ARTICLE
ClariPhos® coagulant improves UV disinfection for Ontario WWTP
How much can a phosphorus coagulant influence the performance of a wastewater plant’s UV disinfection system?
A lot more than you might think.
After switching to ClariPhos® Rare Earth Coagulant to evaluate its ability to improve phosphorus removal, operators at an Ontario WWTP noticed that UV disinfection also experienced a big boost. It turns out that better settling in the clarifier led to higher UV transmittance in the effluent, and a significant improvement in UV disinfection.
Better clarifier performance = higher UVT
UV transmittance, or UVT, is a measurement of the UV energy that passes through a water column relative to the energy emitted by a UV lamp. Low UVT means that suspended or dissolved contaminants are blocking or absorbing UV light and preventing the UV energy from reaching target pathogens.
High UVT means the opposite. In this case, UV light can easily pass through the water column and effectively inactivate pathogens.
Prior to switching to ClariPhos, the plant was using ferric chloride to precipitate phosphorus. With this chemical, the plant typically achieved UVT in clarified effluent of about 55 – 60%.
With ClariPhos, the plant was able to consistently achieve UVT above 60%, enabling better performance from the UV disinfection system.
ClariPhos outperforms Al- and Fe-based coagulants
ClariPhos improves clarifier performance because it is made with the rare earth elements cerium and lanthanum, which have a very high affinity for phosphorus. These elements form a tight ionic bond with phosphorus to create rhabdophane (Ce/LaPO4), a dense and insoluble precipitate.
ClariPhos Rare Earth Coagulant
ClariPhos precipitate is also more stable and heavier than that produced by Al- or Fe-based coagulants so it settles up to two times faster. The results are improved clarifier performance and reduced risk of carryover of suspended solids.
Switching to ClariPhos is easy. In most cases, plant operators can simply replace conventional alum or ferric coagulants with ClariPhos to easily and cost-effectively improve the chemical precipitation and settling of phosphorus. ClariPhos requires no special chemical feed equipment and will often work with existing feed pumps.
