COMPARING THE EFFICIENCY OF UAFF AND UASB WITH HYBRID REACTOR IN TREATING WOOD FIBER WASTEWATER

There are several kinds of anaerobic systems that are widely used for municipal and industrial wastewater treatment. Upflow Anaerobic Fixed Film (UAFF), Upflow Anaerobic Sludge Blanket (UASB) and hybrid reactor (combination of UASB and UAFF) are the mostly used in treating industrial wastewater. As several operational problems have normally been experienced in both UASB and UAFF systems such as long start-up periods and instability, a hybrid reactor has been conceptualized which addressed these problems but retained the positive aspects of these reactors, such as, high cell concentration, good mixing and tolerance to high loading rates. The wastewater has been obtained from Iran Wood Fiber Company which is located in Hassan Rood city, Gilan Province. After period of starting up the reactors and adaptation, the amount of influent COD was being increased stepwise. After the removal rate was reached to its maximum, the next period for increased load was started as after six months, the reactors could accept about 15 Kg/m3.d with high COD removal rate of about 58.5, 58.9 and 65 percent after 3 days detention time. After 5 and 6 months, maximum growth of granule and biofilm was observed. Diameter of 6 mm and mass to surface and COD removal of 0.25 g/cm2 were the highest measured parameters. The comparison of three studied systems showed that their efficiencies were close to each other. As the effective part of UAFF in hybrid reactor was only one third of the reactor, it acted as a separator of solidliquid-gas phases and UASB had the most effect on treatment. In each UAFF and UASB, all percent removal was resulted by each reactor. It can be concluded that hybrid reactor do have the advantages of both systems with at least half of the height of two reactors. Similar results could be obtained with each UAFF or UASB if higher height can be used.