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The cash register, the digital clock, the frost-proof freezer, professional football, the yo-yo, and … the insourcing of biosolids processing. What do these have in common? All were developed and innovated in Dayton, Ohio.

In 1986, the city was outsourcing its biosolids processing operations. Prior to this, Dayton used sludge lagoons. A biosolids processing facility was built within Dayton’s Water Reclamation Facility (WRF) that was owned and operated by a private contractor for a 20-year term with 5-year review periods.

However, with escalating unit costs and annual appropriations for biosolids processing and disposal, in addition to the absence of competition due to private ownership, Dayton staff looked inward. The city conducted a benefit–cost evaluation (BCE) to determine the 15-year life-cycle costs across a series of alternatives and used its best asset — its employees — to save costs.

Biosolids processing facility operationThe City of Dayton’s WRF consists of a preliminary, primary,

and two-stage biological treatment system with effluent filtration, chlorination, dechlorination, and postaeration (see Figure 1, p. 46).

The Dayton WRF is designed for an average daily flow of 273,000 m3/d (72 mgd) and a maximum design flow of 719,000 m3/d (190 mgd). Waste activated sludge from the second stage biological treatment system is thickened in a dissolved air flotation thickener before it is sent to anaerobic digesters. Methane gas from the anaerobic digesters is used for cogeneration. After dewatering, the biosolids are land-applied. The facility is staffed by more than 70 employees across the disciplines of administration, laboratory, operations, maintenance/electrical, and industrial pretreatment.

The biosolids processing facility consists of sludge storage tanks, a polymer system, two gravity belt thickeners, and two centrifuges. Anaerobically treated sludge at 2.5% total solids (TS) is pumped from sludge storage tanks to the gravity belt thickeners to create a slurry ranging from 6.0% to 7.0% TS. This slurry is collected within surge tanks and processed through the centrifuges. Both the surge tank and the centrifuge stations are hit with a cationic polymer mix. The 28% TS final product meets Ohio’s Class B land application requirements.

Biosolids production averages around 10,400 Mg/yr (11,500 dry ton/yr). Dayton’s land application program includes more than 8500 ha (21,000 ac) of land in a five-county region. During wet

From private to public Dayton’s journey into the biosolids processing businessJason Tincu, Tom Dempsey, and Bryan Taulbee

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From private to public periods and winter, land application is banned and Dayton uses onsite storage with landfilling as needed.

Operations under this arrangement were convenient to Dayton: There were no stipulations on liquid feed concentrations or sludge transfer intervals. The relationship between owner and operator was amicable. But as costs continued to rise and funding began to tighten up (see Figure 2, p. 46), the City of Dayton began to consider other arrangements. Contract provisions allowed for the acquisition of the processing facility through a depreciation schedule at each 5-year review interval. This buyout clause included all permanent structures and assets, including the process building and office area, sludge storage tanks, dewatering equipment, the conveyance system, weight scale, and a 3700-m2 (40,000-ft2) sludge storage barn.

Evaluation yields $20 million savings Dayton considered the status quo in its evaluation. The

existing condition option would keep all agreements, services, and provisions the same (private ownership, turnkey operation of the dewatering facility, and biosolids disposal) with subsequent inflationary rates. The insourcing option would use the contract buyout clause within the existing agreement and insource operation of the dewatering facility while contracting out biosolids disposal services in a competitive bid process.

When evaluating these options, Dayton added conservative

placeholders in the insourcing option for labor, polymer addition, and capital rehabilitation and replacement. The BCE evaluation results were staggering — the city discovered it could save over $20 million in a 15-year period (see table, p. 47). This option also had the benefit of securing local control of facility operation and securing public sector jobs. The insourcing option also would save the jobs of four full-time employees that would otherwise be lost through attrition.

Transitioning to inhouse controlAt this point, Dayton aimed its sights at the insourcing

option and moved toward execution of all related tasks within an extremely aggressive period of 5 months: ■ Execute buyout appropriation and processing.■ Put out biosolids land application and disposal services for competitive bid.■ Procure a bulk polymer supply.■ Develop a training program.■ Upload and integrate assets within the city’s computerized maintenance management system program.■ Conduct a capital needs assessment.■ Develop a biosolids sampling and analysis plan.

