Multi-stage submerged membrane distillation water treatment apparatus

A multi-stage submerged membrane distillation water treatment apparatus comprising:

• a plurality of raw water tanks arranged in multiple stages ranging from a first stage to an n-th stage to store raw water, and configured such that the raw water sequentially flows from the first stage (foremost stage) to the n-th stage (last stage);
• a plurality of membrane distillation (MD) modules arranged in multiples stages and submerged in the respective raw water tanks, the MD modules discharging a portion of raw water as vapor;
• a plurality of heat exchangers arranged in multiple stages and submerged in the respective raw water tanks, each heat exchanger performing heat exchange using the vapor supplied from a previous-stage MD module of the MD modules, thereby enabling the raw water in the corresponding raw water tank to be maintained at a predetermined temperature;
• a vapor generator generating high-temperature vapor and supplying the generated high-temperature vapor to the heat exchanger in the first-stage raw water tank;
• a crystallizer receiving raw water discharged from the n-th-stage raw water tank and extracting crystals of valuable resources contained in the raw water;
• a turbidimeter detecting a turbidity of the raw water supplied to the crystallizer from the ni-th-stage raw water tank;
• and
• a controller controlling operation of the crystallizer such that crystals of valuable resources in the raw water are collected when a turbidity detected by the turbidimeter is equal to a predetermined reference value.