A submerged membrane separator includes: a plurality of membrane cartridges arranged at predetermined spaces; a flow generating device for generating flows in one direction along the membrane surfaces of the membrane cartridges; and wall members on both sides of a channel of the flow in the one direction formed between the membrane cartridges adjacent to each other. The membrane cartridges can be attached and detached from another direction substantially orthogonal to the flows in the one direction and substantially orthogonal to the arrangement direction of the membrane cartridges.

Disclosed are membrane separation cleaning processes and clean in place compositions for such membranes. The cleaning compositions can remove proteins, fats, and other food, beverage, and brewery based soils and offer an environmentally friendly alternative surfactant system to NPE. Branched extended chain PO/EO nonionic surfactants with certain characteristics may be used to provide superior cleaning to membranes. The specific surfactants may be used alone or in combination. In some embodiments, the surfactant package is used as part of a cleaning composition.