Kwang-Ho Choo

Kyungpook National University | KNU · Department of Environmental Engineering

Bacterial quorum quenching (QQ) (e.g., degradation of N-acyl homoserine lactones (AHLs)) has been utilized to mitigate biofouling in membrane bioreactors (MBRs). However, the anti-biofouling efficiency of QQ bacteria may decrease...

Membrane bioreactors (MBRs) play a crucial role in wastewater treatment, but they face considerable challenges due to fouling. To tackle this issue, innovative strategies are needed. This study investigated the effectiveness of membrane reciprocation and quorum quenching (QQ) to control fouling in MBRs. The study compared MBRs using membrane recipr...

Quorum quenching (QQ) has effectively prevented biofouling in membrane bioreactors (MBRs) employing isolated QQ bacterial strains. However, the influence of QQ on the microbial population still needs to be fully understood. This research aims to analyze the microbial population in MBRs over an extended period (>250 days) under different conditions,...

Biofouling of the membrane surface of the filtration module remains a major challenge. Various types of quorum quenching (QQ) media have been studied to mitigate membrane biofouling in membrane bioreactors (MBRs). However, a physical fouling issue occurred due to trapping of QQ media in the hollow-fiber module, and this was considered to be one of...

The study has investigated the use of an Algae-Sludge Membrane Bioreactor (AS-MBR) for wastewater treatment. Its performance, in terms of pollutant removal and membrane fouling mitigation, was compared to that of a previously reported conventional MBR. Results showed that it has a COD removal efficiency that is only slightly higher than that in the...

Anaerobic membrane bioreactors (AnMBRs) have received increasing attention because of their low energy requirements; however, membrane fouling is the major deterrent to their widespread application. Here, we report a novel composite biomedium composed of quorum quenching (QQ) bacteria (Rhodococcus sp. BH4), porous silica, and polyelectrolytes for b...

Anaerobic membrane bioreactors (AnMBRs) enhance carbon neutrality with biomethane recovery from wastewater; however, microbial signaling, which may affect biological performances, was poorly understood. Here, we thus evaluate quorum sensing (QS) dynamics while monitoring acyl-homoserine lactones (AHLs) and autoinducer-2 (AI-2) levels during long-te...

Bacterial quorum quenching (QQ) media with various structures (e.g., bead, cylinder, hollow cylinder, and sheet), which impart biofouling mitigation in membrane bioreactors (MBRs), have been reported. However, there has been a continuous demand for membranes with QQ capability. Thus, herein, we report a novel double-layered membrane comprising an o...

In membrane bioreactors (MBRs), N-acyl homoserine lactones (AHLs)-related quorum sensing (QS) has been described as one of the main causes of biofouling during wastewater treatment. Quorum-quenching (QQ) bac- teria for the mitigation of QS in MBRs have been applied but limited to entrapping methods only. Thus, this study investigates the direct i...

At a low COD:TN ratio (≤5) in influent, maintaining a longer HRT (≥9 h) and longer SRT (≥30 d) are suggested to improve higher N removal efficiency in case of operation at low DO (Dis-solved oxygen) level (0.9 ± 0.2 mg-O2/L). However, in case of operation at high DO level (4.0 ± 0.5 mg-O2/L), short HRT (1 h) and typical SRT (17 d) make it possible...

Electrochemical membrane technology, which incorporates electrical and electrochemical reactions into membrane filtration, opens up a new horizon in membranes and membrane processes. Novel electroconductive materials and more efficient process designs are of great interest to make this technology viable in the real field. Regular membranes are util...

Photolytic quorum quenching by ultraviolet A (UVA) irradiation is an effective strategy for controlling membrane bioreactor (MBR) biofouling; however, its effects on MBR microbial communities and functional genes have not yet been explored. Here, we report on the effects of the UVA irradiation, which mitigates membrane biofouling, on the microbial...

