Abstract
In situ injection of Fe(II)-activated persulfate was carried out to oxidize chlorinated hydrocarbons and benzene, toluene, ethylbenzene, and xylene (BTEX) in groundwater in a contaminated site in North China Plain. To confirm the degradation of contaminants, an oxidant mixture of persulfate, ferrous sulfate, and citric acid was mixed with the main contaminants including 1,2,3-trichloropropane (TCP) and benzene before field demonstration. Then the mixed oxidant solution of 6 m3 was injected into an aquifer with two different depths of 8 and 15 m to oxidize a high concentration of TCP, other kinds of chlorinated hydrocarbons, and BTEX. In laboratory tests, the removal efficiency of TCP reached 61.4% in 24 h without other contaminants but the removal rate was decreased by the presence of benzene. Organic matter also reduced the TCP degradation rate and the removal efficiency was only 8.3% in 24 h. In the field test, as the solution was injected, the oxidation reaction occurred immediately, accompanied by a sharp increase of oxidation–reduction potential (ORP) and a decrease in pH. Though the concentration of pollutants increased due to the dissolution of non-aqueous phase liquid (NAPL) at the initial stage, BTEX could still be effectively degraded in subsequent time by persulfate in both aquifers, and their removal efficiency approached 100%. However, chlorinated hydrocarbon was relatively difficult to degrade, especially TCP, which had a relatively higher initial concentration, only had a removal efficiency of 30%–45% at different aquifers and monitoring wells. These finding are important for the development of injection technology for chlorinated hydrocarbon and BTEX contaminated site remediation.
Highlights
After decades of high-speed economic development, the chemical industry has released a large volume of miscellaneous chemicals into soil and groundwater in China [1,2,3]
To investigate the remediation efficiency of oxidation with activated persulfate for chlorinated hydrocarbons, especially TCP in groundwater, an in situ injection experiment was conducted in hydrocarbons, especially
1,3-dichloropropane, contaminated site with high concentrations of TCP, 1,2-dichloropropane, 1,3-dichloropropane, hydrocarbons, especially an inThe situchanges injection was conducted in a dichloromethane, trichloromethane, and some BTEX
Summary
After decades of high-speed economic development, the chemical industry has released a large volume of miscellaneous chemicals into soil and groundwater in China [1,2,3]. Public Health 2019, 16, 2752 because of increased recognition of its occurrence in groundwater In some of these sites, groundwater contaminated by TCP poses high risk to the health of local residents and will continue to do so for decades if no remediation measures are taken. As a common remediation technology, ISCO can effectively degrade most organic pollutants or decrease their toxicity by adding chemical agents directly into contaminated soil or groundwater [13,14]. Based on previous studies, activated persulfate was believed to be effective for in situ oxidation of TCP in groundwater. Laboratory and in situ tests were carried out to explore the effectiveness of persulfate oxidation on TCP remediation, which would provide a significant technical reference for the remediation of TCP-contaminated sites
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