microfloc

Microfloc, in the context of coagulation and flocculation in water treatment, refers to small floc aggregates formed during the early stage of particle aggregation. Microflocs are typically smaller than mature, larger flocs and tend to be on the order of a few micrometers up to a few tens of micrometers, with exact sizes depending on water characteristics and treatment conditions. The concept is that these small aggregates act as building blocks for subsequent growth into larger flocs that can settle or be removed by filtration.

Formation of microflocs occurs after rapid mixing when coagulants neutralize colloidal charges and bridging agents or polymers promote particle linking. The process relies on controlled shear; too much shear can break forming microflocs, while too little may prevent effective bridging. Appropriate coagulant dose, pH, and the use of polymeric aid can enhance microfloc development and stability.

Applications and purpose of microflocculation include improving the removal of fine suspended solids, color, and natural organic matter in drinking water treatment and some wastewater treatment processes. By producing uniformly small, bridgeable aggregates, microflocs can enhance sedimentation and filtration rates, enable lower coagulant dosages, and reduce turbidity downstream when properly managed.

Measurement and optimization typically involve jar tests, particle-size distribution analysis, turbidity reduction assessments, and settling tests. Operators adjust coagulant dose, mixing intensity, and flocculation time to achieve a desirable microfloc size distribution that balances stability with the ability to form larger aggregates for efficient solid-liquid separation.

Limitations include sensitivity to water chemistry (pH, ionic strength) and potential re-suspension or over-flocculation under inappropriate conditions.