Hazardous and Radioactive Waste Treatment Technologies Handbook - Chapter 10 (end) ppsx

Schwinkendorf Idaho National Engineering and Environmental Laboratory Idaho Falls, Idaho Introduction Selection and design of systems and technologies for treatment of mixed low-level wa

© 2001 by CRC Press LLC

Chapter Ten

© 2001 by CRC Press LLC

10 Planned Life-Cycle

Cost Estimates

William E Schwinkendorf

Idaho National Engineering and Environmental Laboratory

Idaho Falls, Idaho

Introduction

Selection and design of systems and technologies for treatment of mixed low-level waste (MLLW) requiresknowledge and understanding of the expected costs, schedules, risks, performance, and reliability of thetotal engineered system These factors are all related For example, cost is a function of:

• Schedule The longer the schedule required to treat a given quantity of waste, the greater theoperating and maintenance cost

• Reliability The greater the system reliability, the lower the maintenance cost, the greater the systemavailability, and therefore the shorter the schedule However, increased reliability may increasecapital cost for more reliable equipment A system with low reliability will increase operationaland economic risk associated with increased probability of equipment failure, increased mainte-nance and a drawn-out schedule

• Risk Additional costs are required to mitigate environmental safety and health (ES&H) risksassociated with handling and treating mixed waste The design requirements for risk mitigationwill depend on the waste content and the technologies used in the treatment process

• Performance A system that performs poorly in terms of meeting treatment goals and regulatoryrequirements may require post-treatment, re-treatment, or system modifications, all of which willincrease cost and schedule

The purpose of this section is to provide the reader with insight into factors involved in determiningthe cost of a mixed waste treatment system, the relative cost of various treatment concepts, and the trade-offs that should be considered when developing an economic system design

This section is based on the results of an integrated process analysis project (Feizollahi et al., 1994;Feizollahi and Quapp, 1996; Biagi et al., 1997) commissioned by the Department of Energy (DOE), Office

of Science and Technology (OST), to evaluate thermal and non-thermal treatment systems for DOEmixed low-level waste (MLLW) The purpose was to evaluate and compare the performance and cost ofvarious treatment technologies in the context of a complete treatment system capable of treating thewide variety of mixed waste in the DOE complex Subsequent to these initial studies, additional analyseswere performed to obtain greater insight into the cost sensitivities and trade-offs associated with operatingparameters that differed from those used in the initial studies

These studies did not include the time value of money, escalation for expenditures occurring at differenttimes, or salvage value of the facility Many textbooks on engineering economy and cost engineering areavailable that provide methods for taking these factors into account for commercial operations

Thus, costs identified in subsequent subsections are for specific systems designed to treat specific DOEwaste streams for the integrated process analysis project These costs should not be taken to representthe costs of different treatment systems designed to process other combinations of waste streams Rather,the relative costs, their trends with respect to system parameters and waste characteristics, and theimplications of these factors on life-cycle cost are the important factors to consider in evaluating the life-cycle cost of a mixed waste treatment facility.

Standard Cost Factors

Total life-cycle cost of a mixed waste treatment system is a function of six major work breakdown structure(WBS) components Contingency should be included in all costs and generally should be higher forsystems using less-developed technologies to reflect operational uncertainties However, increased con-tingency cost for less-developed technologies is one factor that makes such technologies and associatedsystems less economically desirable than more mature technologies (Harvego and Schafer, 1997) Thesix cost components of the WBS are (Feizollahi et al, 1994; Feizollahi and Quapp, 1996):

1 Studies and bench-scale tests and demonstration Costs for treatability studies and bench-scaletesting include research personnel, equipment, facilities, and project management before Title Idesign Demonstration costs include personnel, design and inspection, construction and equip-ment including construction management, project management, waste disposal, and decontami-nation and decommissioning

