Maria De Fátima Nunes De Carvalho,Ana Rita da Silva Prazeres,Francisco javier Rivas Toledo, Escola Superior Agrária de Beja-Instituto Politécnico de Beja, TECNOLOGIAS E CIENCIAS APLICADAS, mfcarvalho@ipbeja.pt
Abstract
The use of aluminium (Al2(SO4)3) and iron (FeSO4) salts to treat acid cheese whey wastewater (CWW) requires a previous pH adjustment with alkali agents like hydrated lime and sodium hydroxide. In this work, four different sequences have been tested: Al2(SO4)3+NaOH; Al2(SO4)3+lime; FeSO4+NaOH and FeSO4+lime. When using Al2(SO4)3+NaOH the percentage removal of chemical and biological oxygen demands (COD and BOD) obtained were 13% and 21%, respectively. However, application of Al2(SO4)3+lime demonstrated to be more effective, with COD and BOD eliminations of roughly 36%. The FeSO4+lime coagulation process led to COD and BOD removals in the range 43-67%. The clarified supernatant showed an almost complete turbidity removal and a decrease ≥70% of the absorbance measured at 220, 254, 292 and 410 nm. Sodium hydroxide presents some advantages such as less conductivity of supernatant (-20%) and sludge volume, but the lime alkalinizing agent is favoured from the point of view of economics and removal efficacy.
Keywords: Cheese whey wastewater; coagulation-flocculation; alkali agents