection and Flow Measurement Facilities

Industrial Wastewater Treatment Complex

The Stover Group was retained by a government agency to perform an alternative process evaluation and concept engineering design, as well as detailed engineering design services, for construction of disinfection and flow measurement facilities for its industrial wastewater treatment plant. The concept engineering and alternative process evaluation was performed on a very short time frame to assist the government agency in satisfying the requirements of an administrative compliance order. After the process was selected, detailed engineering design was performed for chlorination/dechlorination facilities and effluent flow measurement equipment for the five MGD treatment plant. The design included site work, yard piping details, concrete structural details, architectural drawings for the chlorination/ dechlorination equipment and storage building, electrical details, and related instrumentation.

Paper Coating Wastewater Characterization, Treatability Process Design and Cost Estimate

Paper Company

The Stover Group was retained to perform bench-scale treatability studies to compare two-stage biological treatment with the PACT process. The Stover Group performed a water use/wastewater survey, wastewater characterization study, and conducted a bench-scale physical/chemical pretreatment and biological treatability study, in order to develop the necessary data required for a process design and cost estimate for a pretreatment system to a local sewer. An in-depth water balance and wastewater characterization program was performed to define major water sources and quantities discharged to the process sewer. Physical/chemical pretreatment studies evaluated coagulation/flocculation/gravity settling with lime, alum, and inorganic polymers as a process step prior to biological treatment. The bench-scale treatability studies compared two-stage activated sludge (with and without pretreatment) with a PACT activated sludge system. The selected alternative for process design was the pretreated two-stage activated sludge system which produced a stable effluent and met all effluent discharge criteria. A process definition was developed and cost estimates were prepared.

Project: Wastewater Generation/Toxicity-Inhibition Screening Characterization Evaluation

Chemical Transportation Company

The Stover Group was retained to provide an inhibition/toxicity evaluation of the effluent from the chemical tank truck wash and maintenance facility’s wastewater pretreatment plant. This was in response to a Request for Information from the City’s industrial pretreatment section alleging that the wastewater discharged to the POTW was toxic. The program developed by The Stover Group included a review of the wastewater characterization data available; an on-site program to review and minimize hazardous wastewater generation; wastewater quality characterization; performance of an inhibition/toxicity analytical evaluation procedure developed by The Stover Group; microtox analysis; and preparation of a response to the City. This successful program was instrumental in the City’s acceptance of the findings that the pretreated wastewater was not inhibitory or toxic for treatment by the POTW.

Activated Sludge Wastewater Treatment Plant

Paper Coating Facility

This client was an activated sludge/PACT package plant designed to provide treatment of the wastewater 24 hours per day. This wastewater results from manufacturing in two distinct divisions: a division devoted to production of a highly specialized ingredient in the company’s carbonless paper coating; and a division which applies the coating to paper. Wastewater from the former is generally low in TSS and COD, high in dissolved solids, and is inhibitory to biodegradation. The wastewater from the paper coating division is high-strength in terms of suspended solids and COD, is highly variable, and includes wastes which are resistant to biodegradation. The paper coating division makes frequent changes in the types of product it manufactures, and therefore places a severe impact on the wastewater treatment facilities.

The treatment facility consists of oil and grease removal; pH neutralization; wastewater flow and organic loading equalization, batch aerobic activated sludge with addition of powdered activated carbon for non-biodegradable organics, aerobic sludge digestion; and solids clarification prior to discharge to the municipal sanitary sewer system. Sludge is dewatered by a recessed plate and frame filter press. The Stover Group provided complete operations and management services including technical support seven days a week.

Activated Sludge/Pact Facility Evaluation and Operations Assistance

Chemical Transportation Company

The Stover Group was retained by Chemical Leaman Tank Lines to evaluate the powdered activated carbon assisted activated sludge wastewater treatment facility at its Coal Grove, Ohio truck wash, maintenance, and dispatch terminal. The scope of services included an investigation of the truck wash procedures; waste minimization; assessing the capabilities of the treatment plant; evaluation of plant operations and the process control procedures; and submittal of recommendations regarding optimization of current operations and recomendations for plant upgrade alternatives. The treatment plant had a history of difficulties in achieving NPDES discharge compliance. Chemical Leaman sought assistance to develop operations and design recommendations which would achieve discharge quality compliance.

Physical/Chemical Treatment Contract Operations

Industrial Wastewater Treatment Facility

The Stover Group was retained to provide contract operations of an industrial wastewater treatment facility. The wastewater source was a truck cleaning station where the client provided cleaning and maintenance to trucks used to transport different types of chemical products. The wastewater treatment facility consisted of equalization basin, flocculation/coagulation basins, Dissolved Air Flotation (DAF) unit, sludge holding and conditioning tank, and plate and frame filter press. The treated effluent was discharged to the municipal collection system for further treatment. Ferric chloride, lime, and polymer were used in the flocculation/coagulation basins and DAF unit for solids and oil and grease separation. Also, sludge conditioning was provided prior to sludge dewatering. Jar tests to select the chemical doses were performed every day as part of the operational process control.

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The Stover Group
P.O. Box 2056
Stillwater, Oklahoma 74076

Phone: (405) 624-0018
Fax: (405) 624-0019

E-mail: [email protected]