TREATMENT OF WASTEWATER FROM BIODIESEL GENERATION AND ITS TOXICITY EVALUATION BY Raphidocelis subcapitata

Abstract

Biodiesel was developed to solve vast economic and environmental problems related to the use of petroleum as fuel. However, large quantities of water are necessary for biodiesel production, generating a high volume of effluent waste. Therefore, it is important to treat this wastewater in order to meet the environmental legislations according to the Brazilian Resolution Number 430/2011 (CONAMA). This work aimed to treat this effluent by coagulation/flocculation (CF) and an electrochemical advanced oxidation process. The combination of CF techniques (pH = 6.5) and electrochemical oxidation (boron doped diamond-BDD-electrode with NaCl) led to 78.5% removal of total organic carbon. The evaluation of the toxicity with Raphidocelis subcapitata indicated that the treated samples (IC50 72h = 1.66%) had lower chronic toxicity when compared to raw effluent samples (IC50 72h = 0.17%). This indicates that the proposed treatment was effective to decrease the organic load and reduce the environmental impact of these effluents in water bodies.

Impact of biodiesel production on wastewater generation

“…Electrooxidation showed efficiency in reducing COD and O&G of BW (JARUWAT et al, 2016), and electrocoagulation resulted in high removal of DOC and TOC (TANATTI et al, 2018). In addition, the combination of treatments, flocculation/coagulation and electrochemical, has also been shown to be effective, in terms of the removal of organic load and toxicity of BW (TORRES et al, 2018).…”

“…In these processes, a previous step with pH adjustment is usually required, and the commonly applied coagulants are aluminum sulfate (TORRES et al, 2018) and ferric chloride . Despite being widely used, it has the disadvantage of using chemical products that lead to the formation of a large volume of sludge, which makes its disposal more expensive.…”

“…Some studies have produced important results regarding the application of the coagulation/flocculation process in the treatment of wastewater from biodiesel production. Torres et al (2018) applied this treatment procedure to raw effluent and achieved a reduction of ~60% in the total organic carbon (TOC) content, demonstrating the need to implement additional treatment, since the percentage of remaining TOC was high. While Daud et al (2018) reported the removal of turbidity, COD, and soluble solids (32%, 34%, and 39%, respectively).…”

“…The combination of treatments is relevant for complex effluents, such as biodiesel, and allows combining the efficiency of physical/chemical/ biological processes, which is interesting, especially in the case of recalcitrant compounds, which are hardly removed by conventional methods (BHANOT et al, 2020). In this context, combined treatments have aroused the interest of researchers to evaluate the combination of two or more treatments; as an example of combined treatments, we have radiation UVC and H 2 O 2 (COSTA et al, 2017), oxidation and coagulation (YANG et al, 2017), membrane filtration and Fenton , flocculation/ coagulation and electrochemical (TORRES et al, 2018), and HMBB/Fenton (GONÇALVES et al, 2019), and among these, FM-Fenton resulted in greater removal of COD and O&G. et al (2019) reported that BW had low biodegradability (BOD/COD ratio = 8.6 × 10 −3 ), making the application of wet air oxidation (WAO) treatment conducive, in which the insoluble organic matter is transformed into simpler soluble compounds. WAO occurs through a radical oxidation mechanism involving organic radicals and peroxides; however, a recalcitrant effect was noted, probably due to the high temperature resistance of the oxidation intermediates generated after treatment.…”

Extraction of biodiesel from wastewater using microalgae Chlorella Vulgaris

“…The remaining algae is then mixed with hexane, filtered and cleaned so that to ensure no chemical is left behind in the oil. The second method is the super critical fluids method which can extract oil upto 100% from algae [10]. The supercritical fluid used in the carbondioxide.…”