2 Facility capital costs This cost element consists of five subcomponents described below that involvedesign, equipment costs, and building costs Design, inspection, management, and indirect costsare dependent costs that are calculated as a fraction of the purchase costs for the building structureand equipment

a Design: preliminary and detailed designs

b Inspection: this includes engineering support during construction

c Project management: management costs incurred by site management and the contractor

d Construction: Facility construction costs are developed from the preconceptual design packageand include site development, construction of buildings and structures for alpha and non-alpha waste, processing and material handling equipment, installation, and indirect costs such

as subcontractor overhead and fees

e Construction management: this includes material and services procurement and control ities, allowances for project scope change, management reserve, and contingency reserves toreduce the impact of missed cost or schedule objectives

activ-3 Operations budget funded activities These are preconstruction and preoperational activities Thiscost element includes conceptual design, safety assurance, National Environmental Policy Act(NEPA) compliance efforts for government projects, permitting, preparation for operations, andproject management Conceptual designs may consist of process functional diagrams, facilitylayouts, equipment lists, personnel requirements, and material mass balances

4 Operating and maintenance costs This cost element includes operating labor, utilities, consumablematerials, maintenance (parts, equipment and labor), and transportation Transportation costsinclude transportation of wastes to the treatment facility and transportation of treated waste to adisposal site Allowances for management reserve and contingencies should be included

5 Decontamination and decommissioning costs These costs include decontaminating the facility,removing the structures and equipment, and decontaminating the site

6 Disposal This cost includes the price charged by the disposal facility This is usually a one-timecost based on the volume of waste to be disposed However, the per-unit volume cost may vary,depending on the type and quantity of hazardous species and radionuclides remaining in thewaste

Facility Design Issues

Facilities handling MLLW are placed in Seismic Category 1 and are classified as moderate-hazard facilities(Kennedy et al., 1992) A major area of concern for ES&H and a major cost driver is the design for alphacontainment All systems and critical operations related to handling alpha-contaminated MLLW areclassified according to safety They should have high-quality, low-maintenance features to keep personnelexposure as low as reasonably achievable Operations with alpha-MLLW should be confined, to thegreatest extent practical, to remote cubicles

All process steps with potential for generating airborne alpha contamination should have a tertiarycontainment system Thus, equipment used to process alpha-MLLW should be placed in triple confinement,airtight cells with personnel access through airlock doors Such cells should operate at slightly negativepressure to avoid releasing contamination outside the units Only two levels of containment are requiredfor other processes involving materials with a limited potential for becoming airborne However, thisrequirement should be carefully assessed to avoid potential worker inhalation risks Personnel entering alphacells must wear Level A protective equipment, including self-contained breathing equipment

The facility should be designed and equipment selected to minimize maintenance requirements andminimize the personnel exposure time while performing maintenance operations Large corridors may

be required next to each cell for equipment removal and maintenance In this corridor, equipment may

be disassembled, decontaminated (if required), and sent to the maintenance shop for further repair.There are two maintenance issues to be considered The first issue is the basic maintenance costs (e.g.,labor, equipment, parts and material, and lost production due to downtime, which can be minimizedwith a just-in-time supplier or an inventory of spare parts or replacement equipment) The second issue

is the need to have sufficient staff to prevent any single individual from exceeding his/her daily or annualradiation exposure limits while performing maintenance functions

Facility concepts and confinement levels require detailed analysis and refinement when processingalpha-MLLW to determine the most cost-effective design that meets ES&H requirements The risk ofcost overruns may be high when the system is applied to alpha-MLLW because most system componentsmust be further developed to allow ease of decontamination and maintenance for application in an alphacell environment and to prevent the inadvertent release from processing systems Of particular concernare high temperature processes and the entrainment of actinides in the off-gas

Facility Subsystems

MLLW consists of organic and inorganic solids and liquids comprising a wide variety of materialscontaminated with hazardous organics, toxic metals, and radionuclides Such waste matrices may includeany of those shown in Table 10.1 (Huebner et al, 1994)

