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ABSTRACT:The aim of this study was to monitor the stabilization of a sequential batch reactor (SBR) regarding the partial nitritation of poultry slaughterhouse wastewater, aiming at preparing it for a reactor with bacteria that promote anaerobic ammonia oxidation (anammox). A cylindrical reactor with a useful volume of 3.5 L, mechanical agitation (50 rpm), and suspended biomass was used in the experiment. The strategies adopted for nitrite-oxidizing bacteria (NOB) inhibition were cycle time (CT: 24, 16, 6, 5, 4 h and real-time monitoring), free ammonia accumulation, alkalinity restriction and low concentrations of dissolved oxygen (DO). The ammonification process, observed at all experimental phases, negatively influenced the control of partial nitritation process. Alkalinity restriction under low cycle times (4 and 5 h) conditions, together with low dissolved oxygen concentration, was a key factor for nitrite-oxidizing bacteria inhibition. Stability of partial nitritation was only reached by real-time monitoring, being the cycles stopped when 50% N-NH4 + and 50% N-NO2 − were present in the reactor.

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Biological nitrogen removal via Anammox is an advantageous technology in the nitrogen treatment effluents with a low Carbon/Nitrogen ratio, a process that makes this route interesting for the most different types of industries, agribusinesses, and urban effluent treatment plants. Achieving robust Anammox biomass for use in full-scale plants is still a challenge that motivates studies of biomass enrichment and the search for kinetic parameters of substrate consumption rate that help optimize the conduction of reactors. According to the previously mentioned, this work aimed to carry out the kinetic study of nitrogen consumption by the Anammox process in a membrane aerated biofilm reactors operated in sequential batches (MABR-BS). 6 MABR-BS reactors were used, each one of them inoculated with a specific Anammox sludge, obtained from the enrichment of anaerobic and aerobic sludges coming from 3 different sludge sources, namely, a municipal wastewater treatment plant, a landfill leachate treatment plant, and a swine slaughterhouse effluent treatment plant. For the kinetic study, 6 reactors were used, made in glass flasks with a total volume of 1L, with a useful volume of 500 mL, with the 300:200mL ratio between synthetic effluent (with 100mgN-NH4+.L-1) and sludge from the sources: R1 - anaerobic sludge from a UASB reactor for urban sewage treatment; R2 - mixed sludge from a UASB reactor, consisting of waste sludge and supernatant scum; R3 - anaerobic sludge from landfill leachate treatment; R4 - mixed sludge consisting of aerobic and anaerobic sludge from landfill leachate treatment plant; R5 - anaerobic sludge from the swine slaughter effluent treatment plant and R6 - aerobic and anaerobic sludge from the swine slaughter effluent treatment plant. The experimental apparatus had 3 aerators coupled to 3 flowmeters with an air flow regulated at 1.0 L.min-1; 30 cm of silicone membrane in a curved shape with one of the inlets connected to the aerator and flowmeter, the other outlet was immersed in a 75 cm water column, exerting negative pressure on the air inside the tubular silicone membrane, forcing the air to exit through the microporosity of the membrane. Aeration was intermittent, with an interval of 0.16 h between each minute of aeration, the reactors were shaken in a water bath at 30 rpm and temperature of 32°C. The kinetic test had a duration of 24 hours with sampling every 2.5 hours. The nitrogen removal efficiencies (%) determined in the kinetic test were 61.36 (R1); 61.01(R2); 59.03 (R3); 56.70 (R4); 62.77 (R5) and 64.40 (R6). Regarding pH, all reactors had an initial pH above 8.0 and a final pH close to neutral. The specific nitrogen removal rates (in mgN.gVSS-1h-1), were on average 29.43 (R1); 33.50 (R2); 33.62 (R3); 33.42 (R4); 28.90 (R5) and 30.34 (R6). The best performance in the kinetic assay was obtained in the R1 reactor, obtaining a specific activity of maximum nitrogen removal of 57.61 mgN.gVSS-1h-1 and molar generation of residual nitrate with a stoichiometric coefficient of 0.018 mol.

Based on the observation of the effects of energy generation on climate change, efforts have been carried out to develop technologies to reduce polluting energy sources. In this context, the rational use and improvement of the efficiency of water heating systems can play an important role, contributing to lower energy consumption. This study evaluated a prototype for water heating for use in agroindustry. The prototype was designed for a possible utilization of mechanical energy in order to change the magnetic flux produced by permanent magnets, generating thermal energy by Foucault currents. This system presented yields of 64.74%, 65.13% and 64.48% for the rotor configurations with six magnets without pole reversal (6ISI), four magnets with reversal (4ICI), and four magnets without reversal (4ISI), respectively. For comparison purposes, a resistive water heating system was also evaluated for the same study conditions, obtaining an efficiency of 89.21%. The proposed inductive system did not present satisfactory results for constructive conditions presented in the study.