Search Results (6)

Control of natural organic matter (NOM) reversible and irreversible fouling with ceramic membranes for drinking water applications with chemically enhanced backwash (CEB) protocols is limited. This research examines the efficiency of various chemical combinations with non-ionic surfactants to control the NOM fouling caused by humic acid (HA) and protein foulants. Two commercially available non-ionic surfactants, Tween 80 and Triton X100, combined with conventional cleaning solutions, were analyzed with respect to membrane fouling and cleaning using the resistance in series (RIS) model, membrane permeability, carbon mass balance, and contact angle measurements. The results demonstrated that in all cases, CEB outperformed hydraulic backwashing; in addition, the inclusion of surfactants demonstrated enhanced the fouling control with protein foulants more than humic acid. The transmembrane pressure (TMP) with surfactant CEB was controlled to within a range of 83–105 kPa compared to hydraulic backwash at approx. 128 kPa for HA and BSA. The carbon mass balance analysis indicates that Tween 80 surfactant-based CEB demonstrated effective fouling control, leaving only 20% irreversible fouling with HA and 30% with BSA while the hydraulic backwash resulted in 57% irreversible fouling of carbon on the membrane for HA and BSA. Full article

Water purification by ultrafiltration (UF) requires regular membrane cleaning via backwashing. In the case of chemically enhanced backwashing (CEB), it can result in the formation of unwanted by-product precursors due to reactions with organic matters present in the backwashing water and accumulating on the membrane. After subsequent disinfection, these precursors are prone to generate trihalomethanes (THMs) and haloacetic acids (HAAs), posing potential risks to the chemical safety of drinking water. However, limited information was available regarding the removal of these disinfection by-products. In this study, biological activated carbon (BAC) pretreatment followed by UF with chemically enhanced backwashing (CEB) (BAC-UF-CEB) was investigated to mitigate membrane fouling and reduce by-product formation. It was tested in parallel with UF with CEB (UF-CEB) and UF with sole physical backwashing. Compared to UF-CEB, BAC pretreatment prior to UF-CEB reduced transmembrane pressure (TMP) by 49.0%. BAC achieved high removals of dissolved organic carbon (59.99%) and UV254 absorbance (80.82%) in the BAC-UF-CEB effluent. Moreover, BAC-UF-CEB substantially decreased trihalomethane and haloacetic acid formation potentials by 83.28% compared to UF-CEB. BAC alleviated irreversible membrane fouling by 78.7%. By removing disinfection by-product precursors, BAC-UF-CEB markedly improved treated water quality and chemical safety. This study demonstrates BAC pretreatment effectively mitigates membrane fouling and controls disinfection by-products during UF water treatment. Full article

The treatment of wastewater from the iron and steel industry is difficult due to its complex and changeable characteristics. This paper introduces the application of polyvinylidene fluoride (PVDF)-pressurized ultrafiltration membrane with low packing density that produced via thermally induced phase separation (TIPS) in wastewater of iron and steel industry, to study the effects of packing density of ultrafiltration membrane modules as well as the membrane performance under different operation conditions, in order to provide guidance for the subsequent development of other ultrafiltration applications in wastewater of iron and steel. The results show a significant positive effect of smaller packing density on the transmembrane pressure difference (TMP) reducing and higher permeability. Under 30 min filtration cycle and 65 L m⁻² h⁻¹ (LMH) operation flux, the permeability can be stabilized to 200 L/(m²·h)/0.1 MPa, which is two times higher than that of the membrane module with 0.3 m²/m³ higher packing density under the same condition. It is obvious that compared with enhanced flux maintenance (EFM), chemically enhanced backwash (CEB) is a more effective cleaning method for iron and steel wastewater, which maintains TMP (30 kPa) without any significant increase under the premise of ensuring the high-flux (65 LMH) operation. The results also suggest reasonable parameters based on the test water quality, which include the filtration cycle and operation flux. The scanning electron microscopy (SEM) analysis and the turbidity of the permeate show that the ultrafiltration membrane has good intercept ability and high anti-pollution performance. Full article

Membrane fouling in surface waters impacted by cyanobacteria is currently poorly controlled and results in high operating costs. A chemically enhanced backwash (CEB) is one possible strategy to mitigate cyanobacteria fouling. This research investigates the potential of using an ozone CEB to control the fouling caused by Microcystis aeruginosa in filtered surface water on a ceramic ultrafiltration membrane. Batch ozonation tests and dead-end, continuous flow experiments were conducted with ozone doses between 0 and 19 mg O3/mg carbon. In all tests, the ozone was shown to react more rapidly with the filtered surface water foulants than with cyanobacteria. In addition, the ozone CEB demonstrated an improved mitigation of irreversible fouling over 2 cycles versus a single CEB cycle; indicating that the ozone CEB functioned better as the cake layer developed. Ozone likely weakens the compressible cake layer formed by cyanobacteria on the membrane surface during filtration, which then becomes more hydraulically reversible. In fact, the ozone CEB reduced the fouling resistance by 35% more than the hydraulic backwash when the cake was more compressed. Full article

This study investigated the improvement of operating efficiency through physical cleaning and chemical enhanced backwashing (CEB) using ceramic membranes with high permeability and chemical safety compared to organic membranes. The turbidity and DOC (Dissolved Organic Carbon) concentrations were selected to ensure that the degree of contamination was always constant. The operating pressures were fixed at 100, 200, and 300 kPa, and the filtration was terminated when the effluent flow rate decreased to 30% or less from the initial value. After filtration, backwashing was performed at a pressure of 500 kPa using 500 mL backwash water. The membrane was cleaned by dipping in NaOCl, and a new washing technique was proposed for steam washing. In this study, we investigated the recovery rate of membranes by selectively performing physical cleaning and CEB by changing the influent water quality and operating pressure conditions. Full article

This study assessed the issue of membrane fouling in a Hybrid Membrane Process (HMP) due to the export of powdered activated carbon (PAC) fines from a pretreatment contactor. Two parallel pilot-scale ceramic and polymeric membranes were studied. Reversible and irreversible foulings were measured following three cleaning procedures: Physical backwashing (BW), chemically enhanced backwashing (CEB) and Clean-in-Place (CIP). The impacts on fouling of membrane type, operation flux increase and the presence/absence of the PAC pretreatment were investigated. Membranes without pretreatment were operated in parallel as a control. In addition, CIP washwaters samples were analyzed to measure organic and inorganic foulants removed from the membranes. It was observed that for the polymeric membranes, fouling generally increased with the presence of the PAC pretreatment because of the export of fines. On the contrary, the ceramic membranes were not significantly impacted by their presence. The analysis of CIP washwaters showed a greater total organic carbon (TOC) content on membranes with a PAC pretreatment while no similar conclusion could be made for inorganic foulants. Full article