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The presence of colonial and solitary ciliated peritrichous protozoa was determined in a Sequencing Batch Reactor system filled with tezontle, a volcanic rock, economic, and abundant material that can be found in some parts of the world, like Mexico. The presence of these protozoa was related to the removal efficiencies of organic matter. Also, two novel staining techniques are proposed for staining both colonial and solitary peritrichous protozoa. The results show that tezontle promotes the growth of solitary and colonial ciliated peritrichous protozoa, which, once identified, could be used as indicators of the efficiency of the wastewater treatment process. Additionally, the staining techniques established in the current study allowed the precise observation of protozoan nuclei. They can represent a useful complementary methodology for identifying protozoan species present in water treatment processes, along with the already existing identification techniques. The number and variety of protozoa found in the system may be considered potential bioindicators of water quality during biological treatments.

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This paper proposes and develops a protocol for measuring the aerobic granulation potential of sludge, aiming to provide an affordable and simple alternative that can facilitate the development of aerobic granulation technology. In this sense, the protocol comprises a set of parameters and considerations that interact to create a controlled environment and stimulate cell population clustering. All of this is done in the context of procedural simplicity, low cost, and the speed at which results are obtained. The protocol is essentially a three-stage method: preparation of the substrate, adaptation of the inoculum, and implementation of the protocol. Simple parameters were measured to evaluate the granulation process: SVI, settling velocity, and morphological parameters. The protocol was validated according to optimal ranges and criteria previously established in the literature. For this purpose, an activated sludge inoculum from a domestic wastewater treatment plant was submitted to the protocol, obtaining an optimal response of the biomass (SVI5 =13.90 mL g-1, settling velocity= 25,79 m h-1, Diameter > 0.2 mm) in a relatively short time (7 d). The results show that this protocol can constitute a tool for evaluation and decision-making using traditional laboratory equipment and is applicable at different scales.

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Production of polyhydroxyalkanoates (PHA) has generated great interest as building blocks for bioplastic production. Their production using mixed microbial cultures represents an interesting alternative, since it enables the use of organic wastes as a carbon source. Feast/famine strategy is a common way to promote selection of microorganisms with PHA accumulation capacity. However, when using waste sources, changes in substrate concentration are expected, that may affect performance and efficiency of the process. This study showed how the dissolved oxygen level can be used for online control of the cycle time, ensuring that the desired feast/famine ratio is effectively applied. An operation strategy is presented and validated, using sequential batch reactors fed with acetate as the carbon source. Production of polyhydroxybutyrate (PHB) was studied, which is the expected type of PHA to be synthetized when using acetate as substrate. Two reactors were operated by applying the proposed control strategy, to provide F/F ratios of 0.2 and 0.6, respectively. A third reactor was operated with a fixed cycle time, for comparison purposes. Results showed that the reactor that operated at an F/F ratio of 0.6 promoted higher biomass productivity and PHB content, as a result of a better use of available time, preventing unnecessary long famine times. The application of the tested strategy is a simple a reliable way to promote a better performance of feast/famine-based bioreactors involving mixed microbial cultures for PHB production.

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ABSTRACT This study aimed to verify if coal ash, a residue from thermal power plants, could act as a granulation nucleus, cations source, and abrasive element to favor granules formation and stability in aerobic granular sludge (AGS) systems. Two simultaneous fill/draw sequencing batch reactors (SBRs) (R1 and R2) were operated with 6-h cycles, i.e., the filling and drawing phases occurred simultaneously, followed by the reaction and settling phases. R1 was maintained as control, while R2 was supplemented with coal ash (1 g·L-1) on the first day of operation. Granulation was achieved in both reactors, and no significant differences were observed in terms of settleability, biomass retention, morphology, resistance to shear, and composition of the EPS matrix. However, the ash addition did not change the settleability, biomass retention, granule morphology, shear resistance, and extracellular polymeric substances (EPS) content significantly. COD removal was high (≥ 90%), while nitrogen (~50%) and phosphorus (~40%) removals were low, possibly due to the presence of nitrate during the anaerobic phase. With granulation, microbial population profile was altered, mainly at the genus level. In general, the operational conditions had a more considerable influence over granulation than the ash addition. The possible reasons are because the ash supplementation was performed in a single step, the low sedimentation rate of this particular residue, and the weak interaction between the ash and the EPS formed in the granular sludge. These factors appear to have decreased or prevented the action of the ash as granulation nucleus, source of cations, and abrasive element.