As a universal quorum sensing (QS) signal, autoinducer-2 (AI-2) is utilized by both Gram-negative and Gram-positive bacteria to coordinate several group behaviors, such as biofilm formation, virulence, and motility, when the bacterial cell density exceeds the thresholds. The determination of the AI-2 level is essential to understand the physiologic...

Alkaline chlorination, an efficient but high chemical cost process, is commonly employed for cyanide (CN−) removal from CN-rich wastewater streams. CN− removal and recovery through the precipitation of Prussian Blue (Fe4III[FeII(CN)6]3, PB) or Turnbull’s Blue (Fe3II[FeIII(CN)6]2, TB) were realized using iron salts, leading to a cost-effective and s...

Membrane filters are core materials for water treatment, reuse, and desalination. However, their fouling caused by biofilm growth is a major challenge, needing resolution. Here, we report the new strategies and efficacy of anti-biofouling membranes fabricated through the immobilization of quorum quenching (QQ) bacterial strains (Rhodococcus sp. BH4...

Full-scale anaerobic, anoxic and aerobic (A²O) process is used worldwide for biological nutrient removal (BNR). However, operation parameters for nitrogen removals and information of microbial communities related to nitrogen removal in full-scale A²O wastewater treatment plants (WWTPs) having low and high COD/TN ratios are not available. Based on t...

Water is life, and without water, there would be no civilizations and a vacant Earth. Water is considered an abundant natural resource on the earth. Water covers 3/4 of the surface. However, 97% of the available water on the earth is salty oceanic water, and only a tiny fraction (3%) is freshwater. This small portion of the available water supplies...

The performance of an electrochemical reduction process was investigated for the treatment Cr(VI)-containing electroplating wastewater using a continuous-flow scrap iron packed column as an sacrificial anode. The effects of the key operating parameters including hydraulic retention time (HRT), current supply ratio (CSR), and inlet Cr(VI) concentrat...

A complete removal of Cu from CuEDTA complexes by replacement/precipitation reactions using ferrous ions was realized. The effects of pH, iron dosage and reactions time on Cu removal were evaluated. The results were explained with the aid of chemical equilibrium modeling. Fe(III) ions effectively liberate Cu(II) ions from CuEDTA complexes by the re...

The effect of addition of algae to activated sludge as active biomass in membrane bioreactors (MBRs) and electro-MBRs (e-MBRs) for wastewater remediation was examined in this study. The performances of Algae-Activated Sludge Membrane Bioreactor (AAS-MBR) and electro Algae-Activated Sludge Membrane Bioreactor (e-AAS-MBR) were compared to those obser...

Introduction Self-forming dynamic membrane (SFDM) technology has been gaining significant interest due to its potential advantages, notably lower capital and operational cost and easier fouling control, over conventional membranes used in membrane bioreactors. SFDM technology utilizes inexpensive support material integrated with a dynamic membrane...

Membrane fouling is a major challenge in membrane bioreactors (MBRs) for wastewater treatment. This study investigates the effects of disturbance and solid retention time (SRT) on quorum-quenching (QQ) MBRs relative to antifouling efficacy and microbial community change. The fouling rate increases with the applied disturbance at a short SRT, counte...

Considerable attention has been recently given to possible transmission of SARS-CoV-2 via water media. This review addresses this issue and examines the fate of coronaviruses (CoVs) in water systems, with particular attention to the recently available information on the novel SARS-CoV-2. The methods for the determination of viable virus particle an...

Removal of nitrosamines from water intended for consumption is an important topic due to the carcinogenic risks they pose to human health. In this study, we measure and compare nitrosamine removal by four individuals and three combinations of water treatments applied in situ as a pilot study and in the laboratory. Of the two advanced oxidation proc...

The first case of Coronavirus Disease 2019 (COVID-19), which is caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), in Europe was officially confirmed in February 2020. On 11 March 2020, after thousands of deaths from this disease had been reported worldwide, the WHO changed their classification of COVID-19 from a public health...

