Sino Agro Food Inc (fka SIAF)

[viking86]

That's another possibility. If they have a large water holding tower (or several) they actually donot need any pumps at the tanks and save a lot of money installing and maintaining thousands of small pumps. It works like this: the water is fed to each tank inlet (say the biofilter pitch) from a distant water tower by gravity via large pipes. By opening the valves at each inlet just enough for the water to fill the 2.5m high biofilter pitch and spill into the full tank and flow back out at the other end they can vary the cycle frequency, say once per minute or half minute as desired. The water coming out of the individual tanks is collected via channels to another sump from where it is pumped back to the main sump of the water towers from where it is pumped vertically back into the tower and recirculated into the tanks. In one of the hydraulic labs I have worked in Germany in the 70's that's how we fed water to about a dozen different tanks of various size. Only one water holding and pumping station was needed for a lot of tanks. They may need to build several central stations like that to each feed a certain # of tanks small or large. Just an idea.