The influence of acidic and alkaline conditions on the solubilisation process of waste activated sludge (WAS) was investigated using HCl and NaOH at pH 2, 10, 11 and 12. The rise in concentration of solubilised compounds, the influence of reaction time, and the influence of the concentration of total solids (TS) during the solubilisation process were determined. Physical and chemical tests demonstrated that pre-treatment provided a release of compounds from the sludge floc matrix into the soluble fraction, characterising the solubilisation process. The highest degree of WAS solubilisation was observed when a pH of 12 was applied. Although largest effects were already attained after 0.25 h, WAS solubilisation continued reaching an increase in total dissolved solids by a factor 10.4 after 720 hrs. Under these conditions, the dissolved organic carbon (DOC), proteins, and carbohydrates resulted in releases up to 15, 40 and 41 times, respectively; and phosphorus increased 5.7 times. Results indicate that by applying alkaline pre-treatment, higher TS concentrations can be treated per reactor volume compared to non-pre-treated WAS. Aerobic and anaerobic biodegradability tests showed increased bioconversion potentials in full-scale treatment plants. The respirometry tests ratify the improvement in solubilisation, with O2 consumption rates increasing 1.4 times, concomitant with an additional 261 mg·L−1 of the COD used, which represents 90% bioconversion of waste activated sludge. Biomethanisation test indicated an increase of 3.6 times relative to the blank.

The ammonia nitrogen stripping process at open horizontal flow reactors was evaluated and is described in this paper. The ammonia came from landfill leachate. Superficial loads of 650 kgN-.ha-1.day-1 (phase 1), 750 kgN-.ha-1.day-1 (phase 2), and 850 kgN-.ha-1.day-1 (phase 3) were applied with a hydraulic retention time of 51.2, 64.9, and 55.6 days, respectively. The experimental system setup was designed, built, and monitored at EXTRABES (Estação Experimental de Tratamentos Biológicos de Esgotos Sanitários) and consisted of a series of four open horizontal flow reactors fed with in natura leachate. The study was based on a stripping process with no alkaline chemical species addition, nor air flow for ammonium gas drag, and aimed to reduce the landfill leachate ammoniacal nitrogen concentration. The studied process showed a removal efficiency of 99.0% in the first phase, 99.3% in the second, and 99.5% in the third. Regarding the organic matter expressed in terms of CODtotal, the removal efficiency was 69.20% in phase 1, 40.12% in phase 2, and 29.23% in phase 3. It was noted that ammonia removal efficiency was directly proportional to the applied superficial load and the carbonaceous material removal was proportional to the organic matter applied in influent, since in phase 1 the CODtotal concentration removal efficiency was 1.7 times greater than that of phase 2, and 2.3 times that of phase 3. Briefly, the ammonia nitrogen stripping process by open horizontal flow reactor is a promising technological alternative for ammonia nitrogen reduction, mainly at regions with available area and temperature greater than 25°C. It is promising because it has no costs in terms of chemical reagents to raise the pH, nor does it require electric costs.

This work aims to investigate the influence of polishing ponds (PP) depth on the post-treatment of sanitary sewers. Two treatment systems were designed and monitored. One system was an upflow anaerobic sludge blanket (UASB) rector and intermittent flow sand filter; followed by a PP of 0.20 m depth with low superficial application rate (24.9 kgBOD 5 .ha ) and enough biological carbon dioxide used to raise the average pH to 9.6, ensure an average removal of 81% orthophosphate and concentration of Escherichia coli lower than 10 3 UFC/100 ml, which are the meeting requirements for unrestricted irrigation. The other system was a UASB followed by two PPs operated in parallel, at 0.20 and 0.60 m depths. The 0.20 m PP depth removed 80% of total Kjeldahl nitrogen, 53% of total phosphorus and 44% of orthophosphate. The 0.60 m pond depth showed low nutrient removal and a poor E. coli removal efficiency, 98.33% equivalent to 2 logs units. The ponds were fed by continuous systems.

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O inadequado gerenciamento de resíduos orgânicos é uma prática ambientalmente ultrapassada que deve ser evitada em pequena, média e larga escala. Por outro lado, a adequada disposição final desses resíduos implica em elevados custos operacionais, que se forem mal geridos ainda podem desencadear danos ambientais de difícil remediação, como a poluição de corpos hídricos, solo e atmosfera com a dispersão irrestrita de gases de efeito estufa, além das questões de saúde pública. É uma problemática que demanda soluções técnicas e integradoras que transformem essas adversidades em oportunidades sociais e econômicas. Nesse contexto, a digestão anaeróbia (DA) tem sido amplamente utilizada no tratamento de resíduos, tanto para reduzir o volume final desses resíduos como para recuperar recursos como nutrientes, energia e água. De fato, a recuperação de energia, na forma de gás metano, tem sido o recurso mais visado. No entanto, recentes pesquisas demonstram que a utilização de dois ou mais resíduos, em processo de codigestão anaeróbia, pode elevar satisfatoriamente a produção de metano. O presente estudo avaliou a utilização de macrófitas aquáticas (MA) (Landoltia punctata, Pistia Stratoties e Salvinia molesta) como cossubstrato para digestão anaeróbia de resíduos sólidos orgânicos (RSO) de um restaurante universitário. A metodologia de pesquisa foi desenvolvida em três etapas: caracterização das macrófitas e do RSO, cálculo teórico de produção de metano da codigestão de ambos os substratos e uma etapa experimental avaliando os índices teóricos. A produção acumulada de metano utilizando somente RSO, e as proporções 10MA/90RSO e 50MA/50RSO foram de 236,98, 288,5 e 289,06 Nml.gSV-1. Foi verificado que a adição de pequenas porções de MA do tipo Landoltia punctata ao RSO eleva a produção de metano e que foi obtido acréscimo de 17% de metano para codigestão com 10 e com 50 % de Landoltia punctata. A redução de sólidos voláteis (SV) foi aproximadamente 28% superior nos processos de codigestão frente à DA de RSO, o que em escala real pode apresentar grandes benefícios econômicos e ambientais. Palavras-chave: Codigestão. Macrófitas aquáticas. Landoltia punctata. Resíduo sólido orgânico. Metano.