National Academies Press: OpenBook

Guidance for Treatment of Airport Stormwater Containing Deicers (2013)

Chapter: Chapter 4 - Selecting Deicer Treatment Technologies

« Previous: Chapter 3 - Identifying Deicer Treatment Technologies
Page 55
Suggested Citation:"Chapter 4 - Selecting Deicer Treatment Technologies." National Academies of Sciences, Engineering, and Medicine. 2013. Guidance for Treatment of Airport Stormwater Containing Deicers. Washington, DC: The National Academies Press. doi: 10.17226/22440.
×
Page 55
Page 56
Suggested Citation:"Chapter 4 - Selecting Deicer Treatment Technologies." National Academies of Sciences, Engineering, and Medicine. 2013. Guidance for Treatment of Airport Stormwater Containing Deicers. Washington, DC: The National Academies Press. doi: 10.17226/22440.
×
Page 56
Page 57
Suggested Citation:"Chapter 4 - Selecting Deicer Treatment Technologies." National Academies of Sciences, Engineering, and Medicine. 2013. Guidance for Treatment of Airport Stormwater Containing Deicers. Washington, DC: The National Academies Press. doi: 10.17226/22440.
×
Page 57
Page 58
Suggested Citation:"Chapter 4 - Selecting Deicer Treatment Technologies." National Academies of Sciences, Engineering, and Medicine. 2013. Guidance for Treatment of Airport Stormwater Containing Deicers. Washington, DC: The National Academies Press. doi: 10.17226/22440.
×
Page 58
Page 59
Suggested Citation:"Chapter 4 - Selecting Deicer Treatment Technologies." National Academies of Sciences, Engineering, and Medicine. 2013. Guidance for Treatment of Airport Stormwater Containing Deicers. Washington, DC: The National Academies Press. doi: 10.17226/22440.
×
Page 59
Page 60
Suggested Citation:"Chapter 4 - Selecting Deicer Treatment Technologies." National Academies of Sciences, Engineering, and Medicine. 2013. Guidance for Treatment of Airport Stormwater Containing Deicers. Washington, DC: The National Academies Press. doi: 10.17226/22440.
×
Page 60
Page 61
Suggested Citation:"Chapter 4 - Selecting Deicer Treatment Technologies." National Academies of Sciences, Engineering, and Medicine. 2013. Guidance for Treatment of Airport Stormwater Containing Deicers. Washington, DC: The National Academies Press. doi: 10.17226/22440.
×
Page 61

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

55 4.1 Overview of Alternatives Analysis Process The process for selecting one or more deicer treatment technologies typically flows through an alternatives analysis. An alternatives analysis is a systematic comparison of the relative merits, constraints, and costs of alternatives. While a variety of alternatives analysis techniques can be applied, the methods presented here are drawn from direct experience with deicer treatment technology implementation. An overview of the deicer treatment technology selection method presented in this chapter is illustrated in Figure 13. In the following sections, guidance is provided on the screening and comparative analysis methods. Details of the cost-assessment methodologies are presented in Chapter 6. 4.2 Techniques for Technology Screening Process When considering potential deicer treatment technologies for new or enhanced treatment applications, it is typically not feasible to perform a detailed quantitative comparison of all potential technologies. As a result, execution of a screening (fatal-flaw) analysis to narrow the field to a small number of technologies is recommended. In a screening analysis, criteria that characterize the site-specific needs and constraints are compared to criteria for potential treatment technologies, as illustrated in Figure 14. As shown in Figure 14, if the values of the criteria that characterize the airport’s needs and constraints fall outside of the values for the same criteria associated with a specific technology, the technology is eliminated from consideration. The following steps in the screening process are recommended: Step 1: Determine and document criteria describing airport’s needs and constraints. Step 2: Review treatment technology fact sheets and airport summaries (summaries in Appendix D). Step 3: Gather information on technologies of interest from consultants, vendors, and other airports. Step 4: Eliminate technologies by comparing site characterization and technology criteria values. Step 5: Calculate order-of-magnitude capital, operating, and annualized costs for short list. Step 6: Eliminate technologies by comparing costs to budgets. Figure 15 illustrates this proposed screening process. Not all parameters describing the airport’s needs and constraints are suitable for use in a screening analysis. Criteria used in a screening analysis should be easily definable for both the airport site and the technologies that are being considered. Figure 16 provides examples of C H A P T E R 4 Selecting Deicer Treatment Technologies