RESUMO O objetivo deste estudo foi verificar se a cinza de carvão mineral, um resíduo de usinas termelétricas, poderia atuar como núcleo de granulação, fonte de cátions e elemento abrasivo em sistemas de lodo granular aeróbio (LGA) para favorecer a formação e estabilidade dos grânulos. Dois reatores em batelada sequencial (RBS) (R1 e R2) foram operados em regime de alimentação/descarte simultâneos com ciclos de 6 h, ou seja, as fases de alimentação e descarte do efluente ocorreram simultaneamente, seguidas das fases de reação e de decantação. O R1 foi mantido como controle, enquanto o R2 foi suplementado com as cinzas (1 g·L-1) no primeiro dia de operação. A granulação foi alcançada em ambos os reatores, não havendo diferenças marcantes em termos de sedimentabilidade, retenção de biomassa, morfologia do grânulo, resistência ao cisalhamento e conteúdo de substâncias poliméricas extracelulares (SPE). A remoção de DQO foi alta (≥ 90%), enquanto as remoções de nitrogênio (~50%) e fósforo (~40%) foram baixas, possivelmente pela presença de nitrato na fase anaeróbia. Após a granulação, o perfil da comunidade microbiana mudou, especialmente em termos de gênero. Globalmente, as condições operacionais tiveram maior influência sobre a granulação do que a adição das cinzas, possivelmente porque elas só foram adicionadas uma vez e possuem baixa velocidade de sedimentação, bem como devido a uma fraca interação das cinzas com a matriz de SPE formada no lodo aeróbio. Esses fatores podem ter diminuído, ou mesmo impedido, a ação das cinzas como núcleo de grânulo, fonte de cátions ou elemento abrasivo.

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Chlorophenols are inhibitory compounds that can be biodegraded by aerobic granules in discontinuous processes. Many industrial wastewaters are characterized by transient pH variation over time. These pH changes could affect the overall granule structure and microbial activity during the chlorophenol biodegradation. The objective of this research was to evaluate the effects of transient pH variation on the specific degradation rate (q), granule integrity coefficient (IC), and size in sequencing batch reactors treating 4-chlorophenol (4-CP). First, aerobic granules were acclimated for efficient 4-CP degradation (>99%). The acclimated granules consisted of 55.7% of the phyla Proteobacteria and 40.6% of Bacteroidetes. The main bacteria belong to the order Sphingobacteriales (24%), as well as Amaricoccus, Acidovorax, Shinella, Rhizobium, and Flavobacterium, some of which are new genera reported in acclimated granules degrading 4-CP. Then, pH changes were applied to the acclimated aerobic granules, observing that acid pHs decreased to a greater extent the specific degradation rate (67% to 99%) than basic pHs (34% to 80%). These pH changes caused the granule disaggregation but with lower effects on the IC. The effects of pH change were mainly on the microbial activity more than the physical characteristics of aerobic granules degrading 4-CP.

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This work investigated the effect of Ca2+ (100 mg L-1) addition on the formation and maintenance of aerobic granular sludge in a simultaneous fill/draw mode sequencing batch reactor (SBR), operated with a low liquid upflow velocity (0.92 m h-1), in order to verify if Ca2+ presence compensates the low selection pressure imposed. Additionally, carbon and nutrients removals, granules characteristics and microbial community were evaluated. For this, two SBRs (R1, control, and R2, Ca2+-supplemented) were operated (6-h cycle). In general, Ca2+ supplementation affected positively the sludge settleability, although a larger fraction of inert solids was found in the granules. The total extracellular polymeric substances were the same for both reactors, and no remarkable differences were observed between their polysaccharides and proteins contents. Overall, Ca2+ addition in a simultaneous fill/draw mode SBR neither accelerated the granule formation nor improved the operational performance. The microbial community structure, especially in terms of bioactivity, was not affected as well. Therefore, the effect of divalent cations might be more pronounced in conventional SBRs, in which the selection pressure is higher.

