Combined anaerobic/aerobic processes for municipal wastewater treatment is quite recent; the studies developed have shown these processes are feasible for the removal of organic, nutrient substances and reduction of sludge produced. Previous studies developed at the Marrero Wastewater pilot plant (fully aerobic system) revealed that the minimum solids contact chamber hydraulic residence (HRT) time in which bioflocculation occurs satisfactorily (effluent SS concentrations < 20 mg/L) is 15 min; however, in the combined anaerobic/aerobic system HRT< 100 minutes resulted in poor floc settling properties and turbid supernatants. Exocellular polymeric substances (EPS) have been found to be the key factor for bioflocculation to occur. Past studies in fully aerobic pilot plant demonstrated that the concentration of EPS increased with mixed liquor concentration and solids retention time. The main purpose of this research is to determine the effect of mixed volatile suspended solids(MLVSS), solids retention time(SRT), and dissolved oxygen(DO) in the production of EPS in the combined anaerobic/ solids contact chamber and its relationship with settling parameters. To carry out the objectives of this investigation three experimental phases were developed : 1) The MLVSS concentration was varied between 1000-4000 mg/l, keeping the SRT and DO as constant as possible 2) The SRT was changed between 2-8 days, keeping the MLVSS concentration between 1500-3500 mg/l and DO between 2-3 mg/l 3) the DO concentration was varied between 0-5mg/l. For a DO of zero, EPS were extracted from the sludge produced in the anaerobic reactor. Analysis of the data showed that the combined system proved to be unstable producing unexpected results such as no clear relationship between MLVSS and EPS. For a DO of zero, no EPS are produced and no flocculation takes place; therefore, effluents with poor quality can be expected from anaerobic treatment units. To meet secondary effluent standards in aeration chamber, capable of promoting the transformation from anaerobic to aerobic biota, and the generation of EPS, high SRT and HRT is required. Under these conditions the system anaerobic/solids contact chamber has an excellent potential for providing secondary treatment for municipal wastewater; nevertheless, the system is not as stable as the conventional aerobic one and bulking problems are common and difficult to content.

Sequencing batch reactor (SBR) systems were used for the development of a system and operating procedures for the high production of polyhydroxyalkanoates (PHAs) by wastewater treatment (activated sludge) bacterial cultures. It was found that unbalanced growth conditions stimulated massive PHA production in activated sludge biomass. Operating conditions had a significant effect on PHA production and the composition of the accumulated copolymer when either laboratory prepared mixtures of organics or a high acetic acid industrial wastewater were used as the organic substrate mixture. Fully aerobic (AE) conditions with nitrogen (N) and phosphorus (P) limitations were the optimum conditions for PHA production when the laboratory prepared mixtures of orgnics were used, while fully AE with the combinations of N, P, and potassium (K) limitations were better for PHA production using a high acetic acid industrial wastewater as the substrate. One nutrient limitation or partial limitation of either N or P as used for commercial production using pure cultures did not promote massive PHA production in activated sludge biomass compared to the combination of nutrient limitations. A maximum cellular PHA accumulation of 70%TSS was obtained under fully AE conditions with multiple alternating periods of growth and N&P limitations. Microaerophilic/aerobic (MAA/AE) or anaerobic/aerobic (AN/AE) cycling promoted less PHA production compared to fully AE conditions. The relative amounts of the PHA copolymers formed, i.e., polyhydroxybutyrate (PHB) and polyhydroxyvalerate (PHV) were different under different operating conditions, even though the types and amounts of volatile fatty acids (VFAs) in the feed were the same. It was determined that high total phosphorus (TP) content inside the bacterial cells had a significant detrimental impact on PHA production by activated sludge biomass. A two-stage bioprocess was a better approach for obtaining activated sludge PHA accumulation because a growth phase was necessary to grow the bacterial population that contains minimal TP before starting the subsequent PHA accumulation phase. Seeding sludge obtained from a conventional fully aerobic wastewater treatment system was more suitable than seed obtained from a biological phosphorus removal (BPR) system because bacterial populations from BPR systems tended to convert organic substrates to intracellular carbohydrate content rather than PHA under nutrient limitation conditions. The molecular weights and melting point temperatures of PHAs produced by the mixed culture of activated sludge biomass were comparable to those obtained from pure cultures and have the potential to be used for commercial applications. The results of this study indicate that activated sludge biomass has considerable potential for PHA production for commercial purposes, and likely could do so utilizing wastewater sources of organics. In particular organic rich, nutrient limited wastewaters have potential for efficient PHA production. / Ph. D.

