Treatment of dairy wastewater in UASB reactors inoculated with flocculent biomass

This work assesses the possibility of using flocculent sludge in UASB reactors applied to the treatment of dairy wastewater and studies the effect of hydraulic retention time (6, 8, 12 and 16 h) on the performance of the reactors. The results show that the performance of flocculent sludge is similar to what has been reported in literature for granular sludge. It was observed that by raising the HRT from 6 to 12 h the performance of the system is improved concerning the maximum applicable load, the COD removal efficiency and methane production, but by raising the HRT from 12 to 16 h the differences are not meaningful. To attain soluble COD removals, VFA removals and protein mineralisation near 80% and fat removals above 60% it is necessary to operate the UASB reactors at an HRT of at least 12 h. In addition to this the reactors must be operated at loads under 2.5 g COD/l·d in order to attain a conversion to methane of the removed COD above 70%.