Ion exchange (IEX) resins can remove natural organic matter (NOM) from drinking water sources. However, the IEX system produces a waste brine rich of sodium, chloride, NOM and sulfate. The treatment of the waste brine aims to recover a clean solution rich of sodium chloride, that can be reused to regenerate IEX resin. Previous research showed that ceramic nanofiltration partially removes NOM from the waste brine, but sulfate removal requires additional treatment. Sulfate removal by chemical precipitation was previously studied either on brines with low NOM concentrations or water with low concentrations of NOM and salts. The current work focussed on sulfate removal from NOM-rich brines by chemical dosing of (1) BaCl₂, resulting in precipitation of barite (BaSO₄), and (2) CaCl₂, Ca(OH)₂ and NaAlO₂, resulting in precipitation of calcium sulfate and, subsequently, ettringite (Ca₆Al₂(SO₄)₃(OH)₁₂). Additionally, the effect of NOM on SO₄²⁻ removal was studied. Modelling and batch experiments were conducted with IEX and synthetic brines within the typical ion strength range of 0.1 to 1 M. With doses of 2.2 g of BaCl₂ per g of initial sulfate, BaSO₄ precipitation removed more than 83 percent of sulfate, resulting in final concentrations below 0.4 g/L even in the presence of NOM. However, NOM inhibited the precipitation of calcium sulfate and, subsequently, ettringite. With doses of 1.3 g of CaCl₂, 0.5–0.7 g of Ca(OH)₂ and 0.4–0.6 g of NaAlO₂ per g of initial sulfate, calcium sulfate and ettringite precipitation removed between 8 and 95 percent of sulfate from NOM-rich brines, resulting in final concentrations between 0.8 and 2 g/L. As a reference, NOM-free brines required doses of 1.3 g of CaCl₂, 0.2–0.7 g of Ca(OH)₂ and 0.1–0.6 g of NaAlO₂ per g of initial sulfate for 89 to 99 percent of sulfate removal, resulting in final concentrations of 0.2 g/L. The inhibition might be attributed to covering of crystal sites by NOM molecules, and to NOM coagulation with aluminium.

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Natural organic matter (NOM) in drinking water sources causes several problems in water consumption and distribution, and decreases the efficiency of water treatment steps. Ion exchange (IEX) with anion resin can be used to remove NOM in combination with or as an alternative to other techniques, such as coagulation and activated carbon. IEX resins require periodic regeneration with an electrolyte solution that is usually made of sodium chloride. A crucial problem of IEX for NOM removal is related to waste management of the regenerant electrolyte. The regenerant solution is reused several times before disposal, which increases the concentrations of NOM and anions like sulfate. The resulting spent IEX brine is a pollutant and is expensive to dispose, which hampers full-scale applications. In this research, we proposed a spent IEX brine treatment that is based on ceramic nanofiltration. Ceramic membranes have potential advantages over polymeric membranes, such as higher fluxes and lower fouling characteristics. The treatment aims to recover a permeate of a reusable IEX regeneration salt solution, which is typically sodium chloride, by removing NOM and other anions from the spent IEX brine. Also, concentrated NOM could be used in agriculture and industry, due to the presence of humic substances. @en

Natural organic matter (NOM) fractions cause problems in drinking water treatment and supply. In the North Sea region, anionic ion exchange (IEX) in non-fixed bed configurations has been considered for NOM removal in drinking water treatment plants. This paper discusses several experiences of the impact of anion IEX on NOM removal and on NOM-related problems in water treatment locations of the North Sea region, considering the specific situation of the sites. The investigated parameters include the effect of anionic IEX on the removal of total NOM and specific NOM fractions, the amount of chemicals used for coagulation, the development of trans membrane pressure in microfiltration, the formation of assimilable organic carbon and the energy consumption during advanced oxidation, the removal of organics by activated carbon, and the formation of disinfection by-products. The pilot experiences at three treatment locations in Belgium, United Kingdom and the Netherlands show that anionic IEX (1) removed typically 40 to 60 percent of total NOM; (2) targeted mostly humic NOM fractions, and was not effective to remove biopolymers (3) contributed to lower coagulant doses and energy consumption in UV/advanced oxidation; (4) had limited influence on limiting the fouling of microfiltration membranes; (5) lowered the formation of disinfection by-products; and (6) it can improve biological stability.@en

In drinking water treatment, natural organic matter (NOM) is effectively removed from surface water using ion exchange (IEX). A main drawback of using IEX for NOM removal is the production of spent IEX regeneration brine, a polluting waste that is expensive to discharge. In this work, we studied ceramic nanofiltration as a treatment for the spent NOM-rich brine, with the aim to reduce the volume of this waste and to recycle salt. Compared to polymeric nanofiltration, the fouling was limited. When NOM is rejected and concentrated, a clean permeate with the regeneration salt (NaCl) could be produced and reused in the IEX regeneration process. Bench scale studies revealed that NOM could be effectively separated from the NaCl solution by steric effects. However, the separation of NaCl from other salts present in the brine, such as Na₂SO₄, was not sufficient for reuse purposes. The low sulphate rejection was mainly due to the low zeta potential of the membrane at the high ionic strength of the brine. The permeate of the ceramic nanofiltration should be treated further to obtain a sodium chloride quality that can be recycled as a regenerant solution for ion exchange. Further treatment steps will benefit from the removal of NOM from the brine.

