A review of the role of the physicochemical environment in the production of certain floc properties

The aggregation of suspended particles in water and wastewater treatment processes is one of the oldest practices in solid-liquid separation. However, most treatment operations at least occasionally experience poorly settling flocs or extensive deagregation. These problems, and the increasing attention paid to sludge volume reduction and product water quality, have stimulated interest in floc behavior and aggregate characteristics. And although it is clear that overall process performance may depend upon floc properties such as size, strength, density and permeability, these floc attributes are the result of the interaction of nonlinear, stochastic hydrodynamics with the products of a number of sequential and concurrent physicochemical processes. Failure to understand these interactions has constrained efforts to improve the design and operation of coagulation processes.