A comparative study for hybrid UASB reactor performance using polyethylene media and luffa sponge as biofilm support

This paper study the performance of a lab-scale hybrid up-flow anaerobic sludge blanket (UASB) reactor treating low-strength synthetic wastewater using different biofilm supporting materials. Two identical reactors are constructed and operated at constant up-flow velocity of 0.1 m/hr., inflow rate of 9.76 L/d, and hydraulic retention time (HRT) of 8.26 hours. The Start-up phase, using seed sludge for existing wastewater treatment plant, lasted until the efficiency of chemical oxygen demand (COD) removal of both reactors reached 80%. Polyethylene (PE) media are added to one of the reactors and luffa sponge is used in the second reactor. Results show increased COD removal efficiency up to about 90% at 20 °C and biogas production rates from 3.8*10^-3 till 7.5*10^-3 m³ CH₄/kg COD_r using PE media. The COD removal efficiency reaches about 95% at 20 °C using luffa sponge and biogas production rates up to 6.5*10 ^-3 m³ CH₄/kg COD_r are achieved before clogging problem is observed. Effect of HRT reduction, from 8.26 to 4.13 hours, on removing clogging is investigated. Reduction in COD removal efficiencies is observed at low ambient temperatures during seasonal variations of 15-25 °C. AFM and SEM analysis are used to examine sludge granulation and biofilm formation.