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There are hundreds of full-scale upflowanaerobic sludge blanket (UASB) reactors in operation in various parts of the tropical world, notably in India and Latin America, Brazil being the holder of the largest park of anaerobic reactors for sewage treatment in the world. Despite the recognized advantages of UASB reactors, there are problems that have prevented their maximum operational performance. Neglecting the existence and delaying the solution of these challenges can jeopardize the important advances made to date, impacting the future of anaerobic technology in Brazil and in other countries. This work aims to evaluate the operational performance of five full-scale UASB reactors in Brazil, taking into account a monitoring period ranging between two and six years. The main observed design, construction, and operational constraints are discussed. Some outlooks for important upcoming developments are also provided, considering that most of the observed drawbacks can be tackled without significant increases on reactor costs. [ABSTRACT FROM AUTHOR]

A small unit of cogeneration of energy and heat was tested at the Centre for Research and Training on Sanitation UFMG/COPASA - CePTS, located at the Arrudas Sewage Treatment Plant, in Belo Horizonte, Minas Gerais, Brazil. The unit consisted of an engine power generator adapted to run on biogas, a thermal dryer prototype and other peripherals (compressor, biogas storage tank, air blower, etc.). The heat from engine power generator exhaust gases was directed towards the thermal dryer prototype to dry the sludge and disinfect it. The results showed that the experimental apparatus is self-sufficient in electricity, even producing a surplus, available for other uses. The tests of drying and disinfection of sludge lasted 7 h, leading to an increase in solids content from 4 to 8% (50% reduction in sludge volume). Although the drying of sludge was not possible (only thickening was achieved), the disinfection process proved very effective, enabling the complete inactivation of helminth eggs. [ABSTRACT FROM AUTHOR]

This work investigated the occurrence of pharmaceuticals and endocrine disrupting compounds (EDC5) in raw sewage (from Belo Horizonte city, Minas Gerais state, Brazil) and assessed their behavior in demo-scale upflow anaerobic sludge blanket reactors (UASB reactors) operated at different hydraulic retention times (HRT). The dissolved concentration of the studied micropollutants in the raw and treated sewage was obtained using solid phase extraction (SPE) followed by analysis in a liquid chromatography system coupled to a hybrid high resolution mass spectrometer consisting of an ion-trap and time of flight (LC-MS-IT-TOF). The natural (estradiol) and synthetic (ethinylestradiol) estrogens were hardly detected; when present, however, their concentrations were lower than the method quantification limits. The concentrations of bisphenol A and miconazole in raw sewage were similar to that reported in the literature (around 200 ng L-1 and hardly detected, respectively). The antibiotics sulfamethoxazole (median 13.0 ng L-1) and trimethoprim (median 61.5 ng L-1), and the other pharmaceutical compounds (diclofenac and bezafibrate, with median 99.9 and 94.4 ng L-1, respectively) were found in lower concentrations when compared with reports in the literature, which might indicate a lower consumption of such drugs in Brazil. The UASB reactors were inefficient in the removal of bisphenol A, and led to an increased concentration of nonylphenol in the effluent. The anaerobic reactors were also inefficient in the removal of diclofenac, and led to a partial removal of bezafibrate; whereas, for sulfamethoxazole there seemed to be a direct relationship between the HRT and removal efficiencies. For trimethoprim the sludge retention time (SRT) seemed to play an important role, although it was only partially removed in the UASB reactors. [ABSTRACT FROM AUTHOR]

The paper analyses the concept and performance of different configurations of compact UASB/TF systems, without the final clarification stage, in relation to the removal of organic matter. The experiments were carried out in two sets of UASB/TF systems operating without secondary clarifiers, as follows: (i) four shallow (2.50 m height) TFs, each one filled with a different packing material; and (ii) two deep (4.20 m height) TFs, one filled with polyethylene corrugated sheets and the other with mixed polyethylene and sponge sheets. For the conditions tested (different packing material in shallow and deep TF), the UASB/TF systems had consistently complied (90 to 100% of the results) with the Brazilian discharge standards regarding to BOD, COD, and TSS parameters. The average BOD, COD and TSS effluent concentrations stayed below 40 mg BOD L-1, 100 mg COD L-1 and 50 mg TSS L-1, respectively. UASB/TF systems can constitute an attractive alternative for domestic wastewater treatment in small communities in developing countries, especially considering its operational simplicity and very low running costs. [ABSTRACT FROM AUTHOR]

