Quality improvement of industrial aquaculture recycled water by sand filters

Two groups of three parallel ordinary sand filter tanks were used in the experiment. According to the physical and geometric principles, quartz sand with particle size of 3 mm was selected as the middle-level, while 2 mm and 5 mm as the upper and lower level, respectively. The particle densities of the upper and lower levels were less than that of the middle one. An experiment of water treatment on factory recycled water by sand filter and its backflushing renewable effect was carried out. The results showed that suspended solids removal efficiency was extremely significant (P＜0.01), which removal rate reached 99.83%, and sand filter tank after backflushed was renewable to be used.