From ‘yuck’ to ‘ahhh’: a focused review on the bacteriophage-based strategy for malodour mitigation to improve the aspirational quotient of toilets

Most of the user-interface of toilets is associated with in-situ , decentralised wastewater treatment systems. Specifically, on-site sanitation systems (OSS) and decentralised wastewater treatment systems (DEWATS) are mainly used to treat toilet blackwater (faeces, urine, and flush water). Though ideal, malodour generated within these systems can hinder their adoption, especially where sanitation infrastructure is limited. Perceived desirability and social acceptability of toilets are negatively influenced by malodour and is a major contributor to its non-use and disuse. Obnoxious odours emanate largely from bacterial activity under anaerobic conditions, through the production of volatile organic sulphur compounds, nitrogenous compounds, and volatile fatty acids. Conventional odour-abatement strategies are plagued by substantial operational inputs and generation of secondary waste streams. Against this backdrop, bacteriophages are being investigated as a precision biological option, due to their host-specificity, and ability to self-amplify. This review examines bacteriophage-based strategies alongside established approaches for managing odour-causing microorganisms, with emphasis on emission points, biochemical processes, toxicity, translational bottlenecks, and research priorities.