Influence of Variable Inlet Jet Velocity on Failure Modes of a Floc Blanket in a Water Treatment Process Train

Abstract

Abstract

Improving designs of facilities that employ floc blankets in a water treatment process train to ensure stable performance is desirable, as is an understanding of suitable operating conditions to maintain a functional floc blanket in the system. By considering sequential processes when choosing design parameters, the whole system can be optimized to produce high quality effluent at low cost. A lab scale water treatment system with flocculator, floc blanket, and lamellar sedimentation was used to evaluate the effect of energy dissipation rates (EDR) in the inlet jet to the floc blanket on performance of the system as a whole. Results show that presence of a floc blanket provided an additional factor of 8 decrease in settled water suspended solids concentration at an upflow velocity 1.2 mm/s. Inlet jet EDR did not impact system performance until ∼300 mW/kg after which settled water turbidity increased. At the lower end of inlet jet EDR tested, the jet was unable to resuspend settled flocs. Given that plant performance was acceptable at higher inlet jet EDR, smaller inlet jets with a higher velocity could be used to ensure resuspension of flocs for continuous hydraulic cleaning.