Hollow fiber membrane filament and circulating water and sewage treatment system

The utility model relates to the field of circulating water blow-off water treatment, and discloses a hollow fiber membrane filament and a circulating water blow-off water treatment system. The hollow fiber membrane filament is a tubular fiber filament formed by a composite membrane, wherein the composite membrane comprises a separation layer, a middle layer and a supporting layer from outside to inside; wherein the thickness of the separation layer ranges from 15 nm to 25 nm. The circulating water and sewage treatment system comprises a self-cleaning filter, a special nanofiltration device and a common nanofiltration device which are communicated in sequence. The special nanofiltration membrane formed by the hollow fiber membrane filament provided by the utility model can intercept organic matters with very small molecular weight, and has very high removal rate on COD (Chemical Oxygen Demand); according to the circulating water sewage treatment system, the yield of circulating water sewage can be effectively