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RESUMO Esta pesquisa propôs o desenvolvimento de um sistema de biofiltros submersos (SBS), modificados com base na configuração de filtros de pedra, visando ao pós-tratamento do efluente de lagoas de estabilização, inicialmente para a remoção de algas. Foram implantados 2 conjuntos de biofiltros submersos para captar esgoto tratado de duas diferentes profundidades de uma lagoa de maturação - a 60 cm (em uma zona dessa lagoa chamada superficial - ZS) e a 180 cm (em outra zona dessa lagoa chamada intermediária - ZI). Foi utilizada, como recheio dos biofiltros submersos, pedra brita nº 3, nas seguintes alturas de leito filtrante: 50, 100, 150 e 200 cm, tendo por objetivo avaliar a influência desse fator sobre a eficiência de remoção de algas mediante análise de clorofila A e outras 16 variáveis de qualidade associadas neste estudo. Obtiveram-se eficiências para demanda química de oxigênio (DQO) no intervalo de 65 a 80% para ZS e, para ZI, os resultados dessa eficiência tiveram muita variação, sem estabilidade - de forma prática, portanto, o ponto de coleta na ZI mostrou-se não recomendado. Quando às eficiências para clorofila A, para ZS, o intervalo alcançado variou de 65 a 99% e, para ZI, esses resultados foram inferiores aos da ZS. Concluiu-se que a extração a partir da zona superficial da lagoa de maturação e uma profundidade de leito entre 150 e 200 cm foram os parâmetros operacionais que levaram a um melhor desempenho global dos biofiltros submersos modificados e, mais especificamente, quanto às seguintes variáveis: DQO, demanda bioquímica de oxigênio (DBO), clorofila A e sólidos totais.

This article reports a study of five designs of vinasse biorefineries that incorporate anaerobic bioreactors followed by a concentration technology such as evaporation, reverse osmosis, or forward osmosis. Different techniques of draw solution regeneration – evaporation, reverse osmosis, and membrane distillation – were also analyzed. Exergy analysis, a method that evaluates the resource conversion efficiency of systems, was used to compare the alternatives. The results indicated that among the alternatives analyzed, the combination of anaerobic digestion and reverse osmosis presented the highest exergy efficiency (62%). However, evaporators were the most feasible in terms of costs. Both alternatives are interesting and the final choice depends on the technology available and local economy. In any case, the treatment of 491.76 m3/h of vinasse (exergy rate of 60513.8 kW) to recover 70% of water could reduce external water requirement by 66% and generate 28% additional electricity for the sugarcane plant. In this case, the water recovery could represent an economy of 8,490,435.76 USD/year for the Brazilian alcohol industry.

Recirculation of treated effluent is usually used to prevent organic overloading events in anaerobic digestion of high concentrated wastewater. The aim of this study was to determine the influence of effluent recirculation in anaerobic baffled reactors (ABR) treating high concentrated wastewater as the literature is not conclusive about its effects. To achieve this, an innovative experimental and mathematical modeling dual approach was used. A bench-scale ABR was fed with sugarcane vinasse (COD = 18.0 g L−1) and monitored for 273 days. Real kinetic and mass transfer parameters were obtained and used to create a mathematical model for the organic matter conversion. Operating data and the kinetic parameters showed that at high COD concentrations the ABR does not behave as a two-stage system as expected. Both results, i.e. the mathematical model and the operational data, showed that in terms of conversion capacity using high recirculation ratios is not necessary for suitable ABR performances, only increasing operational costs due to pumping.

The gradual increase in organic loading is a strategy that has been used in reactor operation of wastewater treatment to adapt the microbial community and its metabolic activities. Within this context, the aim of this research was to investigate the microbial community present in an anaerobic chambered reactor (ACR) operating for 270 days treating ethanol distillery stillage. The operation the ACR reactor started with low feed rate which was increased gradually so that the organic load rate (OLR) ranged from 0.5 to 2.5 g COD m−3 day−1. Performance monitoring included physicochemical analyses, methane production, microscopy, and biomolecular analyses. The operational data shows satisfactory performance in terms of COD removal, averaging over 92.5%. DGGE analyses revealed that the structure of the microbial community of Bacteria domain is more sensitive to reactor operational conditions than that of the Archaea domain, when the OLR increased. A clear relationship was observed between the microbial diversity and the dominance for Bacteria and Archaea domains to different OLR, indicating adaptation of communities to the operating conditions imposed on the ACR.

