Magnetic Ion Exchange Treatment Research Articles

MIEX resin and enhanced coagulation treatment of high-bromide natural water: Chlorine reactivity and DBP precursors removal

Both organic and inorganic constituents play a major role in the formation and speciation of disinfection by-products (DBPs) under chlorination. In this study, the removal of organic and inorganic precursors to DBPs by ion exchange and coagulation was examined, and the relationships between characteristics of dissolved organic matter (DOM), chlorine reactivity, and the formation of DBPs in high-bromide natural water were investigated. Formation potential tests were conducted for trihalomethanes (THMs) and haloacetronitriles (HANs) before and after the different treatments (coagulation, magnetic ion exchange (MIEX) resin, and combined MIEX/coagulation). At a low resin dose, MIEX was more effective than coagulation for DOM removal. The advantages of the MIEX resin were more prominent at a high resin dose because substantial amounts of DOM and bromide were simultaneously removed. The maximum bromide uptake on the MIEX resin was 0.02 mg-Br/mL. A 4-component PARAFAC model was developed using a dataset of 148 fluorescence excitation-emission matrices (EEMs) generated from pre-chlorinated and post-chlorinated samples. The maximum fluorescence intensities of humic-like components were found to be strongly correlated to THMs formation (R2 = 0.79–0.89). The MIEX treatment substantially lowered the formation of THMs (19–51%) and HANs (70–95%) due to its ability to remove humic-like DOM and bromide. The fluorescence loss for humic-like DOM was found to increase over a chlorination time of 3 days, suggesting that these compounds had stronger reactivity to chlorine compared to protein-like DOM. The chlorine reactivity of protein-like DOM increased after treatments as the residual chlorine was able to react with the less reactive fractions of DOM after chlorine-reactive compounds were removed.

Magnetic ion exchange resin for reducing disinfection byproducts in drinking water: Pilot-scale study and organic matter characterization

Disinfection is an essential step in drinking water treatment to prevent waterborne illnesses. However, reaction of disinfectants with organic matter in the water can produce carcinogenic disinfection byproducts (DBPs), including trihalomethanes (THMs) and haloacetic acids (HAAs). Magnetic ion exchange (MIEX) resin has been used as a pretreatment to remove organics and reduce DBPs. In this study, a pilot-scale water treatment plant in Birmingham, AL (USA) that employed MIEX as a pretreatment to the conventional pilot treatment train was compared against an adjacent full-scale train that did not use MIEX. THM and HAA formation was tested via simulated distribution system (SDS) testing, and changes in organic character were assessed using fluorescence spectroscopy. MIEX treatment provided 20 % and 25 % removal of THMs and HAAs, respectively, compared to the full-scale treatment under typical SDS conditions. With higher residence times and incubation temperatures (15 days at 35 °C), MIEX treatment reduced HAAs by 36 %. Parallel factor (PARAFAC) analysis revealed that MIEX treatment reduced loadings for a terrestrial humic-like component. Additionally, MIEX treatment resulted in secondary benefits, including a reduction in the coagulant feed rate and a more stable pH and chlorine residual in the MIEX-treated water compared to full-scale treatment.

Removal of Dissolved Organic Matter by Magnetic Ion Exchange Resin

This article provides a state-of-the-art review on the uses of magnetic ion exchange (MIEX) resin in drinking water and wastewater treatment, with emphasis on removal of dissolved organic matter (DOM) from drinking water and wastewater, regeneration efficiency, removal of inorganic and synthetic organic chemicals, comparison with other anion exchange resins, and integration with other physical-chemical processes. Through laboratory jar tests, pilot plant tests, and full-scale installations for a variety of drinking water sources, MIEX resin can achieve 30–80 % removal of dissolved organic carbon (DOC), which is often higher than alum or ferric coagulation. In addition, MIEX resin has been shown to remove hydrophilic, transphilic, and hydrophobic fractions of DOM and a wide range of molecular weight fractions of DOM. As a result, MIEX pretreatment results in substantial reductions in the formation of trihalomethanes and haloacetic acids upon chlorination. MIEX resin can achieve bromide removal in the range of 10–50 %, with higher bromide removal in waters with low DOC, low alkalinity, and low sulfate. However, there are commercially available anion exchange resins that are more selective for bromide than MIEX resin. MIEX resin has been investigated in combination with coagulation, activated carbon adsorption, membrane separation, lime softening, and ozonation. MIEX pretreatment has been shown to reduce downstream chemical requirements and improve the operation of downstream processes. This is most evident for coagulation and ozonation where the coagulant dose can be reduced by 50–75 % and the ozone concentration can be increased by 40–65 %. In general, MIEX pretreatment shows minor reductions in membrane fouling. Future research should continue to investigate the integration of MIEX treatment with other processes.