Dayton gathered a transition team that would help execute these tasks consisting of operations, maintenance, administration, and laboratory staff.

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Contract land application and disposal

One of the initial undertakings was seeking bids for biosolids land application and disposal. The four bid options offered to qualified contractors were ■ traditional land application services per wet ton, ■ land application service plus landfilling up to 4500 wet Mg (5000 wet ton),■ landfilling trip charges to three local landfills (per 18,000 Mg, or 20,000 wet ton load), and ■ turnkey operation (dewatering and land application) per dry ton.

These options were developed strategically for the best pricing for services. The first and third were meant to complement each other while the second was a stand-alone option for comparison. The last option resembled the existing arrangement, operation by a contractor, yet allowed for competitive pricing due to the city’s role as owner. The second option was vetted as the best option.

Training program In concert with these efforts, the city

began to develop meticulously a training program for 22 operators who would take over dewatering operations without compromising throughput, regulatory compliance, or efficiency. A three-part training series was developed consisting of classroom learning, job shadowing, and post-transition support.

The classroom phase included big picture, midlevel, and ground-level training modules that brought operators from a high level of instruction (Intro to Biosolids Processing and Dewatering) down to standard operating procedures. As part of the classroom phase, a group of operations and maintenance staff visited other local treatment facilities with similar dewatering technologies.

Operators also shadowed outgoing contractor staff on a daily basis. Anywhere from one to four city employees were assigned to the dewatering facility during the final few months of the contract. This provided a great opportunity for staff to review operational requirements and learn the ins and outs of the facility. During post-transition support a few

DAF = dissolved air flotation.TWAS = thickened waste activated sludge.

Figure 1. Dayton (Ohio) water reclamation facility schematicsLiquid

Solids

Figure 2. Cost per dry ton (in dollars)

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weeks after city staff began operating the facility, the contractor sent a trained employee onsite to support Dayton’s operations staff. This person aided in system evaluations, made operational recommendations, and provided general support to city staff.

Capital needs assessmentThe capital needs assessment was completed prior to the

insourcing transition and focused on operational optimization, quality of life, worker safety, and contingency planning. These included enhancements such as■ addition of a closed-circuit TV for monitoring critical process points;■ installation of a fiber connection and a supervisory control and data acquisition client to monitor tank levels and other process items;■ update of all interiors, including the addition of a small breakroom/kitchen;■ installation of a permanent gas detection system with alarms;■ lighting upgrades; and■ redundant equipment, including critical spare parts, spare pumps, and a spare centrifuge rotating unit.

For the first 6 months of inhouse operation, the city is pleased with the performance. More than 235,000 m3 (62 million gal) of liquid sludge and over 16,000 wet Mg (18,000 wet ton) of biosolids have been processed under the city’s control with absolutely no regulatory, performance, or contractual problems. System capture rates have been in the 90%+ range and the facility has run an average 16 hours per day since the takeover. Costs also are in line with the initial BCE projections. Dayton has saved more than $680,000 and is extremely pleased with the decision to bring insource biosolids processing in-house to retain city jobs, save millions of dollars, and secure local control of a major operation.

Jason Tincu is the manager of the Division of Wastewater Reclamation, Tom Dempsey is a research and control specialist, and Bryan Taulbee is assistant to the city manager for the City of Dayton, Ohio.

Savings for insourcing operation of the biosolids processing facility

Cost per dry ton Expenditures, year to date Projected annual costs

“Existing Condition” option (Contract

Year 13)$256.55 $1.44M $2.8M

In-house operation $145.95 $760,000 $1.5M

Savings $110.60 $680,000 $1.3M

Due to the efforts of the Dayton operations team (left) and maintenance staff (right), the city has saved more than $680,000 by insourcing biosolids processing. The project also retained city jobs and secured local control of a major operation. Jason Tincu

The City of Dayton’s Water Reclamation Facility conducted a benefit–cost evaluation to determine the 15-year life-cycle costs across a series of alternatives and used its best asset — its employees — to save costs. Jason Tincu