Anaerobic digestion is widely used for stabilization of solids in sewage sludges. Recent changes in the priorities and goals of digestion processes are focusing more attention on the efficiency of these processes. Increasing hauling cost and restrictions for land applications are two factors which are driving the increased attention to digestion efficiency. Noxious odor production from the land applied biosolids is another important issue related to digestion efficiency. Existing anaerobic digestion or aerobic digestion processes failed to provide simultaneous solution to biosolids related problems i.e. simultaneous VS reduction, better dewatering of biosolids and lesser odors from the biosolids. Studies done by Novak et al. (2004) using different activated sludges show that anaerobic-aerobic digestion and aerobic-anaerobic digestion both increase volatile solids reduction compared to a single digestion environment. They proposed that there are 4 VS fractions in sludges: (1) a fraction degradable only under aerobic conditions, (2) a fraction degradable only under anaerobic conditions, (3) a fraction degradable under both anaerobic and aerobic conditions, and (4) a non degradable fraction. It has also been found (Akunna et al., 1993) that anaerobic-aerobic sequential treatment of wastewater can help in achieving substantial nitrogen removal. These results suggest that sequential anaerobic-aerobic digestion can address multiple biosolid related problems. This study was designed to understand the effect of sequential anaerobic-aerobic digestion on the properties of resulting effluent biosolids. The study was carried out in two operation phases and during both phases one digester was maintained at thermophilic conditions and the other at mesophilic temperature conditions. In first operation phase (Phase-I) thermophilic digester was operating at 20 day SRT and mesophilic anaerobic digester was at 10 day SRT. The aerobic digesters following anaerobic digesters were operating at 6 day SRT. In second operation phase (Phase-II), both thermophilic and mesophilic anaerobic digesters were operating at 15 day SRT and both had two aerobic digesters operating in parallel at 3 day and 6 day SRTs. In addition, batch experiments were also conducted to measure the performance of aerobic-anaerobic digestion sequence. Another study was carried out to understand the nitrogen removal mechanism during aerobic digestion of anaerobic digested sludge. The feed sludge was spiked with four different concentrations of nitrate and nitrite. It was observed during the study that aerobic digestion of anaerobic sludge helps in achieving higher Volatile solid reduction (~65% vs ~ 46% for mesophilic digestion and ~52% for thermophilic digestion). This result supports the hypothesis concerning the different fractions in volatile solids. Experimental results also show that the increase in VSR upon increasing anaerobic digestion SRT (more than 15 days) is less than the increase in the VSR due to the same increment of aerobic digestion SRT. Reduction in COD and VFA were also measured to be more than 50% during aerobic digestion. Investigation of nitrogen fate during the sequential anaerobic-aerobic digestion show more than 50% total nitrogen removal. Higher nitrogen removal was in thermophilic anaerobic – aerobic digester combination than that in mesophilic anaerobic–aerobic combination. The most probable reason for the removal was simultaneous nitrification and denitrification. Higher concentration of readily available VFA from thermophilic anaerobic digested sludge provide advantage in denitrification in following aerobic digester. The resulting biosolids produced during sequential digestion process were also analyzed for dewatering properties and odor production. Proteins and polysaccharides concentrations were observed to decrease during aerobic digestion for thermophilic anaerobic - aerobic digestion combination, while in another combinations polysaccharide concentrations increases at aerobic phase with 3 day digestion. The concentration of polysaccharides decreases at higher digestion period of 6 and 9. The result of decrease in polysaccharide and protein was reflected by the reduction in the polymer dose consumption and decrease in the optimum CST for the biosolids resulting from the sequential anaerobic aerobic digestion. Experimental results from odor experiments show that odor production potential of the biosolids decreases with increase in both anaerobic phase SRT and aerobic phase SRT. Thermophilic biosolids produces comparatively low odors but for longer periods, while mesophilic biosolids produces higher magnitude of odors during storage but only for comparative shorter period. Aerobic digestion of anaerobic sludge helps in reducing more than 50% odor production, but freeze-thaw cycle experiment shows that in both anaerobic and sequential anaerobic – aerobic digested sludges have higher potential for odor production. Higher aerobic digestion SRTs (6 days and above) shows more potential of reducing odors, but more experimental work is required to be done. / Master of Science