Treatment of such a wide variety of waste streams requires a complex treatment system consisting ofmany subsystems to handle separate waste matrices and, in some cases, specific contaminants The types

of subsystems that may be required are as follows

1 Front-end handling Waste is received and characterized Instrumentation can include real-timeradiography (RTR), gamma-spectroscopy, and passive/active neutron (PAN) assay The waste isremoved from the incoming drums, sorted, separated, size reduced, and transferred to the nextprocess Contaminated empty drums can be decontaminated for reuse, melted for metal recovery,

or compacted for disposition, depending on the waste content and residual contamination

2 Primary treatment For thermal systems, primary treatment generally consists of a single process

to destroy the organic waste components, and in some cases to vitrify the inorganic components(incinerator, plasma furnace, steam reformer, etc.), although some variations may exist For non-thermal systems, the primary treatment consists of a treatment train such as a separation process(thermal desorption or washing) to remove organics from inorganic waste matrices and a chemicaloxidation process to destroy organic waste

3 Aqueous waste All aqueous waste, including secondary waste generated internally (e.g., fromwashing or decontamination processes or from off-gas scrubbers, etc.), will require treatment.

4 Air Pollution Control (APC) APC systems may be required for various subsystems such as theprimary treatment unit, stabilization process, metal melter, or decontamination system Detailsand size of the air pollution control system depend on the specific process and contaminants inquestion The components of thermal and non-thermal APC systems are similar and performsimilar functions However, because approximately an order of magnitude more non-toxic gasesare emitted from thermal systems than from non-thermal systems, more fume, particulates, andcontaminants can be carried over with the off-gas from the thermal systems Thermal systems arealso more likely to generate specific hazardous compounds and volatile off-gas constituents (e.g.,dioxins/furans, NOx, Cd, Pb, Hg, etc.) Thus, the off-gas from thermal systems requires morecomplex treatment and the APC system must be much larger and more effective than that fornon-thermal systems to achieve the same level of performance

5 Metal recovery Melters can be used to produce ingots from ferrous metal wastes that cannot bedecontaminated for subsequent recycle or disposal Metal and lead decontamination can use anabrasive water jet or CO2 pellets to decontaminate the metals Mercury can be removed frominorganic wastes with a retort or by a leaching process

TABLE 10.1 Mixed Waste Matrices and Contaminants

• Acidic wastewaters and aqueous slurries • Organic contaminated soils (halogenated or nonhalogenated)

• Basic wastewaters and aqueous slurries • RCRA metal contaminated soils

• Aqueous/halogenated or nonhalogenated organic liquids • Metal debris

• Pure halogenated or nonhalogenated organic liquids • Concrete

• Inorganic particulates • Reactive metals

• Absorbed aqueous or organic liquids • Explosives/propellants

• Calcined solids

• Inorganic sludges

• Wastewater treatment sludges

• Plating waste sludges Inherently Hazardous Waste

• Paint waste-liquids/sludges, chips/solids • Elemental mercury

• Activated carbon (halogenated or nonhalogenated) • Beryllium

• Organic resins (halogenated or nonhalogenated) • Batters – Cd/Pb/Hg

• Organic absorbents (halogenated or nonhalogenated) • Batters – Cd/Pb/Hg

• Organic sludges (halogenated or nonhalogenated) • Cadmium metal/alloys

• Organic particulates (halogenated or nonhalogenated)

• Biological materials

• Organic Chemicals (halogenated or nonhalogenated)

6 Stabilization Several stabilization options are available as indicated in previous portions of thisHandbook Stabilization is generally required to meet Resource Conservation and Recovery Act(RCRA) Land Disposal Restriction (LDR) requirements.

