Abstract
Peracetic acid (PAA) stands out as a safe and environmental-friendly oxidant and disinfectant which has been effectively used in wastewater treatment. Chemical oxygen demand (COD) is a very popular analysis in wastewater treatment; however, the interference of residual PAA on the COD measurement is still unknown. In this context, this study investigated the implications of applying the COD analysis in PAA-based treatment. Each 1 mg·L-1 of PAA increased the COD concentration around 13.5 mg O2·L-1. Residual PAA and hydrogen peroxide (H2O2) were efficiently neutralized by sodium metabisulfite (SMBS) at the optimal SMBS/PAA ratio of 10.2:1 in a wide pH range (5 to 9). The effect of PAA addition on the COD concentration was evaluated in different water matrices (potassium hydrogen phthalate and wastewater solutions). The COD results with the SMBS addition at optimal SMBS/PAA ratio were lower than the ones without it. It may happen due to the neutralization of residual H2O2/PAA and the complexity of the water matrices which can interfere in the COD results. This study discussed the impact of the residual H2O2/PAA neutralization before the COD analysis, and this investigation can be used as a practical guideline for the correct COD measurement in PAA-based treatment.
Highlights
Disinfection is a very important process in wastewater treatment to minimize the release of pathogens into the receiving water bodies, which can endanger the public health and ecosystems (Dippong et al 2017; Otter et al 2020; Rosca et al 2020)
This study investigated the interference of residual peracetic acid (PAA) in the Chemical oxygen demand (COD) measurement, which is still unknown in the literature
Each 1 mg·LÀ1 of PAA increased the COD concentration around 13.5 mg O2·LÀ1, while no COD values were detected below the concentration of 15 mg H2O2·LÀ1
Summary
Disinfection is a very important process in wastewater treatment to minimize the release of pathogens into the receiving water bodies, which can endanger the public health and ecosystems (Dippong et al 2017; Otter et al 2020; Rosca et al 2020). Chlorine is the most popular chemical disinfectant applied globally in the wastewater treatment, because of its efficiency, easy application, long-lasting effect, and low cost (El-Rehaili 1995; Quartaroli et al 2018). The chlorine reactions with the organic compounds present in wastewater can produce harmful disinfection byproducts (e.g. haloacetic acids and trihalomethanes) (Luo et al 2020). PAA has been attracting greater interest in wastewater treatment for disinfection and oxidation of targeted compounds (Falsanisi et al 2006; Appels et al 2011; Amerian et al 2019; Luukkonen et al 2020; Freitas et al 2021). PAA is commercially available as a stabilized equilibrium mixture containing PAA (typically 5 to 15% w/w), H2O2, acetic acid (CH3COOH), and water (Equation (1)) (Kitis 2004; Luukkonen et al 2014)
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