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Agro-industrial effluents are capable of causing great impact on water bodies if released without adequate treatment. The removal of the organic load in the conventional biological treatments is achieved with high generation of sludge and energy consumption. The usual techniques of biological removal of nitrogen load demand high deployment and maintenance costs in wastewater treatment units. Seeking the development of a technology that can be employed in treatment units already in operation without high costs of installation and operation, an anaerobic and aerobic reactor using the technique of bioaugmentation and a fixed bed reactor for nitrification were built in scalebench. Real effluent was collected from a meat packing company and microorganisms of high rate of consumption for bioaugmentation were purchased commercially. The biological system was operated continuously with the anaerobic and aerobic reactor in sequence and with recirculation of supernatant from the anaerobic reactor to the nitrifying one. After percolating in the nitrifying reactor, the supernatant was drained back to the bottom of the anaerobic reactor, so that came in contact with the clay formed the bottom of it, making possible the denitrification of nitrogen compounds. Assays were performed under two conditions of flow rate: 2.5 and 5.0 L/day, resulting in organic loading conditions (COA) corresponding to 3.7 and 19.6 gDQOsolúvel/day under constant temperature of 30°C. The anaerobic reactor was evaluated at temperatures of 20 and 30ºC. The nitrification system was tested only for 19.6 gDQOsolúvel/day condition of load. The variations of chemical oxygen demand (COD), soluble COD, NH3, turbidity and suspended solids in each reactor and in the whole system were analized. Were obtained removal of 76.9% soluble COD in the system to the condition of lower COA and 71.1% to 19.6 gDQOsolúvel/day. The microorganisms tested presented solids generation rate (μ) from 0.035 to 0.19 gSSV/gSSV*day, these values are about 10 times lower than those reported for systems without bioaugmentation. The coefficients of biomass growth (Y) and maximum specific substrate consumption (k) were close to those systems without use of the bioaugmentation, indicating that the main advantage of this technique is the lower generation of sludge. It was found that the anaerobic system with bioaugmentation is more resistant to temperature changes compared to the usual system as to reduce the temperature 10°C, there was a reduction of only 27.6% for COD removal. The removal efficiency of NH3 in the system before and after use of the nitrifying reactor was 38.8 and 62%, respectively, indicating that binding of recirculation of the supernatant of the anaerobic reactor to a nitrification reactor designed specifically to allow removing the ammonia load in the effluent. / Efluentes agroindustriais são capazes de causar grande impacto em corpos d água se lançados sem tratamento adequado. A remoção da carga orgânica nos tratamentos biológicos convencionais é conseguida com elevada geração de lodo residual e consumo energético. As técnicas usuais de remoção biológica da carga nitrogenada demandam altos custos com implantação e manutenção nas unidades de tratamento de efluentes. Buscando o desenvolvimento de uma tecnologia que possa ser empregada em unidades de tratamento já em funcionamento sem elevados custos de instalação e operação, um reator aeróbio e um anaeróbio com uso da técnica da bioaumentação e um reator para nitrificação de leito fixo foram construídos em escala de bancada. Efluente real foi coletado de uma empresa frigorífica e microrganismos de alta taxa de consumo para a bioaumentação foram adquiridos comercialmente. O sistema biológico foi operado de forma contínua, com o reator anaeróbio e aeróbio em sequência e com recirculação do sobrenadante do anaeróbio ao reator nitrificante. Após percolar no reator nitrificante, este sobrenadante era drenado de volta ao fundo do reator anaeróbio, de forma com que entrasse em contato com o lodo formado ao fundo