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This paper compares the competitive bidding and evaluation approaches used to procuremembrane equipment for large water and membrane bioreactor (MBR) projects. The authorshave collaborated on the design, procurement and construction of several water and MBRprojects. Their experience with the evaluation and procurement of membrane equipment forlarge water plants and MBRs, including a recent 10-mgd (40,000 m3/day) MBR installationin Traverse City, Michigan, forms the basis for this comparison.There are many similarities, as well as some critical differences, in the use of membranes forwater and MBR applications. Selection of the most appropriate membrane equipment forboth applications depends on a variety of factors, in addition to the fundamental capital andoperating costs. Key criteria such as the method and frequency of cleaning, the history andprojected life of the membrane equipment, experience in comparable applications, and theavailability of technical support and spare parts, can each be evaluated for both watertreatment and membrane bioreactor applications. The configurations and sizes of thecompeting equipment can also be considered, as they affect the sizes and shapes of therequired tanks and structures. For both water and MBR applications, the above factorstypically justify a competitive procurement process that is conducted during the preliminarydesign phase of a project. The similarities for water and MBR applications, however, arelimited to the above elements.While similarities exist between water and MBR applications, critical differences in theselection and use of membrane equipment also exist. There are several significant technicaldifferences: two distinct groups of equipment vendors; dramatically different approaches topeak flow design criteria; and, most importantly, a critically different relationship betweenprocess performance and equipment performance.The latter relationship between process performance and equipment performance will beexplored more fully. For both water and MBR applications, the treatment process design isseparate from the membrane equipment design. With water applications, the produced waterquality, flux and cleaning requirements may be fairly well known, and can be evaluated foreach type of equipment being evaluated, although most municipal projects include pilottesting to verify design criteria. For MBR applications, the effluent quality, flux andcleaning requirements are not as well known, and vary greatly from project to project. Theyare in fact a function of a variety of parameters, including the Solids Retention Time,phosphorus removal method, and the Mixed Liquor concentration (typically 8,000 to 15,000mg/L in the area of the membranes). The evaluation of equipment bids, assessment of risk,and determination of life cycle costs for MBR projects are therefore complex. Greaterreliance on long term performance guarantees and equipment warrantees may be required forMBR projects, at least until a greater database of information is available. Includes 7 references, tables, figures.

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Edition: Vol. - No. Published: 03/05/2003 Number of Pages: 16File Size: 1 file , 330 KB