Treatment of biodiesel wastewater by indirect electrooxidation: Effect of additives and process kinetics

Abstract

Due to the presence of growth inhibitor and high impurity concentration in biodiesel wastewater, both biological and chemical processes are ineffective for treating such wastewater. In this work, biodiesel wastewater was treated by electrooxidation via Ti/RuO 2 electrodes in batch and continuous modes. Effects of the additive type, hydrogen peroxide (H 2 O 2 ) and sodium chloride (NaCl), and concentration on the treatment efficiency, monitored in terms of the reduction in the biological oxygen demand (BOD), chemical oxygen demand (COD) and oil and grease level, were explored. The addition of NaCl gave higher treatment efficiency than H 2 O 2 , and both were higher than no addition, due to the continuous generation of the oxidizing chloride species. The removal of almost all the COD and oil and grease and ~95% BOD was obtained in the presence of 0.061 M NaCl at an applied current density of 4.28 mA/ cm 2 for 7 h. In continuous operation mode, the steady state condition was reached within 11 h and the treatment efficiency decreased as the wastewater feed rate increased. By using wastewater feed rate of 2 mL/min, approximately 83.56, 61.43 and 91.72% of BOD, COD and oil and grease levels were respectively removed. The rate of pollutant removal fitted a first order reaction for both the batch and continuous operation modes.

Impact of biodiesel production on wastewater generation

“…Electrooxidation and electrocoagulation are called electrochemical treatments, and these treatments are known for their high efficiency, low need for treatment space, and ease of operation (GUO et al, 2017). 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).…”

“…It is noteworthy that most of the treatments resulted in relevant data regarding the reduction of potentially polluting compounds; however, some authors did not evaluate the toxicity of BW before and after treatment (JARUWAT et al, 2016;YANG et al, 2017;FERNANDES et al, 2018;TANATTI et al, 2018). For treatments that employ photo-Fenton or Fenton, consider the analysis of fundamental toxicity, since residual H 2 O 2 can have a toxic effect PÉREZ-MOYA et al, 2017), not contributing to the reduction of dangerousness in the BW even after treatment.…”

Optimal Hydrogen Production Coupled with Pollutant Removal from Biodiesel Wastewater Using a Thermally Treated TiO2 Photocatalyst (P25): Influence of the Operating Conditions

“…This process allows the use of higher (e.g., C 4 ) alcohols in the process and produces a less polar and corrosive fatty acid methyl ester mixture with reduced cloud and pour points [ 4 ]. However, for every 100 L of biodiesel produced, approximately 20 L of wastewater are generated, which contains a high content of several impurities, such as saturated and unsaturated free fatty acids (FFA), glycerol, methanol, water and soap [ 5 , 6 ]. In Thailand, it is expected that the biodiesel consumption will grow by 8% to 1.27 × 10 9 L in 2017, compared to 1.18 × 10 9 L in 2014.…”

“…This means that at least 2.54 × 10 8 L of biodiesel wastewater will be produced, which will have to be managed and treated prior to discharge into the environment. Currently, several processes have been developed to treat or improve the properties of biodiesel wastewater, such as biological [ 5 ], physical [ 8 , 9 ], chemical [ 10 , 11 , 12 ], electrochemical [ 6 , 13 , 14 , 15 , 16 ] and combined chemical-electrochemical [ 17 , 18 ] processes. However, most of these processes can function only in organic pollutant degradation/removal and leave the chemical substances in the treated wastewater or generate large volumes of low density sludge, which still leaves economic and environmental problems with its disposal.…”

Simplified electrocoagulation for efficient biodiesel washing water treatment

“…To address this issue, researchers have explored various technologies for biodiesel wastewater treatment, including biological, physicochemical, electrochemical, and combined processes (An et al, 2017;Jaruwat, Pitakpoolsil and Hunsom, 2016;Gomes, Arroyo and Pereira, 2015;Sari-erkan, 2019;Goés et al, 2021a;Desai et al, 2017;Savci, 2017;Alves et al, 2016;Daud, Nasir and Awang, 2013;Ngamlerdpokin et al, 2011, Nidheesh, Zhou andOturan, 2018). Among these methodologies, electrocoagulation has gained significant interest in the past decade due to its simplicity, ease of operation, shorter treatment time, rapid sedimentation of electrostatic flakes, lower sludge production, and high efficiency (Chen et al, 2021;Goés et al, 2021b;Shahedi et al, 2020).…”