This work presents a compact plant's development and performance evaluation for the decentralized treatment of domestic sewage. The plant was conceived and installed in a house with four residents in Vicente Pires, Federal District, Brazil. Its purpose was to remove organic matter and solids using a low-cost biological treatment process that was simple to operate. The plant was essentially anaerobic, composed of an up-flow anaerobic reactor and an anaerobic filter, both associated with lamella settlers. It was operated under real conditions and monitored for nineteen months, with removal efficiencies (calculated over the medians) of 81% for COD, 83% for BOD, 51% for Total Solids, 55% for Total Volatile Solids, 87% for Total Suspended Solids, and 100% for Settleable Solids. The plant performed adequately, with no clogging between the plates of the lamella settlers or no offensive odours, and limited amounts of sludge and scum.

This work evaluated the behaviour of a Pilot Plant to receive and pre-treat septage collected and transported by trucks from decentralized sewage treatment systems and greasy residues from grease traps. This Pilot Plant was installed at the Brasília Sul Sewage Treatment Plant and was composed of a grid, equalization tank, rotating screen, crusher and a Central Unit for separating settleable solids (SetS) and floating solids, mainly oils and greases (O&G). The Central Unit consists of an adaptation of an aerated grit chamber to receive intermittent loads of septage dumped from trucks. The Central Unit was tested in four operating modes to investigate the influence of the presence of greasy residues and aeration in the initial third of the length of its chamber: Mode 1 - Central Unit without aeration and receiving only septage; Mode 2 - Central Unit with aeration and receiving only septage; Mode 3 - Central Unit without aeration and receiving mixtures of greasy residues and septage; and Mode 4 - Central Unit with aeration and receiving mixtures of greasy residues and septage. It was verified that there is a tendency of the Central Unit to behave better when receiving mixtures of septage and greasy residues. Comparing Modes 1 and 2, Mode 2 showed only 6% more O&G removal than Mode 1, on average. Comparing Modes 3 and 4, Mode 4 reached 32% more removal of O&G than Mode 3, on average. However, the use of aeration was not statistically significant. The Pilot Plant on average reduced 72% of O&G and 90% of SetS in Modes 1 and 2, and 95% of O&G and 90% of SetS in Modes 3 and 4.

<p><strong>Abstract</strong></p><p>In the Federal District of Brazil, the cleaning waste from on-site sanitation facilities is transported by septage trucks to sewage treatment plants (STPs) to be treated in conjunction with sewage. This research aimed to characterize the waste from septage trucks that were discharged in the two STPs in Brasilia, Federal District of Brazil. The methodology included the characterization (sampling and laboratory tests) of waste samples collected from septage trucks that discharged waste at the two STPs in Brasília, and the collection of information on the origin of this waste and the frequency of cleaning the on-site sanitation units. Great variability was found in the frequency of cleaning cesspools and septic tanks. The cleaning of the on-site sanitation facilities took place daily in some places and monthly in the remaining sites, and eventually, facilities with annual cleaning were reported. The characteristic that had the lowest variation coefficient was the pH. The presence of large concentrations of oils and greases in the residues of the septage trucks is a major inconvenience. The results obtained contribute to the knowledge of the characteristics of waste from septage trucks, its management and proper treatment.</p><p><strong>Keywords</strong>: septage; grease trap waste; septage collection and transport truck; oil and grease.</p><p> </p><p align="center">CARACTERIZAÇÃO DOS RESÍDUOS DOS CAMINHÕES LIMPA-FOSSAS NO DISTRITO FEDERAL, BRASIL</p><p><strong>Resumo</strong></p><p>No Distrito Federal, os resíduos da limpeza das instalações de tratamento descentralizado de esgoto são transportados por caminhões limpa-fossas para as estações de tratamento de esgoto (ETEs) para serem tratados em conjunto com o esgoto. Esta pesquisa teve como objetivo caracterizar os resíduos de caminhões limpa-fossas que descarregaram nas duas ETEs de Brasília, Distrito Federal, Brasil. A metodologia incluiu a caracterização (amostragem e exames laboratoriais) de amostras de resíduos coletadas dos caminhões limpa-fossas que descarregaram lodo de fossa nas duas ETEs de Brasília, e a coleta de informações sobre a origem desses resíduos e a frequência de limpeza das unidades de tratamento descentralizado de esgoto. Encontrou-se grande variabilidade nas frequências de limpeza de fossas e tanques sépticos. A limpeza das instalações de tratamento descentralizado de esgotos ocorria diariamente em alguns locais e mensalmente nos demais e, eventualmente, foram registradas instalações com limpeza anual. O pH foi a característica que apresentou o menor coeficiente de variação. A presença de grandes concentrações de óleos e graxas nos resíduos dos caminhões limpa-fossas é um grande inconveniente. Os resultados obtidos contribuem para o conhecimento das características dos resíduos de caminhões limpa-fossas, sua gestão e tratamento adequado.</p><p><strong>Palavras-chave</strong>: lodo de fossas e tanques sépticos; resíduos de caixas de gordura; caminhões limpa-fossas; óleos e graxas.</p>