In this study, pyrite-based denitrification using untreated pyrite (UP) and acid-pretreated pyrite (AP) was evaluated as an alternative to elemental sulfur based denitrification. Pyrite-based denitrification resulted in a favorable nitrate removal rate constant (0.95 d (1)), sulfate production of 388.00 mg/L, and a stable pH. The pretreatment of pyrite with acid led to a further increase in the nitrate removal rate constant (1.03 d (1)) and reduction in initial sulfate concentration (224.25 +/- 7.50 mg/L). By analyzing the microbial community structure using Denaturing Gradient Gel Electrophoresis, it was confirmed that Sulfurimonas denitrificans (S. denitrificans) could utilize pyrite as an electron donor. A stable pH was observed over the entire experimental period, indicating that the use of a pH buffer reagent would not be necessary for pyrite-based denitrification. Therefore, pyrite could effectively replace elemental sulfur as an electron donor in autotrophic denitrification for nitrate-contaminated groundwater remediation. (C) 2014 Elsevier Ltd. All rights reserved.