do mesmo e possibilitasse e denitrificação dos compostos nitrogenados. Os ensaios foram realizados sob duas condições de vazão: 2,5 e 5,0 L/dia, que resultaram em condições de carga orgânica aplicada (COA) correspondentes a 3,7 e 19,6 gDQOsolúvel/dia e sob temperatura mantida constante em 30ºC. O reator anaeróbio foi avaliado sob as temperaturas de 20 e 30ºC. O sistema de nitrificação foi testado somente para a condição de 19,6 gDQOsolúvel/dia de carga. Foram avaliadas as variações nos teores de DQO, DQO solúvel, NH3, turbidez e sólidos suspensos em cada reator e no sistema todo. Obteve-se até 76,9% de remoção de DQO solúvel no sistema para a condição de COA mais baixa e 71,1% para COA de 19,6 gDQOsolúvel/dia. Os microrganismos testados apresentaram taxa de geração de sólidos de 0,035 a 0,19 gSSV/gSSV*dia, valores estes em torno de 10 vezes menor que os reportados para sistemas sem bioaumentação. Os coeficientes de crescimento de biomassa (Y) e de taxa máxima específica de consumo de substrato (k) ficaram próximos aos valores para sistemas sem uso da bioaumentação, indicando que a principal vantagem do uso desta técnica está na baixa geração de lodo. Verificou-se que o sistema anaeróbio bioaumentado resiste melhor a variações de temperatura frente aos sistemas usuais, pois para redução de 10ºC na temperatura, observou-se a redução de apenas 27,6% na remoção de DQO. A eficiência de remoção de NH3 no sistema antes e depois da utilização do reator nitrificante em paralelo foi de 38,8 e 62%, respectivamente, indicando que a ligação do sistema de recirculação do sobrenadante do reator anaeróbio até um reator desenvolvido especificamente para nitrificação possibilita a remoção da carga amoniacal do efluente.

The treatability of a high strength industrial wastewater, 9,000 mg/L as chemical oxygen demand (COD), by three sequencing batch reactor (SBRs) systems operated under alternating redox environments: anaerobic/aerobic (ANA), anoxic/aerobic (ANX), and aerobic was investigated. A synthetic wastewater was modeled after a wastewater from an existing chemical processing facility. The largest component, hydroxypivaldehyde, was unavailable for the use in this research and was substituted by pivalic acid, both of which have a tertiary carbon. No significant degradation occurred in the anaerobic phase of operation; however, 55-65% of the COD was removed during anoxic operation. Simultaneous removal of pivalic acid and acetic acid was seen in both the anoxic and aerobic reaction phases. The anoxic/aerobic SBR provided the best overall treatability of the synthetic wastewater based on: effluent quality, sludge characteristics and settling properties. The results suggested that anoxic/aerobic treatment schemes are a viable treatment alternative for industrial wastewaters containing high concentrations of organic acids, including acids with tertiary carbons. The treatability of the three alternating redox environments on the Industry's wastewater was also investigated. Again, no significant degradation of the industrial wastewater occurred during the anaerobic reaction phase. During the anoxic reaction phase, 15-20% of the COD was removed from the industrial wastewater in contrast to the high removals seen with the synthetic wastewater. The aerobic SBR provided the best COD removal for the industrial wastewater. The performance differences between the synthetic and industrial wastewaters stress the importance of treatability studies on the actual industrial wastewater. Biological treatment of the synthetic and Industry wastewaters was unable to achieve the effluent goal of 100 mg/L as COD. Sand filtration followed by granular activated carbon adsorption treatment of the effluent from the synthetic wastewater-fed ANA SBR provided the COD removal necessary to achieve the effluent goal. / Master of Science

Solids handling can contribute to a significant portion of the operational costs of a wastewater treatment plant, contributing up to 50% of the total expenses in certain instances. Sludge dewatering and drying therefore become necessary not only from the operational perspective, but also from the economical viewpoint. The J-Vap process combines the above-mentioned processes, by pressure filtration of sludge followed by application of vacuum and heat. However, when cationic polymer conditioned sludge is dewatered in the J-Vap, the polymer is suspected to interact with the filter media at high temperatures, resulting in the formation of a skin layer that hinders efficient dewatering. The first part of the study has looked at various digestion processes and how they