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Sustainability
Sustainability and green engineering principles are not new ideas for FOX Engineering. We have a long-standing commitment to making responsible choices about not just our clients’ resources but those of our planet as well. Read more about our experience and the approach we take toward designing and creating efficient, sustainable solutions.
Newton, IA
Aeration System Replacement
Developments in technology often allow for dramatically improved “payback” opportunities when it comes time to repair or replace treatment systems. This was the case when FOX Engineering was called to help Newton replace its aeration system.
The Newton Water Pollution Control Plant (WPCP) was constructed in 1985 and included a two-stage roughing filter/activated sludge secondary treatment system. Although the original system (consisting of a draft tube submerged turbine aeration system) had performed well, it had reached the end of its useful design life and had, in effect, become outdated as modern fine bubble aeration systems operate much more efficiently.
FOX Engineering recommended replacement of the aeration system in a 2008 Facility Plan. The study found that the potential electricity savings associated with a fine bubble aeration system would pay back the projected project costs in less than eight years.
Despite the projected savings, the city was hesitant to replace equipment that was still in working condition. That changed in late 2009, when FOX Engineering successfully applied for a “Green Reserve” forgivable loan (grant) for the project. Under this program, more than 20% of the project costs were funded through the American Recovery and Reinvestment Act (ARRA) program, while the remainder of the project costs were funded through a State Revolving Fund (SRF) loan.
In addition to the new fine bubble aeration system, the project included five new positive displacement blowers installed inside sound insulated enclosures. FOX provided design, bidding and construction administration services associated with replacement of the aeration system. The resultant project has a direct pay back of less than four years.
Davenport, Iowa
Water Pollution Control Plant Biosolids Dewatering
In many Midwestern communities, poor performance at water treatment plants can have major consequences for the quality of life of local residents. In Davenport, Iowa, the biosolids facilities were experiencing problems with odors, high operating costs, and poor performance. FOX Engineering was hired to design improvements which would address these issues in a community known for its high quality of life.
FOX developed a plan to replace the vacuum filters with belt presses, discontinue the thermal biosolids conditioning process and construct two additional anaerobic digesters to ensure that all biosolids could be anaerobically treated. The digester project included two 600-kW electrical generators to burn the biogas produced in the digesters.
As a result of the project, the plant signed a long-term alternate energy contract with Mid-American Energy that pays the city for the energy produced from its biogas. The net result of the new digester and generator project, along with the alternate energy contract, resulted in a reduction in energy costs of about $350,000 per year. Additional energy-saving changes in the plant have now reduced the energy cost from the initial amount of nearly $1,000,000 per year to a net income of about $50,000 per year. (See our News Archive – 2005 for a complete version of this project.)
Newton, IA
Water Pollution Control Plant
FOX has evaluated and implemented several energy efficiency projects at the Newton WPCP. The plant uses the trickling filter/activated sludge process for secondary treatment. FOX evaluated the operation of the secondary treatment to determine if a change in operation could still maintain final effluent permit limits while reducing energy consumption. Through process modeling using computer models developed by FOX, we were able to determine that the trickling filter portion of the plant could meet the limits without using the activated sludge portion. FOX presented this change to the city and they implemented the operational changes in 2005. The plant has continued to meet effluent limits while saving over 60 percent or 100,000 kW hrs per month. This has resulted in a current savings of $80,000 per year without any capital cost.
FOX implemented a temperature phased anaerobic digestion project in 2002 to increase gas production and further stabilize the biosolids. This project included insulated digesters to conserve energy and sludge to sludge heat exchangers to recover heat from the thermophilic stage of the digester. Improved energy efficient mixing was also employed in the digesters. A grit removal project to replace energy intensive aerated grit removal with Headcell technology was also suggested by FOX in 2008. Improved HVAC systems with heat recovery were also installed with the project.
Council Bluffs, Iowa
Water Pollution Control Plant – Trickling Filter Recirculation Pump Station MCC Replacement
Increased focus on environmentally green projects and sustainable business practices have led to multiple opportunities to access substantial new sources of funding. FOX Engineering is active in scoping and pursuing these opportunities on behalf of its clients, and recommending them where appropriate, to help municipalities secure these funds.
For example, in 2009 FOX initiated a conversation with the city of Council Bluffs WPCP staff which led to them requesting a plan to upgrade the trickling filter recirculation pump station and replace the motor control center.
The five large trickling filter recirculation pumps (150-200 hp each) and two humus return pumps (40 hp each) were paired with adjustable frequency drives to pace fluid flow based on process requirements thereby reducing energy consumption. In addition, the effluent water pumps were replaced and adjustable frequency drives installed as part of the project to increase the pressure and capacity throughout the plant. Together, the more efficient drives and controls delivered not only automatic operation but also significantly reduced operating costs.
FOX completed the design and the project was bid and constructed in 2010. This project was awarded an American Recovery and Reinvestment Act (ARRA) Green Project grant due to the impressive decrease in energy consumption as a result of the improvements.
