Porównanie efektywności procesów podczyszczania odcieków składowiskowych

Dumping is the most frequently used method of municipal waste management. According to the data of Central Statistical Office of Poland at present there are over 390 municipal landfills in our country. Dumping of municipal waste is connected with generation of leachates. Treatment of leachates is difficult because of the variability of their composition. Leachates are generated as a result of penetration of rainwater through the waste layer. Rainwater leaches organic and inorganic compounds from waste material. Treatment method of leachate depends on its physicochemical properties, susceptibility for biodegradation and further management. Pretreatment of leachate is necessary before their treatment in wastewater treatment plant (WWTP). WWTP can be a part of dumping place infrastructure. Pretreated leachate can also be discharged into sewerage system. The most effective methods of leachate treatment are reverse osmosis and evaporation. The methods mentioned above are, however, not energy-efficient and as a result expensive. Frequently used method is also leachate recirculation onto waste pile. This method is not a good solution. Because of this it is expedient to examine effective and cheap methods of leachate pretreatment. The aim of the investigation was to compare the effectiveness of pre-treatment of landfill leachate using the processes of pre-filtration on the sand and gravel bed, ultrafiltration membrane module, coagulation, or sorption/precipitation in the solidified mixture of ash and water. These studies were carried out using effluent from two municipal landfills. The leachate was collected from the afore-mentioned landfills four times in the period from March to June. The efficiency of contaminants removal in the adopted process conditions were varied. The pH value, conductivity, color, turbidity, odor, alkalinity, acidity, free CO2, COD, total hardness, calcium and ammonium nitrogen in the raw leachate (collected from landfills) and after pre-treated processes were determined. The effectiveness of the removal of organic and inorganic compounds does not depend on the characteristics of the raw leachate. The highest effectiveness of contaminants removal was obtained in the filter bed of fly ash (27-93%). The percentage losses of the values of indicators, reaching 86% in the ultrafiltration process were achieved. The efficiency of treatment leachate in the coagulation or pre-filtraton process was at a lower level. It is proposed to integrate the processes of filtration or coagulation with ultrafiltration process in a 2- or 3-stage system. In an integrated 3-stage system for the leachate treatment, the preliminary stage could be filtration on a bed of sand and gravel, the next step - pretreatment in a bed of fly ash, and the final step – ultrafiltration process. In an alternative arrangement of leachate treatment system, a preliminary step would be using coagulation process.