High-rate MIEX filtration for simultaneous removal of phosphorus and membrane foulants from secondary effluent

This work was designed to evaluate the effectiveness of magnetic ion exchange (MIEX) resin under the best possible conditions, passage through a fixed-bed of resin as opposed to the alternative of directly adding resin into a flowing stream. The possibility of using a very small amount of alum in addition to MIEX treatment was also investigated not only to adsorb residual EfOM in the effluent from a bed of MIEX but also to produce a porous cake layer that would keep away foulants from the surface of membrane or its pore walls. The MIEX treatment alone reduced fouling, but to a much lesser extent than for MIEX combined with an under-dosing coagulation (which uses a considerably low amount of alum). Almost all of colloids and organic acids were removed and the nearly complete removal of phosphorus was achieved by MIEX in a fixed-bed even for an extremely short hydraulic retention time of wastewater in the resin bed. MIEX resin removed phosphorus, but organic acids in EfOM were preferentially removed and the effects of competing anions on the removal of EfOM were insignificant. The MIEX treatment with added alum (only 0.5 mg Al L−1) dramatically improved the performance of MF and UF membranes and the subsequent membrane filtration also achieved ≤0.01 mg L−1 of residual phosphorous. This condition also allowed good flux recovery after hydraulic flushing.

Investigation of 2,4-dichlorophenoxyacetic acid adsorption onto MIEX resin: Optimization using response surface methodology

This study investigated the optimization of process parameters in terms of 2,4-dichlorophenoxyacetic acid (2,4-D) removal from raw water by using magnetic ion exchange (MIEX) resin. Response surface methodology was applied to find out the major parameters influencing 2,4-D removal efficiency. Moreover, the optimal values of these parameters and the interactions between them were investigated (pH, MIEX dose and reaction time). The experimental data of variables showed a high correlation with the second-order polynomial model, with a coefficient of determination value (R2) of 0.9945 in terms of 2,4-D. Multiple response optimization was also employed to the experimental data to discover the optimal conditions for a set of response, simultaneously, by using a desirability function. The optimum pH, adsorbent dose and reaction time were found to be 6.06, 1.0mL/L and 52.33min, respectively. The highest removal of 2,4-D (97.02%) was reached under these conditions. After the process optimization, the MIEX treatment was proven to be a good option for the removal of 2,4-D.

Magnetic Ion Exchange (MIEX) Treatment of Surface Water, Groundwater, and Landfill Leachate Wastewater: Effect on Organic Matter Fluorescence

Dissolved organic matter (DOM) is increasing in many drinking water supplies, which can have adverse impacts on treatment. Magnetic ion exchange (MIEX) is an advanced treatment process that has been shown to effectively remove DOM from different water sources. DOM removal efficiency is typically determined through dissolved organic carbon (DOC) and ultraviolet absorbance (UVA) measurements, but these methods can be limited in the amount of information they provide on DOM. Fluorescence spectroscopy has been suggested as a more robust characterization technique for monitoring DOM, but there remain gaps in knowledge between DOM removal processes and fluorescence characterization of DOM. Accordingly, the goal of this research was to evaluate the impact of MIEX treatment on DOM fluorescence for diverse water sources. MIEX jar tests were conducted using surface water, synthetic water, groundwater, and landfill leachate wastewater, and analyzed for DOC, UVA, and fluorescence excitation-emission matrix (EEM). Fluorescence EEMs were used to determine fluorophore location, intensity, and fluorescence index. MIEX removal of DOC and UVA were strongly correlated with MIEX removal of peak fluorescence intensity across all water sources. Peak fluorescence location indicated that MIEX preferentially removed terrestrial DOM. Fluorescence is a promising tool for monitoring DOM removal efficiency by MIEX treatment.

Using UV Spectroscopy and Molecular Weight Determinations to Investigate the Effect of Various Water Treatment Processes on NOM Removal: Australian Case Study

AbstractNatural organic material (NOM) has been the focus of many studies because of its ability to compromise water treatment processes. This case study utilized ultraviolet (UV) spectroscopy and molecular weight distributions to investigate the impact of six water treatment processes (alum coagulation, magnetic ion exchange (MIEX) resin treatment, chlorination, ozonation, powdered activated carbon (PAC) adsorption, and biological sand filtration) on the removal of NOM from an Australia water source, Myponga Reservoir. Each of these processes displayed different effects on the concentration and character of NOM. The removal of dissolved organic carbon (DOC) and UV absorbance at 254 nm (UV254) by MIEX and the biological sand filter was shown to follow first-order kinetics with rate constants ranging from 9.0×10−8 s−1 (biological sand filter) to 6.3×10−5 s−1 (MIEX treatment). UV spectroscopic investigations showed the potential to predict the formation of disinfection by-products from chlorination with s...