7 Certification and shipping The physical and radiological properties of the packaged waste arecertified in accordance with transportation, storage, and disposal requirements The containers ofpackaged waste are weighed, examined with an RTR to ensure that the matrix is homogeneousand contains no free liquid, and beta and gamma radioactivity is assayed

8 Administration and support This includes all technical and administrative functions required tomanage the operation of a waste management facility These functions include security, accesscontrol including personnel decontamination, maintenance of uncontaminated areas and equip-ment, health physics and radiation badges, sanitary facilities, work control and personnel support,public relations communications, emergency response provisions, analytical laboratory, environ-mental field sampling, environmental regulatory reporting, and records management

Treatment systems that accept fewer types of waste matrices, contaminants, or wastes with low levels

of contamination will naturally require fewer subsystems However, most treatment systems will requiresome form of sorting and segregation of the waste to prevent accidents, inadvertent releases or equipmentdamage Many waste treatment technologies have limits on feedstream chemical content, physical com-position, and particle size Systems using a rotary kiln or plasma furnace for primary thermal treatmentrequire the least feed preparation In contrast, fixed-hearth controlled-air incinerators, indirectly firedpyrolizers, and non-thermal systems require a well-sorted feed

In general, it is undesirable for materials such as bulk lead and mercury to enter a thermal treatmentunit because they are particularly hazardous volatile materials that are difficult to collect in the off-gassystem If these materials can be found using RTR performed on containers of intact waste, the containersshould be emptied and the prohibited items removed and treated separately Similarly, if RTR detectsother bulk metals (e.g., steel, and aluminum), these metals should also be removed to minimize challenges

to the shredder and physical damage to the thermal treatment unit’s refractory

These constraints, coupled with the nature of the waste, dictate at least some degree of feed materialsorting and separation and, if there is a limitation on particle size, some level of shredding may berequired The extent to which waste feed must be sorted and shredded to produce an acceptable feedstockhas a significant impact on system cost Manual sorting is labor intensive, and automated sorting requireshighly sophisticated and costly instrumentation and involves high programmatic risk

Trade-offs between manual sorting by direct contact, or using telerobotics and automated sorting, willdepend on several factors, including labor costs, costs associated with sufficient personnel on staff tomeet daily exposure limits, and the cost of personnel protective equipment These costs can be compared

to the labor costs of operating telerobotic or automated equipment, the reliability of identifying wasteitems to be sorted, capital cost and maintenance cost of the equipment, and equipment reliability andavailability

Excessive shredding is mechanically demanding and significantly increases maintenance cost speed shredders have been identified as the best candidates because they can tolerate the widest variation

Low-in waste feedstreams, are the least costly, and are least prone to operational problems (Soelberg andReimann, 1994) However, commercial low-speed shredders reduce waste to 1 to 12 in in size — toolarge for many potential MLLW treatment technologies The reaction rate for most non-thermal processes

is surface-area limited; thus, such processes require particle sizes of 0.5 in or less The maximum feedsize for molten salt oxidation and supercritical water oxidation is approximately 0.125 in To achievethese small particle sizes requires low-speed shredding followed by high-speed sizing, typically a hammermill It has been estimated that separating and shredding combustible waste to a size range of 1 to 12 in

at a rate of 1 ton/hour would cost $700/ton Reducing the maximum particle size to 0.125 in would raisethe cost to $1600/ton with the incremental cost attributable to the hammer mill, its inert gas system,

additional separation equipment and maintenance requirements Reducing the particle size to less than0.004 in would increase the pretreatment costs to approximately $2100/ton due to additional screeningand recycling of waste through the hammer mill, and higher hammer mill operating and maintenancecosts The processing rate also affects sizing costs; reducing the processing rate by a factor of 10 increasesthe pretreatment unit costs by a factor of 4 to 5 because most of the equipment is the same so fixedcapital costs are spread over less waste.

