Water Treatability Database | US EPA The literature identified studies for total microcystins and for M-LR, M-LA, M-RR, M-YR and M-LY. See the individual treatment processes (below) for which microcystins were evaluated by those processes. This summary will address microcystins in general. The following processes are considered effective for the removal/oxidation of microcystins: ozone (up to 100%), ozone with hydrogen peroxide (up to 100%), membrane filtration with ultrafiltration (up to 98%), membrane separation with reverse osmosis (up to 99%), membrane separation with nanofiltration (up to 99%), powdered activated carbon (up to 100% for some microcystins but less so for others), granular activated carbon (time-dependent from 100% near start up to 38 to 73% at 3.5 months), slow sand filtration (time-dependent ranging 65 to 100%), bank filtration (see other treatment) (one assessment at 61%), chlorine (up to 95%), permanganate (up to 90%), and conventional treatment (up to 42 percent, but more effective for intracellular microcystins than for extracellular (dissolved) microcystins). Even though ozone coupled with hydrogen peroxide is effective, it is not significantly more effective than ozone alone. UV irradiation and UV coupled with hydrogen peroxide were marginally effective but relatively long contact times were required. Chloramine, chlorine dioxide and hydrogen peroxide were not effective under typical operating conditions. Research was identified evaluating the following treatment technologies for the removal or inactivation of microcystins: Chloramine - One study showed that inactivation of total microcystins in water by monochloramine is not effective. A dose of 20 mg/L at a contact time of 5 days was only able to reduce the toxin concentration by 17% at room temperature. Chlorine - Oxidation of microcystin M-LR in water by chlorine is effective (up to 100 percent removal) in bench-scale studies where the effectiveness is dependent on chlorine dose, contact time, pH, temperature and water quality characteristics. Data fr... Chlorine Dioxide - Data show moderate to high reduction of microcystin-LR by chlorine dioxide, yet using doses or contact times much greater than practiced in water treatment plants. Conventional Treatment - Removal of microcystins in water by coagulation and clarification can be little to moderately effective (42 percent maximum reported). The process effectiveness is dependent on initial toxin concentrations and the form of the toxin (intracellular ... Direct Filtration - One study showed tha direct filtration is not effective at reducing dissolved microcystins and may contribute to an increase in concentration. GAC Isotherm - Based on isotherm studies, adsorption of microcystins in water by granular activated carbon (GAC) can be very effective. Six microcystins were studied on eight GACs. The effectiveness of the adsorption depends on the GAC material type. Granular Activated Carbon - Removal of total microcystins, M-LR, and M-LA, in water by granular activated carbon (GAC) can be very effective where the effectiveness is based on the empty bed contact time, the carbon's age, and possible biodegradation of the toxin. Time-depen... Hydrogen Peroxide - Two studies showed that oxidation of the microcystin M-LR in water by hydrogen peroxide is not effective. No significant control of M-LR was observed. Membrane Filtration - Removal of total microcystins in water by ulfiltration is moderately to very effective. One study indicated that microfiltration is not effective at removing microcystins. It should be noted that there were no increases of the total micr... Membrane Separation - Removal of microcystins in water by membrane separation is very effective for various microcystin covariants, and for a wide range of microcystin concentrations. Other Treatment - Removal of total microcystins and M-LR in water by combined treatment processes can be moderately to very effective, up to 100 percent removal. Due to the unique nature of each combined treatment process, performance must be evaluated on a case-by... Ozone - Oxidation of microcystins in water by ozone is moderately to very effective (up to 100 percent removal of M-LA and M-LR in several studies) where the effectiveness is highly dependent on temperature, ozone dose, contact time, and water quality. pH... Ozone + Hydrogen Peroxide - Oxidation of microcystin M-LR in water by ozone (O3) with hydrogen peroxide (H2O2) at 0.5:1 H2O23 is effective with 45 to 100 percent removal. However, H2O23 was not significantly better than ozone alone. Permanganate - Oxidation of microcystins in water by permanganate addition is little to very effective. Performance is highly dependent on potassium permanganate dose. Greater than 90 percent control was achieved at a dose of 1.25 mg/L, neutral pH and ambient te... Powdered Activated Carbon - Removal of microcystins in water by powdered activated carbon (PAC) is moderately to highly effective, up to 100% depending on the microcystin cogener being removed and the PAC dose, PAC type and contact time. Based on three references, M-RR is th... Slow Sand Filtration - Elimination of microcystins in water by slow sand filtration can be very effective, where the effectiveness is based on contact time. Greater contact times increase the effectiveness of slow sand filtration. Ultraviolet Irradiation - Two studies indicate that the oxidation of microcystin-LR in water by ultraviolet irradiation (UV) can be moderately effective. However, testing conditions included exposure times that are far in excess of typical exposure time... Ultraviolet Irradiation + Hydrogen Peroxide - Oxidation of the microcystin M-RR in water by ultraviolet irradiation (UV) with hydrogen peroxide (H2O2) is moderately to very effective. Most tests utilized a very high dose of hydrogen peroxide.