| 摘要 |
A sewage treatment system includes a pair of substantially identical unitary fluid treatment modules, each module having a central sedimentation tank surrounded by a peripheral wetland. The sedimentation tanks are coupled through a dosing device to an input source of sewage and, as an outlet, to a leaching field. The dosing device includes a switching mechanism isolated from the fluids, which mechanism provides in one cycle for one treatment module to be filled with the incoming sewage while maintaining its outlet closed. When the liquid level in the sedimentation tank in the first treatment module reaches a predetermined level the dosing device switches the sewage input to the other treatment module, while opening the outlet from the first treatment module to the leaching field. The dosing device switching mechanism employs pinch valves arranged so that when the inlet on one treatment module is closed, the inlet on the other treatment module is substantially simultaneously opened. Similarly, when one sedimentation tank outlet module is opened, the outlet module from the sedimentation tank in the other treatment is substantially simultaneously closed. The switching mechanism is actuated in response to sensed liquid levels in the sedimentation tanks in the two treatment modules. |
