Study On The Influential Factors Of Oxygen Transfer Capacity And Alpha Values In Wastewater Treatment Aeration Systems

Urban wastewater treatment has become one of energy-intensive industries in China, and aeration accounts for the largest fraction of a total wastewater treatment plant’s (WWTP) energy bill, ranging from 45% to 75%. However, how to solve the problem of high energy consumption for aeration has become the key of cost-effective energy conservation in the wastewater treatment industry currently.Now there is less research about the influence factors of oxygen transfer capacity and a value in wastewater aeration systems which lead to be blind on the design of aeration system and engineering application. This research aimed at the oxygen transfer ability and its influence mechanism of fine bubble diffused aeration in the complex multiphase flow system of factual wastewater treatment, which adopt the research methods of pilot plant test, in order to solve the bottleneck problem of design and operation control of aeration system in actual application - how to determine the parameters of oxygen mass transfer and water quality correction coefficient alpha value, which are the foundation problems in engineering application, and reveal the law and factors and influence mechanism of oxygen transfer in the factual wastewater treatment process. The results are to provide theoretical guidance in improving the optimization control and cost-effective energy conservation of aeration in the application.1. The research on the influence factors of oxygen transfer capacity in clean water with desorption methods. (1) Within the air flow rate range of 4m3/h～20m3/h, the SOTR, KLa2o and SSOTE value are incresing with the increase of air flow rate.(2) Under the same air flow rate conditions, the SOTR, KLa20 and SSOTE value in fine bubble aeration systems is larger than coarse bubble aeration systems, and the results of 4 coarse bubble diffusers are better than 2 coarse bubble diffusers.(3) The results of SOTR, KLa20 and SSOTE value in secondary sedimentation tank are better than in clean water. As the temperature and the density of TDS in secondary sedimentation tank are higher than in clean water.(4) Under the same air flow rate conditions, the SOTR value incerased with the increase of water depth from 2.74m to 5.74m. However, the KLa2o and SSOTE value reduced within the water depth range from 2.74m to 4.24m, and increased with the water depth increasing.(5) With the increasing of filters dosing rate in the range of 0%～50%, the results of SOTR, KLa20 and SSOTE value increased. However, we must control the filters dosing rate to keep filters fluidfying from reducing the oxygen transfer capacity.(6) With the increasing of temperature in the range of 13.5±0.5℃～29.5±0.5℃, the results of SOTR, KLa20 and SSOTE value increased. 2. The research on the influence factors of SOTR and a value in the factual wastewater treatment process with off-gas methods.(1) The results of SOTR and a value are larger in low density of MLSS conditions than in high density of MLSS conditions.(2) The KLa20 and α value keep stable when the temperature and density of MLSS stable; With the increasing of temperature and density of MLSS, the KLa20 and value increased. MLSS concentration has a negative effect to KLa20 and a value, and the temperature has a positive effect to KLa20 and a value.But the influence of temperature to KLa20 and a value is higher than the influence of MLSS concentration.(3) High density of COD lead to larger results of SOTR and α value.(4) In the factual wastewater treatment process, with the increasing of filters dosing rate in the range of 0%-50%, the results of SOTR and a value increased.