Cherokee, Iowa
Wastewater Treatment Plant
In many cases, technology and capacity needs make repair and replacement projects a necessity. Such was the case with the activated sludge wastewater treatment plant for the city of Cherokee, Iowa.
Built in the 1970s, problems with the main pumping station, preliminary treatment, inefficient aeration system, inadequate final clarifier capacity, and insufficient sludge handling facilities led the city to retain the team of FOX Engineering and Kuehl & Payer to prepare a comprehensive wastewater treatment facility plan. FOX was responsible for the wastewater treatment plant portion of the project, while Kuehl & Payer handled the collection system and pumping station.
Working closely with city staff, the team developed several alternatives for improvement, and performed cost evaluations to recommend the best options. The planning effort resulted in a two-phase approach which would create facilities and a treatment process that would be more reliable, easier to operate, and more efficient while meeting all treatment requirements.
Phase I included design and construction of a new preliminary treatment building, aerobic digester, and sludge storage tank, as well as modifications to the main pumping station.
Phase II involved construction of a new aeration basin, replacement of the aeration system diffusers and blowers, and the addition of a new final clarifier along with rehabilitation of the existing clarifiers.
In addition, changes to the city’s NPDES permit required disinfection at both the municipal plant and the city industrial wastewater treatment plant. While both treatment plants had existing chlorine contact tanks, they had not been utilized for disinfection for many years. However, since effluents continued to flow through the tanks prior to discharge, FOX Engineering was able to design and install ultraviolet disinfection systems to be fitted into the tanks, along with the addition of some fill and new walls. All of the existing piping was retained and used in the new configurations. These projects began construction in spring of 2009 with completion in spring 2010.
Council Bluffs, Iowa
Water Pollution Control Plant - Primary Digester Cover Repair
In many cities, existing water pollution control plants are in need of repairs after decades of conscientious maintenance. Such was the case in Council Bluffs.
Built in the early 1970’s, the Council Bluffs plant was showing signs of its age. So, in 2009, after assisting with repairs to the SW primary digester cover, FOX was contracted to design improvements to the NW cover.
Structural stability evaluations revealed repairs needed to be made to the support beams and gas collection dome due to corrosion. The project included removal of existing roofing, reuse of the precast concrete roofing panels, and repair of the structural portions of the cover. The cover was then reinsulated and new membrane roofing was installed. The digester gas compressor and controls for digester mixing were replaced. In addition, the original gas safety equipment and the hoses to remove methane gas and biosolids were replaced.
As a result, substantial costs were avoided through the repair and commissioning of the existing cover instead of replacement, and the city was able to continue to provide reliable digestion and gas collection.
Council Bluffs, Iowa
East Manawa Porous Asphalt Paving
The residential area known as East Manawa was in dire need of sanitary sewer and water lines, and new streets. It was without storm sewer and, with a water table at 5 feet, was chronically muddy, wet, and prone to flooding. The soils were corrosive, soft, and unstable. The area was flat – less than 1 foot of fall per mile, and the nearest drainage channel was a mile away. Lake Manawa State Park, adjacent to the project and a prime location to outlet the storm sewer, is the most impaired water body in Iowa, according to the IDNR. Conventional storm sewer would need to be deep (20 feet below the water table), require an expensive storm water pump station, and would have drained the lake. To make matters worse, the allowable right-of-way was 30 feet wide and housed electric, gas and telephone lines as well as the city’s utilities.
FOX Engineering designed an asphalt porous pavement system. It was constructed in the available right-of-way and discharges treated stormwater to Lake Manawa. The system utilizes shallow construction methods that did not require dewatering. The design incorporated 100% erosion control during construction. The 18-inch rock layer used for the base is able to withstand poor soil conditions and high groundwater. The system detains up to a 10-year storm event and treats stormwater with 90% contaminant removal prior to discharge into Lake Manawa. The porous pavement can lose 98% of its porosity and still function sufficiently. In the event the pavement becomes 100% plugged, a backup system of intakes with treatment features was installed.
The benefits? A true “green” street. The look of the street changed from grungy to spiffy. Lake Manawa is recharged with clean water and the area does not have a drainage/standing water issue. The cost of the porous pavement drainage system saves millions in drainage costs – a conventional storm sewer system for the 430-home residential area was estimated at $18-20 million. With porous pavement the cost dropped to $14-15 million. The need for an expensive storm sewer pump station is eliminated. The use of limestone for the rock base drastically reduces the corrosivity of the soils so that the underground utilities will last longer. The pavement can be visually monitored for effectiveness and when needed, it is vacuumed – by one person using a machine the city already has in inventory.
The project was one of the first in the nation to use porous asphalt for a public street. It was honored with the “Innovation” award by the Asphalt Paving Association of Iowa and a white paper was presented at the International Public Works Congress in Denver, Colorado. in September 2011.