A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Environment, Resources and Development

Thesis (M.Eng.) - Asian Institute of Technology, 1979

This research was conducted in an attempt to develop useful design criteria of inclined square tube settlers for their application in surface water treatment system. The pilot unit was designed keeping the similarities of a conventional settling tank. The experiments were per formed with various influent turbidities under different flow rates and tube lengths. From the model developed, it was found that 14.9 is the economical critical value for square tube dimension L (i.e. L = t/d, d is the size of tube, tis the length of tube) . Both flow rate and influent turbidity affect this critical value. It is desirable to keep the flow rate at less than 0.3 cm/s (10.8 m3/m2-h). The optimum flow rate is 0.2 cm/s (7.2 m3/m2-h), and the corresponding tube dimensions Lare 12.5, 19, 28 for 20, 40, 60 JTU turbidity of raw water, respectively. Diagrams, tables and mathematical model are developed for E = (1 + C) (g(T) f'(T)) in which C is a constant; overflow rate; E removal efficiency. On the basis of this information, the designer can easily make decisions as to what dimensions of tube to be used and surface area required.