Blockage and cleaning issues of tubular ultrafiltration membranes

With increasingly strict environmental emission standards, stable, reliable, and efficient operating environmental protection equipment is also increasingly favored by polluting units. Tubular ultrafiltration membrane equipment has become an indispensable part of high concentration organic wastewater such as landfill leachate, but membrane tube blockage problems are often encountered in the application of tubular membranes. Today, let's talk about the solutions to membrane tube blockage.

Before cleaning the tubular membrane, the following four conditions must be met first

1. When the processing capacity of the membrane system does not meet the design or operational requirements.

2. The membrane flux has decreased by 20% compared to the normal flux, and chemical cleaning is necessary.

3. If the system is shut down for more than 3 days, chemical cleaning must be carried out.

4. Generally, it should be cleaned once every 1-2 months.

There are two types of blockages:

1. The surface blockage of the membrane tube is mainly manifested as: there is no significant change in the circulating flow rate and inlet membrane pressure, and the production water flow rate is low; The main reasons for this blockage are as follows:

① Incomplete biochemistry, poor sludge characteristics, and high viscosity; Solution: Mainly improve the sludge characteristics by checking the water quality and design indicators of the front-end process.

② The water enters the contaminated membrane material, which contains high molecular weight substances such as PAM and silicon containing defoamers. Kitchen oils and other pollutants are factors that affect the flux of fouling membranes.

For membrane wall fouling, suitable cleaning agents can be used to solve it through online chemical cleaning, restoring flux. The agent must be used in accordance with the requirements of the product manual. The following is a comparison table of the composition of common acid-base cleaning solutions and the main target pollutants.

2. Membrane tube blockage (i.e. filter channel blockage) is mainly manifested as: a decrease in circulating flow rate, an increase in inlet membrane pressure, and a decrease in produced water flow rate; The main reasons for this blockage are as follows:

① The lack of sludge washing and screening during the addition of activated sludge in biochemical culture resulted in a large amount of fibers being present in the biochemical system, causing blockage in the membrane tube during system operation. In the early stage of ultrafiltration operation, the filter should be used first without entering the membrane system for filtration, and the filter should be cleaned for more than one day before entering the membrane system;

② The filter after the raw water pump should be selected with an 800um filter aperture and the intercepted fibers should be cleaned in a timely manner;

③ After the ultrafiltration is shut down, it should be rinsed in a timely manner (open the production water valve, clean the inlet valve, and the reflux valve to the biochemical tank). The concentrated water should return to the biochemical tank without going through the circulation pump and be thoroughly rinsed;

④ In case of power outage or emergency stop of the system, manually empty the sludge inside the membrane tube in a timely manner to avoid agglomeration;

⑤ Set protection for inlet flow rate, circulating flow rate, and pressure to avoid dead end filtration.

There are several methods to deal with membrane tube blockage

1. Low pressure and high flow flushing can be carried out using a cleaning pump. Generally, if the blockage is not tight, this method can be used to flush it out.

2. In cases where the effectiveness of the above methods is not significant, our company's developed membrane cleaning tool can be used for efficient dredging. Please consult our company's professionals for details.