Giardia spp. and Cryptosporidium spp. removal efficiency of a combined fixed-film system treating domestic wastewater receiving hospital effluent.

Giardia and Cryptosporidium have caused numerous outbreaks of diarrhea as a result of the ingestion of water contaminated with sewage. In Brazil, the efficiency of Giardia and Cryptosporidium removal by combined fixed-film systems has rarely been studied. The aims of the present study were therefore to verify the removal efficiency of Giardia and Cryptosporidium by a combined system (anaerobic/anoxic filter and aerated submerged biofilter) and to perform the genetic characterization of these parasites. The (oo)cysts were detected by centrifuge concentration and membrane filtration from raw sewage, effluents, adhered biomass, and sludge samples. Immunofluorescence assay and differential interference contrast microscopy were used for the visualization of the (oo)cysts. Nested PCR was applied to confirm Giardia and Cryptosporidium. Giardia and Cryptosporidium were detected in 27% and 5.5% of the 144 analyzed samples of raw sewage and effluents, respectively. A total of 33,000 cysts/L were recovered in the adhered biomass samples (n = 25) from different points of the aerated submerged biofilter, while 6000 oocysts/L were registered in a single point. An average of 11,800 cysts/L were found in the sludge samples (n = 5). The combined system exhibited a removal efficiency of Giardia cysts of 1.8 ± 1.0 log removal. The C and BIV assemblages of Giardia were identified in the raw sewage while AII was found in the treated effluent sample. It was not possible to calculate the removal efficiency of Cryptosporidium oocysts by the combined system. The combined system exhibited some potential as a suitable treatment for the removal of parasites from sewage.

Tratamento de esgoto sanitário por escoamento superficial no solo: remoção de metais / Wastewater treatment by overland flow: removal of metals

RESUMO Com o objetivo de avaliar a remoção e a concentração dos metais cádmio (Cd), cromo (Cr), cobre (Cu), chumbo (Pb), ferro (Fe), níquel (Ni) e zinco (Zn) em águas residuais municipais, foram conduzidos ensaios de campo utilizando o método do escoamento em duas taxas de aplicação superficial, 0,30 e 0,20 m3.m-1.h-1, em uma rampa de 4,25 × 40 m, com 3,5% de declividade, plantada com Tifton 85 (Cynodon spp.). Em amostras coletadas durante o estudo de 15 meses, apenas Cu, Cr e Pb excederam os limites de lançamento de acordo com a Resolução do Conselho Nacional do Meio Ambiente (CONAMA) nº 430/2011 (BRASIL, 2011). A taxa de aplicação não influencia na remoção superficial de Cd, Cr, Cu, Fe, Ni e Pb, no entanto maior remoção de Zn ocorreu ao empregar taxas de aplicação superficial de 0,30 m3.m-1.h-1. A taxa de aplicação não influencia a incorporação de Cd, Cr, Fe, Ni e Zn na biomassa, porém maior incorporação de Pb ocorreu ao aplicar 0,20 m3.m-1.h-1.

ABSTRACT In order to evaluate the removal and concentration of the metals cadmium (Cd), chrome (Cr), copper (Cu), lead (Pb), iron (Fe), nickel (Ni) and zinc (Zn) in municipal wastewater, we conducted field tests using the method of overland flow under two rates of surface application, 0.30 and 0.20 m3.m-1.h-1, on a ramp of 4.25 × 40 m with a slope of 3.5%, planted with Tifton 85 (Cynodon spp.). In samples collected during the 15-month study, only Cu, Cr and Pb exceeded the discharge limit according to the National Environment Council (CONAMA) Resolution n. 430/2011 (BRASIL, 2011). The application rate does not influence the surface removal of Cd, Cr, Cu, Fe, Ni and Pb; however, higher Zn removal occurred by applying rates of surface application of 0.30 m3.m-1.h-1. The rate of application does not influence the incorporation of Cd, Cr, Fe, Ni and Zn in the biomass, but greater incorporation of Pb occurred when applying 0.20 m3.m-1.h-1.

Degradação de formaldeído tratado em conjunto com esgoto sanitário em sistema combinado anaeróbio-aeróbio / Degradation of formaldehyde treated in conjunction with municipal sewage in combined anaerobic-aerobic system

O estudo visou a investigação da degradação de formaldeído em um sistema combinado anaeróbio-aeróbio, de fluxo ascendente e com biomassa imobilizada, constituindo-se por um filtro anaeróbio seguido de biofiltro aerado submerso. As concentrações de formaldeído aplicadas ao sistema variaram de 26 a 1.055 mg HCHO.L-1, resultando em eficiências de remoção de formaldeído de 97±3% e de DQO de 90±6%. A partir dos resultados obtidos, conclui-se que o sistema combinado se apresentou adequado para o tratamento de esgoto sanitário contendo formaldeído, uma vez que além de eficiências de remoção representativas, apresentou estabilidade de operação durante o decorrer do estudo.

The study aimed to investigate the degradation of formaldehyde in an anaerobic-aerobic combined system, upflow and with immobilized biomass, consisting of an Anaerobic Filter (AF) followed by Aerated Submerged Biofilter (ASB). The concentrations of formaldehyde applied to the system ranged from 26 to 1,055 mg HCHO.L-1, resulted in a removal efficiency of formaldehyde of 97±3% and chemical oxygen demand (COD) of 90±6%. From the results, it is concluded that the combined system was suitable for treating wastewater containing formaldehyde, since besides representative removal efficiencies; operation was stable during the course of the study.

Remoção de nitrogênio em sistema combinado anóxico-aeróbio com biomassa imobilizada / Nitrogen removal in combined anoxic-aerobic system with imobilized biomass

Este trabalho visa estudar o desempenho de um sistema combinado na remoção de matéria orgânica e nitrogênio de esgoto sanitário, por meio da recirculação interna do efluente. Os reatores, em escala de bancada, foram: filtro anóxico (32,6 L), biofiltro aerado submerso (17,6 L) e decantador secundário (7,2 L). As razões de recirculação foram 0,5; 1,5; 2,0 e 4,0 sem adição de carbono externo ou alcalinizante. Na razão de recirculação de 4,0 foram aplicadas taxas de carregamento orgânico e de nitrogênio ao sistema de 0,7±0,3 Kg DQO.m-3.d-1 e 0,08±0,02 kg N-NH4 +.m-3.d-1, atingindo remoções de demanda química de oxigênio e nitrogênio total de 92±4% e 83±8%, respectivamente. Os resultados mostram viabilidade do uso da recirculação do efluente, uma vez que as concentrações finais de nitrogênio total (12±3 mg N.L-1) estão abaixo do valor estipulado pela Resolução CONAMA nº 430/2011.

This work aims to study the performance of a combined system in the removal of organic matter and nitrogen from sanitary sewage through internal recirculation of the effluent. The bench scale reactors were: anoxic filter (32.6 L), submerged aerated biofilter (17.6 L) and secondary settler (7.2 L). The recirculation rates were 0.5; 1.5; 2.0 and 4.0 without added external-carbon or alkalising. In 4.0 recirculation rate, the organic and nitrogen loading rates applied to the system were 0.7±0.3 kg chemical oxygen demand.m-3.d-1 and 0.08±0.02 kg N-NH4 +.m-3.d-1, reaching removals of chemical oxygen demand and total nitrogen of 92±4% and 83±8%, respectively. The results show the feasibility of using recirculation of effluent, once the final concentrations of total nitrogen (12±3 mg.L-1) are below the value stipulated by CONAMA Resolution nº 430/2011.