The rough guidelines for the number of feed inlet points required in UASB reactor is presented by Lettinga and Hulshoff for different concentration of the sludge inside the reactor and applicable loading rates. In general, the area to be served by each feed inlet point should be between 1 and 3 m2. Lower area per inlet point (1 m2) is to be adopted for reactor designed for OLR of about 1 kg COD/m3.d, and higher area (2 to 3 m2) per inlet point can be provided to the reactor designed for OLR greater than 2 kg COD/m3.d. Apart from the number of feed inlet points, the minimum
and maximum outflow velocity