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The effects of domestic wastewater and a coastal warm climate on granular sludge and biological nutrient removal were evaluated using a pilot-scale sequencing batch reactor (SBR). The reactor operation employed two different operational strategies (OS) based on up-flow feeding regimes, defined as fast (OS1, flow rate = 18.0 L min-1 and flow velocity = 22.0 m h-1) and slow (OS2, flow rate = 3.5 L min-1 and flow velocity = 4.3 m h-1). Under slow feeding, larger (OS1: 290 µm; OS2: 450 µm) and faster settling granules were obtained (OS1: 109; OS2: 74 mL g-1 TSS). The slow feeding regime was also advantageous for the hydrolysis of particulate organic matter (OS1: 1.3; OS2: 3.1 g CODtot g-1 VSS d-1) and for phosphorus removal (OS1: <33%; OS2: >97.5%). Neither strategy resulted in substantial biomass accumulation in the reactor (OS1: 0.7; OS2: 1.5 g VSS L-1), and high concentrations of nitrite were observed in the effluent (9-27 mg [Formula: see text] L-1). Ordinary heterotrophic organisms dominated the granular sludge developed under both feeding regimes (OS1: 30% of Thauera; OS2: 56% of Comamonas), while polyphosphate-accumulating organisms (PAOs) were only detected during OS2 (2.3-3.4% of total bacteria). A successful granular sludge process should be able to cope with high fluctuations in wastewater loads caused by rain events (82-182 mm month-1 in Florianopolis, Brazil). In order to achieve higher water quality, strategies identified for an efficient granular sludge SBR operation included (i) management of an anaerobic phase for PAO selection, and (ii) aeration control for successful nitrification/denitrification.

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Vinasse, from sugar and ethanol production, stands out as one of the most problematic agroindustry wastes due to its high chemical oxygen demand, large production volume, and recalcitrant compounds. Therefore, the viability of using glycerin as a co-substrate in vinasse anaerobic digestion was tested, to increase process efficiency and biogas productivity. The effect of feeding strategy, influent concentration, cycle length, and temperature were assessed to optimize methane production. Glycerin (1.53% v/v) proved to be a good co-substrate since it increased the overall methane production in co-digestion assays. CH4 productivity enhanced exponentially as influent concentration increased, but when temperature was increased to 35 °C, biogas production was impaired. The highest methane productivity and yield were achieved using fed-batch mode, at 30 °C and at an organic loading rate of 10.1 kg COD m-3 day-1: 139.32 mol CH4 m-3 day-1, 13.86 mol CH4 kg CODapplied, and 15.30 mol CH4 kg CODremoved. Methane was predominantly produced through the hydrogenotrophic route. In order to treat all the vinasse produced by a mid-size sugar and ethanol plant, nine reactors with 7263.4 m3 each would be needed. The energy generated by burning the biogas in boilers would reach approximately 92,000 MW h per season and could save up to US$ 240,000.00 per month in diesel oil demand.

