AN INVESTIGATION INTO THE SUITABILITY OF BIOGAS HYDROGEN CONCENTRATION AS A PERFORMANCE MONITOR FOR ANAEROBIC SEWAGE-SLUDGE DIGESTERS

On-line measurement of hydrogen in the biogas of a continuously stirred laboratory scale sewage sludge digester was conducted to determine whether this variable could provide advanced warning of digester failure. Reactor failure was achieved by decreasing the hydraulic retention time (HRT) from 20 to 8 days. At the onset of digester failure a marked decrease in the volume and methane content of the biogas was accompanied by an increase in volatile acid production and a concomitant decrease in pH. During this period, hydrogen accumulation in the biogas was not evident. An increase in hydrogen was noted, however, well after reactor failure had occurred. Hydrogen concentration in the biogas cannot, therefore, be used as an indicator of incipient digester failure, at least when volumetrically overloaded.