Anaerobic treatment of winery wastewater in moving bed biofilm reactors

The treatment of winery wastewater in two anaerobic moving bed biofilm reactors (MBBR) (R9 and R30) with low-density polyethylene carriers differing in size, shape, structure, and specific surface area was investigated. The carrier packed in R9 was bioflow 9 with diameter of 9 mm, height of 7 mm, density of 0.84 g/cm(3), and specific surface area of 800 m(2)/m(3), while the carrier filled in R30 was bioflow 30 with diameter of 29-35 mm, height of 29 mm, density of 0.94 g/cm(3), and specific surface area of 320 m(2)/m(3). Both reactors were run in parallel for 232 days. A maximum organic loading rate (OLR) of 29.59 g COD/L day with more than 80% soluble chemical oxygen demand (COD) removal efficiency was achieved in R9 at hydraulic retention time (HRT) of 1.55 days, whereas a maximum OLR of 18.43 g COD/L d with 80% soluble COD reduction was attained in R30 at HRT of 2.49 days. Biogas production of each reactor was increased and strongly correlated with its OLR. The experimental results showed that R9 performed better than R30 in achieving OLR and in attaching biomass, implying that the performance of the anaerobic MBBR was enhanced by an increase in the specific surface area of the carrier used. Both the reactor performances can be promoted by short-term supplementation of some essential trace metals needed in anaerobic digestion of winery wastewater. The study provided not only a good basis for comparing the effect of packing material to the efficiency of anaerobic digestion system, but also an approach on how to optimize the performance by short-term dosing of trace elements.