Patziger M, Kainz H, Hunze M, Józsa J
Institute of Urban Water Management and Water Landscape Engineering, Graz University of Technology, Stremyrgasse 10, 8010 Graz, Austria.
Water Sci Technol. 2008;57(9):1413-9. doi: 10.2166/wst.2008.221.
In activated sludge systems the mechanically treated wastewater is biologically cleaned by biomass (activated sludge). The basic requirement of an efficient biological wastewater treatment is to have as a high biomass concentration in the biological reactor (BR) as possible. The activated sludge balance in activated sludge systems is controlled by the settling, thickening, scraper mechanism in the secondary settling tank (SST) and sludge returning. These processes aim at keeping maximum sludge mass in the BR and minimum sludge mass in the SST even in peak flow events (storm water flow). It can be, however, only reached by a high SST performance. The main physical processes and boundary conditions such as inhomogeneous turbulent flow, geometrical features of the SST, wastewater treatment plant (WWTP) load, return sludge flow, sludge volume index etc. all influence settling thickening and sludge returning. In the paper a novel mass transport model of an activated sludge system is presented which involves a 2-dimensional SST model coupled with a mixed reactor model of the biological reactor. It makes possible to investigate different sludge returning strategies and their influence on the sludge balance of the investigated activated sludge system, furthermore, the processes determining the flow and concentration patterns in the SST. The paper gives an overview on the first promising model results of a prevailing peak flow event investigation at the WWTP of Graz.
在活性污泥系统中，经过机械处理的废水通过生物质（活性污泥）进行生物净化。高效生物废水处理的基本要求是在生物反应器（BR）中尽可能保持高生物质浓度。活性污泥系统中的活性污泥平衡由二次沉淀池（SST）中的沉降、浓缩、刮泥机制以及污泥回流来控制。这些过程旨在即使在峰值流量事件（暴雨径流）期间，也能在BR中保持最大污泥量，在SST中保持最小污泥量。然而，这只有通过高效的SST才能实现。主要的物理过程和边界条件，如不均匀的湍流、SST的几何特征、污水处理厂（WWTP）负荷、回流污泥流量、污泥体积指数等，都会影响沉降、浓缩和污泥回流。本文提出了一种新型的活性污泥系统传质模型，该模型涉及一个二维SST模型与生物反应器的混合反应器模型相耦合。这使得研究不同的污泥回流策略及其对所研究活性污泥系统污泥平衡的影响成为可能，此外，还能研究决定SST中水流和浓度模式的过程。本文概述了格拉茨污水处理厂一次主要峰值流量事件调查的首批有前景的模型结果。