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The ceramic Nanofiltration membranes are studied in TU Delft to treat the brine. It has abilities to concentrate NOM and separate it from salts, and chemical precipitation to recover a clean solution with regeneration salt (i.e., NaCl) from the membrane permeate.For achieving this, the first step should build up the Setup. Therefore, this additional thesis aims to upscale a previous ceramic nanofiltration setup, which should run overnight without supervision. This thesis is divided into two parts: (1) design and building, and (2) experiment. The results show that although the recirculation pump limits the potential of the setup, it can still provide high recovery and stable permeability.

The presence of organic and inorganic contaminants in aquatic ecosystem has been threat to public health and environment. To produce drinking water, removal of natural organic matter has been of importance due to formation of DBPs. Of the many available treatments, ion exchange (IEX) has the potential to remove natural organic matter (NOM). However, IEX resins need to be regenerated upon saturation with NOM, which generates brine. Usually, NaCl is used to regenerate the resins, hence the desorbed NOM ends in the brine with sodium chloride and other ions like sulphate and nitrate which are present in surface or ground water. The disposal of high saline brine is complex due to aftereffects on the environment and the associated costs. Therefore, an interesting physical alternative is to separate the NOM from brine that can be further reprocessed as fertilisers for agriculture. Ceramic nanofiltration (NF) appears to be an alternative to treat the brine. This type of membrane is chemically and mechanically robust, can be operated at extreme pH conditions, withstands backwashing and chemical cleaning. Besides, ceramic nanofiltration membranes have the capability to separate multivalent ions which makes it suitable to treat the brine. However, NOM possess a complex matrix and relies on various factors for its high removal. In this research, it was interesting to recognize the NOM fractions and the behaviour alleviating NOM retention. Various IEX brines from water treatment plants were studied. For this, NOM was characterised using two different methods i.e., LC-OCD and NSM. The LC-OCD characterization done by Het Waterlaboratorium characterized NOM fraction based on the size of fractions into Humic substances, building blocks, Low molecular weight neutrals and low molecular weight acids. Characterisation of NSM was done by Udine University, Italy wherein the characterization of humics was done on the principle of the selective resin adsorption and precipitation. The characterisation of NOM by LC-OCD predicted the NOM rejection on membrane quite accurately. The effect of ionic strength was investigated to reflect NOM removal. NOM rejection for same NOM source and membrane pore size remained unaffected by the ionic strength of the brine. However, when different membrane pore sizes (600Da and 900Da) for different NOM source, NOM removal by ceramic nanofiltration was governed a combination of steric exclusion, electrostatic repulsion and hydrophobic nature of the humic content and. In longer duration, ceramic NF membranes may foul due to filtration process. To reflect the same, fouling test was conducted. Fouling test was conducted with the high ionic strength brine because during the filtration experiments, it showed highest permeability drop. The sudden drop in permeate flux was due to osmotic pressure difference. However, during NOM filtration period, the flux and permeability were quite steady which suggested no major fouling in that phase. Irreversible fouling did not affect the membrane pore size.

In drinking water production, natural organic matter (NOM) is sometimes removed using ion exchange (IEX) resin. This treatment method has a limitation based on the exchanging capacity on the resin. Therefore, the resin needs to be regenerated when it is saturated with adsorbed NOM which leads to the production of brine. In general, NaCl is used to regenerate the resin, hence, the brine will contain NOM, high sodium and chloride concentrations. Moreover, some other anions are also found in the IEX brine, such as sulphate that is usually present in surface water and ground water. Because of its salinity, the disposal of IEX brine is not possible to be done conventionally due to its impact on the environment and high cost. Therefore, separating chloride from the brine is an interesting alternative that can be reused for the regeneration of the IEX in the later process.

Ceramic nanofiltration (NF) emerges to be an interesting alternative for water treatment. Compared to polymeric membranes, this type of membrane offers great mechanical robustness and can be operated under extreme conditions, and tolerates high-pressure backwash, chemical cleaning, and high-temperature sterilization, which leads to longer periods of reliable performance. Moreover, ceramic NF membranes are potentially capable to separate multivalent ions from monovalent ions. Hence, this method could be applicable to treat IEX brine. Alternatively, chemical precipitation using barium and calcium is widely used to remove sulphate from water which is more straight forward than membrane filtration. The precipitates can be mechanically separated from the supernatant for further treatment or use.

