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| Although the use of partial nitrification, or nitritation, for nitrogen removal via nitrite is an energy-saving method for treating high-strength ammonia wastewater, its stable operation with sufficient enrichment of ammonia-oxidizing bacteria (AOB) is difficult to maintain in activated sludge systems. In this study, an aerobic granulation technique was developed for the effective and stable nitritation treatment of ammonia-rich inorganic influent. Granular activated carbon (GAC) was added to the bioreactor to enhance the granulation of slow-growing AOB. The results show that aerobic granules could be formed for partial nitrification through the selective discharge of small and slow-settling sludge flocs, with or without activated carbon addition. However, dosing GAC into the sludge greatly accelerated the granulation process and shortened the granulation period from about 6 weeks to less than 3 weeks with the formation of large and fast-settling granules. Compared to activated sludge flocs, sludge granulation with selective sludge discharge was found to help halt ammonia oxidation to the level of partial nitrification rather than complete nitrification. |
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| Keywords:Aerobic granulation; Partial nitrification; Granular activated carbon |
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