Washing method for preventing reverse osmosis membrane or nano-filtration membrane from being polluted

Abstract

The invention belongs to the technical field of seawater desalting and water treatment and relates to a washing method for preventing a reverse osmosis membrane or a nano-filtration membrane from being polluted. The washing method comprises the following steps of: firstly carrying out gas-water two-phase flow washing or simultaneous chemical washing; then extracting reverse osmosis concentrated water to wash the surface of the reverse osmosis membrane; discharging the reverse osmosis concentrated water through a concentrated water discharging valve; then, conveying pretreated water to a reverse osmosis module and displacing and discharging washing concentrated water on a reverse osmosis concentrated water side until the conductivity is recovered to 98% of the conductivity of the pretreated water; finally, closing a washing water discharging valve and opening the concentrated water discharging valve to recover normal operation of the reverse osmosis module; and sequentially washing other sets of reverse osmosis modules. The washing method disclosed by the invention is reliable in process, simple and convenient to operate, lower in energy consumption, good in economic benefits and social benefits, and environment-friendly.

Description

Technical field: [0001] The invention belongs to the technical field of seawater desalination and water treatment, and relates to a reverse osmosis membrane or nanofiltration membrane used to prevent reverse osmosis membranes or nanofiltration membranes from desalination / softening of seawater, brackish water, surface water treatment, and industrial waste water and urban sewage treatment. A process for filter membrane pollution, especially a cleaning method for preventing reverse osmosis membrane or nanofiltration membrane pollution in seawater desalination or water treatment technology. Background technique: [0002] Reverse osmosis membrane or nanofiltration membrane system is widely used in seawater desalination / softening or surface water treatment or industrial wastewater and urban sewage treatment and reuse process. Generally, traditional pretreatment methods such as sand filtration are used, or ultrafiltration membrane is used as pretreatment , the water after these pre...

AI Technical Summary

Problems solved by technology

Next, the generated gas-liquid mixed cleaning liquid is input into the reverse osmosis membrane device by another high-pressure pump to clean the organic pollutants on the membrane, and then the cleaning liquid is circulated back to the original water tank, but the microbubbles cannot reach the sufficient turbulence of the gas-liquid two-phase flow. The effect of moving and scrubbing the membrane surface; Japanese patent JP2009202063 (A) discloses a method for cleaning the reverse osmosis membrane module, the cleaning pipeline is connected with the reverse osmosis water inlet pipe, and the cleaning water pump delivers the liquid or gas-liquid mixture to the membrane surface of the element , so that the cleaning solution flows through the membrane surface at low pressure, effectively removing the pollutants stuck on the surface of the reverse osmosis membrane

The technical solutions disclosed in these patents all use air washing or a combination of air washing, water washing, and drug washing to remove the pollutants on the membrane surface when the surface of the reverse osmosis or nanofiltration membrane has been seriously polluted. It is a passive cleaning process. When the membrane fouling is quite serious, it is difficult to restore the flux by air washing and water washing, which cannot prevent it. Moreover, air washing alone cannot provide sufficient shearing force and takes a long time.

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