BACKGROUNDSecond cheese whey is a strong organic and saline effluent whose characterization and treatment have not been sufficiently addressed. RESULTSIndigenous microorganisms from second cheese whey were isolated for its aerobic biological degradation. Experiments in suspended and attached growth reactors (lab and pilot scale) were carried out using different feed whey concentrations. These concentrations corresponded to three different dilutions with tap water, using 25%, 50% and 75% whey (concentrations C-25, C-50 and C-75, respectively), as well as without dilution (100% whey, C-100). The maximum degradation rate of the organic load obtained in the suspended growth reactors was achieved for the concentration C-100 (10.06 g d-COD L-1 day(-1)). Degradation was more rapid (26.3 g d-COD L-1 day(-1)) in a lab-scale packed bed reactor with recirculation and concentration C-75. Experiments in a pilot-scale reactor with recirculation were also performed with high degradation rates (6.41 g d-COD L-1 day(-1)) under various environmental conditions. The long-term degradation efficiency (12 month operation period) and the effect of environmental and operating conditions on filter performance were studied. CONCLUSIONSAerobic biological treatment at the proposed pilot-scale filter proved to be a sufficient method. The simplicity of the installation provides an effective solution to a serious environmental and social problem. (c) 2014 Society of Chemical Industry