ABSTRACT
Aerobic granulation of activated sludge was successfully achieved in a full-scale sequencing batch reactor (SBR) with 50,000 m(3) d(-1) for treating a town's wastewater. After operation for 337 days, in this full-scale SBR, aerobic granules with an average SVI30 of 47.1 mL g(-1), diameter of 0.5 mm, and settling velocity of 42 m h(-1) were obtained. Compared to an anaerobic/oxic plug flow (A/O) reactor and an oxidation ditch (OD) being operated in this wastewater treatment plant, the sludge from full-scale SBR has more compact structure and excellent settling ability. Denaturing gradient gel electrophoresis (DGGE) analysis indicated that Flavobacterium sp., uncultured beta proteobacterium, uncultured Aquabacterium sp., and uncultured Leptothrix sp. were just dominant in SBR, whereas uncultured bacteroidetes were only found in A/O and OD. Three kinds of sludge had a high content of protein in extracellular polymeric substances (EPS). X-ray fluorescence (XRF) analysis revealed that metal ions and some inorganics from raw wastewater precipitated in sludge acted as core to enhance granulation. Raw wastewater characteristics had a positive effect on the granule formation, but the SBR mode operating with periodic feast-famine, shorter settling time, and no return sludge pump played a crucial role in aerobic sludge granulation.
Subject(s)
Bioreactors/microbiology , Sewage , Waste Disposal, Fluid/methods , Water Purification/methods , Aerobiosis , Bacteria/metabolism , Sewage/chemistry , Sewage/microbiologyABSTRACT
A modified oxidation ditch (MOD) with an adjustable volume intraclarifier was proposed and used to achieve aerobic sludge granulation in continuous flow process. This MOD with working volume of 60L treated onsite wastewater from a town. Excellent aerobic granules with mean diameter of 600µm and sludge volume index (SVI) of 44mL/g were obtained in 120day. Bacterial community analysis revealed that most species from seed sludge were preserved in both MOD and granule SBR (G-SBR) except bacteria (Bacteroidetes) might be easily washed out during granulation. Some different bacterial communities were found in sludges from sequencing batch and continuous flow reactors. Presence of metal ions and inorganics in raw wastewater had positive effect on granule formation, but an adjustable volume intraclarifier for controlling selection pressure and deleting return sludge pump played a key role in aerobic sludge granulation.
Subject(s)
Sewage/chemistry , Aerobiosis , Bacteria/genetics , Base Sequence , Biodegradation, Environmental , Bioreactors/microbiology , DNA, Ribosomal/genetics , Denaturing Gradient Gel Electrophoresis , Oxidation-Reduction , WastewaterABSTRACT
Over the last decade, the chelator-based strategy for protein immobilization has received considerable attention. Here, we describe a stepwise approach for the modification of polyurethane (PU) surfaces which involves the introduction of a poly(ethylene glycol) (PEG) layer to shield the PU substrate surface against nonspecific protein adsorption and a chelator head (quinolin-8-ol, HQ), to provide relatively high-target protein binding capacity. The surface properties, the immobilization of proteins on the surface, and the bioactivity of the immobilized proteins were investigated by various techniques. It was demonstrated that this approach provides a powerful means for surface immobilization of proteins with high density, with a homogeneous distribution and retaining the bioactivity of the immobilized proteins.
