Anaerobic treatment, such as the Upflow Anaerobic Sludge Blanket - UASB - has many advantages: a compact system, with practically no equipment in the anaerobic vessel, low operational costs, very low energy consumption, and low excess sludge produced. However, taking into account its poor effluent quality, and the legal water quality standards, post treatment is a must. Brazil is experiencing the scheme UASB plus aerobic secondary treatment, aiming reduction in investment and mainly in operational costs, with excellent results. Three cases are discussed in this paper: two small plants, Barreto (0,14 m3/s) and Itaipu (0.07 m3/s, 1.6 MGD); and the Rio Preto plant (1.34 m3/s), the first two already operational. All adopt the UASB plus activated sludge process, the last two with denitrification. Several other important plants are in the stage of design or construction in Brazil, with flows as high as 3.35 m3/s, UASB plus activated sludge with nitrogen and phosphorus removal and UASB plus trickling filters. Design criteria for the anaerobic reactor and for the different secondary treatment processes, and available operational data as well, are discussed in the paper. Particular attention is given to special restraints with activated sludge as post treatment, such as the higher sludge age required for nitrification, and the difficulty in denitrifying the anaerobic effluent.

Cost-effective solutions are a must in developing countries, not only regarding investment costs, but also in respect to technology and operating practices. With these two goals in mind, in Brazil a particular effort has been directed for the development and application of the Chemical Enhanced Primary Treatment (CEPT) process and of the Upflow Anaerobic Sludge Blanket (UASB) process, both followed by complementary secondary treatment. Both technologies are under current expansion in Brazil. Large CEPT plants have been designed and built, up to 3.7 m3/s average design flow, as well as large UASB reactors, up to 3.0 m3/s average design flow. The applied technologies are cost-effective: they present low investment and efficiencies of BOD removal of up to 50% to 70%. They allow the plant construction in steps, an initial phase with efficiency over the usual primary treatment, and in order to achieve best effluent quality and meet legal water quality standards, a logic upgrade post-treatment can later on be implemented. The higher initial reduction of BOD and TSS also permits savings in construction and operational costs of secondary treatment, due to lower organic load and lower energy consumption. Sludge represents a particular point of attention: in the cases when the CEPT was used, Chemical Stabilisation of the Sludge (CSS) has also been practiced, eliminating the high construction costs of the digesters, all the plant staying chemically operated. In the cases when the UASB is used preceding secondary treatment, sludge can easily return to the anaerobic vessel, the costly sludge digestion unit being avoided. UASB reactors have practically no equipment in the anaerobic vessel, no energy consumption, low sludge production, and when applied in hot climates as in Brazil, heating devices are not required. The Brazilian experience, some particular cases, special comments on design and different secondary treatment processes are presented in this paper, as a contribution to the discussion of cost and benefits, a prime point to be considered.

RESUMOJá existe no Brasil uma mentalidade bem formada visando a economia de água, o reuso de água, e a economia de energia em sistemas de abastecimento de água. O mesmo não ocorre ainda em relação aos sistemas de esgotos. Neste trabalho se busca enfatizar a possibilidade e importância de economia de energia nas Estações de Tratamento de Esgotos, nas quais o consumo energético representa cerca de 20% dos custos. Mostra-se ainda que nas ETEs clássicas de lodos ativados, a fase de aeração representa mais de metade do consumo energético, e que diferentes processos apresentam características de consumo de energia bastante diversos.O trabalho conclui e recomenda que se realizem Auditorias de Energia regulares nas ETEs, e que um Programa de Economia de Energia venha a ser implantado, com capacitação de operadores, engenheiros, e gerentes. ABSTRACTThe idea of water economy, water reuse, and economy of energy is well accepted for water supply systems, in Brasil. Yet, the same is not true for sewage systems. This paper emphasizes the possibility and importance of economy of energy in wastewater treatment plants, where energy is responsible for around 20% of their operational costs. It shows that as far as an activated sludge plant is concerned, aeration alone represents more than 50% of energy, and that different processes may present a wide range of energy consumption.

As referências internacionais para a parcela relacionada aos custos de energia nas Estações de Tratamento de Esgoto (ETEs) indicam que ela pode se situar entre 25% e 50% dos custos operacionais (WEF, 2002). No Brasil, esse percentual é reduzido pela influência maior que tem a parcela de pessoal nos custos de operação da ETE, como mostra a Figura 1, referente à ETE Barueri (SP), com vazão média de 12 m 3 /s (JORDÃO; PES-SÔA, 2014); no caso específico, os custos com pessoal representam 48% do total, reduzindo, assim, o peso do quesito energia elétrica para 20%. Considerando, no entanto, que há a tendência de melhorar os processos de controle e automação e reduzir o número de operadores nas ETEs, é razoável admitir como significativo entre nós o peso da energia nos seus custos operacionais. Consumo de energIa É razoável admitir também que o consumo de energia varia com o processo adotado. O processo de lodos ativados é, de longe, o que apresenta maior consumo, sendo sua variável de "aeração estendida" a que mais requer energia. • lodos ativados no processo convencional: 1.200 a 1.700 kJ/m 3 ; Figura 1-Custos operacionais (%) na ETE Barueri (anteriores a 2015).

The incorporation of oil base mud cutting from drilling operations within the manufacture of clay bricks, is considered as one alternative for reuse and final disposal of the OBMC. To evaluate such alternative, on site OBMC amended bricks were produced (15000 bricks at Plant “A”, in Rio Bonito, RJ, and 4000 bricks at Plant “B”, in Jundiai, SP). Plant “A” produces 100000 bricks per day, and Plant “B” 40000; in both plants the cuttings were added in controlled amounts to the normal clay used in the manufacture process. The on-site experiments included the production of conventional bricks, 2.5% and 5% amended bricks. The laboratory tests included:–properties, leachate, and solubilization tests of the cuttings;–leachate and solubilization tests of the normal and OBMC bricks;–compression strength of the normal and OBMC bricks. The paper describes the process employed in the brick manufacture and the laboratory experiments. It also presents the properties of the OBMC bricks, and the benefits to both the manufacturer and to environmental control programs.