affect the skin formation phenomenon. The results showed that temperature played a significant role in determining the amount of polymer that adhered to the filter media. The second part of the study focused on different kinds of digestion processes and their effects on extracellular polymeric substances, bound water content and dewatering. Bound water tests were used to determine the maximum achievable solids concentration on dewatering. Bound water content of solids obtained from field centrifuges run at different torques and g values were evaluated and fitted on a standard graph obtained from lab pressed sludge with different solids concentration. The bound water was seen to decrease with increasing solids content till 20%, after which a nearly constant 1.0 g of bound water was present for every gram of dry solids seen. The results indicate that nearly 50% solids concentration could be achieved on mechanical dewatering. In reality, only 30 to 35% solids concentration was attained both in the lab and on the field. It was determined that dilatometry attributed the increase in cake solids to the decrease in bound water. However, the use of bound water as a predictive tool for determining cake solids was not practical since the bound water calculations use the solids content in the calculations. / Master of Science

<p> The anaerobic-to-aerobic power ratio is a useful tool to evaluate the strengths and weaknesses of both the aerobic and anaerobic energy systems. The traditional method of calculation has shown this ratio to increase with age in children and to plateau by late adolescence or early adulthood. However, by using the traditional approach, the aerobic component of the ratio is likely highly influenced by anaerobic sources and therefore, may not demonstrate the true proportional changes observed in the respective physiological capacities comprising this ratio with age through childhood and adolescence. The purpose of this study was to examine the age-related development of the power ratio using two new approaches. The lactate threshold (LT) and ventilatory anaerobic threshold (VAT) were identified in 31 competitive male hockey players ranging from 10 to 21 years of age and compared across three discrete age groups. Peak mechanical anaerobic power was obtained from a Wingate test (WAnT) and incorporated into the numerator of the power ratio, while peak mechanical aerobic power was obtained from a modified McMaster all-out progressive test and included into the denominator of the ratio. Mechanical power at the LT and VAT were also identified and integrated into the denominator of the power ratio and results compared to the traditional approach to identify similarities or differences in developmental trends with age. Furthermore, the reliability of the traditional, LT and VAT approaches was examined with retests of six subjects using intra-class correlation analysis and Method Error analysis. When power ratio approaches were compared among discrete age groups, significant differences (P≤0.05) were found between the youngest and oldest age groups for each of the three approaches. Notwithstanding the trend for progressive increases with advancing age group for all approaches, significant correlations with age were only found for the traditional approach (r=0.36). Finally, the VAT approach was the most reliable (r=0.95; ME=0.13) while the LT and traditional approaches demonstrated strong but non-significant test-retest correlations. Results of this study suggest that the LT and VAT approaches may theoretically be more accurate methods of measuring the power ratio than the traditional approach, as there is likely less anaerobic contribution to the denominator of the ratio. Each of the new approaches demonstrates expected age-related trends, and notwithstanding methodological and sample limitations, the VAT in particular, appears to be a more reliable and accurate means of assessing the power ratio compared to the traditional or LT approach.</p> / Thesis / Master of Science (MSc)

