Feasibility of nitrate reduction combined with persulfate oxidation in the remediation of groundwater contaminated by gasoline

Wang, Huan; Chen, Yudao; He, Lewei; Jiang, Yaping; Xia, Yuan; Yang, Pengfei

Feasibility of nitrate reduction combined with persulfate oxidation in the remediation of groundwater contaminated by gasoline | Etude de faisabilité de la réduction du nitrate combinée à l’oxydation du persulfate dans la remédiation d’eaux souterraines contaminées par de l’essence Factibilidad de la reducción de nitratos combinado con la oxidación de persulfatos en la remediación de aguas subterráneas contaminadas por gasolina 硝酸盐还原联合过硫酸盐氧化修复汽油污染地下水的可行性 Viabilidade da redução por nitrato combinada com oxidação por persulfato na remediação de água contaminada por gasolina

2022

Enhanced bioremediation combined with in-situ chemical oxidation has the potential to remediate groundwater contaminated with organics. To explore the remediating effects of these two approaches and to evaluate their combined feasibility, traditional gasoline (no ethanol) and ethanol-gasoline (10% ethanol, v/v) were released into experimental sand tanks (TG-tank and EG-tank, respectively) under the same water-flow conditions. Nitrate and sulfate were added to enhance bioremediation and then persulfate was injected to encourage chemical oxidation. Two push–pull tests, using persulfate and bromide respectively, were conducted to compare their behavior. The results showed that nitrate reduction, rather than sulfate reduction, enhanced BTEX (benzene, toluene, ethylbenzene, and xylene) biodegradation, but the presence of ethanol inhibited these processes. The detected concentration of BTEX in the TG-tank was lower than that in the EG-tank, and the first-order decay rate constants of BTEX in the TG-tank and EG-tank under nitrate-adjusted conditions were 0.0058 and 0.0016 d⁻¹, respectively. The first persulfate injection (10 g L⁻¹) resulted in 86 and 94% concentration decreases of BTEX in the TG-tank and EG-tank, respectively, at first-order decay rates of 0.0180 and 0.0181 d⁻¹, respectively. However, the subsequent persulfate injections at 20 and 50 g L⁻¹ had no significant removal effect on BTEX. Persulfate oxidation made pH decrease (but it quickly recovered) and did not significantly inhibit nitrate reduction. This study suggests that enhanced nitrate reduction can be combined with persulfate oxidation for the in-situ remediation of groundwater contaminated by petroleum hydrocarbons.

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