This study investigated the influence of a previous sugarcane vinasse coagulation, by using a calcium-based biopolymer, on anaerobic treatment in a lab-scale reactor. Two anaerobic reactors (R1 and R2) were operated for 155 days. R1 was fed only with raw sugarcane vinasse and R2 was fed with pretreated effluent. The operation was divided into three stages: E1 (inoculation and adaptation); E2; and E3. The major difference between E2 and E3 was the fact that R2 failed at the end of E2. Thus, R2 was recovered by applying a low organic loading rate (OLR) of raw vinasse for 29 days. In E2 and E3, for both reactors, pH, alkalinity, COD (influent and effluent samples), and methane production were monitored. During E1, an OLR of 2.0 kgCOD. m-3.d-1 1 was applied, and R1 and R2 sludges showed good adaptation to the wastewater in this condition. Then, the OLR was progressively increased to 7.0 kgCOD.m-3.d-1 in both systems. The average COD removal efficiencies were 82.9 ± 4.4% and 72.2 ± 18.1% for R1 and R2, respectively. R2, operated with pretreated vinasse, showed a decrease in the COD removal and methane production, which could be caused by the biopolymer presence. The average COD removal efficiencies in E3 were 77.5 ± 9.4% and 79.2 ± 9.7% for R1 and R2, respectively. After 155 days of operation, a decrease in the COD removal and methane production was identified again in R2, indicating a new failure. The quality of sludge granules from the inoculum and also from the granules developed at the end of R1 and R2 operation was analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). These analyses indicated a rise in the rugosity of R1 and R2 granules, possibly due to the deposition of sedimentable compounds present in both raw and pretreated vinasse. The EDS analyses indicated a high presence of calcium in R2 granules, indicating that this compound acted in the reduction of mass transfer between organic load from vinasse and the granules’ microbiota.

Due to the complexity of some managerial problems, especially those related to sanitation, academic studies have shown the need to use appropriate methods to assist in this type of decision. Within this context, this research aimed to provide a review of the literature from the field of decision sciences to the field of water resource management. It was identified in this study that the use of multi-criteria methods, including Analytical Hierarchy Process, Measuring Attractiveness by a Categorical based Evaluation Technique, Multiattribute Utility Theory, Elimination et Choice Traduisant la Realité, Preference Ranking Organization Method for Enrichment Evaluations, Technique for Order Preference by Similarity to Ideal Solution, and game theory, including cooperative and non-cooperative bargaining games, are useful for creation and comparison of scenarios, reducing the time needed to reach a solution for complex problems involving a large number of criteria and agents. It also demonstrated the benefits of creating greater transparency in the decision-making process, thus increasing the potential for a solution acceptable to all the parties involved. Although still little explored, discussions of sanitation problems can and should be enhanced with the use of techniques and methods of decision sciences, and multi-criteria and game theory techniques are particularly suitable for this task.

Nitrous oxide (N

Nitrous oxide (N2O) is one of the gases with the greatest impact in the atmosphere due to its persistence and significant contribution to the greenhouse effect. This study provides an insight into the dynamics of N2O production in wastewater nitrogen removal systems. A 10 L sequencing batch reactor containing enriched anammox biomass was subjected to different operational conditions, i.e., temperature, feed time, NO2−/NH4+ ratio and the initial concentrations of NH4+ and NO2−. Tests showed no significant differences in maximum N2O production when the system was operated with a shorter feed time and no increase in the operating temperature. A higher N2O production was observed when the initial NO2−/NH4+ ratio increased from 1.3 to 1.7 and 1.9. The highest initial concentration of NO2− was linked to an increase in residual N2O at the end of the batch cycle, probably due to heterotrophic denitrifying metabolism.

The microbiological characterization by molecular techniques (DGGE and quantitative PCR) of Archaea, Bacteria domain and sulfate-reducing bacteria (SRB) from a laboratory scale Up-flow Anaerobic Sludge Blanket (UASB) processing sugar cane vinasse was performed during the operational phase with increasing organic loads. The organic load removal efficiency was between 97% and 75% for volumetric organic loads (VOL) in the range of 0.6 to 15.4 kgCOD.m-3.d−1 and for higher VOL (until 27.0 kgCOD.m-3 .d−1) the removal efficiency decreased to 48%. Archaea represented the majority of the estimated population (107 copies of 16S RNA ribosomal gene. mL-1) followed by bacteria (106 copies of 16S RNA ribosomal gene. mL-1) and sulfate-reducing bacteria (SRB) (105 copies of dsrB gene. mL-1). There was a significant difference between the populations of Archaea and SRB with increasing VOL. DGGE profiles show differences among populations with increasing VOL, especially with respect to sulfate-reducing bacteria. The presence of SRB together with a high sulfate removal percentage (97%) of about 15 kgCOD.m-3d-1h, indicates the establishment of a sulfidogenic process.

