Abstract:
In this experimentation, the removal of TKN in the clarified septage was tested by using an activated sludge system and an aerated lagoon system. The activated sludge system had been experimentally operated at SRT of 5, 10, 15 and 20 days while the aerated lagoon system had been operated at HRT of 3, 5, and 10 days. It was found that nitrification could effectively occur at either SRT and HRT of 10 days or more for the activated sludge and aerated lagoon respectively. At the same time, the pH and DO concentration in both system should be maintained at sufficient high levels. The importance of the alkalinity in the water had been also realized since the nitrification reaction usually consumed tremendous amount of alkalinity. In this case, sodium, bicarbonate was added into both systems to supplement for the insufficient alkalinity found in the clarified septage. If no external alkali was added, the pH of the reactors would be markedly decreased and dropped to the level of less than 6 It was also revealed that both activated sludge and aerated lagoon could effectively remove TKN. For example, the TKN concentration could be removed from about 300 or more to less than 1 mg/l. by the activated sludge system operated at the SRT of 10 days or more. However, the final effluent from the aerated lagoon contained much higher SS concentration than the effluent from the activated sludge system. When considering the final effluent quality goals to meet the Thai effluent standard, the activated sludge system was more appropriate than the aerated lagoon system since the former produced much clearer effluent than the latter.