The present invention relates to membrane bioreactor ("MBR") system that includes a mechanical membrane reciprocation system to reduce or eliminate membrane fouling. The disclosed MBR system can be operated with higher flux and lower fouling than MBR systems using air scouring. Furthermore the system can remove nitrogen and phosphorous with one RAS and one or no internal recirculation line. The membrane can be reciprocated by a low RPM motor connected to a pulley via belt to rotate rotor to convert rotational motion into reciprocating motion of membrane. Various mechanical means can also be employed to create the reciprocating motion.