56 Guidance for Treatment of Airport Stormwater Containing Deicers Site value outside of technology range Values from site-specific characterization criteria tables Values of treatment technology process selection criteria Screening process Site value within technology range Figure 14. Overview of treatment technology screening process. Figure 13. Deicer treatment technologies alternatives assessment method. Screening Eliminates technologies not meeting airport’s constraints Comparative Analysis Ranks short list of technologies based on quantitative comparison Life-Cycle Cost Analysis Calculates site-specific conceptual costs of alternatives Range of Possible Technologies Selected Technology or Combination of Technologies criteria that are often used in a screening analysis to eliminate deicer treatment technologies from further consideration. Table 5 further defines a common set of screening criteria. Data on corresponding values for these criteria for individual treatment technologies are found in the treatment technology fact sheets. Each screening step is briefly summarized in the following. 1. Determine and document criteria describing airport’s needs and constraints. In the screening step, identify those criteria describing the airport’s characteristics that can easily be used to rule out particular treatment technologies.

Selecting Deicer Treatment Technologies 57 Needed Treatment Capacity Governing Limits for Discharges Influent Stormwater Characteristics Airport Site Constraints Airport Operations and Management Constraints Activated Sludge Short-Listed Technology 1 Short-Listed Technology 2 Short-Listed Technology 3 Aerated Lagoons Anaerobic Fluidized Bed Distillation Mech Vapor Recompression Moving Bed Biofilm Reactor Reverse Osmosis Passive Facultative Tech POTW Discharge Private Recycling Emerging Technologies Aerated Gravel Beds CHARACTERIZATION DATA (Chapter 2) FACT SHEETS AND AIRPORT SUMMARIES (Appendix D) SHORT LIST FOR SELECTION Screening-Level Capital and Operating Cost Curves LIST OF TECHNOLOGIES FOR COMPARATIVE ANALYSIS Figure 15. Details of proposed treatment technology screening process. Figure 16. Criteria frequently used in deicer treatment technology screening analyses. Legend *- Available or Not Available ! - Airport Willing or Unwilling to Rely Minimum PG Minimum EG Minimum BOD5 Stormwater Characteristics Land Available for On-Site Treatment* Maximum Available Footprint Maximum Allowable Height Open Water* Treatment Plant Operations* Reliance on POTW to Accept Discharge! Reliance on Off- Site Recycling and Market for Recycled Glycol! Maximum Capital Funding Maximum Annual O&M Funding Site and Operational Conditions Typical Screening Criteria

