A concept for the molecular design of readily treatable chemicals

Existing chemicals assessment and management approaches focus on chemical behavior in the natural environment and humans, including using chemical-specific inherent properties such as persistence (P), bioaccumulation potential (B), and mobility (M). To prevent chemical pollution, concepts such as safe-by-design and benign-by-design consider P, B, M, toxicity, and other hazardous properties when selecting existing chemicals or developing new ones. However, certain applications rely on chemical properties that inherently conflict with safe-by-design (e.g., high stability during use often results in P). In such cases, in addition to applying such chemicals only for essential uses and reducing emissions, early consideration of effective removal using available (water) treatment technologies may also be advisable. This may serve as a second line of defense to safe-by-design by minimizing environmental exposure. Here we explore inherent chemical properties relevant to "treatability", focusing on commonly used and widely available water treatment technologies. These technologies include (i) biodegradation in wastewater and drinking water treatment, (ii) advanced separation technologies such as activated carbon and membrane-based separation, and (iii) oxidation processes. Our conceptual framework sheds light on "treatable-by-design" chemicals for specific applications where safe-by-design chemicals are not (readily) feasible, offering potential for further exploration by the broader community.