Online cleaning system for micro-polluted nanofiltration membranes using forward osmosis and process of online cleaning system

An online cleaning system for micro-polluted nanofiltration membranes using forward osmosis, comprising

• a nanofiltration raw water tank (1), a nanofiltration membrane assembly (2), a pure water tank (3), a forward osmosis feed solution tank (4), a forward osmosis draw solution tank (5), a first saline water tank (6), a second saline water tank (6′) and a water bath temperature control device (7), wherein a concentrated saline water outlet of the second saline water tank (6′) is pumped into the forward osmosis feed solution tank (4) through a second peristaltic dosing pump (18′) and a pipeline;
• a second electronic balance (8′) is arranged at the bottom of the forward osmosis feed solution tank (4), a feed solution in the forward osmosis feed solution tank (4) sequentially passes through a forward osmosis system feed solution side conductometer (16), a forward osmosis system feed solution water inlet side one-way valve (21), a forward osmosis system feed solution water inlet main flowmeter (12), a forward osmosis system gear pump I (9), a forward osmosis feed solution side pressure gauge (22), the water bath temperature control device (7), an electromagnetic valve (34) and a pipeline to enter the nanofiltration membrane assembly (2);
• the nanofiltration membrane assembly (2) is respectively connected with a first forward osmosis system three-way valve (32), a second forward osmosis system three-way valve (32′), a third forward osmosis system three-way valve (33) and a fourth forward osmosis system three-way valve (33′);
• fresh water from the nanofiltration membrane assembly (2) passes through a nanofiltration system fresh water outflow electromagnetic valve (20), a nanofiltration system fresh water outflow flowmeter (15) and a pipeline to enter the pure water tank (3);
• raw water in the nanofiltration raw water tank (1) is sequentially connected with a nanofiltration system water inlet main electromagnetic valve (30), a nanofiltration system water inlet side one-way valve (24), a nanofiltration water inlet main flowmeter (11), a forward osmosis system gear pump II (10), a nanofiltration system raw water side pressure gauge (23), the water bath temperature control device (7) through pipelines to enter the nanofiltration membrane assembly (2);
• according to the reading of a forward osmosis system draw solution side conductometer (17), concentrated saline water in the first saline water tank (6) is pumped into the forward osmosis draw solution tank (5) through a first peristaltic dosing pump (18) so as to keep the concentration of a draw solution unchanged;
• the draw solution is sequentially connected with a forward osmosis system draw solution water inlet electromagnetic valve (31), the nanofiltration system water inlet side one-way valve (24), the nanofiltration water inlet main flowmeter (11), the forward osmosis system gear pump II (10), the nanofiltration system raw water side pressure gauge (23) and the water bath temperature control device (7) through pipelines to enter the nanofiltration membrane assembly (2);
• concentrated water in the nanofiltration membrane assembly (2) is sequentially connected with a nanofiltration system concentrated water backflow flowmeter (13), a nanofiltration system backflow electromagnetic valve (26), a nanofiltration system concentrated water backflow side one-way valve (27) and a nanofiltration system concentrated water backflow electromagnetic valve (29) through pipelines to flow into the nanofiltration raw water tank (1), and a first electronic balance (8) is arranged at the bottom of the forward osmosis draw solution tank (5).