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Abstract(s)
Os agregados artificiais podem constituir um material alternativo para processos de
tratamento de águas residuais por filme-fixo (leitos percoladores, leitos filtrantes,
trincheiras filtrantes, biofiltros e leitos de macrófitas, por exemplo). Este trabalho
avaliou a capacidade de adsorção de um agregado geopolimérico artificial (AGA),
produzido por activação alcalina de lamas residuais das minas da Panasqueira, e de
um agregado leve de argila expandida (de nome comercial Filtralite), na presença de
acetato, amónio, fosfato e nitrato, através de ensaios “batch”. Utilizaram-se inibidores
do crescimento biológico e uma temperatura próxima dos 20ºC.
Os resultados demonstram que a CQO não deve ser utilizada para avaliar a adsorção
de moléculas orgânicas neste tipo de agregados, uma vez que o respectivo método
pode levar à determinação de valores que resultam da oxidação simultânea de
material inorgânico libertado pelos agregados, de material orgânico utilizado como
adsorvato e da azida de sódio (inibidor do crescimento microbiológico). Por outro lado,
este inibidor não é adequado para ensaios onde se utiliza o acetato, uma vez que este
último elemento pode ser reduzido a álcool etílico, deixando de ser detectado
convenientemente.
Independentemente dos agregados utilizados, as taxas de adsorção mostram que
houve uma variação pouco significativa ou muito irregular das concentrações de
acetato, amónio e nitrato, e uma adsorção mais significava e regular do fosfato,
comprovadas pela análise dos erros de determinação, levando a admitir que os
agregados estudados têm mais afinidade para a remoção deste último ião. As taxas de
adsorção obtidas para o fosfato foram de 0,1 mg/g (AGA) e 0,2 mg/g (Filtralite).
Com este trabalho, pretendeu-se, também, avaliar a importância da capacidade
adsortiva destes agregados quando colocados em processos de tratamento, tendo-se
observado que a sua utilização será mais vantajosa para a adesão e crescimento de
biofilme com capacidade para a remoção biológica de poluentes.
A artificial aggregates may constitute an alternative bed material for film-fix wastewater treatment processes (e.g. trickling beds, filter beds, filter trenches, biofilters and constructed wetlands). This study evaluated the adsorption capacity of an artificial geopolymeric aggregate (AGA), produced by alkaline activation of waste mud from the Panasqueira mine, and a lightweight expanded clay aggregate (with the commercial name of Filtralite) for acetate, ammonium phosphate and nitrate, through “batch” experiments. Inhibitors of the microbiological growth were used and the experiments run at 20ºC. The results show that the COD should not be used to evaluate the adsorption of organic molecules in those aggregates, since the respective analytical method can lead to the determination of values resulting from the simultaneous oxidation of inorganic material, released by the aggregates, organic material used as adsorbate, and the sodium azide (inhibitor of the microbiological growth). Moreover, this inhibitor is not suitable for experiments with acetate, since this last element can be reduced to ethyl alcohol, failing to be detected properly. Regardless of the aggregates used, the rates of adsorption show either an insignificant variation or very irregular concentrations of acetate, ammonium and nitrate, and a more regular adsorption of the phosphate, which was reinforced by the analysis of the errors of determination, leading to admit that both aggregates have more affinity for the phosphate ion. The rates of adsorption obtained for phosphate were 0.1 mg/g (AGA) and 0.2 mg/g (Filtralite). With this work, it was intended also to evaluate the importance of the adsorptive capacity of these aggregates when placed in treatment processes, and it was observed that their use will be most advantageous for the adhesion and biofilm growth with capacity for the biological removal of pollutants.
A artificial aggregates may constitute an alternative bed material for film-fix wastewater treatment processes (e.g. trickling beds, filter beds, filter trenches, biofilters and constructed wetlands). This study evaluated the adsorption capacity of an artificial geopolymeric aggregate (AGA), produced by alkaline activation of waste mud from the Panasqueira mine, and a lightweight expanded clay aggregate (with the commercial name of Filtralite) for acetate, ammonium phosphate and nitrate, through “batch” experiments. Inhibitors of the microbiological growth were used and the experiments run at 20ºC. The results show that the COD should not be used to evaluate the adsorption of organic molecules in those aggregates, since the respective analytical method can lead to the determination of values resulting from the simultaneous oxidation of inorganic material, released by the aggregates, organic material used as adsorbate, and the sodium azide (inhibitor of the microbiological growth). Moreover, this inhibitor is not suitable for experiments with acetate, since this last element can be reduced to ethyl alcohol, failing to be detected properly. Regardless of the aggregates used, the rates of adsorption show either an insignificant variation or very irregular concentrations of acetate, ammonium and nitrate, and a more regular adsorption of the phosphate, which was reinforced by the analysis of the errors of determination, leading to admit that both aggregates have more affinity for the phosphate ion. The rates of adsorption obtained for phosphate were 0.1 mg/g (AGA) and 0.2 mg/g (Filtralite). With this work, it was intended also to evaluate the importance of the adsorptive capacity of these aggregates when placed in treatment processes, and it was observed that their use will be most advantageous for the adhesion and biofilm growth with capacity for the biological removal of pollutants.
Description
Keywords
Tratamento de águas residuais Tratamento de águas residuais - Agregados artificiais Tratamento de águas residuais - Geopolímeros Tratamento de águas residuais - Absorção Tratamento de efluentes