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The overall world consumption rate of rubber tends to increase by an average of 2.8% per year in the period between 2017 and 2025. Rubber residues represent a severe problem to both health and environment due to their cross-linked structure that offers a prolonged degradation rate. A good solution to eliminate this problem is recycling and recovery, aiming at the production of new materials. The tire crumb can be recycled by chemical/biological recovery, where the elastomer is devulcanized, or by physical recovery, where the three-dimensional network is transformed into small fragments. In this study, we investigated the bio-degradation effect caused by Mealworms (the larvae of Tenebrio molitor Linnaeus) on vulcanized SBR-rubber and tire crumb as a desulphurization method. The surface modifications of both rubbers were studied by instrumental techniques: FTIR-ATR, TGA, XRD, and SEM. The cross-linking degree of the rubber was determined via circular condensation method. The obtained results show that the Tenebrio molitor could survive after three weeks of direct contact with SBR-rubber and tire crumb as the only alimentation. There was a declining effect of cross-linking degree by increasing the contact time between the rubbers and larvae. The FTIR results indicate surface/chemical modifications of the rubbers and the SEM results show the free sulfur after it was released in the form of sulfur flower-like. Also, the TGA results highlight a difference in the degrading behavior and residues of the treated and non-treated rubbers. Therefore, the reported results were promising, demonstrating the biodegradation effect caused by the Tenebrio molitor mealworms, highlighting an alternative and natural mean of degrading vulcanized rubber residues.

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The most common approach to deal with vinasse (sugarcane stillage) is fertigation, but this technique compromises soil structure and surrounding water bodies. A possible solution is to transport vinasse to local cheese whey producers and perform the co-digestion of these wastewaters together, reducing their organic load and generating bioenergy. Therefore, this study investigated the application of an AnSBBR (anaerobic sequencing batch biofilm reactor) operated in batch and fed-batch mode, co-digesting vinasse and whey at 30 °C. The effect of influent composition and feeding strategy was assessed. In all conditions, the system achieved high organic matter removal (approximately 83%). Increasing the percentage of vinasse from 0 to 100% in the influent resulted in a decrease in methane productivity (76.3 to 51.1 molCH4 m-3 day-1) and yield (12.7 to 9.1 molCH4 kgCOD-1), but fed-batch mode operation improved reactor performance (73.0 molCH4 m-3 day-1 and 11.5 molCH4 kgCOD-1). From the kinetic metabolic model, it was possible to infer that, at the best condition, methane is produced in a similar way from the acetoclastic and hydrogenotrophic routes. A scheme of four parallel reactors with a volume of 16,950 m3 each was proposed in the scale-up estimation, with an energy recovery estimated in 28,745 MWh per month.

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Cometabolic consumption of 2-chlorophenol (2-CP) by a nitrifying sludge was evaluated in two SBR reactors fed with 60 mg 2-CP-C/L and different initial ammonium concentrations (100, 200, 300, 400, and 500 mg NH4+-N/L). Irrespectively to the increase in ammonium concentration and throughout the operational cycles, the sludge achieved a complete nitrification in 14 days, accounting for ammonium consumption efficiencies close to 99% and nitrate production yields between 0.93 and 0.99. The sludge was able to completely consume 2-CP within 7 days. The increase in ammonium concentration provoked an increment in the specific rates of both ammonium (qNH4+-N) and 2-CP (q2-CP-C) consumption up to 5.2 and 3.1 times, respectively. The cometabolic effect of the increase in ammonium concentration on 2-CP consumption was supported by a direct and significant relationship between the qNH4+-N and q2-CP-C (r = 0.83). Moreover, batch assays conducted with ammonium, 2-CP, allylthiourea as specific inhibitor of the ammonium monooxygenase (AMO) enzyme, and the sludge inoculated into the reactors, resulted in a decrease of 34% in q2-CP-C, evidencing the participation of the AMO in the consumption of 2-CP. When the same assays were carried out with the sludge obtained from the SBR reactors after 13 operating cycles, a higher participation of the AMO in 2-CP consumption was noticed with a decrease of 53% in q2-CP-C. According to these results, the use of nitrifying sludge and high ammonium concentrations in SBR systems can be a suitable alternative for increasing the cometabolic consumption of recalcitrant compounds like 2-CP.