58 Guidance for Treatment of Airport Stormwater Containing Deicers 2. Review treatment technology fact sheets and airport summaries. The treatment technology fact sheets list typical values for criteria that describe the technology’s performance and application. The airport summaries in Appendix D can also be used to provide context on the technology application by describing field experiences at the airports. 3. Gather information on technologies of interest from consultants, vendors, and other airports. Draw on the specific experiences of others to more specifically define criteria associated with particular technologies. 4. Eliminate technologies by comparing site characterization and technology criteria values. At the screening level, the comparison of characterization criteria values to technology criteria values results in a straightforward comparison—if the characterization criteria (i.e., your site’s treatment needs and constraints) fall outside of the technology criteria (i.e., the technology’s capabilities), then the technology should be eliminated from further consideration. Table 6 provides an example template that can be used to compare the criteria. A comparison table should be completed for each technology considered. 5. Calculate order-of-magnitude capital, operating, and annualized costs for short list. Within each treatment technology fact sheet, graphs are provided by which the order-of- magnitude capital and operating costs can be estimated from that mass loading capacity Technology Criteria Value or Rating Description Typical area (footprint) 1. <1 acre 2. >1 acre Typical area required for the treatment facility. • Includes building, associated structures, parking, access. • Excludes storage structures, collection pump stations, deicer application areas. Typical building/equipment height 1. <20 ft 2. >20 ft Typical maximum height of the treatment facility. • Includes buildings and treatment-related structures. • Excludes storage tanks. Reliance of disposal on outside entities 1. Reliance (describe) 2. No reliance Is ability to discharge or dispose of flow streams typically dependent on the actions of an entity not under the airport’s control? Examples: • Ability of POTW to accept discharge. • Ability to accept a recycled product. Treatable stormwater constituent mix 1. Can be treated by technology 2. Can be treated by technology with additional process 3. Cannot be treated by technology Applied to each constituent in stormwater that may need to be treated (for glycols, glycerin, acetate, formate, urea). Minimum PG, EG, or BOD concentrations 1. >1% (10,000 mg/L) 2. >2,100, <10,000 mg/L 3. <2,100 mg/L What is the range of influent concentrations where 90% of the collected concentrations in the deicer-affected stormwater fall? Open-water surface 1. Open water 2. No open water Core technology typically has or does not have open-water surface that might present wildlife attractant or reflectivity issues. Applied only to core treatment technology, not storage. Table 5. Example treatment technology criteria list used in screening process. Table 6. Example screening-level comparison table for technology: [name]. Criteria Characterization Value Technology Value Do Criteria Eliminate the Technology? Stormwater characteristics Site constraints Operational constraints

Selecting Deicer Treatment Technologies 59 (see Chapter 5 for guidance on mass load determination and Chapter 6 for guidance on costs). These cost curves are provided to support the screening-level costs only and are based on a typical installation. They are based on the core elements of each technology and do not include other necessary components of the deicer management system. The costs also do not account for site-specific aspects of treatment system installation (e.g., decisions on treatment building size). 6. Eliminate technologies by comparing costs to budgets. The order-of-magnitude capital and operating costs can be compared to the airports’ budgets for capital and annual costs to further eliminate potential deicer treatment technologies. An example cost comparison table is provided in Table 7. Please note that the capacity of the treatment system can also be used as a factor to fit treatment costs within the available budget. (Such a decision may sacrifice the ability to manage effects of extreme deicing conditions and require the system to be expanded at a sooner date.) The result of the screening process is a short list of technologies that can be efficiently analyzed in more detail in the comparative analysis process. 4.3 Comparative Analysis Process for Assessing Alternatives Use of a quantitative method to compare potentially applicable treatment technologies can be a great aid in the process of selecting deicer treatment technologies. Often when the choice is between two to four equally viable technologies, the differences between the technologies are complex and subtle. Use of a comparative analysis method can promote discussion and aid selection. Comparative analyses typically use multiple criteria to compare alternatives and can incor- porate systems for ranking or numerically rating alternatives. It is generally recommended that comparative analyses initially be performed without incorporation of cost into the comparisons, especially for those methods involving numeric scoring. The reasoning behind this recommen- dation is that cost as a criterion has the tendency to take precedence and outweigh other criteria. If cost is initially set aside, the importance of other criteria can be better explored. Cost can be integrated into the analysis after the other factors have been considered. Potential methods for comparative analysis processes are summarized in the following. Please see the References section at the end of this guidebook for additional information on the processes described here. 1. Analysis of alternatives to determine pros and cons. This method is one of the simplest comparison methods to use for treatment technology selection. Typically in a pro/con analysis, there is an evaluation of criteria that considers how the deicer treatment technology will be used within the airport’s specific deicer management system to meet the airport’s goals. Pros and cons are developed for each treatment technology alternative. The lists of the pros and cons for each alternative are compared directly to one another, and a somewhat qualitative assessment Treatment Technology Order-of- Magnitude Capital Costs Capital Cost Budget Order-of- Magnitude Operating Costs Annual Operating Cost Budget Do Cost Criteria Eliminate the Technology? Reverse osmosis AFBR MVR Table 7. Example screening-level cost comparison table.

