A high performance chemical additive for water and wastewater treatment.

Water Innovate have utilised special zirconium compounds to develop ZR-Coag®, a product that enables high efficiency coagulation of potable supplies and waste treatment effluents.

Existing coagulants are typically based on iron and aluminium salts such as sulphate and chloride. These coagulants characteristically dissociate into strongly charged ions and their charge density is a significant factor in determining the efficiency of coagulation and particle removal. Zirconium ions are more effective as coagulants because they have a 4+ charge which is more charge per mole than the 3+ charge of both iron and aluminium. More importantly they exhibit a lower tendency to dissociate into lower charged intermediates, or complete hydrolysis species, over a broader range of pH than either iron or aluminium.

ZR-Coag® flocs (left) produced in a coagulation jar test (right) on an upland reservoir water high in natural organic matter (NOM).

The higher charge density of ZR-Coag® significantly improves the charge neutralisation coagulation mechanism and results in better organic and suspended particle removal. This can be achieved at lower dose rates, and with less pH adjustment and sludge production than with either iron or aluminium. In addition, larger flocs are produced (see photos) that are easier to separate in subsequent unit operations such as sedimentation, allowing these processes to be operated at higher flow rates.

Tom Stephenson, Water Innovate's Technical Director said, "Any water or wastewater treatment process that currently uses iron or aluminium based coagulants is a potential application for ZR-Coag®."

ZR-Coag® was originally developed with a specific focus on natural organic matter (NOM) removal from difficult to treat upland waters, but it is equally applicable to removal of other typical pollutants including turbidity, DOC and colour. Applications include industrial processes that treat effluents or process liquids by using coagulants to aid the removal of organics and suspended or colloidal negatively charged particles e.g. wastewaters from paper and pulp manufacturing, meat processing, metal processing, textile manufacturing, hydroelectric plants, atomic energy plants, and tanneries.

The product can also be effectively employed in membrane pre-filtration applications where technologies such as ultrafiltration or microfiltration currently utilise enhanced coagulation techniques to improve operating efficiency.

Coagulants are increasingly being used in municipal sewage treatment works either to improve the performance of sedimentation processes for suspended solids removal, or to reduce effluent phosphate concentrations to satisfy the requirements of the EU Urban Wastewater Treatment Directive. Trials are already underway with ZR-Coag® and initial results are promising.

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