Abstract
This study investigated of the potential value of the integration of the coagulation/flocculation, Advanced Oxidation Processes (AOP) (Fenton reagent) and slow sand filtration technologies, with the aim of treating laboratory wastewater. The treatment system was designed in laboratory scale through coagulation/flocculation. It involved the use of Jar Test equipment with a sequence of two rotational phases: fast mixes to 300 rpm for 20 seconds and slow mixes to 30 rpm for 6 minutes and 10 seconds, with the addition of anionic polymer and sedimentation for 60 minutes at ambient temperature. In the treatment via Fenton reagent, two rotational phases were used: rapid mixing at 300 rpm for 20 seconds with the addition of iron (Fe2+) and slow mixing at 30 rpm for 6 minutes and 10 seconds with the addition of hydrogen peroxide, followed by 60 minutes of sedimentation at ambient temperature. A cylindrical tank of polyvinyl chloride, sands and non-woven synthetic fabrics were used in the slow filtration. The filtration rate adopted was 3 m3 m-2 d-1 with a hydraulic retention time of 264 minutes. The best concentrations of chemical reagents used in the treatments were: 0.80 mg L-1 of polymeric anionic, 200.00 mg L-1 of H2O2 and 13.00 mg L-1 of total soluble iron. The integration of the treatment technologies made it possible to achieve a removal rate of 75.27% of COD and 94.12% of total phenols. Furthermore, the conjugation of the processes allowed the removal of 87.58% of TOC.
Highlights
The cosmetic industry in Brazil showed a rapid growth up to 2014, compared with other industrial sectors
Coagulation/Flocculation treatment The most interesting results obtained in the preliminary tests (22 factorial planning) were anionic polymer concentration 0.60 mg L-1 and pH value 6.00 (31.16% chemical oxygen demand (COD) removal), where the negative charges of the effective particles which led to chemical interactions were neutralized, causing the formation of flake and incurring a lower cost, compared with the high cost of the chemical reagents involved in the process
The removal of the organic matter increased around 11% when there was a concentration of polymeric anionic of 0.80 mg L-1, which is a considerable value for treating recalcitrant compounds
Summary
The cosmetic industry in Brazil showed a rapid growth up to 2014, compared with other industrial sectors. According to Banerjee and collaborators (2016), the effluents of the cosmetic industry are harmful from an environmental standpoint; they include high concentrations of organic compounds of slow biodegradability, as well as the presence of anionic surfactants, grease and oils. These impede the aeration of the medium and the transfer of soluble substrates to microorganisms that might have been able to accomplish the degradation of the organic matter and which will reduce the rate of the substrate conversion. More than 10.000 tons of dyes are used, and approximately 100 tons are released into watercourses (Ashrafi et al, 2017)
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