Abstract
This study investigates how the non-thermal plasma (NTP) process leads to advanced oxidation of sewage using response surface methodology. For environmentally viable and efficient operation of the NTP process, temperature and contact time were selected as two important independent variables. Their impacts on the performance were tested following an experimental design to figure out optimal operating conditions. Based on obtained treatment efficiency, statistically optimized conditions were derived by using an approach adapting the central composite design. Results show that coupling 40 °C of temperature and 4 h of contact time demonstrate optimal performance for total chemical oxygen demand (TCOD, 59%) and total suspended solids (85%), respectively. This implies that NTP may present efficient particulate destruction leading to organic solids dissolution. Statistical analysis reveals that the contact time shows more significant dependency than the temperature on the advanced oxidation of TCOD, possibly due to dissolved organic material. For total nitrogen removal, on the contrary, the optimal efficiency was strongly related to the higher temperature (~68 °C). This work provides an inroad to considering how NTP can optimally contribute to better oxidation of multiple pollutants.
Highlights
Applying conventional oxidants such as chlorine or ozone (O3 ) can destroy target pollutants but has a crucial disadvantage in that certain organic substances turn into residual by-products during the oxidation [1,2]
Using the non-thermal plasma (NTP) system, this study evaluates NTP’s impacts on effluent quality by variation of temperature and contact time (CT)
The main hypothesis is that the dynamics of pH, TOC, Total suspended solids (TSS), and total nitrogen (TN) in the effluent are strongly interrelated with temperature and CT for optimal performance
Summary
Applying conventional oxidants such as chlorine or ozone (O3 ) can destroy target pollutants but has a crucial disadvantage in that certain organic substances turn into residual by-products during the oxidation [1,2]. Continuous disinfection with chlorine produces by-products such as trihalomethanes and halo-acetic acids that are problematic for human health [3].To compensate for such drawbacks, advanced oxidation processes (AOPs) have been applied alternatively [4]. Numerous methods have been attempted such as Fenton oxidation, peroxone, catalyzed. Fenton oxidation, using oxidants formed from ferrous salts plus H2 O2 in acidic solution, produces excessive sludge and demonstrates low efficiency when organic contents are high [6,7]. Peroxone needs proper control over the ratio between O3 and hydrogen peroxide (H2 O2 ) [9].
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