A pilot-scale upflow anaerobic sludge blanket (UASB) reactor (120 L) was operated for biogas production by vinasse degradation. The reactor was operated for 700 days using a recirculation rate of 1:3 with organic loading rates (OLR) ranging from 0.5 to 32.4 kgCOD.m−3.d−1, upflow velocities ranged from 0.008 to 0.292 m h−1(feed added with recirculation) and the hydraulic retention time ranged from 33.33 to 0.86 days. The reactor demonstrated a stable performance at OLR at all applied loads. The COD removal efficiencies throughout the experiment were 87.5 ± 5.3 and 90.5 ± 3.6% for raw and soluble COD, respectively. Total volatile acids ranged from 59 mg L−1 to 585 mg L−1. The concentration of acetic and propionic acids at the reactor effluent reached 28 mg L−1 on OLR 20 kgCOD.m−3.d−1. The methane content in the biogas was 68.8 ± 7.14%.The methane yield of 0.299 ± 0.066 LCH4.g−1COD corresponds to about 76.4% of the theoretical methane yield. The methane productivity reached the highest value of 8.059 LCH4.L−1.d−1 at 32.27 kgCOD.m−3.d−1., corresponding to 83.9% of the theoretical value (9.611 LCH4.L−1.d−1). This result is very promising for power generation in the sugar and ethanol industry, complementing the energy balance of sugarcane, as shown by an energy balance evaluation.

This paper assesses a wastewater treatment plant (WWTP) regarding the technology used, as well as organic matter and nutrient removal efficiencies aiming to optimize the treatment processes involved and wastewater reclamation. The WWTP consists of a dissolved air flotation (DAF) system, an upflow anaerobic sludge blanket (UASB) reactor, an aerated-facultative pond (AFP) and a chemical-DAF system. The removal efficiencies of chemical oxygen demand (COD) (97.9 ± 1.0%), biochemical oxygen demand (BOD) (98.6 ± 1.0%) and oil and grease (O&G) (91.1 ± 5.2%) at the WWTP, the nitrogen concentration of 17 ± 11 mgN-NH3 and phosphorus concentration of 1.34 ± 0.93 mgPO4−3/L in the final effluent indicate that the processes used are suitable to comply with discharge standards in water bodies. Nitrification and denitrification tests conducted using biomass collected at three AFP points indicated that nitrification and denitrification could take place in the pond.

Pulp and paper mill effluents represent a challenge when treatment technologies are considered, not only to reduce organic matter, but also to reduce the toxicological effects. Although anaerobic treatment has shown promising results, as well as advantages when compared with an aerobic system, this process alone is not sufficient to reduce recalcitrant compounds. Thus, an advanced oxidation process was applied. This experiment was performed to determine the effect of ozone and ozone/UV treating a horizontal anaerobic immobilized biomass reactor effluent from a kraft cellulose pulp mill for 306 days with an organic volumetric load of 2.33 kgCOD/m3/day. The removal of organic compounds was measured by the following parameters: adsorbable organically bound halogens (AOX), total phenols, chemical oxygen demand (COD), dissolved organic carbon and absorbance values in the UV-visible spectral region. Moreover, ecotoxicity and genotoxicity tests were conducted before and after treatment with ozone and ozone/UV. At an applied ozone dosage of 0.76 mgO3/mgCOD and an applied UV dosage of 3.427 Wh/m3, the organochlorine compounds measured as AOX reached removal efficiencies of 40%. Although the combination of ozone/UV showed better results in colour (79%) and total phenols (32%) compared with only ozone, the chronic toxicity and the genotoxicity that had already been removed in the anaerobic process were slightly increased.

This study reports on the application of an innovative structured-bed reactor (FVR) as an alternative to conventional packed-bed reactors (PBRs) to treat high-strength solid-rich wastewaters. Using the FVR prevents solids from accumulating within the fixed-bed, while maintaining the advantages of the biomass immobilization. The long-term operation (330days) of a FVR and a PBR applied to sugarcane vinasse under increasing organic loads (2.4-18.0kgCODm-3day-1) was assessed, focusing on the impacts of the different media arrangements over the production and retention of biomass. Much higher organic matter degradation rates, as well as long-term operational stability and high conversion efficiencies (>80%) confirmed that the FVR performed better than the PBR. Despite the equivalent operating conditions, the biomass growth yield was different in both reactors, i.e., 0.095gVSSg-1COD (FVR) and 0.066gVSSg-1COD (PBR), indicating a clear control of the media arrangement over the biomass production in fixed-bed reactors.

