Rectangular surface aerators.

Aeration experiments were conducted in two rectangular surface aeration tanks of L/B ratios 1.5 and 2 along with a square tank (L/B=1) to study their relative performance due to shape on oxygen transfer process while re-aerating the same volume of water such that the cross-sectional area of all the three tanks is the same. An identical rotor with six flat blades was used in all the three tanks. The geometric dimensions, which were developed to produce maximum aeration in square tanks by a previous study, were used in the present study as well. Results have confirmed that at lower dynamic conditions of the rotor the oxygen transfer coefficient is maximum in square tanks followed by rectangular tank of L/B=2 and it is the least in rectangular tank of L/B=1.5. However, the rectangular tank of L/B=1.5 produces always lower k values for any given rotor speed when compared to square tank, whereas the performance of rectangular tank of L/B=2 is marginally better than square tanks when rotor speeds are higher.