Other required subsystems include primary treatment to destroy the hazardous organic components

in accordance with EPA requirements, and the nonhazardous organics to decrease the volume of waste

to be disposed Under EPA regulations, residues and secondary wastes will require treatment and/orstabilization before disposal if leachability standards are not met Variations of the stabilization processinclude vitrification, polymers, and cement or grout Thus, operations are needed to stabilize the treat-ment residues, unregulated organics that have not been destroyed, inorganic materials, and radionuclidesprior to disposal in a MLLW disposal facility

In general, systems that require complex mechanical, thermal or chemical processes, or precise control

of these processes, are difficult to operate and subject to frequent failures resulting in low operatingefficiency, low availability and reliability, and high maintenance Cost confidence is achieved using proventechnologies Conversely, technologies based on innovative or untested concepts pose a high risk ofoverruns Other factors contributing to system economics are availability of construction materials,system size, and the use of commercial equipment Volume reduction is also a principal cost considerationdue to the costs associated with packaging, shipping, and disposing of secondary wastes However, thecost of achieving significant volume reduction can exceed the savings depending on the complexity ofthe system and its reliability and availability

Cost Comparisons

Systems conceptualized in the integrated process analysis project consisted of all facilities, subsystems,equipment, and methods needed to treat and dispose of the MLLW stored in the DOE complex, includingwaste receiving, characterization, sizing, organic destruction, air pollution control, metal recovery, andsecondary waste residue processing for eventual disposal A generalized configuration is shown in

Figure10.1

Various technologies were assembled into 30 different conceptual systems: 20 thermal systems lahi et al., 1994; Feizollahi and Quapp, 1996), 5 non-thermal systems (Biagi et al., 1997), and 5 enhancednon-thermal systems (Biagi, Schwinkendorf, and Teheranian, 1997) The thermal systems used inciner-ation or other thermal processes for organic destruction, and vitrification, grout, or polymer for stabi-lization The non-thermal systems used wet oxidation processes operating at less than 350°C, such asacid digestion for organic destruction, and grout, phosphate bonded ceramic, or polymer for stabilization.The enhanced non-thermal systems included non-thermal organic destruction and vitrification forstabilization

(Feizol-These systems were compared to understand risks, cost and performance (Schwinkendorf, 1996).Material mass balances were prepared using the Aspen Plus computer code (Aspen Technology, Inc.,1994) to analyze preconceptual system designs The resulting equipment sizes, the “space footprint,” andassociated operating and maintenance staff requirements were estimated to develop the total life-cyclecost (TLCC) that covered everything from current storage through final disposal and release of effluents

in accordance with expected regulations A comparable basis among the various systems was madepossible by maintaining the following assumptions throughout all of the studies

1 The same waste characteristics and distribution of constituents were used for all analyses

2 A single, centralized government-owned and contractor-operated (GOCO) facility capable oftreating all DOE MLLW was assumed

3 About 70% of the current DOE MLLW inventory, or 236 million pounds (107 million kilograms),

of waste was treated over the system lifetime of 20 years

4 Waste was treated at a rate of 2930 lb/hr (1330 kg/hr) with 46% online availability (4030 hr/yr ofoperation out of 8760 hr) due to uncertain equipment life and maintenance requirements withradioactive operations.

5 Because the treatment systems are used for alpha and non-alpha waste, a tertiary containmentsystem was used for all process steps from waste sorting through stabilization

6 Except where a Joule-heated melter is explicitly identified, all vitrification is performed in a temperature plasma furnace that produces a slag

high-7 Waste loadings (i.e., mass of treated waste incorporated into the final waste form divided by themass of the final waste form) of 67 wt% in high-temperature slag, 50 wt% in polyethylene, and

33 wt% in grout were assumed

8 Disposal was in an RCRA engineered on-site disposal facility meeting land disposal restrictionswith a disposal cost of $240/ft3 ($8480/m3)

One of the primary products of these studies was the total life-cycle cost of these systems It should

be recognized that the actual costs of real systems will depend on the waste to be treated, the processesand technologies used, and the marketplace However, the cost estimates developed in these studies areappropriate for system comparisons, identification of major cost elements, and identification of potentialcost savings