60 Guidance for Treatment of Airport Stormwater Containing Deicers is made. The alternative with the strongest pros and weakest cons is preferred. Decisions are often made through iterative discussion and analysis. The process may be supported by analyses conducted by treatment technology experts. Users may want to weight the relative importance of each criteria category. Features of the pro/con method include: • It is the fastest and simplest method, • It is familiar to users and allows for written analysis of complex topics, • It has difficulty quantitatively demonstrating the basis for the choice, and • It does not easily assess the relative and interactive effects of criteria. 2. Weighted-sum scoring. In the weighted-sum scoring method, weights are assigned to various selection criteria categories based on the relative importance of the criteria, and values are assigned to the individual criteria for each alternative. To accurately use this process, all cri- teria values must be in the same units, or total scores will be meaningless. Depending on the criterion, the assessment may be objective (factual) with respect to some commonly shared and understood scale of measurement (e.g., money), or it can be subjective (judgmental), reflecting the subjective assessment of the evaluator. Features of the weighted-sum ranking method include: • It provides simple numeric means of ranking alternatives, • It promotes discussion of relative importance of criteria, • It provides limited comparison of alternatives directly to each other, and • It uses criteria weighting that is somewhat arbitrary. 3. Analytical hierarchy process. The analytic hierarchy process (AHP) is one of several quantita- tive selection processes that are based on head-to-head or pair-wise comparisons of criteria against each other. In the AHP process, subjective assessments of the relative importance of criteria to the success of the deicer treatment alternative are made. The method assumes that evaluators are more capable of making judgments of relative importance between two choices than absolute judgments among all choices. The pair-wise comparisons are used to quantify the most promising alternatives. The AHP process can be executed with individual decision makers providing their own evaluation or in a collaborative fashion as a group. The AHP has proven to be very good for framing the discussion of alternatives, identifying key criteria, understanding the relative importance of criteria, providing a structure for discussion and consensus, and providing some quantitative guidance for the decision-making process. Features of the analytical hierarchy process include: • Adds a high level of quantification to selection to help demonstrate basis for choice, • Is more complex mathematically, • Promotes discussion of relative importance of criteria, • Promotes discussion of all alternatives against each other, • Breaks the evaluation down into small steps, • Promotes comprehensive discussion, and • Uses a weighting of criteria that is somewhat arbitrary but allows for more precise deter- mination than other methods. 4.4 Testing of Assumptions Regardless of the screening and selection method used to determine the treatment technology alternative that is preferred, assumptions were likely made during the course of the analysis. To the extent possible, those assumptions should be tested for the selected technology. If a model

Selecting Deicer Treatment Technologies 61 is used for any portion of the evaluation, sensitivity analyses are an excellent method for testing the significance and developing a level of confidence in the assumptions. In a sensitivity analysis, a series or range of values is assigned to parameters of interest, and the results of the calculations are reviewed to determine if the assumed values have a significant impact on the results. If the outcome is determined to be sensitive to the assumed parameter, the assumption should be revisited. Sensitivity analyses are particularly valuable for establishing the design capacity of the selected treatment technology. 4.5 Value Engineering Value engineering is a systematic method to improve the value of selected alternatives by examining methods by which the same or better results can be achieved for the same or lower cost. Value is defined as the ratio of function to cost. Value can therefore be increased by either improving the outcome (e.g., more treatment capacity for the same cost) or reducing the cost (for the same capacity). In a value engineering exercise, the objective is not to sacrifice the basic functions as a consequence of pursuing value improvements.

Next: Chapter 5 - Designing and Implementing Deicer Treatment Systems »
Guidance for Treatment of Airport Stormwater Containing Deicers Get This Book
×
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

TRB’s Airport Cooperative Research Program (ACRP) Report 99: Guidance for Treatment of Airport Stormwater Containing Deicers offers a process to help airports identify, select, and implement technologies to treat stormwater that has been affected by deicing materials. The guidance also includes suggestions for the design, operation, and maintenance of different treatment technologies.

Eleven fact sheets that address the treatment technologies referenced in ACRP Report 99 are available for download. The fact sheets cover activated sludge; aerated gravel beds; aerated lagoons; anaerobic fluidized bed reactors; distillation; mechanical vapor recompression; moving bed biofilm reactors; passive facultative treatment systems; public wastewater treatment systems; private recycling systems; and reverse osmosis.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!