Comparison of drinking water treatment process streams for optimal bacteriological water quality

Four pilot-scale treatment process streams (Stream 1 – Conventional treatment (coagulation/flocculation/dual media filtration); Stream 2 – Magnetic ion exchange (MIEX)/Conventional treatment; Stream 3 – MIEX/Conventional treatment/granular activated carbon (GAC) filtration; Stream 4 – Microfiltration/nanofiltration) were commissioned to compare their effectiveness in producing high quality potable water prior to disinfection. Despite receiving highly variable source water quality throughout the investigation, each stream consistently reduced colour and turbidity to below Australian Drinking Water Guideline levels, with the exception of Stream 1 which was difficult to manage due to the reactive nature of coagulation control. Of particular interest was the bacteriological quality of the treated waters where flow cytometry was shown to be the superior monitoring tool in comparison to the traditional heterotrophic plate count method. Based on removal of total and active bacteria, the treatment process streams were ranked in the order: Stream 4 (average log removal of 2.7) > Stream 2 (average log removal of 2.3) > Stream 3 (average log removal of 1.5) > Stream 1 (average log removal of 1.0). The lower removals in Stream 3 were attributed to bacteria detaching from the GAC filter. Bacterial community analysis revealed that the treatments affected the bacteria present, with the communities in streams incorporating conventional treatment clustering with each other, while the community composition of Stream 4 was very different to those of Streams 1, 2 and 3. MIEX treatment was shown to enhance removal of bacteria due to more efficient flocculation which was validated through the novel application of the photometric dispersion analyser.

Secondary effects of anion exchange on chloride, sulfate, and lead release: Systems approach to corrosion control

Water treatment processes can cause secondary changes in water chemistry that alter finished water quality including chloride, sulfate, natural organic matter (NOM), and metal release. Hence, the goal of this research was to provide an improved understanding of the chloride-to-sulfate mass ratio (CSMR) with regards to chloride and sulfate variations at full-scale water treatment plants and corrosion potential under simulated premise plumbing conditions. Laboratory corrosion studies were conducted using Pb–Sn solder/Cu tubing galvanic cells exposed to model waters with low (approx. 5 mg/L Cl− and 10 mg/L SO42–) and high (approx. 50 mg/L Cl− and 100 mg/L SO42–) concentrations of chloride and sulfate at a constant CSMR of ∼0.5. The role of NOM during corrosion was also evaluated by changing the type of organic material. In addition, full-scale sampling was conducted to quantify the raw water variability of chloride, sulfate, and NOM concentrations and the changes to these parameters from magnetic ion exchange treatment. Test conditions with higher concentrations of chloride and sulfate released significantly more lead than the lower chloride and sulfate test waters. In addition, the source of NOM was a key factor in the amount of lead released with the model organic compounds yielding significantly less lead release than aquatic NOM.

Magnetic ion exchange treatment of stabilized landfill leachate

Stabilized landfill leachate is characterized by a high concentration of non-biodegradable organic matter, which is similar in chemistry to dissolved organic matter (DOM) in the natural aquatic environment. Magnetic ion exchange (MIEX) resin treatment is well-studied in drinking water for removal of DOM from natural waters. There are fewer studies evaluating MIEX treatment of waste waters, and there is no previous work evaluating MIEX treatment of landfill leachate. This work systematically evaluated MIEX treatment of stabilized landfill leachate and evaluated the results in the context of previous studies of MIEX treatment of natural and waste waters. Five leachates from four landfills were evaluated as a function of MIEX resin dose, mixing time, and regeneration efficiency. MIEX resin removed DOM from landfill leachate, even in the presence of a reported high background concentration of inorganic ions. MIEX resin that was exhausted with leachate DOM was effectively regenerated with a concentrated NaCl solution, and regenerated MIEX resin performed similarly to virgin resin. For a majority of the leachates, the removal trend for MIEX resin was color > UV-absorbing substances > dissolved organic carbon ≈ COD > total nitrogen. Finally, MIEX resin removed a wider range of DOM from leachate than coagulation. The most important contribution of this work is that MIEX treatment of leachate followed very similar trends as MIEX treatment of natural waters, which will allow previous MIEX data to be used to estimate the treatment efficiency of other waste waters.

