Sources and control of geosmin and MIB in midwestern water supply reservoirs

Many Midwestern water utilities face episodic taste and odor problems, and geosmin and MIB (2-methylisoborneol) are often implicated as causative agents. The objectives of this research were: to assess the occurrence and sources of geosmin and MIB in Midwestern reservoirs; to better understand factors influencing geosmin and MIB production and fate; and to evaluate the ability of reservoir management and drinking water treatment techniques to control geosmin and MIB, especially severe episodes.; An analytical method able to detect less than 1 ng/L of geosmin or MIB was developed and used to monitor several Midwestern reservoirs and water treatment facilities with a history of taste and odor problems. Low concentrations of geosmin and MIB were frequently present in most of the reservoirs; high concentrations occurred episodically and exhibited significant spatial variation. Available evidence points to cyanobacteria (blue-green algae), rather than actinomycetes, as the primary source of geosmin and MIB in these reservoirs, so management techniques that control cyanobacteria are likely to also control geosmin and MIB. Mesocosm and reservoir monitoring data indicate that a low N to P ratio may promote cyanobacterial blooms; but other factors can be equally important. Geosmin and MIB production are species and life-stage specific, and the factors causing a particular species to thrive or produce geosmin or MIB usually are poorly understood.; Geosmin and MIB degradation by microorganisms native to Midwestern reservoirs depended on: the source water (the microbial community present); temperature (season); the state of the compounds (intracellular or dissolved); and initial concentration. Geosmin degraded faster than MIB. At concentrations typically encountered, geosmin degradation was first-order and MIB degradation appeared to be zero-order. Adding selected primary substrates adversely affected degradation.; In most cases, the best treatment option is powdered activated carbon (PAC) adsorption. Removal of geosmin and MIB by PAC was influenced by PAC type and by addition of chemicals (potassium permanganate, polymer, chlorine, and chlorine dioxide, but not lime). Process efficiency was improved by using PAC in a solids-contact reactor. A proprietary zeolite was superior to PAC, on a weight basis, for removing geosmin; but further evaluation is needed to evaluate its cost effectiveness.