Colloids stay dispersed because a charged double layer surrounds each particle and repels its neighbours. Understanding that double layer, and the DLVO balance of forces, is the foundation of all coagulation design.
The physical chemistry behind every coagulant dose, from zeta potential to the Camp number.
DAF, clarification and chemical conditioning systems for solids and oil removal.
Dissolved air flotation for coagulated solids, fats and oils.
Colloidal particles in water carry a negative surface charge that surrounds them with a cloud of counter-ions — the electrical double layer — which keeps them mutually repelled and stably suspended. The strength of that repulsion is measured as zeta potential, and stable colloids typically sit between −15 and −40 mV. Coagulation works by compressing or neutralising this double layer so attractive van der Waals forces can dominate and particles can aggregate. Understanding the double layer explains why coagulant dose, pH and ionic strength behave as they do, and underpins the jar-testing and dose-control decisions we make on every clarification design.
Clay, organics, oil droplets and cells carry a net negative surface charge, giving a zeta potential typically between minus 15 and minus 30 mV.
A bound Stern layer and a diffuse layer of counter-ions surround each particle, creating an electrostatic repulsion that prevents contact.
DLVO theory sums attractive van der Waals and repulsive electrostatic energies; the net barrier height decides whether particles aggregate.
Raising ionic strength compresses the diffuse layer and lowers the energy barrier to aggregation.
Coagulants drive zeta potential toward zero (minus 5 to plus 5 mV), removing the repulsion so particles stick on first collision.
Once the barrier falls, particles fall into the primary energy minimum and aggregate irreversibly.
Streaming-current and zeta-potential measurement guide coagulant dose to the charge-neutral point.
Particle and organic concentration set the charge demand and therefore the coagulant requirement.
The required mechanism, neutralisation or sweep, follows directly from the colloidal chemistry.
Reynolds & Bauhm delivers this scope as part of an integrated, single-point engagement matched to your project, programme and regulatory regime.
Our expertise spans multiple industries with sector-specific water treatment solutions.