After operating the ultrafiltration equipment for a period of time, the ultrafiltration membrane will be contaminated to varying degrees, and it is necessary to clean the ultrafiltration membrane to ensure good water quality. Ultrafiltration membrane cleaning usually includes backwashing, rapid flushing, and chemical cleaning. Sometimes, backwashing is performed as needed, and the combination of these steps should be determined based on the actual situation. The cleaning procedures for different water quality, quantity, and ultrafiltration equipment will vary. The editor of this article will talk about the cleaning procedure of ultrafiltration membranes in ultrafiltration equipment.

1. Ultrafiltration membrane backwashing procedure

This is a very effective method unique to hollow fiber membrane ultrafiltration. Other types of films may delaminate or decompose during the backwashing process. In this process, the permeate liquid pressurized through the membrane support and membrane body enters the raw water inlet/outlet, and the water flow direction is opposite to the water flow direction during production, therefore it is called backwashing. The upper and lower raw water outlets can be alternately drained. Water from ultrafiltration can be used for backwashing. The suspension suspended by backwashing will accumulate in the supporting structure, and then particles, bacteria, and TOC will be continuously released, so the original water is not suitable for backwashing.

Based on the quality and pollution of the raw water, dosing can be considered during backwashing. For water with strong microbial activity, chlorination backwashing can be used; The backwash flux is initially low and slowly increases with membrane cleaning. It is usually recommended to equip the backwash pump with a frequency conversion device to adapt to the backwash efficiency of the membrane components as quickly as possible at the recommended maximum water flux under a given pressure.

2. Rapid flushing procedure for ultrafiltration membrane

The main purpose of rapid flushing is to flush a large amount of backwashed particles out of the membrane and system, so the rapid flushing program is usually accompanied by a backwash program. During the rapid flushing process, the water production port is closed, so half of the filtration membrane will have a backwash effect simultaneously, which is caused by the pressure difference between the inlet and outlet. Quick flushing in the staggered direction will make cleaning more effective.

3. Chemical cleaning of ultrafiltration membrane

When the membrane flux cannot be restored through backwashing and rapid flushing (usually manifested as a certain decrease in membrane flux and a certain increase in transmembrane pressure difference TMP), chemical cleaning must be used to restore membrane cleanliness. A chemical cleaning system usually consists of a washing pump, washing tank, and corresponding pipelines. The cleaning agent flows at high speed in the membrane to remove dirt. The chemical cleaning process can be completed in one or several steps (alkali washing, alkali chlorination washing, acid washing), and the washing steps are determined according to different pollution situations.

The above is an introduction to the cleaning procedures for ultrafiltration membranes in ultrafiltration equipment. Nowadays, ultrafiltration equipment is widely used, and we need to maintain it after installing it. In order to ensure good operation of the equipment and qualified water quality, we should pay more attention to the pollution of the ultrafiltration membrane in daily life.