microflocs

Microflocs are small aggregates of suspended particles that form during the coagulation and flocculation steps of water and wastewater treatment. They represent an intermediate stage between individual colloidal particles and larger macroflocs. Their presence can influence the efficiency of subsequent clarification and filtration processes.

Formation of microflocs occurs through charge destabilization and bridging actions induced by coagulants such as aluminum or ferric salts, as well as by polymeric flocculants. Gentle mixing promotes collisions and adhesion between particles, creating microflocs. Excessive shear can break them apart, while insufficient mixing yields fewer aggregates and slower growth into larger flocs.

In terms of size and physical characteristics, microflocs are typically in the micrometer to sub-millimeter range. They have higher density and larger surface area than primary particles, which aids their removal by sedimentation and filtration. However, they can be more susceptible to mechanical breakage and to fouling in membrane processes if not properly controlled.

In practice, the formation of microflocs is considered in the design and optimization of treatment trains. Operators adjust coagulant dose, mixing intensity, and pH to promote stable microfloc formation and growth into larger flocs that settle more readily. In membrane systems, microflocs can contribute to fouling if not managed, so pretreatment aims to minimize their production or modify their properties.

Measurement and control of microfloc populations are part of flocculation optimization. Techniques include particle size distribution analysis, microscopy, and monitoring turbidity trends during jar tests to assess the tendency to form microflocs under specific chemical and hydraulic conditions.