所谓物理脱水就是通过降低淤泥中的含水量来改善其力学性质。主要包括自然晾晒法、机械脱水法。自然晾晒法通过太阳的照晒蒸发去除淤泥中多余的水分，此法只适用于少量淤泥的处理，而且受场地和气候等方面的影响一般实施较为困难。
The so-called physical dehydration is to improve its mechanical properties by reducing the water content in the sludge. It mainly includes natural drying method and mechanical dehydration method. The natural air drying method removes the excess water in the sludge through the sun drying and evaporation. This method is only suitable for the treatment of a small amount of sludge, and it is generally difficult to implement due to the influence of site and climate.
而机械脱水法其原理就是使用脱水机械将淤泥中多余的水分去除，便于使用。此法的优点就是不受自然条件的限制。缺点就是一次性投资较高，不适合发展中国家，而且脱水效率较低，又由于淤泥中含有大量的有机物质、腐殖质和各类有毒有害物质，极易造成二次污染。
The principle of mechanical dewatering method is to use dewatering machinery to remove excess water from sludge, which is convenient for use. The advantage of this method is that it is not limited by natural conditions. The disadvantage is that the one-time investment is high, which is not suitable for developing countries, and the dehydration efficiency is low. Because the sludge contains a large amount of organic matter, humus and various toxic and harmful substances, it is very easy to cause secondary pollution.