This paper discusses the performance of a poultry slaughterhouse wastewater treatment plant (WWTP) in a tropical country and operating strategies that were applied over 84 months to this WWTP. The WWTP consisted of a dissolved air flotation (DAF) system, anaerobic ponds (APs) and a facultative pond (FP). The organic loading rates applied to the APs ranged from 0.26 to 1.05 kg BOD/m 3 day, and the hydraulic retention time ranged from 2.2 to 3.8 days. The resultant COD and BOD removal efficiencies were 42 ± 11% and 38 ± 15%, respectively. The FP surface loading was up to 983 kg BOD/ha day. The main observed events in the WWTP processes over this period were organic overload, low chemical oxygen demand (COD) and biochemical oxygen demand (BOD) removal efficiencies and color change from green to reddish at the FP. Molecular biology techniques were used to identify microbial groups in the FP in the period of low organic matter removal efficiency and when the liquid became reddish. Sunny conditions favored anoxygenic photosynthesis, the growth of purple nonsulfur bacteria (such as Rhodocyclales -like organisms), and green nonsulfur bacteria (such as Chloroflexi -like organisms). Mechanical aeration at the inlet of the FP restored the water to its original color and increased the COD and BOD removal efficiencies. Based on the BOD removal efficiencies of 89%, after the installation of aerators, the operating strategies illustrate the WWTP system's capacity and versatility to adapt to load variations.

The main objective of this work was to evaluate the use of game theory as a strategic tool for watershed management decision-making. An engineering problem case study was used in which three organizations compare various scenarios when deciding where to locate a polluting plant on a watershed. Six games were modeled to provide a variety of conditions that could feasibly be implemented and were simulated using software for finding Nash Equilibria solutions. The results show that game theory can provide key insights, such as the consideration of other players' strategies, and identify possible pitfalls that may occur when the companies seek only to maximize their individual profitability. Resumo O principal objetivo deste trabalho foi avaliar o uso da teoria dos jogos como uma ferramenta estratégica para a tomada de decisão no gerenciamento de bacias hidrográficas. Como estudo de caso foi utilizado um problema de engenharia em que três organizações comparam vários cenários ao escolher um local para instalar uma planta poluidora em uma bacia hidrográfica. Seis jogos foram modelados para fornecer uma variedade de condições que as empresas poderiam ser implementadas e foram simuladas usando um software para procurar Equilíbrios de Nash. Os resultados mostram que a teoria dos jogos pode fornecer informações importantes, como a consideração das estratégias dos outros agentes, e identificar possíveis armadilhas quando as empresas procuram apenas maximizar a sua própria rentabilidade.

Effluents originated in cellulose pulp manufacturing processes are usually toxic and recalcitrant, specially the bleaching effluents, which exhibit high contents of aromatic compounds (e.g. residual lignin derivates). Although biological processes are normally used, their efficiency for the removal of toxic lignin derivates is low. The toxicity and recalcitrance of a bleached Kraft pulp mill were assessed through bioassays and ultraviolet absorption measurements, i.e. acid soluble lignin (ASL), UV280, and specific ultraviolet absorption (SUVA), before and after treatment by an integrated system comprised of an anaerobic packed-bed bioreactor and oxidation step with ozone. Furthermore, adsorbable organic halides (AOX) were measured. The results demonstrated not only that the toxic recalcitrant compounds can be removed successfully using integrated system, but also the ultraviolet absorption measurements can be an interesting control-parameter in a wastewater treatment.

A escolha de uma alternativa tecnológica para tratamento de efluentes, assim como o local para implantação deve ser precedida de um estudo de sustentabilidade do ambiente. Foi proposto um método para avaliação da sustentabilidade de estações de tratamento de esgoto, baseado nas características ambientais, sociais e econômico-financeiras dessas unidades. O método foi aplicado em três ETE, constituídas por lagoas de estabilização, localizadas nos municípios de Cajati, Jacupiranga e Pariquera-Açu, todas pertencentes à bacia do Baixo Ribeira de Iguape (SP). A falta de dados para alguns parâmetros considerados na composição dos indicadores prejudicou a obtenção de valores mais realistas. O método proposto mostrou-se de fácil visualização da condição de sustentabilidade das ETE constituídas por lagoas de estabilização. The choice of an alternative technology for effluent treatment as well as the location for deployment must be preceded by a study of environmental sustainability. A method for assessing the sustainability of wastewater treatment plants, based on environmental, social and economic-financial characteristics was proposed. The method was applied to three wastewater treatment plants using stabilization ponds, located in the municipalities of Cajati, Jacupiranga and Pariquera-Açu, all belonging to the Lower Ribeira de Iguape River basin, in the state of São Paulo, Brazil. The lack of values for some parameters considered in the formulation of indicators undermined the achievement of more realistic values. The proposed method proved to be easy to visualize the condition of sustainability of wastewater treatment stations using stabilization ponds.

