| 摘要 |
<p>Sewage sludge is dewatered in a multi-stage filter press in which a first active period of pumping the sludge with additives of CaO or Ca(OH)2 or FeCl2 is ended when an upper pressure threshold is reached. In several subsequent cycles the pump is switched off on reaching an upper threshold and is started when the pressure has dropped to a lower threshold. At least the first topping-up cycle is started with a time delay relative to the time of reaching the upper pressure threshold which lies between a typical value required in the preceding cycle for the pressure to drop from the upper to the lower threshold, and twice this value. Although the dry matter content of the filter cake may be at most 2-5% deg. than the optimum of 55%, the filtering time is reduced by 30% and more so that a 25% higher throughput is achieved.</p> |
