Nitrate-Contaminated Water Remediation Supported by Solid Organic Carbon and ZVI-Combined System

Abstract

Solid organic carbon and zero-valent iron (ZVI) have been used separately as reactive media in permeable reactive barriers (PRBs) to degrade nitrate in groundwater, but few studies have examined the combination of the two materials in one system for nitrate remediation. In the present study, batch tests are conducted to evaluate three common solid organic carbons and their combination with ZVI for nitrate removal from water. The results show that the combined system achieves better denitrification efficiency than that measured with sawdust or cotton alone. However, no obvious difference is noted between the cornstalk alone and its mixture with ZVI treatment. When complete nitrate removal is achieved in the system that combined ZVI with sawdust or cotton, only 72 and 62.6 % of nitrate removal, respectively, are obtained in which the carbon (C) source is used alone. The results indicate that there are synergistic effects in the combined denitrification system, and the effects depend on the type of carbon material used. Sawdust is an alternative carbon source for nitrate removal in a C-ZVI-combined system. In a sawdust-ZVI system, the accumulation of nitrite and ammonium is affected greatly by nitrate concentration, C/N ratio, and Fe/N ratio.

Study on the properties of denitrifying carbon sources from cellulose plants and their nitrogen removal mechanisms

“…Chemical denitrification refers to the reduction of nitrate using zero-valent iron (Fe 0 ) due to its high reaction rate (Ao et al 2019). However, ammonia generated by the reduction of nitrate results in secondary pollution in groundwater, and the process of adding Fe 0 is difficult to control (Wang et al 2015;Fageeh et al 2017;Wei et al 2018). In biological denitrification pro-cesses, using organic compounds as electron donors can reduce nitrate to nitrogen gas with higher selectivity and rate, and enhancing denitrifying bacterial activities by adjusting the microbial environment (Fowdar et al 2015).…”

“…The organic carbon compounds such as methane (Wang et al 2015), fructose, glucose (Yan et al 2016), methanol, acetic acid, and propionic acid (He et al 2015) have high bioavailability for microorganisms. However, organic carbon compounds are expansive and the implementation process is complicated.…”

Sustaining reactivity of Fe0 for nitrate reduction via electron transfer between dissolved Fe2+ and surface iron oxides

“…Recently, various modified Fe 0 by microbes [16], Fe oxides [17], minerals [18] and organic carbon [19] was used to improve the degradation effect of nitrate. It was found that the reductive efficiency of nitrate by Fe 0 increased as the concentration of dissolved ferrous ion (Fe 2+ aq ) increased in solution [20,21].…”