Effects of Chitin Purity and Proppant Loading on the Bioremediation of Chloroethenes

Abstract

Hydraulic fracturing (or fracking) of substrates and proppants into contaminated soils is a developing, but understudied, practice of stimulating in situ bioremediation. In this work, three different purities of the substrate crab shell chitin (SC-20, SC-40, and SC-80), two proppant loadings (sand:chitin mass ratios of 5∶1 and 15∶1), and three chloroethene concentrations (1 and 10 mg∕L trichloroethene, and 1:5 mg∕L cis-1,2-dichloroethene) were experimentally and statistically examined to determine their effects on halorespiration. The least refined crab shell, SC-20, produced the greatest variety of electron donors, converted the highest percentage of contaminant mass to ethene, and supported a significantly greater Dehalococcoides population than the other substrates. Although influent chloroethene concentration and proppant loading did not significantly affect halorespiration (p-values > 0:079), decreasing the proppant loading from 15∶1 to 5∶1 increased the longevity of electron-donor production. These results indicate that funds need not be expended for purification of crab shell substrates, and that SC-20 should be used with proppant loadings of 5∶1 or lower to maximize the duration of electron-donor production at sites with potential biodegradation rate limitations.

Ensuring the continued success of a mulch biowall at a trichloroethylene‐contaminated superfund site: Lessons learned

“…Therefore, amending the groundwater with a buffering material, such as limestone, could have increased the pH and provided the microbial community with a more suitable condition for dechlorination to occur. Chitin is another alternative that can act both as a slow‐release buffer and an electron donor in the groundwater (McElhoe & Brennan, 2012; Pinto et al, 2018; Robinson‐Lora & Brennan, 2009).…”