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The aim of this work is to develop compatibilization strategies for High Impact Polystyrene (HIPS)/ Acrylonitrile-Butadiene-Styrene (ABS) blends from WEEE in order to add value to these recycled plastics by improving their mechanical performance. Results from a screening study of HIPS/ABS blends compatibilization by the addition of Styrene-Butadiene Rubber (SBR) are presented. Two different weight proportion of HIPS/ABS physical blends were analyzed, 80/20 and 20/80, with three different concentration of SBR: 2, 10 and 20 wt%. Compatibilization efficiency was analyzed from an accurate thermal and mechanical analysis, by comparing each physical blend and corresponding compatibilized blends with SBR. Results were discussed relating glass transition changes with mechanical performance, both aspects were interpreted in terms of blend morphology. Phase and fillers dispersion and distribution as well as SBR amount and its interaction with each phase were accurate analyzed. Compatibilization of HIPS/ABS blends from WEEE with the addition of SBR is effective in blends with HIPS as main component. With the addition of 2 wt% of SBR, strength and toughness have notably increased respect to the corresponding physical blend, 244% and 186% respectively. From this screening study is possible to infer that SBR is a sustainable and efficient compatibilizer of HIPS rich blends allowing to obtain a final blend that can be used as a replacement material of separated resins from WEEE.

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ABSTRACT This study evaluates the influence of initial nitrogen concentration, temperature and stirring speed on specific anammox activity (SAA). The biomass was tested in single batch reactors with different initial nitrogen concentrations (Assay 1) ranging from 60 to 140 mg Ntotal/L in equimolar ratio (NO2--N/NH4+-N) and in another test to 67.3 mg NH4+-N/L and 92.2 mg NO2--N/L (close to anammox stoichiometric ratio). The anammox biomass was also tested in single batch at different temperatures (from 20 to 37° C) to determine the short-term effects on SAA (Assay 2). In the third assay the stirring speed ranged from 50 to 150 rpm in a sequencing batch reactor (SBR) at 37 ºC. SAA was affected by the stoichiometric molar ratio but not by equimolar initial concentrations. The maximum specific anammox activities were 26.2 mg NH4+-N/g VSS.h in the single batch reactor at 37 ºC with NO2--N/NH4+-N stoichiometric ratio and 33.5 mg NH4+-N/g VSS.h in the SBR at 37 ºC and 50 rpm. The NO2--N/NH4+-N molar ratio affected specific anammox activity, and SAA showed to be more hindered by low increases of stirring speed than reported in the literature.

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This study aimed to evaluate the co-digestion of cheese whey and glycerin in an anaerobic sequencing batch biofilm reactor (AnSBBR) with recirculation of the liquid phase applied to biomethane production. The applied volumetric organic load (AVOL) in all conditions was 7.5 kgCOD m(-3) day(-1). The feeding time was equal to half of the cycle time. The best condition for co-digestion was the wastewater with 75 % of cheese whey and 25 % of glycerin (chemical oxygen demand (COD) basis); it achieved a productivity of 101.8 molCH4 m(-3) day(-1) and a yield of 13.3 molCH4 kgCOD(-1) with 89 % of COD removal. This represents an increase of productivity of almost 9 and 30 % when compared to the anaerobic digestion of cheese whey and glycerin alone, respectively. The co-digestion proposed is a promising solution for both pollutants with the advantage of high energy production. A first-order kinetic model was fitted efficiently to the process.

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O objetivo deste trabalho foi estudar o tratamento biológico de efluente de indústria de vegetais congelados em Reator em Batelada Sequencial (RBS), verificando o efeito da concentração de Sólidos Suspensos Voláteis (SSV), Demanda Química de Oxigênio inicial (DQOi) e aeração na remoção biológica de carbono e nitrogênio, a fim de obter um efluente tratado que atenda aos padrões de lançamento recomendados pela legislação ambiental brasileira. Nesta pesquisa, o tratamento dos efluentes foi feito em um RBS, utilizando concentração de SSV variando entre 2000 mg.L-1 e 4000 mg.L-1, DQOi variando entre 300 mg.L-1 e 600 mg.L-1, e quantidade de aeração variando entre 3 L.min-1 e 6 L.min-1. Os resultados mostram que a maior eficiência de remoção para DQO foi de 88%, e para nitrogênio total Kjeldahl (NTK) foi de 74,9%. As condições otimizadas para remoção de DQO e NTK do efluente estudado foram: DQO inicial de 600 mg.L-1, aeração de 4,5 L.min-1 e concentração de SSV de 2000 mg.L-1 .