Differences in the TLCC among systems of thermal technologies are minor Likewise, only smalldifferences were found among systems using non-thermal technologies However, the cost of non-thermalsystems was about 50% more than thermal systems This difference appears significant because the studiesshould be within ±30% owing to the comparative bases used

TLCC costs were estimated to be approximately $2.1 billion for a thermal metal melting system vs

$3.9 billion for a non-thermal acid digestion system The unit costs for treatment (without disposal) varybetween ~$8/lb ($17.60/kg) for thermal systems and $13/lb ($28.70/kg) for non-thermal systems Table

10.2 illustrates a typical distribution of subsystem costs for a rotary kiln system with vitrification and anon-thermal process with grout stabilization Table 10.3 illustrates typical WBS cost components for thesame systems

FIGURE 10.1 Generalized MLLW treatment system (*PBC = phosphate bonded ceramic)

Aqueous Liquids Aqueous Waste Treatment

To Disposal

To Disposal

Clean Metal

to Recycle

Discharge or Recycle Characterization

Sorting

Size Reduction

2927 lbs/hr

Receiving &

Preparation Noncombustible Waste Combustible and

Metals with Entrained Contamination & Lead

Primary Treatment

Polymer Stabilization

Stabilization Vitrification GroutPBC* Metal

Melters

Mercury Retort &

Amalgamation

Metal/Lead Decontamination Abrasive Blasting Special Waste Treatment

Mercury Contaminated Waste

Bulk Metals

& Lead

Special Waste

Primary Waste Secondary Waste

The non-thermal system costs are more than thermal systems because the operations and maintenance(O&M) costs are estimated to be 50% higher due to more waste sorting and preparation, and more unitoperations requiring more personnel, equipment, and facilities This is because non-thermal systems arelimited to the types of waste and waste matrices that can be treated, require greater size reduction, andgenerate more secondary waste than thermal systems Non-thermal systems, using grout for stabilization

vs vitrification used with thermal systems, produced more final waste form volume with the associatedhigher certification, packaging, and shipping cost and higher disposal costs

Non-thermal waste treatment technologies (e.g., alternative oxidation technologies such as acid tion) are also immature technologies that have not been fully demonstrated and implemented in a variety

diges-of waste treatment applications In contrast, incineration is a mature and proven technology that hasgenerally been the primary choice of industry for destroying hazardous waste The technical risks arelow and the costs are well established However, public opposition to incineration is well establishedand growing

Thus, there may be niche applications or site-specific applications where non-thermal technologiescould be used economically or are necessary for treatment Such applications might include difficult-to-treat wastes, orphan wastes that exist in small quantities and that cannot be transported to a centralizedfacility, or wastes that cannot be treated by incineration either due to safety or permitting issues or publicopposition

O&M costs are the highest percentage (50 to 60%) of TLCC, followed by capital cost (23% of TLCC,most of which is facility cost), and then by disposal costs for systems that vitrify waste (11% of TLCC).Systems that use a non-thermal waste form (e.g., grout) have a significantly higher disposal cost — approx-imately 20% of the TLCC Because costs are only modestly affected by the choice of treatment technologies

TABLE 10.2 Subsystem Cost Distribution for Thermal and Non-thermal Systems

Subsystem Life-Cycle Cost% Total Subsystem Life-Cycle Cost% Total

Air pollution control and

aqueous waste treatment 11 Air pollution control and aqueous waste treatment 6

TABLE 10.3 Distribution of Cost Components for Thermal and Non-Thermal Systems

Cost Component Life-Cycle Cost% Total Cost Component Life-Cycle Cost% Total

Capital (facility and equipment) 23 Capital (facility and equipment) 17

or equipment (i.e., equipment purchase costs less than 5% of TLCC), reliability, performance, and safetyare the most important considerations in selecting equipment for treatment of MLLW It is these equipmentcharacteristics that will affect operating and maintenance costs.

