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Size exclusion chromatography with total organic carbon detection (HPSEC-TOC) is a widely employed technique for characterizing aquatic natural organic matter (NOM) into high, medium, and low molecular weight fractions. This study validates the suitability of HPSEC-TOC for a simplified yet efficient routine analysis of freshwater and its application within drinking water treatment plants. The investigation highlights key procedural considerations for optimal results and shows the importance of sample preservation by refrigeration with a maximum storage duration of two weeks. Prior to analysis, the removal of inorganic carbon is essential, which is achieved without altering the NOM composition through sample acidification to pH 6 and subsequent N2-purging. The chromatographic separation employs a preparative TSK HW-50S column to achieve a limit of detection of 19.0 µgC dm−3 with an injection volume of 1350 mm−3. The method demonstrates linearity up to 10,000 µgC dm−3. Precision, trueness and recovery assessments are conducted using certified reference materials, model compounds, and real water samples. The relative measurement uncertainty in routine analysis ranges from 3.22% to 5.17%, while the measurement uncertainty on the bias is 8.73%. Overall, the HPSEC-TOC represents a reliable tool for NOM fractions analysis in both treated and untreated ground and surface water.

Although seawater reverse osmosis (RO) is nearing its thermodynamic minimum energy limit, it is still an energy-intensive process, requiring 2–3 kWh/m³ at a recovery of 50%. Pre-desalination of the seawater by reverse electrodialysis (RED), using an impaired water source, can further decrease this energy demand by producing energy and reducing the seawater concentration. However, RED is hampered by the initial high resistance of the fresh water source, resulting in a high required membrane area (i.e., high investment costs). In this paper, a new process is presented that can overcome this initial resistance and decrease the RED investment cost without the need for additional infrastructure: assisted RED (ARED). In ARED, a small potential difference is applied in the direction of the natural salinity gradient, increasing the ionic transport rate and rapidly decreasing the initial diluate resistance. This decreasing resistance is shown to outweigh any negative effects caused by, for example, concentration polarization, resulting in a process that is more efficient than theoretically expected. As this effect is mainly important at low diluate concentrations (up to 0.1 M), ARED is proposed as a first step in an economic and energy efficient (A)RED-RO hybrid process. Seawater desalination: assisting reverse osmosis Coupling reverse osmosis with assisted reverse electrodialysis can reduce the cost of seawater desalination. While reverse osmosis currently accounts for more than 60% of our worldwide seawater desalination capacity, this crucial process operates at a high energy demand. A reverse electrodialysis (RED) pre-treatment of seawater, diluted with a waste water stream, reduces the energy demand by producing energy and by reducing the concentration of the seawater subjected to reverse osmosis. Nonetheless, low transport rates in RED require high-membrane surface areas, making the costs impractical. A team led by Marjolein Vanoppen at Gent University in Belgium design an assisted RED pre-treatment process, where a small potential difference is applied in the direction of the salinity gradient, increasing the ionic transport rate and decreasing the required membrane surface area, thus offering a more economically viable alternative.

During disinfection of drinking water, natural organic matter reacts with chlorine to produce harmful disinfection by-products. The identification of precursors of disinfection by-products in natural organic matter is challenging because natural organic matter is very complex and poorly known. Therefore, scientists have focused on the fractionation of natural organic matter with membranes or resins to better understand how and which organic matter fractions react during chlorination. Here, we compared the reactivity of various organic fractions with disinfection by-products. For that we did a meta-analysis of 400 water samples published in 80 publications, with focus on chlorination time and dose, SUVA 254 and the column capacity factor used during resin fractionation. SUVA 254 refers to the ultraviolet absorbance at 254 nm divided by the organic matter concentration. We found that hydrophobic compounds have 10–20% higher reactivity to both trihalomethane and haloacetic acid formation compared to hydrophilic compounds in waters with SUVA 254 above 2L/(mg∙m), while hydrophobic and hydrophilic compounds have equal reactivity in waters with low SUVA 254 . On the other hand, hydrophilic compounds are 20–80% more reactive towards emerging disinfection by-products, regardless of SUVA 254 . Chlorination time and dose do not influence the reactivity ratio between the different fractions. An increase in column capacity factor can shift the reactivity ratio from hydrophobic to hydrophilic fractions. Dead-end, stirred cell ultrafiltration membrane fractionation might not always produce sharply separated fractions, which is mainly due to fouling. Therefore, no clear correlation could be found between membrane fractions and all investigated disinfection by-product groups.