Ultrasonic-assisted removal of inorganic scales in high-salinity wastewater treatment using membrane distillation

Abstract

This study focuses on ultrasonic-assisted cleaning of MD membranes for the treatment of high-TDS feed waters. The conditions for the ultrasonic application were explored to increase the cleaning efficiency and to minimize physical damage to the membrane. MD fouling tests were performed using synthetic feed waters with high scaling potential. After the fouling tests, cleaning experiments were performed by immersing the membrane cell in an ultrasonic generator and operated with a citric acid solution. The recovery of membrane permeability, liquid entry pressure, and ion rejection were measured, and scanning electron microscopy was used to visually analyze the membrane surface. Results indicated that the ultrasonic irradiation at low frequencies (28 and 45 kHz) led to either structural damage or wetting of the MD membranes. However, the ultrasonic irradiation at a higher frequency (72 kHz) exhibited a high cleaning efficiency without the structural damage and wetting. Compared with physical and chemical cleaning techniques, the ultrasonic-assisted cleaning resulted in higher flux recovery and foulant removal with a reduction in cleaning chemical consumption.

Strategies to Enhance the Membrane-Based Processing Performance for Fruit Juice Production: A Review

“…Their study also stated that the ratio of the permeate flux with ultrasound to that with zero ultrasound can be expanded. Cho et al [ 88 ] employed ultrasonic cleaning on fouled membranes, and they observed that it is more effective in eliminating membrane foulants and regaining the flux comparison with conventional physical and chemical cleaning techniques. However, the authors reported structural damage to the membranes when the use of elevated ultrasonic power at low frequencies (150 and 300 W at 28 and 45 kHz).…”

Analysis of Polyvinylidene Fluoride Membranes Fabricated for Membrane Distillation

“…The technique of sessile drop contact angle measurement was applied to the fabricated membranes as previously reported [11,40]. An instrument to measure the contact angle (Smart Drop) was supplied by Femtobiomed (Gyeonggi-do, Korea).…”

“…An in-house apparatus was used to measure the liquid entry pressure (LEP) of the fabricated membranes [11,40]. As shown in Figure 1, the apparatus consists of an LEP chamber, a pressure gauge, a high-pressure N 2 gas cylinder, and a pipe.…”

“…The electrical conductivity of the feed and permeate was measured using a conductivity meter (WTW multi 3420, WTW, Munich, Germany). The conductivity was converted to the concentration using a standard curve [11,41]. The weight of the permeate tank was periodically measured using an electronic balance (Explorer Pro, Ohaus, Newark, NJ, USA) and the flux was calculated based on the following equation [13,43]:…”

“…However, the implementation of desalination requires a viable option for the management of brines, which is the remaining stream after the production of fresh water from seawater or impaired water sources [9,10]. Conventional desalination processes including multistage flash (MSF), multi-effect distillation (MED), and reverse osmosis (RO) result in a substantial amount of brines ranging from 40% to 60% of the feed water [11]. Since the brine exhibits a higher salinity than the feed water, its direct discharge may lead to harmful effects on marine environment and aquatic ecosystems [12].…”