Good engineering design for a membrane water treatment plant requires the application of materials and corrosion engineering, sound water chemistry, hydraulics, pollution control, chemical handling, and a sprinkling of fairy dust. Most importantly, a successful, properly applied membrane water treatment plant requires knowledge of the technology. The overall system concepts must be given overriding consideration. The four system concepts discussed are: feed water source and pretreatment (surface water and well water), the membrane process (including recovery, finished water quality, water temperature, energy cost, and level of pretreatment), and post treatment.