Wheat straw, sawdust, and biodegradable plastics as potential carbon sources for synthetic nitrate-polluted groundwater column denitrification

Biological denitrification of nitrate-polluted groundwater involves the selection of an appropriate organic carbon source. This paper aimed to evaluate the effects of wheat straw, sawdust, and biodegradable plastics as carbon sources on denitrification through column experiments. Results showed that the biodegradable plastics group released less nitrogen compounds than the wheat straw and sawdust groups. In the column denitrification experiments, the nitrate concentrations in the effluents obtained from the sawdust and wheat straw columns were below 2.50 and 3.00 mg NO3--N L-1 at 25 degrees C +/- 2 degrees C and steady-state conditions, while the nitrate removal efficiency was about 95% and 94%, respectively. For biodegradable plastics, the nitrate removal efficiency was about 99%. Moreover, the nitrite concentrations were lower than 0.05 mg NO2--N L-1 or undetected at steady-state conditions for all columns. These findings indicated that wheat straw, sawdust, and biodegradable plastics can be used as solid carbon sources for denitrification, and biodegradable plastics had the best performance for denitrification stimulation. Notably, nitrate breakthrough and nitrite accumulation occurred when the temperature was reduced to 16 degrees C +/- 2 degrees C, indicating that the temperature influenced denitrification.