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The SolaeĀ® facility in Ieper, Belgium produces high-quality soy protein and fiber ingredients for various foodservice markets. The facility treats its wastewater through a combination of anaerobic, anoxic and aerobic biological processes and achieves a nominal 99% removal efficiency for BOD, TSS and TKN. However, the local regulatory authority has recently imposed a total phosphorus (P) limit of 2 mg/l that is very technically challenging. The current effluent contains ∼30 mg/l total P with peaks up to 50 mg/l. Also, no increase in soluble salts are allowed, as the receiving stream is a public drinking water supply already near maximum TDS levels at times. A number of biological and chemical P removal technologies were evaluated but either failed to achieve the new concentration limit or would have produced prohibitive amounts of residual sludge and unacceptably high effluent salt concentrations.

“HARDTAC”, a novel crystallization technology, was demonstrated along with lime precipitation through extensive pilot testing to be capable of: 1) achieving the required phosphate removal; 2) while not increasing dissolved salts; and 3) producing very rapid settling and filterable particles. Also, minimal carbonate removal was observed with sludge generation being only one-third that of a complete softening reaction. Filter cakes of 65% solids were produced at low pressure without filter aids.

This successful application of the HARDTAC process despite the widely published influence of inhibitor ions such as CO3 2− and Mg2+ (both significantly present in the wastewater) on calcium phosphate crystallization (Abbona and Franchini-Angela, 1990; Van Der Houwen and Valsami-Jones, 2001) is a significant breakthrough. This finding portends the crucial importance physical chemistry and reactor configuration will have in the design of future state-of-the-art wastewater treatment facilities that are able to meet the increasingly stringent treatment requirements for phosphorus (and potentially other inorganic pollutants). The performance witnessed by this proprietary crystallization process is attributed to the unique design and features of a properly designed and operated crystallizer.

Document Type: Research Article


Publication date: 2003-01-01

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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