Abstract
The significant problem is the treatment of landfill leachate characterized by high chemical oxygen demand (COD) and total organic carbon (TOC) and presence of biodegradation inhibitors such as heavy metals and oily substances. For the case of landfill leachate (pH 7.9, color 1550 mg Pt/L, COD 1880 mg O2/L, TOC 620 mg/L, total nitrogen (TN) 220 mg/L, total phosphorus (TP) 6 mg/L and heavy metals), the effect of elevated pressure and temperature on the decrease COD value by potassium ferrate(VI) (K2FeO4) was investigated. Taguchi method (TM) was employed for optimizing the treatment process parameters (repetition, pH, K2FeO4 concentration, time, temperature, and pressure). Maximizing the criterion function of signal-to-noise (S/N), the optimal parameters were determined: pH 3.5, K2FeO4 2.0 g/L, time 45 min, temperature 30 °C, and pressure of 1 MPa. At optimal conditions, a decrease of color, COD, TOC, and TP was above 91%. Additionally, the decrease of TN was 48.2%. Comparatively, at atmospheric pressure (0.1013 MPa) and at 19 °C, the decrease of color, COD, TOC, TP, and TN was 99.9%, 83.0%, 79.0%, 19.1%, and 100%, respectively. Addition of potassium ferrate(VI) may improve organic compound removal and decreases energy consumption in subcritical water oxidation.Graphical abstract
Highlights
The treatment of wastewater characterized by high chemical oxygen demand (COD) and low biological oxygen demand (BOD5) is a challenging problem (Andreozzi et al, 1999)
The methods applied for determination of total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) are described in detail elsewhere (Thomas et al, 2020)
The determined values of COD, TOC, and Total nitrogen (TN) indicated a presence of a large concentration of various substances in the analyzed leachates
Summary
The treatment of wastewater characterized by high chemical oxygen demand (COD) and low biological oxygen demand (BOD5) is a challenging problem (Andreozzi et al, 1999). A presence of inorganic radical scavengers, mainly carbonate and chloride, Page 2 of 15 decreased pollutant removal in AOPs (Drzewicz et al, 1999; Jankowska et al, 2004). It seems that only highly energy-intensive oxidation processes such as ionizing radiation (γ-radiation, electron beam irradiation, EBI), electric discharge (electrohydraulic cavitation), hydraulic cavitation, and supercritical water oxidation (SCWO) processes are capable to remove organic pollutants from wastewater (Drzewicz et al, 2004; Locke et al, 2006; Marrone, 2013; Carpenter et al, 2017; Takeuchi & Yasuoka, 2021; Wei et al, 2021). Conventional leachate treatment methods, such as air stripping, coagulation, flocculation, and settling, are often costly in terms of initial outlay of plant
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