With the circular economy in mind, recovery of iron phosphate, i.e., ferric phosphate or ferrous phosphate, from industrial wastewater is realized and the products recovered could be used in the synthesis of lithium iron phosphate for Li-ion secondary batteries. The formation of iron phosphate highly depends on pH and dissolved oxygen (DO) level. T...

Metal oxide anode electrocatalysts are important for an effective removal of contaminants and the enhancement of electrode durability in the electrochemical oxidation process. Herein, we report the enhanced lifetime of RuOx−TiO2 composite anodes that was achieved by optimizing the fabrication conditions (e.g., the Ru mole fraction, total metal cont...

The concept of nanomaterials membranes (NMs) promises to be a sustainable route to improve the membrane characteristics and enhance the performance of membrane bioreactors (MBRs) treating wastewater. This paper provided a critical review of recent studies on the use of membranes incorporating nanomaterials in membrane bioreactor (NMs-MBR) applicati...

The reverse osmosis (RO) technology is promising as a key process for water reuse, but the RO brine (concentrate) needs proper treatments for minimal liquid disposals. This study investigated the potential of hybrid electrochemical microfiltration for the treatment of the RO concentrate from a municipal wastewater reuse plant. Two anodes (active Ir...

This study investigated the effect of low and high chemical oxygen demand (COD):N ratios on biological nitrogen removal and microbial distributions in full-scale step-feed (SF) municipal wastewater treatment plants (WWTPs) in Thailand (SF 1) and Taiwan (SF 2). The SF 1 WWTP had a low COD:N (4:1) ratio, a long solids retention time (SRT) (> 60 d), a...

In this study, an electro-replacement/precipitation/deposition/direct reduction (ERPDD) process with scrap iron packed in a Ti mesh cage as a sacrificial anode was investigated for the treatment of wastewater containing CuEDTA complexes. The ERPDD mechanisms were responsible for the removal of Cu from CuEDTA complexes and were verified by a series...

Microbial quorum quenching (QQ) has been recognized as an effective anti-biofouling strategy for membrane bioreactors (MBRs), but long-term hydrogel QQ media durability is uncertain. In this study, we propose a new media design to enhance anti-biofouling efficacy and mechanical media stability. Mobile porous hard-shell balls to hold QQ sheets (name...

Various quorum quenching (QQ) media have been developed to mitigate membrane biofouling in a membrane bioreactor (MBR). However, most are expensive, unstable and easily trapped in hollow fibre membranes. Here, a sol-gel method was used to develop a mesoporous silica medium entrapping a QQ bacterial strain (Rhodococcus sp. BH4). The new silica QQ me...

Ti-based Sb-SnO2 electrodes are attractive due to their excellent catalytic activity but have a short service life. Here, we report a highly stable and efficient Ti/TiONC/Sb-SnO2 electrode, which was fabricated through hydrothermal reactions using urea to form TiONC interlayers and electrodeposition-annealing to coat the active Sb-SnO2 catalysts. T...

Filtration and backwashing during the operation of a membrane bioreactor (MBR) physically induce the cyclic attachment and detachment of microbes on the membrane surface. Thus, permeate flux and backwashing affect the microbial quorum sensing (QS) and quorum quenching (QQ) processes taking place in a biocake layer on a membrane surface. From an ana...

Quorum quenching (QQ), the disruption of microbial communication, has proven to be effective as an innovative anti-biofouling strategy for membrane bioreactors (MBRs). However, QQ bacteria for anaerobic environments have not been extensively analyzed in previous research. This study thus investigated facultative QQ bacterial strains that exhibit po...

Low temperatures produce more biopolymers, leading to severe biofouling. Moving QQ sheets mitigate biofouling under cold weather conditions. QQ activities drop sharply with decreasing water temperatures. QQ sheets remain active during long-term field tests using real wastewater. QQ sheets have no impact on activated sludge treatment performance.

