The ability of three different polymeric organic materials (POMs) to create redox conditions favorable for reductive processes such as dechlorination was evaluated over a period of 70 days. Corn crop residue, unrefined chitin, and wood shavings were mixed with sand, packed into columns, and flushed with fresh groundwater once per day. Extracted groundwater was evaluated for pH, hydrogen, methane, volatile fatty acids (VFAs), alcohols, dissolved organic carbon (DOC), and chemical oxygen demand (COD). The pH measured for all POMs was between 5 and 8.5, with values after 30 days generally between 6 and 8. Hydrogen and methane concentrations indicated that all columns remained anaerobic during the entire experiment. Acetate was the dominant VFA in all columns, although propionate, butyrate, isobutyrate, and isovalerate were detected at much lower concentrations. Also, acetate concentrations were greater at all times in columns containing unrefined chitin (4 to 43 mM) than in those containing either corn crop residue (1 to 7 mM) or wood shavings (0 to 3 mM). Total electron donating capacities for dechlorination (expressed as total chloride removal capacities) were estimated from total COD and hydrogen concentrations. This capacity was greater in the column containing unrefined chitin than in those containing either corn crop residue or wood shavings. Overall the electron donating capacities remaining after 70 days were 40%, 11%, and 44% of the initial values for the corn crop residue, the unrefined chitin, and the wood shavings, respectively. The results indicate that over a 70-day period, anaerobic and nutrient-rich conditions were sustained for all POMs, but that the amount of electron donor available for reductive terminal electron accepting processes varies between POMs and is greatest for unrefined chitin.
ASJC Scopus subject areas
- Environmental Science(all)