Managing habitat and microorganisms for degrading industrial effluents: a study case

Se evaluó la eficiencia de prácticas de manejo de hábitat y microorganismos para degradar efluentes en una industria metalúrgica de Córdoba, Argentina. Para optimizar la actividad de organismos del agua, el suelo y la rizosfera de las plantas, se manejaron tres hábitats: acuático, de humedales y agrícola. Las prácticas fueron: introducción de vegetación palustre y terrestre, aireación del agua, laboreos, remoción de sedimentos e inoculación con bacterias seleccionadas. Se evaluaron los siguientes parámetros: pH y contenido de bacterias en el agua, y contenido de aceites, Cr y Zn en los sedimentos, suelo y napa freática. El pH registrado fue siempre muy elevado (entre 8.4 y 10.9), mientras que la cantidad de bacterias descomponedoras aumentó hasta valores que fluctuaron entre log 3.6 y 8.9/ml. No se observó aumento en la población microbiana después de la inoculación. Los sedimentos presentaron elevado pH, Zn y Cr y escaso contenido de aceites. No se detectaron estos contaminantes ni en el suelo ni en la napa. Mediante el manejo de hábitat se logró una eficiente degradación de los aceites del efluente y una ausencia total de lixiviados, barros y agua remanente. The efficiency of a treatment for industrial effluents based on a combination of habitat and microbial population management was tested in a metallurgic plant in Córdoba, Argentina. Effluents (between 30 - 40 m3 day) were originated from a) zinc process (20%), b) engine washing (70%), and c) sewage (10%). The treatment process included a combination of three managed habitats: aquatic (pond), wetland (flooding plots), and agricultural land (flooding and crop plots). The three habitats were managed to optimize the degrading activity of water, soil, and phyllosphere microorganisms. Management practices included introduction of terrestrial and aquatic vegetation, water aeration, sediment removal, and inoculation of selected native microorganisms. Efficiency was assessed through five years using the following parameters: a) monthly: water pH and abundance of degrading and coliform bacteria in the pond b) yearly: Zn, Cr and mineral oil content in the underground water (9 m deep), sediments in the ponds and organic matter in the subsoil (1 and 2 m deep). Water pH was permanently high (8.4 -10.9), whereas abundance of degrading microorganisms was very low at the beginning (log 1.2/ ml) increasing through the following years and with fluctuations of between log 3.6 and 8.9/ ml. No increase in bacterial abundance was detected after inoculation. Coliform bacteria were scarcely observed. High concentration of Zn (6.48 – 7.08 mg/kg) and Cr (0.19 – 0.50 mg/kg) and low mineral oil content (0.23 – 1.01 mg/kg) were detected in the pond’s sediments. None of these components were detected in underground water and subsoil. Habitat management allowed an efficient degradation of sewage and mineral oils. The system does not produce waste material such as sludge, water, nor underground water pollution.