Evaluating the secondary effects of magnetic ion exchange: Focus on corrosion potential in the distribution system

In order to avoid the adverse effects of corrosion in water distribution systems, it is necessary to evaluate the secondary effects of magnetic ion exchange (MIEX) for the removal of dissolved organic matter (DOM). As DOM concentrations in surface waters increase and surface waters become more prevalent sources of drinking water, MIEX treatment will be increasingly used. This study evaluated the effects of MIEX treatment on iron and lead corrosion potential as measured by the Larson–Skold Index (LI) and chloride-to-sulfate mass ratio (CSMR), respectively. This was accomplished by analyzing data sets from bench- and pilot-scale MIEX experiments, as well as by monitoring a full-scale MIEX treatment plant. It was found that MIEX treatment consistently increased the CSMR, however, the extent of the increase was dependent on influent anion concentrations, MIEX resin regeneration, and other variables. MIEX treatment had only a minor effect on the LI. Both corrosion parameters were variable due to the periodic transfer of excess brine into the process train during regeneration cycles and fluctuations in raw water quality. It was also found that MIEX resin can re-release previously removed anions, such as sulfate and bicarbonate, which reinforces the need to evaluate secondary changes in water chemistry.

Rapid Installation of MIEX® System Helps Wholesaler Retain Customers

This article reports on a situation at the Burr Oak Regional Water District (BORWD), located in Glouster, Ohio, where trihalomethane (TTHM) levels exceeded the U.S. Environmental Protection Agency (USEPA) maximum contaminant level (MCL). Although TTHM levels in water leaving the district's plant were within the USEPA standard, these levels increased within the customers’ distribution systems. The article describes the treatment process at BORWD prior to the water being distributed to the satellite systems, along with maintaining adequate chlorine residual throughout the distribution systems, and detention time. Several treatment options were considered, with a magnetic ion exchange (MIEX) process being selected by BORWD as a more cost‐effective treatment option for reducing levels of disinfection byproduct (DBP) precursors. The MIEX treatment process is discussed, along with bringing the TTHM levels in the distribution systems into compliance as a result of using the process. Fast‐track installation of the MIEX system is described, along with immediate downstream benefits.

Pilot Scale Comparison of Enhanced Coagulation with Magnetic Resin Plus Coagulation Systems

Previous work has shown that magnetic ion-exchange treatment before coagulation gives high natural organic matter (NOM) removal and reduced levels of disinfection byproduct when compared to conventional enhanced coagulation. The impact of the resin process on the downstream floc formation process after coagulation and the subsequent effect on clarification has not previously been shown. Water containing high concentrations of NOM were treated at pilot scale using (1) conventional enhanced coagulation and compared with (2) treatment using magnetic resin followed by coagulation at reduced doses of 50-70%. Bench scale testing was also carried out to determine floc properties for systems with and without resin pretreatment It was demonstrated that pretreatment using magnetic resin was able to significantly reduce the turbidity load onto filters as a result of the formation of a large and more robust floc. Resin pretreatment also improved NOM removal and reduced disinfection byproduct formation when compared with conventional coagulation. The turbidity load on to the filters following resin pretreatment was 1.5 +/- 0.7 NTU, whereas this value was 2.9 +/- 0.3 NTU for conventional coagulation. Flocs produced with resin pretreatment were larger than those produced by conventional coagulation, with a median floc size of 1000 microm compared to 600 microm. The improvement in floc properties following magnetic resin pretreatment was proposed to be due to the removal of NOM thatwas characteristic of carboxylic acids before the coagulation stage.

MIEX for removal of DBP precursors: Pilot‐plant findings

A 10‐gpm pilot plant was operated for four to five weeks at each of four US water treatment plants to evaluate the effectiveness of a magnetic ion exchange (MIEX) process for the removal of disinfection by‐product precursors. Variables examined were resin concentration, contact time, and regeneration frequency. Influent and effluent samples were taken on a regular basis and analyzed for ultraviolet (UV) absorbance at 254 nm, dissolved organic carbon (DOC), and bromide. Samples of the raw water and the MIEX‐treated water were also subjected to hydrophobic/hydrophilic fractionation, molecular size characterization, and chlorination under uniform formation conditions to determine the trihalomethane (THM) and haloacetic acid (HAA) formation potential before and after MIEX treatment. Results indicated that the resin removed substantial amounts of DOC and UV‐absorbing materials, except in one of the waters that had a high concentration of total dissolved solids and a low specific UV absorbance. The MIEX resin also removed bromide to some degree, depending on the presence of other competing anions in the raw water. Overall THM and HAA formation was decreased substantially as a result of MIEX treatment.