A escolha de uma alternativa tecnológica para tratamento de efluentes, assim como o local para implantação deve ser precedida de um estudo de sustentabilidade do ambiente. Foi proposto um método para avaliação da sustentabilidade de estações de tratamento de esgoto, baseado nas características ambientais, sociais e econômico-financeiras dessas unidades. O método foi aplicado em três ETE, constituídas por lagoas de estabilização, localizadas nos municípios de Cajati, Jacupiranga e Pariquera-Açu, todas pertencentes à bacia do Baixo Ribeira de Iguape (SP). A falta de dados para alguns parâmetros considerados na composição dos indicadores prejudicou a obtenção de valores mais realistas. O método proposto mostrou-se de fácil visualização da condição de sustentabilidade das ETE constituídas por lagoas de estabilização.The choice of an alternative technology for effluent treatment as well as the location for deployment must be preceded by a study of environmental sustainability. A method for assessing the sustainability of wastewater treatment plants, based on environmental, social and economic-financial characteristics was proposed. The method was applied to three wastewater treatment plants using stabilization ponds, located in the municipalities of Cajati, Jacupiranga and Pariquera-Açu, all belonging to the Lower Ribeira de Iguape River basin, in the state of São Paulo, Brazil. The lack of values for some parameters considered in the formulation of indicators undermined the achievement of more realistic values. The proposed method proved to be easy to visualize the condition of sustainability of wastewater treatment stations using stabilization ponds.

The purpose of this study was to assess the anaerobic degradation of black liquor with and without additional carbon sources. Batch experiments were conducted using black liquor, from an integrated pulp and paper mill adding ethanol, methanol and nutrients. The PCR/DGGE technique was used to characterize the structure of the microbial community. The addition of extra sources of carbon did not significantly influence the degradation of black liquor under the conditions evaluated and the microbial community was similar in all experiments. It was observed an increase in some members of the archaeal in reactors that had the best efficiencies for removal of black liquor (around 7.5%). Either ethanol or methanol can be used as co-substrates because the produce the same quantitative and qualitative effect.

Recent studies have shown that partial oxidation by advanced oxidation processes (AOP) is able to transform hard-to-degrade compounds and increase their biodegradability. In this work, anaerobic treatment was followed by ozonation, UV radiation and ozonation in the presence of UV radiation, to treat bleaching effluents from a cellulose kraft pulp plant. The anaerobic reactor (horizontal anaerobic immobilized sludge bed, HAISB) was used as a pretreatment to reduce the effluent organic load before applying AOP. The ozone treatments were applied in three different pH environments (3, 8 and 10) with retention times of 10, 30, 45 and 60 min. COD and adsorbable organic halogens (AOX) removal efficiencies at the HAISB were approximately 50%, while the BOD removal efficiency reached 80%. Ozonation promoted further removal of AOX and COD so that the combined efficiency reached 96% for AOX and 70% for COD. In the oxidation process, BOD was either removed in small quantities or actually increased, as intended, so th...

Lagoas de estabilização localizadas em regiões com variações elevadas de temperatura ao longo do dia tendem a apresentar estratificação térmica, um fenômeno que altera o volume útil da lagoa. Neste trabalho, apresentam-se resultados experimentais obtidos em duas lagoas, facultativa e maturação, construídas na região central do estado de São Paulo. O acompanhamento do perfil de temperatura mostrou a ocorrência de estratificação térmica com ciclo nictimeral nas duas lagoas. Os ensaios hidrodinâmicos indicaram comportamento semelhante ao de reatores com mistura completa, com zonas mortas, volume útil de aproximadamente 60% na lagoa facultativa e 30% na lagoa de maturação. Os experimentos corroboraram os resultados teóricos obtidos com o modelo matemático para previsão da estratificação térmica.Stabilization ponds located in places that present high temperature variations along the day have a tendency to present thermal stratification, a phenomenon that changes the useful volume of the pond. This paper presents experimental results from two stabilization ponds, facultative and maturation, built in the central area of the state of São Paulo, Brazil. The observation of the temperature profile showed the occurrence of thermal stratification with the nictimeral cycle in both ponds. Hydrodynamic tests showed a pattern that resembles the behavior of complete mixing reactors with dead zones, resulting in useful volumes close to 60% for the facultative pond and 30% for the maturation pond. The experiments confirm the theoretical results obtained based on a mathematical model to predict thermal stratification.

