Haneline, M.R., and Wherry, L.S., Neo Chemicals and Oxides, USA(free)
The use of rare earth (RE) chloride has been studied and implemented in over 70 municipal and industrial wastewater treatment facilities required to meet a phosphorus discharge limit of 0.5 mg/L or lower. Some facilities have been able to achieve a 0.04 mg/L total phosphorus in the effluent without the need for tertiary filtration. This reduction is due to the unique ability of RE to preferentially react with phosphorus to form an insoluble inert RE phosphate, which results in drastically lower coagulant volumes required (typically 20% or less). RE chloride is stable in a concentrated solution with a pH between 3 and 4, which is significantly less acidic than other Fe/Al-based coagulants (typically 1-2 pH), thus consuming significantly less alkalinity when added. Additional benefits such as a reduction in sludge volume, enhanced clarifier performance (reduction in TSS), and improved dewatering capabilities (typically 20% increase in percent solids) have been observed at these facilities without the need for additional capital equipment. Furthermore, these benefits lead to overall operational cost savings. The results of lab studies and full-scale case studies at both small and large facilities with varying processes will be presented.
Keywords: Chemical coagulant, Dewatering, Nutrient removal, Phosphorus removal, Rare earth, Sludge reduction, Wastewater treatment, Water clarification
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