Abstract
Purpose.Sedimentation by gravity is the most common and extensively applied treatment process for the removal of solids from water and wastewater and it has been used for over one hundred years. Sedimentation tanks are one of the major parts of a treatment plant especially in purification of turbid flows. Horizontal settlers are mainly used for purification of high quantity of water. In these tanks, the low speed turbid water will flow through the length of the tank and suspended particle have enough time to settle. Finding new and useful methods for calculating and increasing hydraulic efficiency of horizontal settlers is the objective of many theoretical, experimental and numerical studies.But currently used models and methods in Ukraine do not allow taking into account geometrical form and various design features. In this paper the numerical model was developed to evaluate the effectiveness of horizontal settler with modified structure. Methodology. Numerical model is based on: 1) equation of viscous fluid dynamics; 2) mass transfer equation. For numerical simulation the finite difference schemes are used. The numerical calculation is carried out on a rectangular grid. For the formation of the computational domain markers are used. Findings.The model allows obtaining the purification process in the settler with different form and different configuration of baffles. Originality. A new approach to investigate the mass transfer process in horizontal settler was proposed. This approach is based on the developed CFD model. The fluid dynamics model was used for the numerical investigation of flows and waste waters purification. To investigate influence of baffles on settler efficiency physical experiment was carried out. Practical value.The developed model has more capacity than the existing models in Ukraine. The developed model allows computing quickly the efficiency of water purification in settlers. The model is not computationally expensive. Calculation time of one variant of the problem takes few minutes.
Highlights
Horizontal settlers are essential hydraulic structures which have to be engineered, designed and constructed at all water treatment plants to remove most of suspended solids which enters the intake by polluted water
For numerical modeling of mass transfer process in horizontal settler CFD model was developed. It consists of two models: mass transfer model and model of viscous fluid flow
Results of physical experiments are presented in the paper. These results show the peculiarities of sludge sedimentation in horizontal settler with additional plates
Summary
Horizontal settlers are essential hydraulic structures which have to be engineered, designed and constructed at all water treatment plants to remove most of suspended solids which enters the intake by polluted water. Improvement of performance and increasing of removal efficiency of horizontal settlers by alternative method is necessary. An approach in present paper for increasing horizontal settler performance is to use system of baffles and plates. To obtain the horizontal settler efficiency the empirical models are used in Ukraine [2, 3]. That’s why it is important to develop CFD models having more capabilities to simulate the process of the ISSN 2307–3489 (Print), ІSSN 2307–6666 (Online)
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