The effect of seed sludge type on aerobic granulation via anoxic-aerobic operation (original) (raw)
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This study was carried out to investigate the effects of seed sludge properties and the selective sludge discharge method on aerobic granulation in biological wastewater treatment. Small-loose flocs and larger-denser flocs were separated from raw activated sludge by sedimentation in a settling column. The two types of sludge were used as seed biomass in two laboratory batch reactors for the granulation experiment. A fixed daily sludge discharge ratio of around 10% of slow-settling sludge was applied to the two reactors. The results showed that aerobic granules could be formed in the reactors from both seed sludge of different structural and settling properties. The initial washout of small-loose sludge flocs during the start-up of the bioreactors did not appear to be a crucial factor for granulation. The key operating parameter was the daily discharge of relatively slow-settling biomass from the reactors. PCR-DGGE analysis showed insignificant differences between the bacterial communities of the mature granular sludge in the two reactors. It implied that continuous discharge of small and slow-settling flocs removed these competitors for substrate uptake from the system and hence made the substrate more available for large and compact flocs and granules. This selective sludge discharge facilitated the growth and accumulation of denser sludge in the reactor, leading to complete granulation.
Critical Reviews in Biotechnology, 2011
Aerobic granular sludge can be classified as a type of self-immobilized microbial consortium, consisting mainly of aerobic and facultative bacteria and is distinct from anaerobic granular methanogenic sludge. Aerobic granular technology has been proposed as a promising technology for wastewater treatment, but is not yet established as a large-scale application. Aerobic granules have been cultured mainly in sequenced batch reactors (SBR) under hydraulic selection pressure. The factors influencing aerobic granulation, granulation mechanisms, microbial communities and the potential applications for the treatment of various wastewaters have been studied comprehensively on the laboratory-scale. Aerobic granular sludge has shown a potential for nitrogen removal, but is less competitive for the high strength organic wastewater treatments. This technology has been developed from the laboratory-scale to pilot scale applications, but with limited and unpublished full-scale applications for municipal wastewater treatment. The future needs and limitations for aerobic granular technology are discussed.
Water Research, 2013
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Water, 2021
Aerobic granular sludge (AGS) comprises an aggregation of microbial cells in a tridimensional matrix, which is able to remove carbon, nitrogen and phosphorous as well as other pollutants in a single bioreactor under the same operational conditions. During the past decades, the feasibility of implementing AGS in wastewater treatment plants (WWTPs) for treating sewage using fundamentally sequential batch reactors (SBRs) has been studied. However, granular sludge technology using SBRs has several disadvantages. For instance, it can present certain drawbacks for the treatment of high flow rates; furthermore, the quantity of retained biomass is limited by volume exchange. Therefore, the development of continuous flow reactors (CFRs) has come to be regarded as a more competitive option. This is why numerous investigations have been undertaken in recent years in search of different designs of CFR systems that would enable the effective treatment of urban and industrial wastewater, keeping ...