Evaluatie zuiveringstechniek voor verwijdering gewasbeschermingsmiddelen III

Dutch greenhouse horticulture has to treat all discharged water from soilless cultivations for the removal of plant protection products, to meet the new Dutch Directive Hoofdlijnenakkoord (2015). Building on previous research, (1) the life span of activated carbon filters, (2) the effect of increasing concentrations of plant protection products on the removal efficacy of ozone and the removal efficacy of (3) multimedia filtration and (4) ultrasonic water treatment have been investigated. It turned out to be difficult to design an active carbon based water treatment system capable of durable treatment of greenhouse discharge water: organic and mineral material in the water blocked the pores, thereby clogging the filter system and causing leakage by pressure build-up. Activated carbon filtration (granular activated carbon, 48 min contact time, 50 μm prefiltration with sand filter) achieved a removal efficacy of >95% for up to 430 bed volumes treated. Combination with advanced oxidation improved the removal efficacy, but the removal time of the filter could not be determined due to leakage. The removal efficacy of ozone oxidation remained >98%, even at increased concentrations (factor 10 and 100) of plant protection products in the untreated water. The multimedia filter removed 75% of the plant protection products by adsorption, biological breakdown within the filter was not determined. Treatment of the water with ultrasonic waves hardly had any effect (maximum 30% efficacy) on the breakdown.