Combination of chemical precipitation and ceramic NF membrane (later called as integrated sulphate removal) was investigated to remove sulphate from IEX brine. Along with that, investigation using synthetic brines consisting of Na2SO4 and NaCl for a binary salt solution and only Na2SO4 for a single salt solution was also conducted to build the understanding in treating the IEX brine. Barium salt was proved to efficiently remove sulphate due to its very low solubility. However, calcium salt was not as effective as barium salt. The treatment was followed by NF using a ceramic membrane with MWCO of 900 Da. In the end, the integrated approach was able to remove 86% of the sulphate and 85% of NOM from IEX brine. Furthermore, the precipitation stage was also modelled in PhreeqC by using Pitzer database.

Barium salt (BaCl2.2H2O) was preferred in this research for precipitating the sulphate. However, due to its toxicity, alternative precipitation was desired. Ettringite (calcium sulfoaluminate) precipitation was considered since the involving salts were not toxic. The efficacy of this method was predicted through modelling in PhreeqC to give some insight to alternatively removing sulphate from IEX brine. Eventually, a comparison using cost estimation and Life Cycle Assessment (LCA) were performed to obtain some considerations to implement the treatment alternative in a full-scale application.

Natural Organic Matter (NOM) is always present in the drinking water sources such as rivers, lakes and reservoirs. It causes several problems, including the unfavourable colour and odour of water, formation of disinfectant by-products and harmful microbial growth. In drinking water treatment, anion exchange (anion-IEX) is used for NOM removal. However, the regeneration of anion-IEX produces a brine, which is a high saline waste stream containing the desorbed NOM and anions (i.e. sulphate) as well as the residual sodium chloride added during the regeneration process. One possible approach to manage the waste brine is to recover the valuable compounds from the brine, and consequently, reduce the brine volume that has to be disposed. The separation could be done by ceramic nanofiltration (NF) membranes. However, the separation performance of ceramic NF membranes at high salinity conditions is still not fully understood. Therefore, the use of ceramic NF membranes to treat the brine-like wastes that contain NOM and high salt concentrations were investigated. Commercial 500 Dalton(Da) ceramic NF membranes were used in the salt experiments. Several experimental conditions such as pH and ionic strength were investigated to understand their influence on the rejection of sulphate (SO42-) and chloride (Cl-). The results show that the salt rejection was governed by charge effect, and it changed depending on pH and ionic strength. When ionic strength was 0.1M, the mitigated charge effect led to a low rejection of SO42- (<20%) and Cl- (<5%) by the 500Da membranes. On the other hand, the 560Da membrane used in salt&NOM experiments exhibited more than 95% rejection of NOM but less than 25% rejection of both SO42- and Cl- when ionic strength was 1M. Since the 500Da membranes were unable to reject divalent ions at high ionic strength, it is suggested to decrease the membrane pore size to achieve the separation of SO42- and Cl-. The size of pores in ceramic membranes can be narrowed down by an approach called Atomic Layer Deposition (ALD) (Shang et al., 2017). In this study, the vacuum TiO2 ALD was applied to coat thin films on the commercial ceramic NF membranes that have Molecular weight cut-off (MWCO) ranging from 600Da to 900Da. After the first coating, the water permeability of the membranes decreased dramatically while the MWCO of the membranes decreased slightly. After the second coating, an increased MWCO was observed, which might be attributed to the plugging of small pores. In addition, the flux distribution and pore size distribution were theoretically analysed to investigate the change of the membrane pores before and after ALD.

In recent years, there has been an international focus on removal of naturally occurring organic matter (NOM) during water treatment. This is because NOM is known to contribute to several water treatment challenges, such as disinfection by-product (DBP) formation, membrane fouling, oxidant demand, biogrowth in distribution systems, and color in water. Investigations of NOM removal have also revealed the influence of NOM on post-filtration processes, suggesting that improved NOM removal helps to improve the performance of these processes by making them more efficient and more cost-effective. This paper will focus on the impact of NOM removal on post-filtration processes, including UV disinfection, chlorine disinfection, granular activated carbon (GAC), and biostability.@en

Natural organic matter (NOM) causes several problems in drinking water treatment and distribution. NOM is a mixture of compounds with different characteristics, which make its characterization and removal particularly challenging. Removing different NOM fractions can require different techniques, and removal is beneficial for many water treatment processes (e.g., membranes, UV disinfection) and NOM removal is beneficial for lowering the formation of disinfection byproducts.@en