Combined anaerobic/aerobic (UASB plus UBAF) system for organic matter and nitrogen removal from a high strength industrial wastewater

The paper presents the experimental results collected from seven months of operation of a combined anaerobic/aerobic system treating an industrial eff luent with averaged content of organic matter and nitrogen of 10.4 g COD /L and 790 mg NKT/L, respectively. The system was formed by an upflow anaerob ic sludge blanket (UASB) and an upflow biological aerated filter (UBAF) con nected in series, with a recycling line of the UBAF effluent into the UASB for its denitrification. The best results were obtained when operating the two reactors, UASB and UBAF, with hydraulic retention times (HRT) of 3.3 an d 1.3 days, respectively, and a recycling ratio of 6.7. Under these conditi ons the system removed 98% of the organic a matter and ammonia and 91 % of the total nitrogen entering the system. The activity of the different microorganisms was followed through activity assays consisting of measuring the consumption or production rate of any sp ecific substrate or metabolism product. Thus when operating the system unde r the aforementioned conditions the reported values for the specific activi ty of methanogenic microorganims and denitrifiers coexisting in the UASB we re 1.05 g COD/g VS d and 32.08 mg NO3--N/g VS d, respectively. While the ac tivity of ammonia and nitrite oxidisers within the UBAF were 47.65 and 4.36 mg O2 /g VS h, respectively.