In all cases, energy costs are less than 1%of the treatment costs (i.e., TLCC without disposal costs).The hourly costs ranged from $80 to $200, with thermal treatment systems using electrical energy (metalmelting and plasma systems) having the highest energy costs Transportation costs were also found to

be only 1% or less of the TLCC

Sensitivity Analysis

Sensitivity studies were performed to determine the effects of varying the assumptions used in comparingtreatment system costs The sensitivity of system life-cycle costs was determined relative to changes insubsystem costs and WBS component cost, facility capacity, operating life, stabilization options andsystem availability

Effects of Changes in WBS Component Costs

For all systems, the most cost-sensitive component is O&M Because this is a major cost contributor toTLCC, a decrease in cost in these areas can have a significant impact on total system cost When annualoperating, utility, material, and maintenance costs are reduced by 50%, the treatment costs (costs withoutdisposal) decrease by an average of 32% and total life-cycle costs (costs with disposal) decrease by 27%.This may amount to as much as $680 million over 20 years for a rotary kiln system with vitrificationtreating DOE’s legacy MLLW

The second most cost-sensitive component is capital costs; a 50% decrease will result in a 12% decrease

in treatment costs and a 10% decrease in total life-cycle cost In this analysis, all dependent costs werechanged; for example, design, inspection, and management costs are a percentage of building andequipment purchase costs If these costs change, the dependent costs increase or decrease by the samepercentage As seen later, equipment reliability and system availability have a significant impact on TLCC

as well as the choice of stabilization technology Thus, an increase in equipment cost due to the purchase

of higher reliability equipment should only have a marginal effect on dependent costs but significantlydecrease O&M and total life-cycle costs

Effects of Changes in Subsystem Costs

Front-end handling is the highest cost subsystem; thus, a decrease in cost in this area can also have asignificant impact on total system cost This subsystem has cranes and forklifts to unload waste containersfrom incoming vehicles, and various instruments to characterize the physical state of the contained waste.Computer software and barcode scanning record and track the waste Containers not requiring sortingare moved directly to the appropriate treatment subsystem If sorting is required, the container is openedand emptied onto a sorting table where the waste is segregated into treatment types If required, thewaste is size reduced

Opportunity exists for reducing front-end handling costs by reducing labor costs, the major O&Mcost driver For example, the integrated process analysis studies defined labor requirements for thereceiving and inspection process to be three 28-person shifts per day to process approximately 150 55-gal drums of waste per day In this case, each person processes 1.8 drums per day at 4.4 hr per drum Ifimproved technology allowed each person to process 5.4 drums per day at 1.5 hours per drum, then onlyone 28-person shift or three 7-person shifts would be required, for a savings of $235 million over 20years (Harvego and Schafer, 1997) This indicates that time and motion studies on labor-intensivesubsystems to identify rate-limiting steps can be an important tool to identify areas for process improve-ments and cost savings

The optimum reliability (or mean time between failure) is indicated by the minimum in the curve foracquisition cost plus operational cost, as shown in Figure 10.3 (Lamb, 1995) Improving reliability —and therefore system availability — reduces the time required to treat a given quantity of waste as well

as maintenance and operational costs However, acquisition costs must generally increase to achievehigher reliability Thus, the objective is to find the optimum balance between investing in improvedreliability during system conceptual design and development and reducing operations and maintenancecosts so that life-cycle cost is minimized

FIGURE 10.2 Percent of total life-cycle costs vs locked-in costs (Adapted from Arsenault and Roberts, Reliabilityand Maintainability of Electronic Systems, Computer Science Press, Potomac, MD, 1980.)

FIGURE 10.3 Reliability optimization to minimize life-cycle cost

Reliability Acquisition Cost

Life Cycle Cost