Denitrification of nitrate-contaminated groundwater using biodegradable snack ware as carbon source under low-temperature condition

Abstract

A considerable increase in nitrate concentration in groundwater has been observed in many countries. This research focuses on nitrate removal using biodegradable snack ware (BSW) as both carbon source and biofilm support for denitrifiers. The denitrification efficiency of a laboratory-scale denitrification reactor packed with BSW was examined in a low-temperature condition. The nitrate removal efficiency supported by BSW decreased to approximately 40% at 12°C from nearly 100% at 25°C with 50 mg/L of nitrate-nitrogen in the influent and 2 h of hydraulic retention time (HRT). The complete nitrate removal was obtained when nitrate-nitrogen concentration was no more than 15 mg/L at 2 h of HRT and at 12°C. If the initial concentration of nitrate-nitrogen was 50 mg/L, 5 h of HRT was needed for the complete nitrate removal. Nitrite concentration in the treated water decreased evidently as HRT was increased from 2 to 5 h, or as nitrate-nitrogen concentration in the influent decreased to 15 mg/L from 50 mg/L. It was observed that varying HRT and nitrate concentration in the influent had no noticeable effect on dissolved organic carbon content in the effluent under the experimental conditions. This study indicated that the complete nitrate removal could be achieved readily even at 12°C using BSW as carbon source by changing HRT or the initial concentration of nitrate in the influent, which has some useful implications in environmental engineering practice.