RESUMO

RESUMEN Los humedales construidos en los últimos años han sido ampliamente usados en la depuración de una gran variedad de aguas residuales, por ser una alternativa que ofrece múltiples ventajas, en comparación con otros sistemas de tratamiento. Este estudio evaluó la eficiencia de seis sistemas de humedales, construidos de flujo subsuperficial horizontal (HCFSSH), a escala piloto, para la remoción de materia orgánica (DQO), nutrientes (N-NO3-, P-PO43-) y plomo (Pb+2), además de la incidencia del tiempo de operación sobre la conductividad hidráulica (Ks) para tratar lixiviados del Relleno Sanitario "El Ojito", del municipio de Popayán, Cauca. Tres humedales fueron plantados con Heliconia psittacorum (HCFSSH-H. p) y tres con Cyperus haspan (HCFSSH-C. h); el medio de soporte utilizado fue grava, operados con un caudal de 0.012m3/día y un tiempo de retención hidráulico de 4 días; las unidades recibieron efluente de una laguna de oxidación. Los resultados mostraron remociones medias de: DQO (51,67 y 64,00%), N-NO3- (45,33 y 48,17%), P-PO43- (53,67 y 62,67%) y Pb+2 (5,74 y 14,75%) para los HCFSSH-H. p y HCFSSH-C. h, respectivamente y valores de conductividad hidráulica, entre 700 y 1000m/día. El sistema de humedales mostró ser eficiente para el tratamiento secundario de lixiviado de rellenos sanitarios maduros, obteniendo eficiencias de remoción, significativamente mayores, en los HCFSSH-C.h.

ABSTRACT In recent years, constructed wetlands have been widely used for the purification of wastewater, representing an alternative method that offers multiple advantages when compared to other treatment systems. The present study assessed the efficiency of six horizontal subsurface flow constructed wetlands (HSSFCW) at pilot scale for the removal of organic matter (COD), nutrients (N-NO3-, P-PO43-) and lead (Pb2+). The study also looked at the operating time on hydraulic conductivity (Ks) to treat leachate from the "El Ojito" Sanitary Landfill in the municipality of Popayán, Cauca. Three wetlands were planted with Heliconia psittacorum (HSSFCW-H. p), and three with Cyperus haspan (HSSFCW-C. h). The support medium used was gravel. They were operated at a flow of 0.012m3/day, and a hydraulic retention time of 4 days. The units received effluent from the oxidation pond. The results showed mean removals of COD (51.67 and 64.00%), N-NO3- (45.33 and 48.17%), P-PO43- (53.67 and 62.67%) and Pb+2 (5.74 and 14.75%) for HSSFCW-H. p and HSSFCW-C. h respectively. Hydraulic conductivity values were between 700 and 1000m/day. The wetland system proved to be efficient for the secondary treatment of leachate from mature landfills, obtaining removal efficiencies significantly higher in HSSFCW-C. h.

RESUMO

The most efficient system of horizontal subsurface flow constructed wetlands (HSSFCW) for removing dissolved organic carbon (DOC) in the presence of chlorothalonil pesticide (CLT) present in synthetic domestic wastewater was determined using the macrophyte Phragmites australis. Two concentrations of CLT (85 and 385 µg L-1) and one concentration of glucose (20 mg L-1) were evaluated in four pilot scale horizontal surface flow constructed wetlands coupled with two sizes of silica gravel, igneous gravel, fine chalky gravel (3.18-6.35 mm), coarse gravel (12.70-25.40 mm) and two water surface heights (20 and 40 cm). For a month, wetlands were acclimated with domestic wastewater. Some groups of bacteria were also identified in the biofilm attached to the gravel. In each treatment periodic samplings were conducted in the influent and effluent. Chlorothalonil was quantified by gas chromatography (GC-ECD m), DOC by an organic carbon analyzer and bacterial groups using conventional microbiology in accordance with Standard Methods. The largest removals of DOC (85.82%-85.31%) were found when using fine gravel (3.18-6.35 mm) and the lower layer of water (20 cm). The bacterial groups quantified in the biofilm were total heterotrophic, revivable heterotrophic, Pseudomonas and total coliforms. The results of this study indicate that fine grain gravel (3.18-6.35 mm) and both water levels (20 to 40 cm) can be used in the removal of organic matter and for the treatment of agricultural effluents contaminated with organo-chloride pesticides like CLT in HSSFCW.

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RESUMO

This study investigates the effects of chlorothalonil (CLT) on chemical oxygen demand (COD) and dissolved organic carbon (DOC) in pilot-scale horizontal subsurface flow constructed wetlands (HSSFCW) planted with Phragmites australis. Physicochemical parameters of influent and effluent water samples, microbial population counting methods and statistical analysis were used to evaluate the influence of CLT on organic matter removal efficiency. The experiments were conducted on four planted replicate wetlands (HSSFCW-Pa) and one unplanted control wetland (HSSFCW-NPa). The wetlands exhibited high average organic matter removal efficiencies (HSSFCW-Pa: 80.6% DOC, 98.0% COD; HSSFCW-NPa: 93.2% DOC, 98.4% COD). The addition of CLT did not influence organic removal parameters. In all cases CLT concentrations in the effluent occurred in concentrations lower than the detection limit of the analytical method. Microbial population counts from HSSFCW-Pa showed significant correlations among different microbial groups and with different physicochemical variables. The apparent independence of organic matter removal and CLT inputs, along with the CLT depletion observed in effluent samples demonstrated that HSSFCW are a viable technology for the treatment of agricultural effluents contaminated with organo-chloride pesticides like CLT.

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