Bulk Chemical Storage and Dosing Cabinets
A pipe flocculator for chemical conditioning
In tank flash mixing chemical tank
DAF system - for separation of wastewater and solids
Lamella - For separation of wastewater and solids
Aquabio Ltd - Wastewater Chemical Treatment
Coagulation and Flocculation of wastewater is a highly effective and commonly used process to remove COD (Chemical Oxygen Demand), Metals, Fats Oils and Greases and Suspended Solids.
Aquabio Ltd utilise these techniques frequently to provide pre-treatment of wastewater before biological treatment in an AMBR system.
Principles of Chemical Treatment
In wastewater treatment operations, the processes of coagulation and flocculation are employed to separate suspended solids from water. These processes, usually undertaken in sequence, are a combination of physical and chemical procedures. Chemicals are mixed with wastewater to promote the aggregation of the suspended solids into particles large enough to float and/or settle and be removed. Floatation of the separated solids can be achieved in a Dissolved Air Flotation (DAF) system, settlement of the soilds can be achieved in an AquaBiosep™ Lamella.
Coagulation and Flocculation are normally optimized for a particular pH. The characteristics of the wastewater may require the addition of pH correction equipment to ensure reliable separation.
Coagulation
Coagulation is the destabilization of colloids by neutralizing the forces that keep them apart. Cationic coagulants provide positive electric charges to reduce the negative charge of the colloids. As a result, the particles collide to form larger particles (flocs). Rapid mixing is required to disperse the coagulant throughout the liquid. Care must be taken not to overdose the coagulants as this can cause a complete charge reversal and restabilize the colloid complex.
Flocculation
Flocculation is the action of polymers to form bridges between the flocs and bind the particles into large agglomerates or clumps. Bridging occurs when segments of the polymer chain adsorb on different particles and help particles aggregate. An anionic flocculant will react against a positively charged suspension, adsorbing on the particles and causing destabilization either by bridging or charge neutralization. In this process it is essential that the flocculating agent be added by slow and gentle mixing to allow for contact between the small flocs and to agglomerate them into larger particles. The newly formed agglomerated particles are quite fragile and can be broken apart by shear forces during mixing. Care must also be taken to not overdose the polymer as doing so will cause settling/clarification problems. Anionic polymers themselves are lighter than water. As a result, increasing the dosage will increase the tendency of the floc to float and not settle. Once suspended particles are flocculated into larger particles, they can usually be removed from the liquid by sedimentation or flotation.
Dissolved Air Floatation (DAF)
When used in conjunction with chemical treatment the DAF system provides a very effective, compact method of removing lighter, floatable material. Generally quality of wastewater from a DAF will be better than from a lamella. The DAF system is also very effective at removing fats oils and greases from the wastewater. The disadvantage of a DAF compared to a lamella is the mechanical and control complexity of the DAF and effectiveness with settleable solids (Although high rate DAF can be fitted with a lamella pack). Please see our DAF page for more details
AquaBiosep™ Lamella
The AquaBiosep™ lamella is a very simple and robust system for settlement of solids. When combined with chemical treatment they provide a robust means of settled solids removal. The disadvantage of the AquaBiosep™ lamella is it's ability to deal with fats. oils and greases and other floatable material. Please see our AquaBiosep™ lamella page for more details.