The objective of this work was to study the biological wastewater treatment from frozen vegetables industry in sequential batch reactor (SBR), verifying the effect of the volatile suspended solids (VSS) concentration, initial Chemical Oxygen Demand (iCOD) and aeration to remove organic carbon and nitrogen in order to obtain a treated wastewater that meets discharge standards recommended by the Brazilian environmental legislation. In this study, the treatment of wastewaters was done in an SBR using VSS concentration ranging from 2000 mg L-1 and 4000 mg.L-1, iCOD ranging from 300 mg.L-1 and 600 mg.L-1, and aeration ranging between 3 L.min-1 and 6 L.min-1. The results show that the major removal efficiency for COD was 88%, and for Total Kjeldahl Nitrogen (TKN) was 74,9%. The optimized conditions for COD and TKN removal of the studied wastewater were: initial COD of 600 mg.L-1, aeration of 4.5 L.min-1 and VSS concentration of 2000 mg.L-1 .

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ATP-binding cassette (ABC) transporters have been associated with drug resistance in various diseases. The MRPA gene, a transporter of ABCC subfamily, is involved in the resistance by sequestering metal-thiol conjugates in intracellular vesicles of Leishmania parasite. In this study, we performed the molecular characterization of the MRPA transporter, analysis of P-glycoprotein (Pgp) and aquaglyceroporin-1 (AQP1) expression, and determination of antimony level in antimony-susceptible and -resistant lines of L. (V.) guyanensis, L. (L.) amazonensis, L. (V.) braziliensis and L. (L.) infantum. PFGE analysis revealed an association of chromosomal amplification of MRPA gene with the drug resistance phenotype in all SbIII-resistant Leishmania lines analyzed. Levels of mRNA from MRPA gene determined by real-time quantitative RT-PCR showed an increased expression of two fold in SbIII-resistant lines of Leishmania guyanensis, Leishmania amazonensis and Leishmania braziliensis. Western blot analysis revealed that Pgp is increased in the SbIII-resistant L. guyanensis and L. amazonensis lines. The intracellular level of antimony quantified by graphite furnace atomic absorption spectrometry showed a reduction in the accumulation of this element in SbIII-resistant L. guyanensis, L. amazonensis and L. braziliensis lines when compared to their susceptible counterparts. Interestingly, a down-regulation of AQP1 protein was observed in the SbIII-resistant L. guyanensis and L. amazonensis lines, contributing for decreasing of SbIII entry in these lines. In addition, efflux experiments revealed that the rates of SbIII efflux are higher in the SbIII-resistant lines of L. guyanensis and L. braziliensis, that may explain also the low SbIII concentration within of these parasites. The BSO, an inhibitor of γ-glutamylcysteine synthetase enzyme, reversed the SbIII-resistance phenotype of L. braziliensis and caused an increasing in the Sb intracellular level in the LbSbR line. Our data indicate that the mechanisms of antimony-resistance are different among species of Leishmania analyzed in this study.

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Los efluentes industriales de las tenerías son altamente contaminantes por las elevadas concentraciones de materia orgánica, nitrógeno y metales pesados como el cromo que contienen. Los sistemas biológicos no convencionales, en especial los que usan reactores por carga secuencial (SBR) han demostrado ser una buena opción de tratamiento de estos efluentes por su flexibilidad y eficiencia en presencia de sustancias inhibidoras, tales como el cromo. El objetivo de esta investigación fue evaluar la eficiencia de un SBR en cuanto a la remoción de materia orgánica, nutrientes y metales pesados utilizando una mezcla de dos de las fracciones de los vertidos de una tenería (curtido con cromo y teñido). Se compararon las eficiencias de remoción obtenidas al alimentar el reactor con afluentes diluidos y concentrados, variando el tiempo de residencia hidráulica en 8 y 12 horas. Durante el tiempo de reacción se combinaron fases anóxicas y óxicas. Se obtuvo que las remociones de contaminantes fueron estadísticamente mayores cuando se usaron afluentes diluidos (DQO£1000 mg/L y [Cr3+]£10 mg/L), independientemente del tiempo de retención utilizado, lográndose la mayor eliminación durante la fase anóxica. Las remociones no mostraron diferencia estadística entre ellas, oscilando para los tratamientos con afluentes diluidos entre 82,5 y 84,2% para la DQO; 58,0 y 73,9% para P-PO4(3-) y 51,2 y 53,9% para el Cr. La eliminación de nitrógeno se realizó por asimilación debido a que los microorganismos nitrificantes fueron más sensibles e inhibieron su actividad frente a la presencia del cromo y altas concentraciones de materia orgánica. La remoción de cromo se logró por precipitación y/o adsorción en el lodo, por lo que fue fundamental controlar el pH en los reactores entre 7,5 y 8,5 unidades.