This paper discusses the main drawbacks and enhancements experienced with the design and start up of two full-scale UASB plants in Brazil. The topics addressed are related to blockage of inlet pipes, scum accumulation, seed sludge for the start-up, corrosion and gas leakage, odour generation and sludge management. The paper describes the main improvements achieved. [ABSTRACT FROM AUTHOR]

This work aimed at evaluating the influence of the excess sludge produced in a trickling filter (TF) on the performance of a UASB reactor used for the combined treatment of domestic sewage and aerobic sludge. During phase 1 of the research, the UASB reactor/TF system was fed with domestic sewage pumped directly from the sewer collector of Arrudas stream, in Belo Horizonte -- Brazil. During phase 2, besides feeding the reactor with domestic sewage, the UASB reactor was also fed with the aerobic sludge from the trickling filter. The UASB reactor, with a volume of 420 litres, was operated at a mean hydraulic detention time of 5.6 hours in both operational phases. After 133 days of continuous monitoring, no detrimental effect was noticed on the performance of the UASB reactor regarding the return of the aerobic sludge produced in the TF. On the contrary, the COD results indicated a higher percentage of compliance with the discharge standards set forth by the Brazilian environmental legislation. During phase 2 of the research, when the UASB reactor was used for combined treatment of domestic sewage and excess aerobic sludge from the TF, the anaerobic effluent presented mean concentrations of 108 mgCOD.L-1, 57 mgBOD.L-1 and 18 mgTSS.L-1. [ABSTRACT FROM AUTHOR]

The paper evaluates and models helminth eggs removal in a combined UASB (Upflow Anaerobic Sludge Blanket) reactor -- maturation pond system (one baffled and one unbaffled pond in parallel). The system is comprised of demonstration-scale units, treating actual domestic sewage from Itabira city, Brazil. The paper addresses the following points: (i) removal of helminth eggs from the wastewater in the system; (ii) comparison of the observed removal efficiency with the predictions using the Ayres et al. model; (iii) accumulation of helminth eggs in the sludge; (iv) viability of eggs in the sludge; (v) distribution of helminth species in the sludge. The removal efficiency of helminth eggs from the wastewater in both ponds was 100% for most of the time (0 counts in the final effluent). The predictions of helminth eggs removal according to the Ayres et al. model can be considered reasonable. After one year of operation, 88% of the eggs in the sludge remained viable. Helminth eggs counts in the sludge tended to decrease along the baffled pond length (from first to last compartment). The prevailing helminth species found in the sludge from both ponds was Ascaris lumbricoides. [ABSTRACT FROM AUTHOR]

This work aimed at developing a mathematical model that could estimate more precisely the fraction of chemical oxygen demand (COD) recovered as methane in the biogas and which, effectively, represented the potential for energy recovery in upflow anaerobic sludge blanket (UASB) reactors treating domestic wastewater. The model sought to include all routes of conversion and losses in the reactor, including the portion of COD used for the reduction of sulfates and the loss of methane in the residual gas and dissolved in the effluent. Results from the production of biogas in small- and large-scale UASB reactors were used to validate the model. The results showed that the model allowed a more realistic estimate of biogas production and of its energy potential.

The paper analyses the concept and performance of compact UASB/TF systems in relation to configuration, use of innovative packing media and operational conditions. For the conditions tested, the UASB/TF systems had consistently complied with the Brazilian discharge standard regarding to COD, BOD and TSS parameters. However, some enhancements are still necessary in order to increase nitrification in the process. The conditions to promote nitrification in shallow TF (packed bed up to 2.50 m height) seem to be compatible with the proposed simplification in the flowsheet, which is to operate the system without secondary clarifiers.

The paper presents the monitoring results of a pilot UASB reactor followed by a baffled polishing pond treating domestic sewage in Brazil. Longitudinal profiles of E coli and helminth eggs along the baffled pond have been undertaken. The experimental results have been compared with von Sperling's model for coliform removal and Ayres' model for helminth eggs removal, and the fitting was considered satisfactory in both cases. The distribution of the helminth species along the system is also presented.