Application of MIEX® pre-treatment for ultrafiltration membrane process for NOM removal and fouling reduction

Abstract

In this study, pretreatment of organic matters with MIEX® was evaluated using bench-scale experimental procedures on three organic matters to determine its effect on subsequent UF or MF membrane filtration. For comparison, a coagulation process was also used as a pretreatment of UF or MF membrane filtration. Moreover, the membrane fouling potential was identified using different fractions and molecular weights (MW) of organic matter. From the removal property of MW organic matter by the coagulation process for the sample water NOM and AOM, the removal efficiencies of high MW organic matter were much higher than those of low MW organic matter. It was shown that the removal efficiency of high MW organic matter (more than 10 kDa) was lower than that of low MW organic matter for the MIEX® process. For the change of permeate flux by the pretreatment process, the MIEX®-UF process showed high removal efficiency of organic matter compared with the coagulation-UF processes, but a high reduction rate of permeate flux was presented through the reduction of removal efficiency of high MW organic matter. From sequential filtration test results to examine the effect of MW of organic matter on membrane fouling, we found that the membrane fouling occurred with high MW organic matter, and the DOC of organic matter less than 0.5 mg/L was acting as the membrane foulant. In sample water composed of low MW organic matter (less than 10 kDa), because the low MW organic matter of less than 10 kDa has a high removal efficiency by MIEX®, a low reduction rate of permeate flux is obtained compared with the coagulation-UF processes. In summary, research on the physical/chemical characteristics of original water is needed before a membrane pretreatment process is selected, and a pertinent pretreatment process should be used based on the physical/chemical characteristics of the original water.

Simultaneous removal of phosphorus and EfOM using MIEX, coagulation, and low-pressure membrane filtration

“…Some other studies have also shown that a combination of MIEX and coagulation resulted in decreased fouling of UF or MF membranes when treating NOM. [21][22][23] Our study appears to be the first to come to the same conclusion when dealing with wastewater effluent. Although fouling was also decreased after sweep floc coagulation with alum, the much higher concentration of new solids could result in operational problems, not only in dead-end applications but also in recirculating systems.…”

“…[11] Other studies have shown that a combination of coagulation and MIEX resulted in decreased fouling in MF or UF. [21][22][23] In this study, we investigated a complete-mix process using MIEX.…”

Pre-treatments to reduce fouling of low pressure micro-filtration (MF) membranes

“…9) which shows the surface foulants are clearly reduced with pre-treatment and that alum provided a significant improvement. In comparing coagulation and MIEX ® pre-treatment for ultrafiltration, Son et al [37] also observed that MIEX ® was less effective for reduction of fouling due to lesser removal of high MW organic matter. For the treatments that included PAC, some residual particulates from PAC can also be seen which is consistent with the obtained resistance data and the work of Matsui et al [24] with submicrometre PAC on microfiltration.…”

Low-pressure membrane filtration of secondary effluent in water reuse: Pre-treatment for fouling reduction

“…Anion exchange resin has been investigated as a means of improving membrane performance by removing a significant fraction of organic matter from drinking water sources [19][20][21]. The small resin particles provide a high-surface area for the adsorption of lower MW and negatively charged organic components [19].…”

“…The small resin particles provide a high-surface area for the adsorption of lower MW and negatively charged organic components [19]. The effects of anion exchange treatment on membrane fouling are dependent on the properties of source water, types of pre-treatment combination and membranes [20,21]. Only one application was found where anion exchange resin was used in wastewater treatment, and this related to a submerged membrane bioreactor system with synthetic wastewater [22].…”