The Minus Approach Can Redefine the Standard of Practice of Drinking Water Treatment

Abstract

Chlorine-based disinfection for drinking water treatment (DWT) was one of the 20th century’s great public health achievements, as it substantially reduced the risk of acute microbial waterborne disease. However, today’s chlorinated drinking water is not unambiguously safe; trace levels of regulated and unregulated disinfection byproducts (DBPs), and other known, unknown, and emerging contaminants (KUECs), present chronic risks that make them essential removal targets. Because conventional chemical-based DWT processes do little to remove DBPs or KUECs, alternative approaches are needed to minimize risks by removing DBP precursors and KUECs that are ubiquitous in water supplies. We present the “Minus Approach” as a toolbox of practices and technologies to mitigate KUECs and DBPs without compromising microbiological safety. The Minus Approach reduces problem-causing chemical addition treatment (i.e., the conventional “Plus Approach”) by producing biologically stable water containing pathogens at levels having negligible human health risk and substantially lower concentrations of KUECs and DBPs. Aside from ozonation, the Minus Approach avoids primary chemical-based coagulants, disinfectants, and advanced oxidation processes. The Minus Approach focuses on bank filtration, biofiltration, adsorption, and membranes to biologically and physically remove DBP precursors, KUECs, and pathogens; consequently, water purveyors can use ultraviolet light at key locations in conjunction with smaller dosages of secondary chemical disinfectants to minimize microbial regrowth in distribution systems. We describe how the Minus Approach contrasts with the conventional Plus Approach, integrates with artificial intelligence, and can ultimately improve the sustainability performance of water treatment. Finally, we consider barriers to adoption of the Minus Approach.

Simultaneously Modulating Nanofiltration Membrane Surface Charges and Pore Size in Pursuit of Effective Cation Separation via a Bi-Functional Monomers-Interfered IP Reaction

“…Nanofiltration (NF) has obtained a variety of applications in the environmental fields, including softening of hard water, − removal of natural organic matter , and emerging contaminants from drinking water, separation of sulfate from chloride for zero liquid discharge, and more recently lithium extraction from natural brines. − In these applications, the requirement for the highly selective separation of some solutes from others could perfectly be satisfied by the rejection characteristics of NF membranes. The membrane properties, however, must be well tuned based on the rejection mechanisms, including steric hindrance effect, electrostatic effects, etc. − Taking the lithium–magnesium separation as an example, if the effective pore size of an NF membrane is in between the sizes of hydrated ions of lithium (0.382 nm) and magnesium (0.428 nm), effective separation of the two types of ions can be achieved by the membrane.…”

Assessing the Health Impact of Disinfection Byproducts in Drinking Water

“…Despite significant research efforts in the field of DBPs, − the understanding of their formation in chlorinated drinking water remains incomplete. It has been observed that the formation of DBPs is affected by certain environmental parameters such as the interaction with various types of NOM, temperature, and pH.…”

Electron Donating Capacity: A Promising Surrogate Indicator for the Optimization of Oxidative Water Treatments

“…During oxidative water treatments, dissolved organic matter (DOM) serves as not only the primary sink for the dosed oxidant , but also the primary precursor of DBPs. − Previous studies have shown that changes of DOM characteristics closely correlate with DBP formation, , and the redox-active moieties of DOM compete directly for the oxidant against MPs. − Therefore, monitoring the changes in DOM characteristics induced by oxidation is a feasible way to determine the appropriate oxidant dosage. , Currently, the surrogate indicators commonly employed to optimize the oxidant dosage include the dissolved organic carbon (DOC), UV absorbance at 254 nm (UV 254 ), and fluorescence index (FI). ,,, However, DOC cannot effectively indicate MP abatement and DBP formation due to limited organic mineralization. , In addition, although the spectroscopic surrogate indicators (UV 254 and FI) have been extensively adopted in oxidative water treatments − and correlate well with MP abatement and DBP formation in lab-scale and full-scale experiments, ,,− they just reflect the changes in the chromophoric moieties of DOM. Therefore, it is necessary to develop a new surrogate indicator to enhance the precision, reliability, and robustness of existing control systems for oxidative water treatments.…”