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Abstract
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.
Acknowledgments
The authors acknowledge the financial support of Colciencias (Colombia) and AlfaTECSPAR Network (European Community), likewise to the 2011-2012 sustainability grant of the Vicerrectorıa de Investigaciones of the Universidad de Antioquia. The Research Group Diagnóstico y Control de la Contaminación (University of Antioquia) and the Environmental Engineering Department, Civil Engineering Faculty (University of Cauca) are thanked for their technical support. The author Tomás R. Florville-Alejandre dedicates this paper to the memory of his father, Dr. Tomás Ramón Florville Andrade (1930–2006).