Many plants at the medium range (0.5 to 5 mgd) have been brought into service over the past five years and have had a period of operation during which there has been opportunity to report on the lessons that have been learned during the design and operation of these facilities. This paper considers issues such as membrane procurement, flow management, constraints on oxygen transfer rate, solids inventory management, nutrient removal, screening and foam control by reviewing the experiences of the authors at a number of North West mid-sized MBR facilities that the authors have designed and/or operated.