Este trabalho buscou avaliar o desempenho de um reator de leito fixo e escoamento ascendente, operado de modo contínuo, com argila expandida e espuma de poliuretano como suportes para imobilização da biomassa, no tratamento de água residuária proveniente de abatedouro de aves. Na primeira fase do trabalho, o reator foi operado em condição anaeróbia e anaeróbia-aeróbia, no tratamento da água residuária bruta proveniente do abatedouro. No entanto, sua eficiência na redução de matéria orgânica pode ser atribuída a processos de adsorção e não biodegradação, o que resultou em períodos de operação curtos devido à obstrução do leito reacional. Na segunda fase, o reator foi alimentado com água residuária coletada após o pré-tratamento por sistema de flotação por ar dissolvido (FAD), realizado no próprio abatedouro, com intuito de minimizar a carga lipídica e a concentração de sólidos na entrada do reator. Assim, a vida útil do reator foi prolongada, com eficiências médias de remoção de DQO e nitrogênio total de 90 \'+ OU -\' 4% e 44 \'+ OU -\' 10%, respectivamente, e eficiência de desnitrificação de 89 \'+ OU -\' 6%, para o reator anaeróbio-aeróbio com razão de recirculação do efluente líquido igual a 1,5. Assim, o reator demonstrou bom desempenho na remoção simultânea de matéria orgânica e nutrientes, desde que seja precedido por sistema de pré-tratamento para remoção parcial de sólidos e óleos e graxas. / This work aimed to evaluate the performance of an up-flow fixed bed reactor, operated in a continuous way, using expanded clay and polyurethane foam as supports for immobilization of the biomass, for treatment of poultry slaughterhouse wastewater. Initially, the reactor was operated under anaerobic and anaerobic-aerobic conditions for the treatment of poultry slaughterhouse wastewater. However, the COD removal efficiency was related to adsorption and not to biodegradation processes. In this way, the operational periods were short due to solids retention in the system. In the second part of this work, trying to reduce the lipids and solids concentration in the reactor\'s affluent, the wastewater was collected after a pre-treatment installed at the poultry slaughterhouse. This pre-treatment was constituted of a dissolved air flotation (DAF) system. As a result, the operational longevity of the reactor was increased and the COD and total nitrogen removal efficiencies were 90 \'+ OU -\' 4% and 44 \'+ OU -\' 10% respectively, and the denitrification efficiency was 89 \'+ OU -\' 6% under an anaerobic-aerobic condition with a recycle ratio of the liquid phase of 1,5. Therefore, the reactor showed a good performance in reducing the organic matter and removing nutrients simultaneously, since it is preceded by a pre-treatment for the partial removal of solids, oils and grease.

O presente projeto avaliou uma célula combustível microbiana (CCM) composta de um reator combinado (anaeróbio e aeróbio), operada em fluxo contínuo com tempo de detenção hidráulico de 12 horas, alimentada com esgoto sintético (487 \'+ OU -\' 115 mg DQO/L) e esgoto sanitário (631 \'+ OU -\' 213 mg DQO/L). A estabilidade da CCM variou conforme as características do substrato aplicado. A eficiência de remoção de DQO ficou em 61 \'+ OU -\' 17; 67 \'+ OU -\' 26%, para esgoto sintético e sanitário respectivamente. Em média tensão obtida com o esgoto sintético foi de 76 mV com picos - 112,5 e 409 mV, enquanto que com o esgoto sanitário foi possível obter 52,1 mV na média e pico de geração em 325 mV. A potência variou de 10-150 mW/\'M POT.2\' com resistências entre 50-650 \'ômega\'. A geração de energia elétrica não apresentou relação linear com a DQO consumida em nenhum dos casos. A aplicação de barras de grafite como eletrodos se mostrou satisfatória na condução da corrente elétrica, o fator limitante foi a transferência de massa, principalmente a transferência de prótons do anodo para o catodo e a difusão de oxigênio para o anodo. Contudo os resultados obtidos demonstraram que é possível gerar eletricidade e, simultaneamente, tratar esgoto sanitário. / This project evaluated a microbial fuel cell (MFC) consisting of combined reactor (anaerobic and aerobic), operated in continuous flow with hydraulic detention time of 12 hours, fed with synthetic wastewater (487 \'+ OR -\' 115 mg COD/L) and wastewater (631 \'+ OR -\' 213 mg COD/L). The stability of the CCM varied according to the characteristics of the substrate applied. The efficiency of COD removal was at 61 \'+ OR -\' 17; 67 \'+ OR -\' 26 for synthetic wastewater and sawage respectively. On a average voltage obtained with synthetic wastewater was 76 mV with peaks - 112.5 and 409 mV, while the wastewater was obtained 52.1 mV on average peaks generation at 325 power was varied from 10-150 mW/\'M POT.2\' with resistances between 50-650 \'ômega\'. The power generation showed no liner relationship with the COD consumed in any case. The application of graphite rods as electrodes were satisfactory in the conduction of electrical of protons from the anode to the cathode and the diffusion of oxygen to the anode. However the results showed that it is possible to generate electricity while simultaneously treating sewage.

