Influence of nitrate and COD on phosphorus, nitrogen and dinitrotoluene (DNT) removals under batch anaerobic and anoxic conditions

In this study, the effects of COD to NO3-N ratio in the feed on PO4-P removal was investigated. Maximum PO4-P uptake was obtained in the anoxic reactor when the COD to NO3-N ratios were between 2 and 3.75. With the influent COD of 800-1500 mg COD/L a total of the maximum removable PO4-P was 56 mg PO4-P/L through 20 days of anaerobic/anoxic incubation, indicating 98% P removal in the anoxic reactor. Similarly, for the COD to NO3-N ratios varying between 2 and 3.75 maximum denitrification was observed. Through anoxic operation the poly-P bacteria are capable of removing NO3-N using VFA, COD as carbon source and NO3-N as the electron acceptor after methanogenesis has been completed. High NO3-N concentrations stopped significantly the P uptake. A total of 97-99% dinitrotoluene removal efficiencies in the reactors containing COD to NO3-N ratio of 2 and 3.75 after 20 days of incubation period. For maximum NO3-N and PO4-P removals optimal COD to NO3-N ratios, COD and NO3-N concentrations were 2-3.75, 2000-4000 mg COD/L and, 800-1500 mg NO3-N/L, respectively. (C) 2004 Elsevier Ltd. All rights reserved.