The main objective of this research was to evaluate the potential use of a bench-scale anaerobic sequencing batchbiofilm reactor (ASBBR) containing mineral coal as inert support for removal of sulfide and organic matter effluentsfrom an ASBBR (1.2 m3) utilized for treatment of sulfate-rich wastewater. The cycle time was 48 h, including thesteps of feeding (2 h), reaction with continuous liquid recirculation (44 h) and discharge (2 h). COD removalefficiency was up to 90% and the effluents total sulfide concentrations (H2S, HS−, S2−) remained in the range of 1.5to 7.5 mg.l−1 during the 50 days of operation (25 cycles). The un-ionized sulfide and ionized sulfides were convertedby biological process to elemental sulfur (S0) under oxygen limited conditions. The results obtained in the benchscalereactor were used to design an ASBBR in pilot scale for use in post-treatment to achieve the emission standards(sulfide and COD) for sulfate reduction. The pilot-scale reactor, with a total volume of 0.43 m3, the COD and totalsulfide removal achieved 88% and 57%, respectively, for a cycle time of 48 h (70 days of operation or 35 cycles).

Neste trabalho foi utilizado um reator anaeróbio de leito fluidificado (RALF), tratando água residuária sintética contendo pentaclorofenol (PCP), submetido a condições operacionais menos idealizadas. Utilizou-se um reator com volume de 16 litros, com partículas de carvão ativado granular como meio suporte. O desempenho do reator foi verificado pelas análises usuais de monitoramento (pH, alcalinidade, DQO, ácidos voláteis) e também por análises de microscopia e concentração de PCP. A presença de PCP no sistema, nas concentrações utilizadas, não alterou de maneira significativa a qualidade da biomassa presente, e nem os parâmetros de monitoramento. Em concentrações afluentes de PCP variando de 1 a 6 mg/L, foram observadas eficiências médias de remoção de 92% e 70%, respectivamente.In the present work, an anaerobic fluidized bed reactor (AFBR) was used for the treatment of a synthetic wastewater containing pentachlorophenol (PCP) subjected to less idealized operating conditions. The reactor was a 16 litres tank with granular activated carbon particles as support media. Evaluation of AFBR performance was done by the analysis of usual monitoring parameters (pH, alkalinity, COD, volatile acids) together with microscopy and PCP concentration analysis. The presence of PCP under the concentrations used did not significantly alter the amount of biomass and the performance monitoring parameters. Removal average efficiencies of the order of 92% and 70% were obtained for PCP inflow concentrations in the range of 1 to 6mg/l.

Um reator UASB em escala piloto (160 l) foi usado com o objetivo de estudar seu comportamento hidrodinâmico quando submetido a variações cíclicas senoidais da vazão afluente. Os ensaios foram realizados com traçador eosina Y para as condições operacionais: vazão média afluente constante e igual a 16 l.h-1 e tempo de detenção hidráulica de 10 h (ensaios 1 e 2), e para vazão afluente submetida à variação senoidal de 40% (ensaios 3 e 4) e de 60% (ensaio 5). A variação da concentração do traçador no efluente foi ajustada pelos modelos teóricos de dispersão de fluxo e de reatores em série. O reator UASB apresentou comportamento similar ao de reator de mistura completa para vazão média afluente constante e similar ao reator de fluxo pistonado com a aplicação das variações senoidais cíclicas, sendo que o modelo de pequena dispersão apresentou melhor ajuste matemático.A bench scale UASB reactor (160 l) was used in stimulus-response assays in order to evaluate its behaviour when submitted to cyclical sinusoidal variations of the influent flow rate. Assays were carried out with eosin Y as the tracer in different operational conditions: constant mean influent flow rate of 16 l.h-1 and hydraulic residence time of 10 h (assays 1 and 2), and influent flow rate submitted to sinusoidal variation of 40% (assays 3 and 4) and 60% (assay 5). The variation of tracer concentration in the effluent was adjusted by the theoretical models of dispersion (low and high) and N-continuous stirred tank reactors in series. Complete mixture behaviour was noted to the application of the constant influent flow rate and a plug flow one to the application of the cyclical sinusoidal variations of the influent flow rate. The low dispersion model demonstrated the best mathematical adjustment in the RTD.