Submitted by Lucienne Costa (lucienneferreira@ufcg.edu.br) on 2018-09-13T17:38:25Z No. of bitstreams: 1 LAIO ARIEL LEITE DE PAIVA – DISSERTAÇÃO (PPGECA) 2016.pdf: 2279883 bytes, checksum: ddf555f3b9251dc01dc78d5b5fe5df71 (MD5) / Made available in DSpace on 2018-09-13T17:38:25Z (GMT). No. of bitstreams: 1 LAIO ARIEL LEITE DE PAIVA – DISSERTAÇÃO (PPGECA) 2016.pdf: 2279883 bytes, checksum: ddf555f3b9251dc01dc78d5b5fe5df71 (MD5) Previous issue date: 2016-02-29 / Capes / Sistemas anaeróbios modernos de tratamento de esgoto doméstico, embora bastante eficientes na remoção de matéria orgânica e sólidos em suspensão, não produzem um efluente com qualidade compatível com os padrões legais para descarga em corpos d’água receptores. Por essa razão esses sistemas têm que ser associados a unidades de pós-tratamento. Este trabalho trata de uma investigação experimental sobre a viabilidade de se aplicar o sistema de lodo ativado como uma alternativa do pós-tratamento, especificamente para o caso em que se prevê o efluente final para reúso. Na investigação experimental se usou um reator de bateladas sequenciais (RBS) em escala de bancada como unidade de pós-tratamento. Os resultados experimentais mostraram que a qualidade de efluente do sistema RBS de pós-tratamento em relação a matéria orgânica é muito boa. Na otimização do reator RBS se desenvolveu um modelo que permite estabelecer o tempo de permanência mínimo para o pós-tratamento em função de dois parâmetros básicos: a constante de utilização de material orgânico biodegradável pelas bactérias heterotróficas do lodo gerado no sistema de pós-tratamento e a sedimentabilidade deste lodo. A constante de utilização de material orgânico foi determinada por testes respirométrico. O lodo gerado no sistema de pós-tratamento surpreendentemente mostrou ter uma sedimentabilidade bem superior àquela normalmente encontrada em sistemas de lodo ativado tratando esgoto bruto, o que constitui um argumento sólido para a aplicação do sistema RBS na prática de pós tratamento do efluente do reator UASB. / Modern anaerobic systems for domestic sewage treatment, although very effective in removing organic matter and solid suspended, do not produce an effluent quality compatible with the legal standards for discharge into water bodies’ receivers. Therefore, such systems have to be associated with post treatment units. This paper deals with an experimental investigation into the feasibility of applying the activated sludge system as an alternative post-treatment, specifically for the case where intended use of the treated wastewater is reuse. In the experimental investigation research, a sequencing batch reactor (RBS) at bench scale was use as post treatment. The experimental results showed that the effluent quality of the RBS post treatment system in relation to organic matter was very good. An algorithm to optimize the RBS reactor was developed and allowed establishing the minimum residence time for the post-treatment in terms of two basic parameters: the utilization constant of biodegradable organic material by heterotrophic bacteria in the post-treatment system and the sludge settleability. The organic material using respirometric constant was determined from the oxygen uptake rate during the post treatment. The sludge from the post-treatment system surprisingly showed a much better settleability than what normally found in activated sludge systems treating raw sewage, which provides a strong argument for the application of the RBS system in practice post-treatment of the UASB reactor effluent.