Intermittent feeding of wastewater in combination with alternating aeration for complete denitrification and control of filaments

摘要

In the present study, a laboratory scale system, consisting of a primary settling tank, a continuousnstirred tank reactor and a clarifier were constructed and operated, using wastewater from thenmunicipal wastewater treatment plant in Xanthi, Greece. The system operated under intermittentnaeration in aerobic/anoxic conditions and feeding of the wastewater once in every cycle.nThe unit was inoculated with sludge, which originated from the recirculation stream of the localnwastewater treatment plant. The wastewater was processed with hydraulic retention time (HRT)nof 12 h, in which various experimental states were studied regarding the combination of aerobicnand anoxic intervals. The wastewater was fed in limited time once in every cyclenof aerobic/anoxic conditions at the beginning of the anoxic period. The two states that exhibitednhighest performance in nitrification and total nitrogen removal were, then, repeated with HRTnof 10 h. The results show that, regarding the nitrification stage and the organic load removal,nthe intermittent system achieved optimum efficiency, with an overall removal of biological oxygenndemand (BOD5) and ammonium nitrogen in the range of 93–96% and 91–95% respectively.nAs far as the total nitrogen removal is concerned, and if the stage of the denitrificationnis taken into account, the performance of the intermittent system surpassed other methods,nas it is shown by the total Kjeldahl nitrogen (TKN) removal efficiency of 85–87%. These operatingnconditions suppressed the growth of filamentous organisms, a fact reflected at the SVInvalues, which were lower than 150 ml/g.