The invention belongs to the technical field of
environmental protection, especially belongs to the technical field of
water treatment, and relates to a method for respectively removing the pollutants in
sewage by using a plurality of membrane separation methods. The method comprises the steps of: 1, carrying out membrane enhanced chemical
softening to remove the alkaline deposits in the water in a manner of a deposit (1); 2, filtering by using
nanofiltration membrane to obtain organic
pollutant concentrated solution (2) and
nanofiltration produced water (3), wherein the
recovery rate of the
nanofiltration membrane is 80-95%; 3, carrying out
reverse osmosis concentration on a small part of the nanofiltration
produced water (3) to obtain
reverse osmosis produced water (4) and dissolving salt concentrated solution (5), wherein the
utilization rate of
reverse osmosis can be up to 80-97%; 4, evaporating and concentrating the organic
pollutant concentrated solution (2), reusing
distilled water (6) and combusting
organic matter strong liquor (7); and 5, carrying out evaporative
crystallization on the dissolving salt concentrated solution (5) and reusing
distilled water (8) to obtain
solid salt. According to the method, the nanofiltration and the reverse
osmosis can be stably carried out under high
utilization rate to remarkably decrease the treating water quantity of an evaporative crystallizer, so that the operation cost is reduced, the scaling problem of
crystallization equipment is avoided at the same time, the
crystallization difficulty of mixture of inorganic salt and organic
pollutant is solved and then the crystallizer can stably run in a long term.