Quorum quenching (QQ) vessels have been used as an effective method of biofouling control for membrane bioreactors (MBRs), but further studies on the effect of entrapped QQ bacterial levels on the antibiofouling efficacy and stability of the QQ vessel are needed. In the present study, we investigated the efficacy and stability of QQ vessels contain...

Quorum quenching (QQ) vessels have been used as an effective method of biofouling control for membrane bioreactors (MBRs), but further studies on the effect of entrapped QQ bacterial levels on the antibiofouling efficacy and stability of the QQ vessel are needed. In the present study, we investigated the efficacy and stability of QQ vessels contain...

In this study, a patterned quorum quenching (QQ) membrane with anti-biofouling characteristics was prepared via a patterning process of an oxidized multiwall carbon nanotube (o-MWCNT) composite membrane followed by immobilization of QQ enzymes. We verified that the o-MWCNTs with a high specific surface area helped the patterned membrane retain 32%...

The impact of the signal molecules present in the wastewater itself on membrane fouling in the membrane bioreactor (MBR) has been unexplored. This study investigates the contribution of these molecules to the degree of membrane fouling and the anti-fouling efficacy using two quorum quenching (QQ) strategies, namely in situ and pre-QQ. The results s...

Microbial quorum sensing induces biofilm formation on the membrane filter leading to severe biofouling. Here we show the novel observation and efficacy of long-wave UV photolysis as it interferes with microbial quorum sensing, particularly investigating anti-biofouling performances in membrane bioreactor systems. Continuous UV radiation significantly mi...

Membrane fouling is the major bottleneck limiting widespread adoption of membrane bioreactors (MBRs), but its root causes are not yet fully understood. In this study, different fouling patterns were observed for replicate MBRs seeded with the same inoculum and maintained under identical operating conditions, with similar levels of biomass, soluble...

Lab-scale membrane bioreactors (MBRs) were investigated at 12, 18, and 25 °C to identify the correlation between quorum sensing (QS) and biofouling at different temperatures. The lower the reactor temperature, the more severe the membrane biofouling measured in terms of the transmembrane pressure (TMP) during filtration. More extracellular polymeri...

An electro-crystallization process equipped with a sacrificial aluminum anode was operated under an optimum condition to promote the formation of crystalline cryolite for the recovery of fluoride from synthetic F-containing wastewater. The effects of pH, Al/F molar ratio, initial F concentration, and electrolytes were investigated experimentally, a...

Ferrous ions are the major Fe species generated from sacrificial iron anodes, but ferric ions are the more active ingredients for the removal of organic matters in the acidic pH region. Therefore, a novel high-pressure electrocoagulation (HPEC) system was devised to facilitate the Fe(II)-to-Fe(III) conversion under acidic pH conditions. The effects...

Efficient media designs for microbial quorum quenching (QQ) are essential to enable maximal biofouling control in membrane bioreactors (MBRs). Here we introduce a novel, double-layered, biocarrier design, which has QQ bacteria in the shell layer with biostimulating agents in the core, for effective membrane biofouling control. Confining the biostim...

In this study, the seasonality of the biofouling behavior of pilot-scale membrane bioreactors (MBRs) run in parallel with vacant sheets and quorum quenching (QQ) sheets using real municipal wastewater was investigated. QQ media delayed fouling, but low temperatures caused severe biofouling. The greater amount of extracellular polymeric substances (...

Membrane biofouling, due to biofilm growth after planktonic bacteria attachment to a membrane, is a major bottleneck limiting the energy-efficient operation and maintenance of membrane bioreactors (MBRs). Microbial communications, known as quorum sensing (QS), are responsible for this biofouling behavior. Novel strategies for stopping this communic...

Versatile electrochemical reactions are effective for removing a wide range of water contaminants. This study focuses on the development and testing of bifunctional electrocatalytic filter anodes as reactive and separating media for the simultaneous removal of refractory dissolved organic and particulate contaminants from real wastewater effluents....

