engleski

Disinfection of urban wastewater and landfill leachate by using wood fly ash

Disinfection implies the elimination of pathogenic microorganisms in water treatment systems that facilitates the safe discharge or reuse of wastewater. Alkaline disinfection is the inactivation of pathogenic bacteria at high pH conditions, usually above 12. Wood fly ash has been known to increase the pH when introduced to water solutions. Fly ash is an industrial by-product of the combustion of different wood materials and is mostly disposed of as waste on landfills. Proposed applications of wood ash are in agriculture and forestry where it serves as a liming agent and increases the availability of nutrients in acid soils, as a component in concrete, cement, and mortar manufacturing, and as a catalyst for biodiesel synthesis. Usage of fly ash as a disinfectant has not been reported in the literature so we tested it by monitoring the removal of typical pathogen indicators (faecal coliforms and intestinal enterococci) in effluents of urban wastewater and landfill leachate treatment plants in order to simulate the disinfection by using wood fly ash as a potential tertiary treatment method. The addition of ash at a concentration of 10 g L-1 (1 %) caused an instant increase of pH in urban wastewater (Wastewater treatment plant of Velika Gorica, Croatia) and landfill leachate (Jakuševec landfill, Zagreb, Croatia). High pH (10.1–12.7) inactivated bacterial populations in both types of wastewater and the removal of faecal coliforms and intestinal enterococci after 6 h of contact was 100 % (below the detection limit ; <1 CFU per mL) when the most efficient ash sample, ash from combustion of beech, was used. Properly chosen wood fly ash, i.e. one that tends to increase the pH to the greatest extent, proved to be a very effective disinfection substrate. Considering that water treated with wood ash has a high pH and needs to be neutralised before discharge, ash would be more suitable for disinfection of leachates since smaller volumes are treated.

faecal coliforms; intestinal enterococci; wastewater; fly ash

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