Alternative Treatment of Recalcitrant Organic Contaminants by a Combination of Biosorption, Biological Oxidation and Advanced Oxidation Technologies

CANDAL, ROBERTO; LITTER, MARTA; GUZ, LUCAS; LOPEZ LOVEIRA, ELSA; SENN, ALEJANDRO; CURUTCHET, GUSTAVO

Organic Pollutants Ten Years After the Stockholm Convention - Environmental and Analytical Update

In Tech

Año: 2012; p. 455 - 472

The results of this study show that coupling processes based on different technologies such as adsorption, biodegradation and photocatalysis are potentially useful in both, the understanding of the dynamics and fate of pollutants in superficial waters such as streams and rivers and for develop alternatives for effluent treatment. The adsorption of dyes on biomass of native bacterial strains is a very fast process that occurs in a wide range of pH with very high specific adsorption (near 30 % of the dry weight). In natural waters, biomass is commonly growing as biofilms on sediment surfaces. This fact could lead to the immobilization of the contaminant. The dye-charged biomass alone or associated with sediments shows dye degradation capacity in composting processes. With respect to potential effluent treatment processes, the isolated native strains show interesting capacities: StA strain shows very high affinity for crystal violet and could be used to treat large volumes of diluted effluents, and StE strain shows very high specific adsorption, and could be used to treat smaller volumes of concentrated effluents. From the technological point of view, adsorption-based processes could be used to reach a very fast separation of the contaminants from large volumes of water. Later use of advanced oxidation technologies could be used to the final polish of the effluent, while composting of the contaminated biomass appears to be an excellent alternative to the treatment of the formed sludge, avoiding secondary contamination or high disposal costs. With regard to the treatment of BKC, the process can be improved if the samples are submitted to a coupled treatment of a photocatalytic treatment combined with a biological system. For this purpose, different configurations of coupled photocatalytic-biological reactors can be adopted, depending mainly on the BKC concentration and the total organic load. For BKC concentrations up to 100 mg/L, the CPBR-HP treatment configuration shows some advantages. In the biological reactor, 50% BKC is degraded and this drastically reduces the COD of the effluent. The subsequent photochemical treatment leads to total BKC removal without losing efficiency by oxidizing other readily degradable compounds present in the matrix. In the case of BKC concentrations below 100 mg/L, the HP pretreatment does not work properly, because the toxicity of the photodegradation byproducts on the biofilm is higher than that of pure BKC. In the case of higher BKC concentrations (180 mg/L), the bacterial biofilm is not able to be sustained over the time; therefore, it is necessary to perform a previous HP pretreatment to reduce BKC concentration. In spite that the biomass activity decreases with time, the deleterious effect of BKC and byproducts on biofilm activity is less important compared with that of an effluent containing a very high charge of BKC and directly submitted to the biological treatment. As shown, if BKC concentration is too high (for example 180 mg/L or more), the biomass is strongly affected and BKC is released to solution. However, if the highly concentrated BKC solution is first photocatalytically treated, the biosystem can support the effluent containing the remaining BKC and its oxidation byproducts.