The present study investigated the influence of electric field on the removal of quorum sensing (QS) and emerging contaminants using an electrochemical membrane bioreactor (eMBR). A significant reduction of N-octanoyl-L-homoserine lactone signal molecules (∼76%) was achieved in the eMBR, with respect to the level observed in the conventional MBR as...

Bacterial quorum quenching (QQ) by means of degrading signaling molecules has been applied to anti-biofouling strategy in a membrane bioreactor (MBR) for wastewater treatment. However, the target signaling molecules have been limited to N-acyl homoserine lactones participating in intra-species quorum sensing. Here, an approach to disrupt autoinduce...

Quorum quenching (QQ) has been recognized as an emerging anti-biofouling strategy for membrane bioreactors (MBRs), but studies on effective QQ bacterial doses are needed. Therefore, in this study, the QQ efficacy for sheet-type media containing different amounts of QQ bacteria (i.e., Rhodococcus sp. BH4) with respect to biofouling control during MB...

Adsorptive removal of phosphorus from wastewater effluents has attracted attention because of its reduced sludge production and potential P recovery. In this study, we investigated granular activated carbons (GACs) impregnated with amorphous ferrihydrite (FH@GAC) for the sorption of phosphorus from aqueous solutions. Preoxidation of intact GAC surf...

A novel sacrificial anode comprised of scrap iron packed inside a cage made of titanium mesh was developed for Cr(VI) reduction. With electric currents applied, the surface passivation of scrap iron electrode could be avoided. Due to the large surface area with open structures provided, the applied current densities (1.18–3.54 mA/cm²) were low, res...

Surface finishing wastewater having low pH ( 2) and high conductivity (>11 mS/cm) was treated by electrocoagulation (EC) or electrochemical Fenton (ECF) processes using sacrificial iron anodes. Under the same theoretical Fe dosage, the effects of electrolytic time, initial pH, and current density on the simultaneous removal of organic and heavy met...

The synergistic combination of membrane filtration with advanced oxidation is of particular interest for next-generation wastewater treatment technologies. A membrane electro-oxidizer (MEO) hybridizing a submerged microfilter and an electrochemical cell was developed and investigated for tertiary treatment of secondary industrial (textile) wastewat...

This study focused on the green synthesis of silver nanoparticles (AgNPs) using grape seed extract and their use for the catalytic degradation of a hazardous dye. The reaction temperature for the synthesis had great impacts to the properties of AgNPs and thereby, contributed to their activity for reductive decomposition of Direct Orange 26 by NaBH4...

A systematic investigation of Cr(VI) reduction using electrochemical reduction revealed that the Cr(VI) reduction was extremely fast with reaction kinetics limited by the anodic generation of Fe(II). The Cr(VI) reduction rate increased with decreasing pH at the initial stage of reaction but the time to reach complete Cr(VI) reduction is pH independ...

Membrane bioreactors are effective and attractive for wastewater reclamation and reuse, but phosphorus polishing is required to meet more stringent environmental regulations. Mixed metal oxide coated beads composed of Fe-Ti bimetal oxides on a sulfonated polymer were fabricated, characterized, and tested for phosphorus removal from membrane bioreac...

A chemical reduction process was proposed to recover copper from the retentate of polyelectrolyte enhanced ultrafiltration (PEUF). Three polyelectrolytes (PSS, PAA, and PEI) containing various functional groups and molecular weights were studied to explore their effects on the copper removal in PEUF and on the copper recovery by chemical reduction...

This study investigated the performance of a membrane photocatalytic reactor (MPR) with respect to the removal of bacteria from secondary effluents. The MPR achieved disinfection through several mechanisms: rejection by a membrane, inactivation by direct UV radiation, adsorption onto photocatalysts, and oxidation by reactive oxygen species. Bacteri...

