Cost-effective integration of enhanced biological phosphate removal in full-scale Two Stage Unitank systems designed for BOD/COD-removal from brewery waste waters
1994
Gerards, R. | Vriens, L. (SEGHERSengineering'water', Wespelaar (Belgium)) | Feyaerts, M. | Norga, K. | Verachtert, H.
Full scale Two Stage Unitank (TSU) systems for the aerobic BOD/COD-removal from brewery waste waters do easily meet current discharge standards for the brewery sector determined by the Flemisch environmental legislation (Vlarem II, 1992). Extension of the legislation of the discharge limits for phosphorus compounds is expected within two years. For the TSU-Haacht (designed for BOD/COD-removal) P total concentrations of 15 mg per litre in the discharged effluent could occur, which sometimes are responsible for 50 per cent of the annual charged taxes. For these reasons tests were performed to introduce enhanced biological phosphate removal in the TSU-Haacht system treating brewery waste water. A 30 minutes anaerobic phase in the fed compartment at the beginning of the main phase, subsequently followed by a 60 minutes aerated phase, was introduced in the first stage of the TSU-Haacht. The sludge of the high loaded stage of the full scale plant showed a clear increase in phosphorus content since the introduction of the anaerobic phase. The BOD Phosphorus ratio did change from the typical assimilative ratio (BOD:P = 100:2). Typical phosphate release and uptake patterns were detected from the beginning of May. Introduction of the anaerobic phase did not affect the removal of the organic compounds. The effluent total phosphorus concentration decreased from more or less 13.5 mg per litre to more or less 7 mg per litre. Although the phosphorus removal is not yet complete a serious improvement has been obtained. The introduction of enhanced biological phosphate removal will probably result in a saving of about 357 600 BEF on yearly basis. From this it can be concluded that Unitank systems are very flexible with respect to process operation, which can result in cost-effective introduction of enhanced biological phosphate removal.
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