[Using paper as the carbon source for groundwater nitrate removal].

The nitrate removal from groundwater was studied in laboratory columns packed with unprocessed paper as the sole substrate for microbial population. The results showed that the reactor with paper as carbon source started up fast, and temperature and hydraulic retention time (HRT) markedly affected the denitrification process. The denitrification rate at 25 degrees C was approximately 1.7 times higher than that at 14 degrees C. When the initial concentration was 45.2 mg x L(-1), 99.6% of nitrate (nitrite was not detected) could be removed after 8.6 h at 25 +/- 1 degrees C. The nitrogen removal rate was only 50% when HRT was 7.2 h. pH and dissolved oxygen (DO) had little effect on denitrification, and the nitrogen removal rate did not changed when pH value ranged between 6.0-9.0 and DO ranged between 0-6 mg x L(-1). Biofilm was formed on the paper and consumed the paper during the whole process. Using the combined paper reactor and activated carbon adsorption at 25 +/- 1 degrees C and HRT 9.0 h, the nitrate could be completely removed if its initial concentration was not higher than 33.9 mgN x L(-1) and the dissolved organic carbon (DOC) in the effluent was less than 11 mg x L(-1).