The impact of ozone oxidation on removing high molecular weight (HMW) organics in order to improve the biodegradability of alkaline bleach plant effluent was investigated using a semi-batch reactor under different initial pH (12 and 7). After the ozonation process, the ratio of BOD5/COD increased from 0.07 to 0.16 and 0.22 for initial pH 12 and 7, respectively. Also, the effluent color decreased by 48% and 61% at initial pH 12 and pH 7, respectively. These changes were primarily driven by reductions of the HMW fractions of the effluent during ozonation.

The main objective of this paper was to perform a preliminary comparative study between chemical and electrochemical coagulation processes, both followed by flocculation and sedimentation of an effluent from an upflow anaerobic sludge blanket ( UASB) reactor treating simulated wastewater from an unbleached Kraft pulp mill. The electrochemical treatment removed up to 67% (with aluminum electrodes) and 82% (with stainless-steel electrodes) of the remaining chemical oxygen demand (COD) and 84% (stainless steel) and 98% (aluminum) of the color in the wastewater. These efficiencies were achieved with an energy consumption ranging from 14 to 20 Wh l −1 . The coagulation–flocculation treatment with ferric chloride and aluminum sulfate removed up to 87% and 90% of COD and 94% and 98% of color, respectively. The addition of a high molecular weight cationic polymer enhanced both COD and color removal efficiencies. The two post-treatment processes proved to be technically feasible; however the economical feasibility could not be assessed since the experiments were performed with small reactors that could distort scale factors.

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO A utilização de usinas termoelétricas torna importante a análise dos efeitos de dispersão de poluentes térmicos em cursos d água. Modelos matemáticos, tais como o modelo Fickiano [5] e o modelo de PAILY E SAYRE [6], tem sido utilizados na análise de tais efeitos. No presente trabalho, foram efetuadas simulações experimentais de dispersão térmica, utilizando-se uma canaleta com injeção de água quente em uma posição arbitrária, tendo sido medido o campo de temperatura criado. Os resultados são comparados com aqueles fornecidos pelos modelos mencionados, aplicando-se o método das fontes imagens. Devido às limitações do modelo de PAILY E SAYRE, generalizou-se o mesmo para fontes térmicas colocadas em uma posição arbitraria no canal. Qualitativamente, o modelo de PAILY E SAYRE mostrou-se mais satisfatório que o modelo Fickiano e o método das fontes imagens foi considerado adequado. The instalation of steam-eletric power plants using either fóssil or nuclear fuels makes important the analysis of the effects of the dispersion of thermal pollutants in water streams. Mathematical models, such as the Fickian model [5] and the modelo of PAILY and SAYRE [6], have been used in the analysis of such effects. In the present work, experimental simulations of thermal dispersion were maden using an artificial channel with injection of hot water posicioned at any place in the middle of the channel and meaurements of the temperature field were taken. The results were compared with the results given by the mentioned models, applying the image sources method. Due to the limitations of the model of PAILY and SAYRE, it was generalized for thermal sources posicioned at any place in the channel. Qualitatively, the model of PAILY and SAYRE proved to be more satisfactory than the Fickian model and the image sources method was considered adequate.

The main purpose of this study was to evaluate the performance of the electrochemical oxidation process as a post-treatment for the effluents of a bench-scale UASB reactor treating simulated wastewater from an unbleached pulp plant. The oxidation process was performed using a single compartment cell with two plates as electrodes. The anode was made of Ti/Ru0.3Ti0.7O2 and the cathode of stainless steel. The following variables were evaluated: current density (75, 150 and 225 mA cm−2) and recirculation flow rate in the electrochemical cell (0.22, 0.45 and 0.90 L h−1). The increase in current density from 75 to 225 mA cm−2 did not increased the color removal efficiency for the tested flow rates, 0.22, 0.45 and 0.90 L h−1, however the energy consumption increased significantly. The results indicated the technical feasibility of the electrochemical treatment as post-treatment for UASB reactors treating wastewaters from pulp and paper plants.

