Pulse water intake: China's UASB reactor with the most significant feature of foreign countries is that many of the pulse water intake. Some researchers believe that the pulse method of water intake, so that the bottom sludge alternately contraction and expansion, which helps the bottom sludge mixing. Figure 3a shows the schematic diagram of a kind of pulse water distributor used by the Beijing Academy of Environmental Sciences, which draws on the water distribution method of siphon filters in feed water. A pipe multi-hole water distribution mode: the way of water distribution in the reactor pool bottom water distribution cross-pipe openings, in order to distribute water uniformly, the water flow rate is required to be not less than 2.0 m/s. This water distribution mode can be used in the pulse water intake system. The problem of one pipe with many holes is that it is easy to be clogged, so it should be avoided as much as possible to have too many holes in one pipe.
Water distribution orifice loading: a water intake point to serve a larger area of the problem is that in-depth experimental research should be carried out. For UASB reactors Lettinga suggests that after start-up is complete, a burden of 2.0 to 4.0 m2 per inlet point is sufficient to obtain satisfactory removal efficiencies. However, at temperatures below 20°C or low loads, low gas production rates and inadequate mixing of sludge and influent, a higher density of water distribution points is required. For municipal wastewater De Man and Van der Last (1990) recommend 1 to 2 m2/well. Table 4 shows the inlet pipe loads recommended by Lettinga et al. based on extensive practice with UASB reactors.