Tannery wastewater are highly pollutant for the high concentrations of organic matter, nitrogen and heavy metals as chrome that they contain. Sequential batch reactors (SBR) have demonstrated to be a good option of treatment of these effluents due to their flexibility and efficiency in presence of inhibiting substances (chrome). The aim of this investigation was to determine the best conditions for removal of organic matter, nutrients and heavy metals of the residual water of a tannery using a SBR fed on a mixture of tanning-dyeing effluent. The efficiencies of removal were compared when using dilute and concentrated influents, under 8 and 12 hour of hydraulic residence time. During the reaction phases anoxics and oxics phases were combined. The removal of pollutants were significantly higher when dilute influent was used (DQO£1000 mg/L and [Cr3+]£10 mg/L), independently of the retention time, being achieved the major elimination during the anoxic phase. The removals fluctuated between 82.5 and 84.45% of DQO, 58.0 and 73.9% of P-PO4(3-) and 51.2 and 53.9% of Cr. The elimination of nitrogen was achieved by assimilation, due to the fact that nitrifying bacteria were more sensitive and their activity was inhibited by the presence of chrome and high concentrations of organic matter. The removal of chrome was achieved by precipitation and/or adsorption on the sludge, being necessary to control the pH between 7.5 - 8.5 in the reactors.

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El curtido de pieles es uno de los procesos más contaminantes de la industria por la serie de tratamientos químicos que involucra y el abundante volumen de agua residual que produce. Los efluentes de las tenerías son ricos en materia orgánica, nitrógeno, sólidos suspendidos, sales y otras sustancias inhibidoras que afectan los procesos de nitrificación y desnitrificación. Los reactores por carga secuencial (SBR) han demostrado ser una buena opción de tratamiento de estos efluentes por su flexibilidad y capacidad de soportar altas cargas de alimentación. En este trabajo se evaluó la eficiencia de un SBR alimentado con una mezcla de las fracciones del efluente de una tenería provenientes de los procesos de pelambre y teñido. El funcionamiento del sistema fue evaluado para dos tiempos de residencia hidráulico (8 y 12 horas) y para dos niveles de concentración del afluente (diluido con DQO máxima de 2.700 mg/L y concentrado con DQO mínima de 25.000 mg/L). Durante el tiempo de reacción se combinaron fases anóxicas y óxicas. Se obtuvo que sólo la concentración del afluente fue el factor que presentó diferencia estadística en los cuatro tratamientos aplicados, siendo mayores las remociones de contaminantes cuando se usaron afluentes diluidos (DQO£2.700 mg/L), lográndose la mayor eliminación durante la fase anóxica. Las remociones estuvieron en el rango de 83,3-85,0% para DQO; 59,6-73,0% para P-PO4(3-) y 83,9-84% para Cr. La eliminación de nitrógeno se realizó presumiblemente por asimilación debido a que los microorganismos nitrificantes mostraron ser los más sensibles cuando se modificaron las condiciones de funcionamiento del reactor.

