Advantages of electro-Fenton over electrocoagulation for disinfection of dairy wastewater

Abstract

This study is focused on the disinfection of raw dairy wastewater by means of a sequential treatment including an electrocoagulation (EC) step with an Fe|Fe cell followed by electro-Fenton (EF) or UVA-assisted photoelectro-Fenton (PEF). The two latter methods were run with an air-diffusion cathode for H2O2 generation and either a boron-doped diamond (BDD) or a RuO2-based anode. The inactivation of heterotrophic and lactic acid bacteria, Escherichia coli and enterococci was assessed. Low removal of organic load was found in all cases, whereas the bacteria were poorly removed by the flocs formed in EC but largely inactivated in EF and PEF. EF was also advantageous because it prevented the formation of harmful sludge containing active bacteria, in contrast to EC. Heterotrophs were the most stable bacteria, whereas the others were totally inactivated in most cases. In the sequential EC/EF process involving a BDD anode in the latter step, the inactivation rate for the lactic acid bacteria was higher at circumneutral pH, due to the great ability of produced active chlorine to oxidize the molecules of the cell walls. The use of a RuO2-based anode also led to a quick inactivation at pH 3.0. A better performance was achieved when PEF replaced EF, regardless of the anode, owing to the enhanced bacterial inactivation by UVA radiation. The raw dairy wastewater at natural pH 5.7 treated by single EF step with a RuO2-anode also yielded a faster removal of lactic acid bacteria, Escherichia coli and enterococci as compared to BDD, always remaining small contents of active heterotrophs in solution.

Electrochemical Recovery of Phosphorus from Acidic Cheese Wastewater: Feasibility, Quality of Products, and Comparison with Chemical Precipitation

“… 19 In particular, it was found that electrochemical treatment can result in the disinfection of dairy wastewater, along with the removal of organic loads. 20 …”

Photo-assisted electrochemical advanced oxidation processes for the disinfection of aqueous solutions: A review

“…M(OH) n ) which act as coagulant agents that catch and destabilize colloidal species in wastewater ( Çalışkan et al., 2020 ). Additionally, the H 2 gas bubbles generated at the cathode cause the flotation of pollutants and, consequently, an electro-flotation phenomenon can take place ( Bruguera-Casamada et al., 2019 ). With the integration of a UV energy source, photo-electrocoagulation processes emerge as an integrated approach in which the electro-dissolution of Fe or Al anodes is used to generate coagulant particles that not only remove suspended solids, colloidal material, pathogens as well as other dissolved solids in contaminated water (Eq.…”

Optimization of electro-Fenton oxidation of carbonated soft drink industry wastewater using response surface methodology

“…The EF process requires a short contact time, corroborating its economic justification. Moreover, there are further advantages, such as biocompatibility, versatility, controllability, and high decomposition rate of organic compounds, because of the continual regeneration of Fe 2+ on the surface of the cathode, which reduces the sludge production content in this process [15]. Despite its great potential window for purification of various kinds of wastewater, including alcoholic, shale gas, dairy, landfill leachate, textile industry, and pharmaceutical wastewaters [16], to date, this method has not been applied to treat effluents of soft drink wastewater.…”