Model improvement for estimating of water turbidity removal efficiency in helical tubular flocculators

ABSTRACT Scientific studies have been demonstrating that helical tubular flocculators (HTFs) have high efficiency in floc formation and low hydraulic retention time when compared to flocculators commonly used in water and wastewater treatment. However, its practical application is still limited because there is still a significant demand for advances in the understanding of the relationship between the hydrodynamics of the unit and the flocculation process, as well as for criteria and methodologies in support to the rational design of HTF. In this context, the objective of this study was to propose an improvement in the model of turbidity removal efficiency developed by Oliveira (2014), which takes into account a set of geometric, hydraulic and hydrodynamic parameters relevant to the flocculation process in this type of reactor, by incorporating one of the most representative parameters of flocculation processes, the normal pressure gradient, as one of its independent variables. The development of the work employs computational fluid dynamics (CFD) in the study of 84 HTFs configurations, considering laminar and turbulent flow regimes. As a result, a new model version for estimating water turbidity removal’s efficiency in helical tubular flocculators was obtained, which, in relation to the original version, has a smaller number of independent variables, presents better fit to the experimental data and is simpler from the operational point of view.

摘要 多项科学研究已证实，螺旋管式絮凝器（helical tubular flocculators, HTFs）相较于当前给水与污水处理领域常用的絮凝装置，具备絮凝体形成效率高、水力停留时间短的优势。但由于当前仍亟需深化对该装置流体力学特性与絮凝过程间关联机制的认知，同时缺乏支撑螺旋管式絮凝器合理设计的相关标准与方法学体系，其实际应用仍存在较大局限。在此背景下，本研究旨在对Oliveira（2014）提出的浊度去除效率模型进行改进：该原始模型已纳入此类反应器絮凝过程相关的几何、水力及流体力学参数，本次改进将絮凝过程最具代表性的参数之一——法向压力梯度作为其新增自变量。本研究采用计算流体力学（computational fluid dynamics, CFD）方法，针对84种螺旋管式絮凝器构型展开研究，同时覆盖层流与湍流两种流态。最终得到了一款用于估算螺旋管式絮凝器水体浊度去除效率的新版模型，相较于原始模型，该新版模型的自变量数量更少，对实验数据的拟合效果更优，且从工程操作视角来看更为简洁易用。