title: Design of a reverse osmosis plant for leachate treatment aiming for safe disposal.
abstract: Leachate treatment is one of the major environmental issues faced by landfill owners. One promising method for reduction of pollutant discharge is reverse osmosis (RO). RO technology was tested at a pilot plant at Hedeskoga Landfill in southern Sweden. This landfill receives municipal solid waste (MSW) and industrial, commercial and institutional (IC&I) waste, and produces about 3000 m3/ha of leachate annually. Annual variations in the volume of leachate produced, estimated from changes in leachate electrical conductivity, were relatively small and should therefore have a minor effect on the main performance parameter of an RO plant, i.e., the achievable volume reduction. The volume reduction (V(permeate)/V(feed)) of polluted water achieved in batch experiments with 200-1000 litres of raw leachate was more than 80% (4MPa) and the remaining 20% was left as retentate. However, raw leachate caused severe fouling problems in a continuous flow run and after 24 hours, the flux had decreased to about 20% of the initial value. By pre-treating the leachate in a storage pond combined with a wetland, the situation was significantly improved and the decrease in membrane flux was only 0.2% per hour during a 200 hour run. The retention in terms of total solids and chemical oxygen demand was 90%, and for ammonia, it was 82%, at a volume reduction of 50%. The HELP-model was used for prediction of the water balance for the Hedeskoga landfill, with special focus on estimation of potential evapotranspiration. With different types of vegetation and a volume reduction of 75% in the RO plant, it was found possible to achieve safe disposal by irrigating 25% to 40% of the leachate-producing landfill area with pre-treated leachate. Pre-treatment with wetlands and nature based systems reduce the need of detergents for cleaning of the membranes and water only can be used. Short pre-treatment by aeration is not sufficient to bring leachate to a condition sustainable for RO-treatment. In that case, it was found necessary with alkaline-acid-alkaline treatment to restore the permeability. The total treatment cost for a full scale treatment plant at Hedeskoga was estimated to be approximately 30 SEK/m3, of which 25 is capital and 5 is operational costs. This can be compared to the total treatment costs for municipal sewage in Sweden, which is 8 SEK/m3.
authors.affiliation: Department of Technology, University of Kalmar, SE-391 82 Kalmar, Sweden. lars.thorneby@home.se
authors.forename: Lars
authors.initials: L
authors.lastname: Thörneby
authors.forename: William
authors.initials: W
authors.lastname: Hogland
authors.forename: Jan
authors.initials: J
authors.lastname: Stenis
authors.forename: Lennart
authors.initials: L
authors.lastname: Mathiasson
authors.forename: Pernilla
authors.initials: P
authors.lastname: Somogyi
mesh_terms: D003902:Detergents; D017753:Ecosystem; D004787:Environmental Pollution / Q000517:prevention & control*; D005160:Facility Design and Construction; D007220:Industrial Waste; D008567:Membranes, Artificial; D008962:Models, Theoretical; D009995:Osmosis; D010539:Permeability; D012037:Refuse Disposal / Q000379:methods*; D012995:Solubility
chemical_list: D003902:Detergents; D007220:Industrial Waste; D008567:Membranes, Artificial