Mathematical modelling of declining rate filtration

Modified O’Melia-Ali model based on particle collector concept and detachment mechanism has been extended for single filter unit operating at declining rate mode with constant inflow The filter removal efficiency depends on variable velocity term which is unknown. The velocity is obtained by solving headloss and water balance equations. This model has been verified with a hypothetical case of declining rate filtration formulated based on past experiences. The two major advantages of declining rate filtration over constant rate filtration, namely prolonged working period and better filtrate quality for same terminal headloss development, are observed in simulations.