Roberto Feijó de Figueiredo

Remoção de matéria orgânica, coliformes totais e nitrificação no tratamento de esgotos domésticos por filtros de areia

According to IBGE (2000) 73% of the Brazilian cities are considered small communities with population smaller than 20,000 inhabitants. The majority of domestic wastewater of these places is normally disposed in rivers with no treatment. As a consequence, the irregular disposal may cause health and environmental problems. To reduce this risk it is necessary to develop treatment systems that are simple, efficient, sustainable and of low cost. The treatment of wastewater using up flow anaerobic filter combined with sand filters would be able to satisfy these exigencies, producing an effluent that could be disposed in rivers or even be reused, safeguarding the sources of potable water. The system achieved BOD removal of 96% and complete nitrification for the application of low loads. The increase of the applied loads caused a reduction in the efficiency; however the final values were still satisfactory.

Accumulation of metals in the soil of an overland flow wastewater treatment system

Accumulation of Co, Cu, Cr, Mo, Ni, Pb and Zn was evaluated in a soil profile of an overland flow system used for the post-treatment of urban wastewater. A pilot version of the overland flow system received urban wastewater from five up-flow anaerobic filters filled with bamboo (Bambusa tuldoides) rings. The anaerobic effluent was applied as feed over 18 months at rates varying from 7 to 28 L min(-1), to a vegetated slope length covered with Tifton 85 (Cynodon) sp. grass. Soil and plant samples were collected in triplicate from the top to the bottom of the slope. In addition, the soils were sampled at the depths 0-20 and 20-40 cm. The metal concentrations found in the overall system were compared to those obtained in a control area located at the beginning of the slope onto which nothing was applied. A month of monitoring the urban wastewater of Limeira City (São Paulo State, Brazil) showed a drastic change in metals concentration due to the irregular discharge of industrial waste. This irregular discharge introduces Cr, Cu, Ni, Pb and Zn into the system used to treat domestic wastewater. The mass balance indicates the accumulation of metals in the soil and the translocation to the plants; also that they could be evapotranspirated, percolated and discharged.