Aerobic granular sludge can successfully be cultivated in a sequencing batch reactor (SBR) treating dairy wastewater. Attention has to be paid to the fact that suspended solids are always present in the effluent of aerobic granular sludge reactors, making a post-treatment step necessary. Sufficient post-treatment can be achieved through a sedimentation process with a hydraulic retention time of 15-30 min. After complete granulation and the separation of biomass from the effluent, removal efficiencies of 90% CODtotal, 80% Ntotal and 67% Ptotal can be achieved at a volumetric exchange ratio of 50% and a cycle duration of 8 h. Effluent values stabilize at around 125 mg l-1 CODdissolved. The maximum applicable loading rate is nevertheless limited, as the stability of aerobic granules very much depends on the presence of distinct feast and famine conditions and the degradation of real wastewaters shows slower kinetics compared with synthetic wastewaters. As loading rate and volumetric exchange ratio are coupled in an SBR system, the potential of granular sludge for improving process efficiency is also limited.

Aerobic granular sludge was successfully cultivated in a lab-scale SBR-system treating malting wastewater with a high content of particulate organic matter (0.9 gTSS/L). At an organic loading rate (CODtotal) of 3.4 kg/(m3 x d) an average removal efficiency of 50% in CODtotal and 80% in CODdissolved was achieved. Fractionation of the COD by means of particle size showed that particles with a diameter less than 25-50 microm could be removed at 80% efficiency, whereas particles bigger than 50 microm were only removed at 40% efficiency. Tracer experiments revealed a dense sessile protozoa population covering the granules. The protozoa appeared to be responsible for primary particle uptake from the wastewater.

Aims:  The applicability of plasmid pNB2 for bioaugmentation of bacteria in model wastewater treatment reactors receiving 3‐chloroaniline (3‐CA) was investigated. Methods and Results:  A setup of three biofilm reactors was studied, all initially inoculated with bacteria from activated sludge. Reactor PB received a Pseudomonas putida pNB2 donor strain not able to degrade 3‐CA. Positive control reactor P received a 3‐CA degrading Comamonas testosteroni pNB2‐transconjugant. The negative control reactor N remained unchanged. Reactor P showed 3‐CA degradation from the beginning of the experiment whereas in reactor PB, degradation started after an initial lag period. No degradation was observed in reactor N. PCR analysis showed that the P. putida donor abundance dropped in reactor PB, whereas the plasmid abundance did not, indicating transfer to other bacteria. A number of different 3‐CA degrading C. testosteroni strains carrying pNB2 could be isolated from reactor PB. Conclusions:  A successful plasmid‐mediated bioaugmentation was achieved with C. testosteroni being the dominant 3‐CA degrading pNB2 transconjugant species active in reactor PB. Significance and Impact of the Study:  The study underlines the potential of gene transfer to contribute to establishment and spread of genetic information in general, particularly emphasizing the spread of xenobiotic degrading potential by dissemination of catabolic genes.

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Aerobic granular sludge was successfully cultivated in a sequencing batch reactor (SBR) treating wastewater from the malting process with a high content of particulate organic a Lehrstuhl für Wassergüte-und matter. At an organic loading rate of 3.2 kg/(m 3 d) COD total and an influent particle concenAbfallwirtschaft, Technische Universität München, tration of 0.95 g/L MLSS an average removal of 50 % in COD total and 80 % in COD dissolved Am Coulombwall, could be achieved. A comparison of granular and flocculent sludge grown under the same 85748 Garching, Germany operating conditions showed no significant difference in removal efficiency although granb 156 Fitzpatrick Hall, University ules exhibited a higher metabolic activity in terms of specific oxygen uptake rate (r O2,X ). of Notre Dame, Notre Dame, Two distinct mechanisms of particle removal were observed for granular sludge: during IN 46556, USA initial granule formation, particles were incorporated into the biofilm matrix. For mature granules, a high level of protozoa growth on the granule surface accounted for the ability to remove particulate COD. Combined evaluation of the development in MLSS content and sludge bed settling rate (i.e., mean derivative of the normalized sludge volume) was found to be an adequate method for monitoring the characteristic settling properties of a granulizing sludge bed. By means of this method, a distinct substrate gradient out of several operating conditions was concluded to have the biggest impact on the formation of aerobic granular sludge. Behandlung von Mälzereiabwässern im SBR mit granuliertem BelebtschlammAerober