Process Study On The Release Of Carbon Sources In The Activated Sludge By A Arbon-release Hydrocyclone

With the popular use of activated sludge process, two major issues have arised in municipal sewage treatment plants. First, excessive surplus sludge was too difficult to disposal. Second, the lack of carbon source in domestic wastewater resulted in low nitrogen removal efficiency. Upon these problems, this paper puts forward to use carbon-release hydrocyclone with low energy consumption for activated sludge disintegration to release nutrients. The nutrients can be used as supplementary carbon source to promote denitrification, while biodegradable metabolites in the activated sludge are consumed, which are benefit for sludge reduction and better denitrogenation effect.According to the feature of internal recirculation mixture in AO (Anaerobic-Oxic) activated sludge process for wastewater treatment, we proposed a new AOH (Anaerobic-Oxic-Hydrocyclone) process and designed the two carbon-release hydrocyclone with the nominal diameters of 25mm and 35mm (DN25 and DN35). The two methods of numerical simulation and experiments were used to investigate the shear strength distribution and carbon-release characteristics of hydrocylcone. AOH25 and AOH35 industrial side-line experiments were emphatically developed to investigate the effects of the improved process on the effluent quality, sludge property, denitrogenation effect, and excess sludge production under continuous operating conditions. The major results are as follows:(1) Three-dimension distribution law of shear strength in the two carbon-release hydrocyclone was quantificationally analyzed. Strong turbulent shear zones focuse on the wall shear zone (SW) and shear zone around the air column (SC), volume of which accounted for about 22% of the flow field. With the increase of the operation flow rate, the shear strength of flow field increased. The flow field with less than 0.05MPa pressure drop can provide up to 104 s-1 shear rate, which provided the possibility of sludge floces breakage by shear forces and autoroatation desorption. After breakage, the floc size decreased, the colloidal substance of cell surface and blockages in the channels were cleard, and partial cell wall ruptured; the SCOD concentration in the supernatant averagely increased by about 50% and the concentration of polysaccharide increased by 2%?12%, both increasing with the increase of inlet flow and breakage time in a certain range. The experimental results were in agreement with the theoretical prediction.(2) Under the actual operating conditions, the AOH process is superior to the traditional AO process in the sludge performance and effluent quality. After long-term acclimation by the vortex shear force, the settling performance of activated sludge in the AOH process became better, sludge size was smaller and more compact, sludge denitrification rate increased by an average of 13%-29%. The activity of sludge was enhanced. In the effluent water quality, compared with AO process, SCOD, TN, TP, and SS removal rates of AOH process increased slightly. AOH25 process was better than AOH35 process, and the SCOD concentration in the effluent decreased 13.0mg/L and the TN removal rate increased 6.96%. In terms of sludge reduction, ompared with the AO process, productions of sludge in the AOH25 and AOH35 processes were reduced by 42.62% and 34.45%. AOH process realized the sludge resource utilization and reduction.With the advantages of low energy consumption and no secondary pollution, the carbon-release process of hydrocyclone has economic and environmental benefits. The conclusions will provide the experimental and theoretical basis for a large scale engineering application of AOH technology.