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. 2024 Nov 26;14(12):251.
doi: 10.3390/membranes14120251.

Fouling and Chemical Cleaning Strategies for Submerged Ultrafiltration Membrane: Synchronized Bench-Scale, Full-Scale, and Engineering Tests

Xiwang Zhu  1 , Chengyue Fan  1 , Yichen Fang  1 , Wenqing Yu  2 , Yawei Xie  1 , Hongyuan Liu  1
Affiliations

Fouling and Chemical Cleaning Strategies for Submerged Ultrafiltration Membrane: Synchronized Bench-Scale, Full-Scale, and Engineering Tests

Xiwang Zhu et al. Membranes (Basel). .

Abstract

This study investigated membrane fouling issues associated with the operation of a submerged ultrafiltration membrane in a drinking water treatment plant (DWTP) and optimized the associated chemical cleaning strategies. By analyzing the surface components of the membrane foulant and the compositions of the membrane cleaning solution, the primary causes of membrane fouling were identified. Membrane fouling control strategies suitable for the DWTP were evaluated through chemical cleaning tests conducted for bench-scale, full-scale, and engineering cases. The results show that the membrane foulants were primarily composed of a mixture of inorganics and organics; the inorganics were mainly composed of Al and Si, while the organics were primarily humic acid (HA). Sodium citrate proved to be the most effective cleaning agent for inorganic fouling, which was mainly composed of Al, whereas sodium hypochlorite (NaClO) combined with sodium hydroxide (NaOH) showed the best removal efficiency for organic fouling, which predominantly consisted of HA and Si. However, sodium hypochlorite (NaClO) combined with sodium hydroxide (NaOH) showed the best removal efficiency for organic fouling and Si; organic fouling predominantly consisted of HA. Based on the bench-scale test results, flux recovery was verified in the full-scale system. Under a constant pressure of 30 kPa, the combined acid-alkali cleaning achieved the best flux recovery, restoring the flux from 22.8 L/(m2·h) to 66.75 L/(m2·h). In the engineering tests, combined acid-alkali cleaning yielded results consistent with those of the full-scale tests. In the practical engineering cleaning process, adopting a cleaning strategy of alkaline (NaClO + NaOH) cleaning followed by acidic (sodium citrate) cleaning can effectively solve the membrane fouling problem.

Keywords: chemical cleaning; flux recovery; fouling control strategies; membrane fouling; submerged ultrafiltration membrane.

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Conflict of interest statement

Wenqing Yu is an employee of Zhejiang Supcon Information Co., Ltd. The other authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Process flow diagram of ultrafiltration system in DWTP.
Figure 2
Figure 2
Schematic diagram of full-scale membrane system.
Figure 3
Figure 3
The membrane filaments: (a) fouled, (b) virgin.
Figure 4
Figure 4
Infrared spectrum of the fouled membranes in different seasons.
Figure 5
Figure 5
Comparison of the relative mass of elements between the virgin membrane and the fouled membranes (summer—July).
Figure 6
Figure 6
EEM spectra: (a) raw water, (b) ultrasonic eluate, (c) sodium citrate eluate, (d) NaClO eluate, and (e) NaClO + NaOH eluate.
Figure 7
Figure 7
Foulant in the eluate: (a) TOC and (b) inorganic element (the TOC of the sodium citrate eluate is obtained by subtracting the TOC of the control group).
Figure 8
Figure 8
Volume porosity of fouled membranes cleaned with different chemicals: (a) sodium citrate, (b) NaClO, and (c) NaClO + NaOH.
Figure 9
Figure 9
Changes in TOC of eluates with cleaning time: (a) NaClO and (b) NaClO + NaOH.
Figure 10
Figure 10
Metal ion concentration in eluates over time.
Figure 11
Figure 11
SEM images of membrane before and after chemical cleaning: (a) virgin membrane, (b) fouled membrane, (c) sodium citrate, (d) NaClO, and (e) NaClO + NaOH.
Figure 12
Figure 12
Variation in membrane flux with cleaning time in full-scale tests.
Figure 13
Figure 13
Changes in TMP before and after membrane chemical cleaning with different cleaning reagents in DWTP.
See this image and copyright information in PMC

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