Views: 1034 Author: Kevin Chen Publish Time: 2020-06-17 Origin: Site
Maintenance cleaning regularly removes contaminants from the membrane surface, inhibits thickening of the contaminated layer and increases the pressure difference across the membrane to achieve stable operation. During the maintenance cleaning, the aeration is stopped and the operation is automatically.
The frequency of maintenance cleaning is usually once a week, and NaClO with an effective chlorine concentration of 300 mg/L to 500 mg/L is used to quantitatively inject into the membrane module from the water-producing side. The injection time is 30 min, and the reagent is allowed to stand after completion of the injection. Soak for 30min. The unit membrane area dose is 2~2.5L/m2, and the total reagent preparation amount should calculate the delivery pipeline capacity.
Online reinforced washing is carried out every 1-3 months or when the suction pressure exceeds the set value (= when the pressure difference between membranes rises), the purpose is to remove the contaminants on the membrane surface and restore the membrane performance to near the initial state. Stop the aeration, the NaOCl solution with an effective chlorine concentration of 2000-3,000 mg/L, and inject the cleaning solution quantitatively from the water-producing side for 30 min. After the injection, let stand for 90 min. The dosage per unit membrane area is 2~2.5L/m2, and the total reagent preparation amount should be calculated. After NaOCl cleaning, if the transmembrane pressure difference is still high, on-line pickling (1-2% oxalic acid, 1-2% citric acid, 0.1-0.2% hydrochloric acid) can be performed to remove inorganic scale. When cleaning the acid, first clean the pipeline and the NaOCl in the pump to avoid chlorine (toxic gas).
When the current two cleaning methods cannot restore the membrane performance, it is necessary to perform offline cleaning, immersing the membrane module in a special cleaning tank, removing contaminants, and returning the membrane performance to a state close to the initial value. Immersion cleaning generally restores membrane performance significantly. For off-line cleaning, immerse the monolithic membrane module or individual membranes in an alkaline cleaning agent (chlorine concentration 2000-3,000 mg/L, pH 10-11 NaClO solution) or acidic cleaning agent (1-2% oxalic acid or citric acid, 0.1 to 0.5% in sulfuric acid or hydrochloric acid). The soaking time is NaClO for 6-24 hours and the acid is 2 h. The membrane is a single-channel tubular ceramic membrane, the channel support is a porous ceramic material, the inorganic membrane (AL2O3) is plated on the inner surface of the channel, and the membrane filtration adopts a cross-flow process, that is, the main body of the activated sludge mixture flows axially through the membrane surface. The filtered water passes through the membrane surface in the radial direction.