How to chemically clean the RO membrane after fouling-Ocpuritech-img

How to chemically clean the RO membrane after fouling?

by:Ocpuritech     2021-05-22
How to chemically clean the RO membrane after fouling? Author: RO reverse osmosis membrane during application, there will always inevitably contaminated insoluble salts and suspended solids in water, resulting in precipitation of calcium carbonate and other substances. These include calcium carbonate scale, calcium sulfate, barium sulfate, strontium sulfate scale, calcium phosphate scale, polymerized silica scale, colloidal pollution, and microbial deposition. Today we are sharing the chemical cleaning operation method after the reverse osmosis membrane fouling, as follows: (1) Low-pressure flushing at 4Bar (60Psi) or lower pressure, that is, from the cleaning water tank (or a suitable water source) to Pump clean water into the pressure vessel and drain for a few minutes. The flushing water must be RO product water or deionized water that is clean, removes hardness, does not contain transition metals (Fe, Mn, etc.) and residual chlorine. (2) Prepare the designated cleaning solution in the cleaning water tank. The preparation water must be RO product water or deionized water that removes hardness, does not contain transition metals and residual chlorine. The temperature and pH of the cleaning solution should be adjusted to the required value. (3) Start the cleaning pump to pump the cleaning liquid into the membrane module, and cycle cleaning for about 1 hour or the required time. In the initial stage, before the cleaning liquid returns to the R0 cleaning water tank, the reflux liquid should be drained to avoid dilution of the cleaning solution with water retained in the system. After the chemical agent comes into contact with the RO device, the pollutants in the device will be flushed out due to the chemical reaction. In order to avoid contaminating the cleaning liquid, these cleaning liquids should also be discharged until the color of the cleaning liquid fades and then enters the circulation. Wash. After cyclic cleaning, slowly adjust the flow rate to 1/3 of the maximum cleaning flow rate, and within the second 5 minutes, increase the flow rate to 2/3 of the design flow rate, and then increase the flow rate to the maximum cleaning flow rate value. If necessary, when the change of p is greater than 0.5, it is necessary to re-add drugs to adjust the pH value. (4) Cycle cleaning and soaking procedures can be used alternately as needed. The soaking time can be selected from 1 to 8 hours according to the manufacturer's recommendations. Care must be taken to maintain proper temperature and pH throughout the cleaning process. (5) After the chemical cleaning is completed, clean water is used for low-pressure flushing, the residual chemical agent is flushed from the cleaning device and related pipelines, the cleaning water tank is discharged and flushed, and then the cleaning water tank is completely filled with clean water. Pump all the flushing water from the cleaning water tank to flush the pressure vessel and discharge it. Until the residual chemicals in the RO device are basically removed. (6) After completely flushing with clean water, the final low-pressure flushing can be done with pre-treated feed water. The feed water pressure should be lower than 4bar, and the final flushing continues until the flushing water is clean and does not contain any foam and detergent residues. Usually this takes 15-60 minutes. The operator can take a sample with a clean flask, shake it well, and monitor the residue of detergent and foam in the flushing water at the drain. The removal of the washing liquid can be carried out by testing the conductivity. For example, the conductivity of the flushing water to the discharge water is within 10-20% of the feedwater conductivity. The flushing can be considered as close to the end point. The p meter can also be used to determine the pH of the flushing water and the discharged water Is the value close. It should be noted that after the low-pressure flushing is completed, the RO device can restart operation, but the initial product water must be discharged and monitored until the RO product water can meet the process requirements (conductivity, p-value, etc.). This period of recovery time sometimes takes from several hours to several days to obtain stable RO product water quality, especially after high pH cleaning. The above is the chemical cleaning operation method after reverse osmosis membrane fouling, please refer to it.
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