The present paper describes the performance of a 1200 m3 UASB reactor treating 5000 m3 municipal waste water per day at Kanpur, India. The reactor was constructed in three parallel compartments of 600, 300 and 300 m3 respectively to study the influence of various design and operational parameters on process performance. The 600 m3 compartment is the reference unit. In one of the 300 m3 compartments the effluent overflow gutters are provided with baffles to prevent overflow of floating material. The other 300 m3 compartment is provided with a double amount of inlet pipes at the bottom of the reactor to assess the effect of a more dense distribution of the influent.
The start-up of the reactor was carried out without addition of seed sludge since the influent contained the necessary seeding material.
Data collected over a period of twelve months showed that there was an average reduction in COD, BOD, and TSS concentrations of respectively 74, 75, and 75 % at a hydraulic retention time of 6 hours. Excess sludge production was 0.2 kg TSS/m3 waste water, having 60-70 percent ash. It could be dried in six days on open sludge drying beds. The biogas yield was 0.05 to 0.10 m3/kg COD removed. The gas had 75 to 80 percent methane. Also during winter time the treatment efficiency and process stability remained good. The compartment provided with baffles showed better removal efficiencies for COD, BOD, and TSS than the other compartments. A double number of inlet points did not show an increase in removal efficiency. A density of one inlet point per 3.7 m2 is sufficient to provide a properly distributed influent in the reactor.