Remediation of phenanthrene-contaminated soil by persulfate and permanganate.

NADIA M. VILLALBA VILLABA; MARINA PELUFFO; MARCELA V. MARTIN; VERONICA C. MORA; IRMA S. MORELLI; JANINA A. ROSSO

San Diego

Congreso; : 19th International Conference on Advanced Oxidation Technologies for treatment of wáter, air and soil.; 2012

Chemical oxidation has been increasingly regarded as a relevant alternative to conventional treatment technologies for remediation of groundwater and soils contaminated by recalcitrant organic contaminants, including PAH. Chemical oxidation is able to degrade PAH but the efficiency in soils is dependent on soil characteristics and PAH properties. The aim of this study was to compare different chemical oxidants, monitoring physicochemical and biological properties of the soil, looking at the phenanthrene degradation (chosen as a model of PAH) and the impact to the microbial population. The soil was spiked (several times) with phenanthrene and then aged for 18 months in a sealed tray at 4ºC, before treatment. Before the experiment: [PHEN] = 400 ± 40 ppm, pH = 6.6 ± 0.2, Electrical Conductivity (EC) = 0.2 ± 0.2 dS m-1, Log of CFU = 8.9 ± 0.5 g-1 of dry soil. Soil microcosms consisting of 250 g of sieved soil were placed in a glass container of 400 g capacity. Three treatments were carried out in triplicate trays and incubated at 24 ± 2 ºC, for 28 days. Chemical oxidants used were persulfate (A), persulfate/Fe-EDTA (B) and permanganate (C), in a rate oxidant:phenanthrene of 0.63:1. Analyses of phenanthrene, persulfate concentration, soil characteristics (pH, EC) and microbial density were performed. At 7 days, the oxidative treatments produced a degradation of phenanthrene of 21, 86 and 71 % for treatments A, B and C, respectively. A decrease of the soil pH values and an increase of EC were observed after the addition of Persulfate (A and B) while the addition of Permanganate (C) drives the pH to slightly alkaline zone without impact on the EC. After 28 days, the degradation of fenanthrene was around 95%, for all the treatments. The values of pH approach to neutrality, due to the buffering capacity of our soil. However, EC stayed far from the initial value at A and C treatments, as consequence of the addition of PS. The number of cultivable heterotrophic bacteria was similar to untreated soil, along the whole experiment, for all the treatments studied. ?The degradation of phenanthrene at 7 days was very important at treatments B and C, in spite of working at a small dose of oxidant ?Treatment with permanganate seems to be the recommended. The perturbation on the soil characteristics was overcome after 28 days. However the impact of the introduction of Mn on the environment has to be studied carefully.