HYDRAULICS OF PADDLE WHEELS IN HIGH-RATE ALGAE PONDS

Analytical and experimental analysis of paddle wheels as used in wastewater treatment high-rate algae ponds were conducted. It was found experimentally that the efficiency of paddle wheels in transfer of mech-anical energy to water flow energy depends primarily on the paddle wheels' geometry such as the radius, the width, the number of paddles and the sub-mergence. An analytical approach based on the concept of the drag coefficient was developed. The drag coefficient was determined by calibrating the analytical model with the experimental data. The calibrated model can be used to estimate the speed of rotation and the power input required from the specified wheel dimensions and flow conditions in the pond. With this analytical design approach, it is possible to improve the efficiency of the paddle wheels from the level of 20-25 percent currently attainable to 40-70 percent. Thus, the foreseeable improvement in efficiency is in the order of two to three fold. Since the paddle wheels constitute the major energy demand in the operation of the ponds, the improvement can have a significant effect on the overall economics of the high-rated algae pond systems