Maintenance of MBR membrane system After the MBR system has been used for a period of time, because the contaminants accumulate on the membrane surface to increase the pressure difference between the membranes, the membrane modules need to be cleaned and maintained. The initial pressure difference between the membranes is about 10KPa , and the MBR membrane module has been filtered for a period of time. After that, when the pressure difference between the membranes is 20 KPa higher than the initial stage, it is necessary to perform chemical cleaning. When the transmembrane pressure difference reaches 35kPa , restorative cleaning must be performed. When the membrane flux cannot be recovered effectively through restorative cleaning, off-line chemical cleaning should be considered.
MBR regularly on-line chemical cleaning can be maintained MBR system is stable, while the two later years, the water flux of the membrane system producing the original initial state of about 90 - 95% .
MBR system online chemical cleaning maintenance steps:
In order to ensure the good water production performance of MBR membranes, the membranes should be cleaned regularly online. If the transmembrane pressure difference reaches or exceeds 35 kPa and then cleaned, the recovery effect will be greatly affected.
The recommended online chemical cleaning method is: maintenance cleaning once a week, restorative cleaning once a month, and pickling at least once every six months.
(1) Type and frequency of medicine cleaning
Commonly used liquid medicines are sodium hypochlorite, citric acid, and oxalic acid solutions.
① Maintenance cleaning: once a week, 500 ~ 1500 mg/L sodium hypochlorite aqueous solution, the concentration of the chemical solution shall be subject to actual engineering needs;
② recovery cleaning: once a month, 2000 ~ 3000 mg / L of aqueous sodium hypochlorite solution;
③ Pickling cycle: once every six months or according to the specific pollution of the membrane filament, 1 ~ 2% (mass fraction) citric acid or oxalic acid solution.
The amount of medicament used per square meter of membrane area is 2 to 4 L , plus the amount required to fill the drug delivery pipeline.
3) Online chemical cleaning steps
① Stop filtering and aeration: first turn off the water production pump and close the water production pneumatic valve for the corridors that need to be cleaned, and turn off the aeration after 1 to 2 minutes . It must be confirmed on site that the aeration has been completely closed. The water inlet and backflow of the corridor are also closed, and then the valve of the medicine supply pipeline is opened;
② Adding chemical solution: In areas with low water temperature, you should consider heating the cleaning solution appropriately. Increasing the temperature can improve the cleaning effect. The recommended cleaning solution temperature is 25 ~ 35 ℃. Open the liquid medicine injection tube and inject the liquid medicine; add the liquid medicine in three batches, each adding one-third of the amount of the medicine. Adding method: dosing at the top for 5 min and rest for 5 min ; after that, do the second dosing, add Do the medicine for 5 minutes and stay for 5 minutes ; do the third dosing, do the medicine for 5 minutes , and then close the corridor medicine supply valve;
③ After the dosing is completed, let it stand for 1 to 1.5 hours , and then empty aerate (only aeration does not produce water). After 0.5 to 1 hour , open the corridor for water inflow and backflow to restore the water production to the automatic state.