The leather tanning is one of the most pollutant processes in the industry for the series of chemical treatments that involves and the abundant volume of residual water produced. Tanneries wastewaters are rich in organic matter, nitrogen, solid suspended, salts and other inhibiting substances that affect the processes of nitrificación and desnitrificación. Sequential batch reactors (SBR) have demonstrated to be a good option for treatment of this effluent because they have flexibility and manage high load charges. The objetive of this work was evaluated the efficiency of a SBR fed on a mixture of two fractions of the tannery wastewater, soak liquour and dyeing effluent. The functioning of the system was evaluated for two hydraulic residence time (8 and 12 hours) and for two levels of concentration of the influent (diluted with maximum DQO of 2700 mg/L and concentrate with minimal DQO of 25000 mg/L). During the reaction two phases were combined: anoxic and oxic. There was obtained that only the concentration of the influent was the factor that presented statistical difference in the four treatments tested, being major removals of pollutants when influents were diluted (DQO£2700 mg/L), the major elimination were achieved during the anoxic phase. The removals were in the range of 83.3-85.0% for DQO; 59.6-73.0% for P-PO4(3-) and 83.9-84.0% for Cr. The elimination of nitrogen was achived presumably by assimilation, due to the fact that nitrifying bacteria were more sensitive when operation conditions were modified in the reactor.

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Este trabalho teve como objetivo propor uma metodologia de dimensionamento para o volume do RSB. O desenvolvimento do modelo matemático para calcular o volume do reator foi realizado a partir da modelagem fenomenológica do comportamento do lodo. A metodologia ora proposta foi aplicada em estudo de caso para comparação com metodologias já consolidadas no dimensionamento do sistema de lodos ativados em batelada. A partir da metodologia apresentada neste trabalho, a determinação do volume do reator e do ciclo operacional mostrou que é possível contribuir para o dimensionamento do RSB sem transgredir o conhecimento da ação do lodo sobre a matéria orgânica e sem admitir fluxo contínuo no comportamento hidráulico do reator.

The purpose of this study was to propose a methodology for sizing SBR volumes. The mathematical model to calculate reactor volume was developed by modeling sludge behavior phenomena. The methodology proposed here was applied to a case study in order to compare it to already consolidated methods used to size the activated sludge batch system. The reactor volume and operational cycle were determined based on the method presented here, showing that it is possible to help size the SBR without challenging knowledge regarding the action of sludge on organic matter, and without allowing continuous flow into the hydraulic compartment of the reactor.

Assuntos

RESUMO

Este trabalho tem como objetivo avaliar a eficiência e a estabilidade do RSB na remoção de nitrogênio no tratamento de esgoto doméstico com DQO baixa. O reator utilizado no experimento possui volume de trabalho de 600 L e trata 1200 L/d de esgoto bruto em três bateladas de oito horas. A partir dos dados obtidos na pesquisa, observou-se que o reator seqüencial em bateladapossibilitou a remoção média de nitrogênio total igual a 88 % no tratamento de esgoto doméstico com DQO média de 257 mg/L. A remoção de DQO foi de 90 %, a média da alcalinidade total no efluente foi 72 mgCaCO3/L e o índice volumétrico de lodo médio ficou em 86 mL/g. Estes resultados indicam que é possível utilizar RSB para o tratamento de esgoto doméstico com matéria orgânica reduzida sem comprometer a qualidade do efluente, a remoção de nitrogênio e a estabilidade operacional do sistema.

This work had the objective of evaluating the SBR efficiency and stability in the removal of nitrogen on the treatment of domestic sewage with low COD. The reactor used in the experiment has a working volume of 600 L, and treats 1200 L/d of raw sewage in three 8-hour cycles. From the data gathered during the research, itwas realized that the SBR fostered an average removal of total nitrogen equal to 88% in the treatment of a domestic sewage with an average COD of 257 mg/L. The COD removal was 90%, the final effluent total alkalinity was 72 mgCaCO3/L, and the sludge volumetricindex was 86 mL/g. The results indicate that is possible to use SBR for the treatment of domestic sewage with low organic matter without compromising the final effluent quality, the nitrogen removal ability, and the stability of the system.