Estudo da remoção de matéria orgânica carbonácea, nitrogênio amoniacal e fósforo em lixiviado pré-tratado de aterro sanitário empregando typha em Wetlands

Abstract

Urban solid waste sanitary landfill leachate results from the interaction between the biodegradation process of the organic portion of such wastes and stormwater percolation that solubilizes both organic and inorganic components. In an effort to promote leachate treatment, efficient and low cost technological solutions are sought in order to fulfill the demands of most Brazilian communities. The regularly applied techniques used in leachate treatment, mainly lagoons, present a nitrogen and phosphorus nutrient removal deficiency. In this respect, wetlands are seen as a possibly efficient solution for leachate treatment, at least as a complement to pre-treatment systems (aerobic and/or anaerobic). Wetlands measuring 1,8m³ were built using a macrophyte plant of the genus Typha. Three shallow wetlands were studied: the first with a horizontal flow (WH), the second with a vertical flow (WV) and the third without any plants (WH0). Wastewater treatment was conducted by leachate dilution into the sewage in different added percentages, from 8%, 16%, 64% and 100% in two different plantings. The first planting took place between the Fall and the Winter and the second occurred during Spring and Summer. The wastewater carbonaceous organic matter, ammoniacal nitrogen and phosphorus removal efficiency was studied and compliance with the standards prescribed by Brazilian regulations was verified. The study results demonstrate a good adaptation during the plants’ acclimation with 0,5% to 2% leachate in the sewage. As for wastewater treatment, results demonstrate that both on the first and on the second plantings WH yielded a higher quantity of more efficient removal events than the other wetlands, even though the statistical analysis did not indicate a significant difference either between the horizontal and vertical flows or between the wetland with and without plants. Under the studied conditions, the treatment units’ discharge points still do not comply with the standards prescribed by laws and regulations. Through this study it became evident that Typha planting in the wetlands must coincide with higher temperature periods, when the best results for both carbonaceous organic matter and nutrient removal were observed. Even for high concentrations present in the leachate, wetlands, particularly the ones with a horizontal flow, proved to remove nutrients in a satisfactory fashion (13% to 56% for ammoniacal nitrogen and from 15% to 67% for phosphorus).