(258c) Hydraulic Retention Time and Temperature Impacts on Biogas Production in Expanded Granular Sludge Bed Reactor

Renewable sources play a significant role in providing sustainable energy with reduced Greenhouse Gas emissions considered to be a significant cause of global warming. Renewable energy resources combined in a hybrid energy system can also provide reduced energy costs. Anaerobic Digestion is one of these renewable energy sources, which involves the degradation of biomass in the absence of air to produce biogas that can be used in many applications. This technology also helps reduce the effluent waste discharged to a waste-water treatment system that further improves the eco-friendly nature of the hybrid system by lowering water loss to the environment.

An expanded granular sludge bed reactor, updated from the up-flow anaerobic sludge reactor, has been used to investigate the effect of hydraulic retention time and temperature on biogas production rate and methane composition of the biogas. The process consists of a two-stage reactor with a pre-acidification stage where hydrolysis and acidogenesis steps occur followed by the main reactor where the acetogenesis and methanogenesis steps occur.

Equivalent specific values of organic loading rates for industrial waste water with different COD levels (20, 30 and 40 g COD/l) have been used. The biogas production increases with decreasing hydraulic retention time (i.e. 24 gallons/ day) and decreases when biogas production is inhibited by lower residence times below that required to complete degradation of the wastes and eventually affect the activity of the overall biodigestion process.

Methane composition and COD removal efficiency are (65-78%) and (90-96.5 %) respectively. A detailed analysis has been conducted for the process effluent using a Benchtop Spectrophotometer to monitor the process stability.