ABSTRACT:The study consisted of the evaluation of the treatment of septic tank sludge in a vertical constructed wetland system (CW), built according to the first stage of the French system. The system operated also for sewage treatment and one of the beds (area of 29.1 m², height of the support medium of 0.7 m and planted with Tifton 85 grass, Cynodon dactylon Pers), began to receive the application of sludge from clean-pit trucks once a week. The percolated liquid was directed to post-treatment in the other two beds of the French system. The application of the raw sludge had average hydraulic loading rate of 13.1 m³/m².year and solids loading rate of 81 kgTS/ m².year. The system improved the quality of percolated liquid in terms of carbonaceous and nitrogenous matter (average COD removal efficiencies of 82% and TKN of 63%), but the percolate post-treatment strategy did not result in substantial improvements. The dewatering of the accumulated sludge on top of the bed occurred satisfactorily (55% of dry solids), the Tifton 85 grass was resistant to the operational conditions and the system proved to be a compact technology (sludge treatment capacity of an equivalent population between 1140 and 3799 inhabitants in the unit of 29.1 m 2 , corresponding to 39 to 131 inhabitants per m 2 of surface area).

This study investigated the performance of sludge drying reed beds (SDRB) at full- and pilot-scale treating sludge from septic tanks in the city of Belo Horizonte, Brazil. The treatment units, planted with Cynodon spp., were based on an adaptation of the first-stage of the French vertical-flow constructed wetland, originally developed for treating sewage. Two different operational phases were investigated; in the first one, the full-scale unit was used together with six pilot-scale columns in order to test different feeding strategies. For the second phase, only the full-scale unit was used, including a recirculation of the filtered effluent (percolate) to one of the units of the French vertical wetland. Sludge application was done once a week emptying a full truck, during 25 weeks. The sludge was predominantly diluted, leading to low solids loading rates (median values of 18 kgTS m(-2) year(-1)). Chemical oxygen demand removal efficiency in the full-scale unit was reasonable (median of 71%), but the total solids removal was only moderate (median of 44%) in the full-scale unit without recirculation. Recirculation did not bring substantial improvements in the overall performance. The other loading conditions implemented in the pilot columns also did not show statistically different performances.

Small vertical-flow constructed wetland units comprising the first stage of the French system were studied in Brazil for the treatment of raw sewage. Planted and unplanted units and different feeding strategies were tested. In the first phase, hourly batches of a daily flow of 13 m3 d−1 were applied over three alternating units, resulting in an average hydraulic loading rate (HLR) on the full system of 0.15 m3 m−2 d−1. A second phase, aimed at reducing land requirements, kept the same daily flow and batch frequency, but used two alternating units, resulting in a HLR on the full system of 0.22 m3 m−2 d−1. Removal efficiencies were very good when the system operated with three units, with mean values of 82% for biochemical oxygen demand (BOD), 81% for chemical oxygen demand (COD), 85% for total suspended solids (TSS) and 59% for NH4+-N. With two units, the equivalent values were 74% for BOD, 59% for COD, 67% for TSS and 51% for NH4+-N. There were significant differences in the median removal efficiencies of COD and TSS. No significant differences were found between planted and unplanted units for most constituents. In both phases, the overall good performance and the simplicity of the system make this treatment process a very attractive alternative for developing countries.

No ano de 2006, quando aproximadamente 97% dos 853 municípios do Estado de Minas Gerais lançavam os esgotos brutos nos corpos d’água, foi publicada a Deliberação Normativa COPAM nº 96/2006, sobre a implantação de sistema de tratamento de esgotos sanitários em todos os municípios. Com isso, no mesmo ano, implantou-se o Programa Minas Trata Esgoto com o objetivo de realizar a gestão estratégica da implantação desses sistemas, monitorando o aumento do percentual de esgoto tratado no Estado por meio do processo de licenciamento ambiental das ETE. Tal monitoramento possui muitas fragilidades e para tentar minimizá-las o Programa realiza campanhas de vistoria, por bacia hidrográfica, para avaliação da situação real do esgotamento sanitário dos municípios. O presente trabalho consiste em uma avaliação ex-post do início do Programa até o ano de 2012, tendo em vista o ciclo de políticas públicas. A implementação ocorreu da forma top-down, sem a consideração de alguns condicionantes sistêmicos importantes para o alcance dos objetivos, ainda assim, nesse período Minas Gerais avançou no enorme desafio da universalização do esgotamento sanitário.