The microbial community in the sludge blanket of a bench scale upflow anaerobic sludge blanket (UASB) reactor with partial recirculation of the effluent, treating wastewater from an unbleached pulp plant, was evaluated by means of the small subunit (SSU) rRNA gene amplified by polymerase chain reaction (PCR) and separated using the denaturing gradient gel electrophoresis (DGGE) technique. The average COD removal efficiency was 80–86% without recirculation and 75–78% with recirculation. Partial recirculation of the effluent did not alter the predominant population in the reactor under the conditions studied. A microscopic analysis revealed the presence of a variety of cellular morphologies. The DGGE results revealed that the structure of the microbial community was found to be complex and most of the population was similar, persisting throughout the experimental period. The microbial community of the Domain Bacteria was more sensitive to operational changes than the Domain Archaea.

This paper presents results from exploratory experiments to test the technical feasibility of electrolytic treatment and coagulation followed by flocculation and sedimentation as post-treatment for the effluent of an UASB reactor treating simulated wastewater from an unbleached Kraft pulp mill. The electrolytic treatment provided up to 67% removal of the remaining COD and 98% of color removal. To achieve these efficiencies the energy consumption ranged from 14 Wh.l−1 to 20 Wh.l−1. The coagulation-flocculation treatment followed by settling required 350–400 mg.l−1 of aluminium sulfate. The addition of a high molecular weight cationic polymer enhanced both COD and color removal. Both post-treatment processes are technically feasible.

The performance of a bench scale upflow anaerobic sludge blanket reactor (UASB) was evaluated for the treatment of diluted black liquor from a Kraft pulp plant. The reactor was monitored over a 635 day period of continuous operation. In the first experimental phase, the hydraulic and organic load rate were changed while, in the second phase, these operational parameters were kept constant to observe the long-term changes in the reactor behaviour. The average chemical oxygen demand removal efficiency during the entire experiment was 80% and, due to the low growth of biomass, it was not necessary to waste the sludge. The microbial consortium became acclimated to the substrate, even though black liquor is potentially toxic for methanogenic cells. The anaerobic biomass presented a good recovery capacity after a thermal shock and subsequent acidification. The UASB reactor was stable, easy to operate with low maintenance and operational costs.

The most widely used treatment system in the pulp and paper industry - the activated sludge - produces high quantities of sludge which need proper disposal. In this paper a modified activated sludge process is presented. A synthetic wastewater, prepared to simulate the effluent of bleached and unbleached pulp and paper plant wastewater, was submitted to treatment in a bench scale aerobic reactor. The excess sludge was lysed in a mechanical mill - Kaddy™ mill - and totally recycled to the aeration tank. In the first phase the synthetic wastewater, without the chlorinated compounds, was fed to the reactor. In the second phase increasing dosages of the chlorinated compounds were used. Total recycle of excess sludge after disintegration did not produce adverse effects. During the first phase average COD removal efficiency was 65% for the control unit, which operated in a conventional way, and 63% for the treatment unit, which operated with total recycle. During the second phase the COD removal efficiency increased to 77% in the control unit and 75% in the treatment unit. Chlorinated organics removal was 85% in the treatment unit and 86% for the control unit. These differences are not significant.

Thermal stratification, which is characterized by a high vertical thermal gradient, is usually observed in deep lakes. However, although waste stabilization ponds have small depths, their high turbidity provides favorable conditions for the occurrence of this phenomenon, mainly during summer. During that time of the year, the layers nearest to the surface concentrate a larger amount of thermal energy compared to the deeper layers, which results in a temperature difference between the surface and the bottom of the pond. As a consequence a density profile appears, with the less dense layers located at the surface of the pond and the densest ones close to the bottom. This stratification in the water column induces alterations in the flow pattern and a decrease of the useful volume of the pond. This paper presents a mathematical model developed to forecast the conditions of thermal stratification in waste stabilization ponds and the volume actually used for wastewater treatment. With these values it is possible to correct the average residence time of the liquid in the pond. The theoretical results were compared with experimental observations, and maximum differences of 15% between the calculated and observed temperature profiles were found.

Aerated thermophilic reactors may have advantages for treating industrial effluents discharged at high temperatures. In this study, the wastewater from a recycled packaging cardboard plant was treated at 55 °C in a moving bed aerated reactor. It was observed that, although the overall dissolved oxygen was maintained at 2–3 mg L −1 , several anaerobic microorganisms are found either in the mixed liquor or in the attached biofilm. This result indicates that both aerobic and anaerobic mechanisms participate in pollutant removal in this reactor, which confers advantages when recalcitrant compounds are found. The median COD removal efficiency of 84% for 36 h of HRT observed in this experiment is expected for non-optimized activated sludge treatment of high temperatures industrial wastewater.