Nitrogen removal in an anaerobic baffled filter reactor with aerobic post-treatment

A new sewage treatment system was studied, which consisted of an anaerobic baffled filter reactor and the following aerobic post-treatment. One of the two studied systems (AN-I) was inoculated with psychrophilic digested sludge, the second one (AN-II) was operated without inoculation. The HRT in anaerobic and aerobic parts of the reactors were about 15 and 4 h, respectively. The temperature in both reactors varied during the year from 4.5 to 23 °C. All monitored parameters were removed with relatively high efficiencies (COD = 78.6–83.0%, BOD5 = 92.5–94.0% and SS = 80.9–92.7%). An intensive nitrification process was observed during the whole year in both reactors (under average temperature of 5.9 °C in January 2000, also). The average removal of the NH4-N varied during the year from 46.4% to 87.3%. In both systems a partial denitrification process was observed, too.