AWWA MTC57635

This paper compares the competitive bidding and evaluation approaches used to procure membrane equipment for large water and membrane bioreactor (MBR) projects. The authors have collaborated on the design, procurement and construction of several water and MBR projects. Their experience with the evaluation and procurement of membrane equipment for large water plants and MBRs, including a recent 10-mgd (40,000 m3/day) MBR installation in Traverse City, Michigan, forms the basis for this comparison. There are many similarities, as well as some critical differences, in the use of membranes for water and MBR applications. Selection of the most appropriate membrane equipment for both applications depends on a variety of factors, in addition to the fundamental capital and operating costs. Key criteria such as the method and frequency of cleaning, the history and projected life of the membrane equipment, experience in comparable applications, and the availability of technical support and spare parts, can each be evaluated for both water treatment and membrane bioreactor applications. The configurations and sizes of the competing equipment can also be considered, as they affect the sizes and shapes of the required tanks and structures. For both water and MBR applications, the above factors typically justify a competitive procurement process that is conducted during the preliminary design phase of a project. The similarities for water and MBR applications, however, are limited to the above elements. While similarities exist between water and MBR applications, critical differences in the selection and use of membrane equipment also exist. There are several significant technical differences: two distinct groups of equipment vendors; dramatically different approaches to peak flow design criteria; and, most importantly, a critically different relationship between process performance and equipment performance. The latter relationship between process performance and equipment performance will be explored more fully. For both water and MBR applications, the treatment process design is separate from the membrane equipment design. With water applications, the produced water quality, flux and cleaning requirements may be fairly well known, and can be evaluated for each type of equipment being evaluated, although most municipal projects include pilot testing to verify design criteria. For MBR applications, the effluent quality, flux and cleaning requirements are not as well known, and vary greatly from project to project. They are 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 15,000 mg/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. Greater reliance on long term performance guarantees and equipment warrantees may be required for MBR projects, at least until a greater database of information is available. Includes 7 references, tables, figures.