Pedro Alem Sobrinho

Aplicação de processos físico-químicos como alternativa de pré e pós-tratamento de lixiviados de aterros sanitários

The aim of this article was evaluate the implementation of the ammonia stripping as a pretreatment for landfill leachate and the use of the coagulation-flocculation-sedimentation process for the removal of refractory organic compounds present in a landfill leachate pretreated in an activated sludge system. The rates of ammonia nitrogen removal ranged between 3.5 and 3.6 mg NH3-N.L-1.h-1in a lab scale reactor (working volume of 20 L) equipped with a mechanical stirrer and 3.2 and 3.3 mg NH3-N.L-1.h-1in a lab scale aerated column (working volume of 10 L). It was possible to achieve removals above 90% of refractory organic compounds (measured as apparent color) applied coagulant dosage about 400 mg Fe+3.L-1 and 400 mg Al+3.L-1.

Characteristics of WWTP sludge after drying in greenhouse for agricultural purposes

The sludge generated by sewage treatment which meets regulatory standards can be used in agriculture. With this understanding, the focus of this study is the evaluation of the agricultural characteristics and inorganic substances in excess activated sludge, which was subjected to drying in a greenhouse. The variables (factor) evaluated during the drying process were: type of sludge (digested or not digested), addition of lime to the sludge, and the physical layout and rotation of sludge in the greenhouse. The parameters monitored for this assessment were moisture, volatile solids and pH. The greenhouse cover and sides were made of translucent plastic to allow the penetration of solar radiation and prevent water from entering. A impermeable floor was used. The sludge was generated in sewage treatment plants located in the metropolitan region of Grande Vitória, Espírito Santo, Brazil. The solar drying of wastewater sludge in a greenhouse presented satisfactory results.

Simultaneous nitrification and denitrification in the activated sludge systems of continuous flow

ABSTRACT This study has investigated the biological nitrogen removal by simultaneous nitrification and denitrification (SND) processes in a system of continuous flow activated sludge (AS) process. The investigation had four stages and evaluated the system behavior under different solid retention times (SRT), food-to-mass (F/M) ratios and dissolved oxygen (DO) concentrations. The data showed that the concentration of DO 0.5±0.2 mgO2/L did not affect the growth of heterotrophic bacteria (2.2–3.1 d−1 at 20°C) and autotrophic nitrifying bacteria (0.16–1.94 d−1 at 20°C), resulting in values very close to those obtained in conventional AS processes. The chemical oxygen demand (COD) removal was over 90% in all stages. The decrease in SRT from 37.2 to 27.8, 19.0 and 10.0 days had no significant influence on the development of SND. In the stage where the carbon/nitrogen (C/N) ratio was 4.3 mgCOD/mgN  L, SND efficiency was of 55%. In the following stages, the C/N ratio was increased and it was possible to achieve efficiencies higher than 98% SND. Overall, the data showed that appropriate controls of carbon and nitrogen input are required to achieve an efficient SND. An established SND technology can save operation time and energy, and might replace the traditional two stages: biological nitrification and denitrification process.

Desempenho de reator integrado de lodo ativado com biofilme em leito móvel

The aim of this study was to evaluate the effects of plastic media carriers presence in the activated sludge process through the operation under different solids retention times, for the removal of carbonaceous organic matter and ammonia nitrogen, of two aerobic systems. One of them, called LAC, was constituted by activated sludge reactors with suspended biomass only and compared with another, LAI, with integrated fixed-film activated sludge reactors. The growth of attached and suspended biomass and environmental conditions in the reactors have been monitored. Respirometric analyzes were used to determine kinetic coefficients related to nitrification. It was possible to apply approximately twice the load supported by an activated sludge system, nitrification was extended until low solids retention times related to the aerobic and suspended biomass, and denitrification has occurred efficiently. The specific growth rate of nitrifying bacteria in attached biomass has resulted similar to that observed in suspended biomass