Geosmin and 2-Methylisoborneol in Drinking Water: An Integrative Review on Sources, Monitoring, Detection, Impacts, and Removal Technologies

Geosmin (GSM) and 2-methylisoborneol (2-MIB) are dominant taste-and-odor (T&O) substances in drinking water and have extremely low human perceptual thresholds (0.004 and 0.01 µg/L, respectively). While nontoxic, their continued presence generates consumer rejection, damages utility credibility, and results in enormous economic losses. The management of GSM and 2-MIB throughout the drinking water supply chain, from source water to tap, is investigated here through an integrative review of representative T&O occurrences across multiple continents, GSM and 2-MIB-producing organisms, environmental influencing factors, and the inadequate removal achieved by strictly conventional treatment processes (coagulation/filtration), which improves only to 36–64% (GSM) and 38–59% (2-MIB) with the addition of low-dose pre-ozonation (0–1 mg/L). An analysis of pre-outbreak detection methods (remote sensing, qPCR, ML, and phycocyanin-based fluorescence detectors) and novel sensors (bio-electronic nose, electronic tongue, and odorant binding protein (OBP2a)-based biosensors) was conducted. Notably, advanced biosensors such as the bio-electronic nose can detect both GSM and 2-MIB below their respective human odor thresholds (<10 ng/L) without the need for sample pre-treatment. In contrast, OBP2a-based platforms show affinity for 2-MIB (but not GSM) and require signal amplification or preconcentration to reach trace-level detection, while the electronic tongue operates near these threshold levels (~20 ng/L). This review presents the first integrated comparison of conventional, biological, integrated, and advanced oxidation treatments in terms of removal efficiency, operating cost, energy consumption, toxicity of byproducts, and technology readiness levels, and concludes that no single current technology can simultaneously achieve >95% removal, maintain operating costs below US$ 0.50/m3, prevent the formation of toxic byproducts, and ensure long-term operational stability. Consequently, the implementation of multi-barrier treatment systems is required. Particular attention is given to scalable and economical treatment alternatives for small- and medium-sized plants in developing countries, such as biological aerated filtration coupled with ultrafiltration and permanganate/bisulfite processes. Future research priorities include life cycle assessment of treatment trains, harmonized ecotoxicological assessment of transformation products, real-time sensor-integrated adaptive treatment, and climate-resilient treatment strategies for intensified eutrophication.