The procedures to implement a chromatographic method for the quantification of linear alkyl benzene sulfonate (LAS) in the influent, effluent and sludge of a wastewater treatment plant (WWTP), and in river water and sediment, are described and evaluated. The columns octylsilane (C8) and octadecylsilane (C18) for high performance liquid chromatography were evaluated for separation of LAS homologues. The results showed that both columns separated the four homologues, but C18 was better for separation of the isomers of each homologue. This enabled to qualitatively evaluate the degradation of homologues in the WWTP, according to their respective isomers. Samples pre-treatment by solid phase extraction (SPE) columns, strong anionic exchange (SAX) and C18, was also evaluated. SPE was necessary for water river samples, either to concentrate LAS or to remove interference in the matrix; however, for WWTP samples, SPE showed unnecessary. The recovery of LAS homologues, after the procedures for sample preparation, was 90 to 110% with an accuracy of 1 to 5%. The WWTP was efficient in LAS removal from domestic sewage; however, the concentrations in water and sediments of the receiving body were higher than the limits established by legislation due to illegal discharges of untreated sewage.

RESUMO: Avaliou-se a remoção do alquilbenzeno linear sulfonato (LAS) em uma estação de tratamento de esgoto (ETE) com reator tipo UASB e lagoa de polimento durante dois períodos, seco e chuvoso. A remoção de LAS também foi avaliada em uma das 8 células do UASB (810 m3). Nessa célula, a remoção, predominantemente por adsorção, foi de 68±52 e 0% para os períodos seco e chuvoso, respectivamente. A eficiência de remoção global do LAS na ETE foi de 80±15 a 98±3%, considerando os dois períodos sazonais. A concentração de LAS no efluente da lagoa de polimento ficou entre 0,1±0,3 e 0,6±0,3 mg.L-1. Portanto, a qualidade do efluente da ETE, em termos de LAS, foi muito satisfatória, com valores inferiores aos da legislação (<0,5 mg.L-1 de LAS - CONAMA) para as substâncias definidas como aquelas que reagem com o azul de metileno, em águas superficiais de classe 1 a 3.

ABSTRACT: We evaluated the removal of linear alquilbenzene sulfonate (LAS) in a sewage treatment plant (WWTP) with a UASB reactor and a polishing pond during two seasonal periods, dry and rainy. The removal was also evaluated in one of the eight cells of the UASB reactor (810 m3). In this cell, the removal was predominantly by adsorption, of 68±52 and 0% for the dry and rainy seasons, respectively. The total removal efficiency of LAS in the WWTP was between 80±15 and 98±3%, considering the two seasonal periods. The LAS concentration in the polishing pond effluent was between 0.1±0.3 and 0.6±0.3 mg.L-1. Therefore, the quality of the final effluent, in terms of LAS, was very satisfactory, with values lower than those defined by the Brazilian legislation (<0.5 mg L-1 of LAS) of CONAMA, for substances reacting with the methylene blue, when the receiving water body is within the classes 1 to 3.

Resumo O objetivo deste trabalho foi avaliar a viabilidade do uso de lodo de esgoto como componente do substrato para produção de mudas de Senna siamea Lam. Testaram-se as seguintes proporções de lodo com solo: 0% (T1), 25% (T2), 50% (T3), 75% (T4) e uma mistura de 25% de lodo com 25% de pó de coco (T5). No experimento, utilizou-se o delineamento inteiramente casualizado, com 5 tratamentos e 5 repetições, totalizando 25 parcelas, com 16 mudas por parcela. O lodo foi previamente higienizado por solarização. Avaliou-se a matéria seca das mudas e foram efetuadas análises químicas dos substratos, três meses após a semeadura. Dentre os tratamentos nos quais foi empregado lodo, a concentração de T5 foi a que apresentou o melhor desenvolvimento das mudas, seguida daqueles com 75% (T4) e 50% (T3) de lodo. Todos os tratamentos apresentaram desenvolvimento superior ao da testemunha (T1). Conclui-se, então, que o uso do lodo de esgoto para produção de mudas é viável e promissor.

Abstract The objective of this study was to evaluate the feasibility of using the sewage sludge as substrate component for seedlings production of Senna siamea Lam. Different proportions of sewage sludge were used: 0% (T1), 25% (T2), 50% (T3), 75% (T4) and a mixture of 25% of sludge, 25% of coconut powder (T5). For the experiment, a completely randomized design was employed, with 5 treatments and 5 replications, totaling 25 units with 16 seedlings per unit. The sludge was disinfected by solarization one month before sowing. The dry matter content in the aerial portion of the seedlings was assessed and chemical analysis of the substrate was performed three months after sowing. Among the treatments using sludge, T5 concentration was best for plant growth followed by T4 (75%) and T3 (50%) concentrations. All seedlings treated with sludge developed better than the control plant. It is concluded that use of sewage sludge for seedlings is feasible and promising.