טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentShlomo Bendory Inbar
SubjectNovel Oscillatory System for Removal of Colloid
Particles by Flocculation
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Professor Eran Friedler


Abstract

Aggregation of colloidal particles is an important stage in potable water treatment, as these particles are not efficiently removed by physical separation methods such as sedimentation and filtration. According to a novel methodology known as “grouping”, which is based on a mathematical model, applying oscillatory wave manipulation on the water enhances aggregation of colloids. In order to verify this theoretical concept, a system that induces wave manipulation in the water was designed and constructed. The system was tested on synthetic water solution simulation surface water and containing ground kaolin clay (Dv(50)=1.97 µm), with alum serving as a coagulant. The system was examined under various chemical (coagulant does, pH), operational (frequency, amplitude, duration) and configurational (beaker shape, paddle type and location within beaker) conditions. Process efficiency was assessed by turbidity removal, particle count and size distribution and microscopic examination of the aggregates formed.

The hydrodynamic properties of the created oscillatory waves were evaluated. The input power transferred to the water was investigated using a load cell that measured the force employed by the system’s paddles. Force measurements were performed under various conditions and were analyzed and filtered through Fast Fourier Transform (FFT). The results were assessed with relation to the turbidity removal obtained in the experiments results and compared to theoretical force calculations. Flow patterns were studied by injecting colored tracer into the water and analyzing the obtained vortices characteristics.

At optimal conditions, the oscillatory system created the theoretically predicted particle aggregation and a "moon shape" sedimentation pattern, and removed turbidity at a higher rate than conventional coagulation. Both configurational and operational conditions had a considerable effect on aggregates size, hence changed the turbidity removal rate. The configurational properties of the system had no significant effect on the final turbidity removal, as opposed to the operational properties. The hydrodynamic investigation provided additional insights to assess system operation abilities and means for upscaling the system. To conclude, the novel methodology appears to be efficient, as significant floc formations were observed during the oscillatory motion. The method has a high potential to contribute to the coagulation-flocculation process, under the optimal conditions found.