Biofilm formation on membrane surface results in the loss of permeability in membrane bioreactors (MBRs) for wastewater treatment. Studies have revealed that cellulose is not only produced by a number of bacterial species but also plays a key role during formation of their biofilm. Hence, in this study, cellulase was introduced to MBR as a cellulos...

Quorum quenching (QQ) bacteria entrapped in a polymeric composite hydrogel (QQ medium) has been successfully applied in MBRs for an effective biofouling control. However, in order to bring QQ technology closer to practice, physical strength and life time of QQ media should be improved. In this study, enforcement of physical strength, as well as an...

Quorum quenching (QQ) has been recognized as an innovative approach for biofouling control in membrane bioreactors (MBRs). Recently, QQ bacteria entrapping beads (QQ-beads) have been developed and verified to have excellent anti-biofouling potential in a pilot-scale MBR with flat-sheet membrane modules. In this study, considering the dense structur...

In the last thirty years, the use of membrane bioreactors (MBRs) for advanced wastewater treatment and reuse have been expanded continuously, but they still suffer from excessive energy consumption resulting from the intrinsic problem of membrane biofouling. One of the major causes of biofouling in MBRs is bacterial quorum sensing (QS) via N-acylho...

The chemical precipitation of Ni ions from industrial wastewater at alkaline pH values creates waste chemical sludge (e.g., Ni(OH)2). We herein focused on Ni removal via chemical reduction using dithionite, by converting Ni(II) to its elemental or other valuable forms. Without the presence of a chelator (e.g., citrate), the nickel reduction efficie...

Recently, MBRs with quorum quenching (QQ) bacteria entrapping beads have been reported as a new paradigm in biofouling control because unlike conventional post-biofilm control methods, bacterial QQ can inhibit biofilm formation through its combined effects of physical scouring of the membrane and inhibition of quorum sensing (QS). In this study, us...

Recently, spherical beads entrapping quorum quenching (QQ) bacteria entrapping spherical beads have been reported as effective moving QQ-media for biofouling control in MBRs for wastewater treatment due to their combined effects of biological (i.e., quorum quenching) and physical washing. Taking into account both the mass transfer of signal molecul...

The removal of bisphenol-A (BPA) from aqueous solutions, where it can interact with natural organic matter (NOM), is of great concern to researchers. In this study, the preparation of goethite iron oxide particles impregnated activated carbon composite (GPAC) has been discussed. The goal of developing an advanced material was to remove BPA in the p...

Biofilm formation (biofouling) induced via cell-to-cell communication (quorum sensing) causes problems in membrane filtration processes. Chorine is one of the most common chemicals used to interfere with biofouling; however, biofouling control is challenging because it is a natural process. This study demonstrates biofouling control for submerged h...

Quorum quenching (QQ) has recently been acknowledged to be a sustainable antifouling strategy and has been investigated widely using lab-scale membrane bioreactor (MBR) systems. This study attempted to bring this QQ-MBR closer to potential practical application. Two types of pilot-scale QQ-MBRs with QQ bacteria entrapping beads (QQ-beads) were inst...

Secondary effluent organic matter (SEOM) is an unwanted constituent that impairs the reuse of wastewater effluent. The potential of a membrane photoreactor (MPR) involving TiO2 photocatalysts and submerged microfiltration (MF) membranes was investigated with regard to SEOM degradation and fouling control. Colloidal particles interfered with the pho...

Volume reduction and the concentration of long-lived radioactive species are critical issues for the management of liquid low-level radioactive waste. This study investigated and compared the performances of low-pressure reverse osmosis (LPRO) and polyelectrolyte-enhanced ultrafiltration (PEUF) for the removal of target metals (Co and Sr) from simu...

A membrane photoreactor (MPR) system was investigated for the purification of textile wastewater effluent containing 1,4-dioxane for potential reuse. The effects of TiO2 dosage, alkalinity, particulate matter, and sunlight radiation on the removal of 1,4-dioxane from the effluent were evaluated. The photocatalytic 1,4-dioxane degradation followed p...