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

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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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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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.

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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