Sentence:  The washing process whereby soils are removed consists basically of <WSD>applying</WSD> mechanical action to loosen the dirt particles and dried matter in the presence of water which helps to float off the debris and acts , to some extent , as a dissolving and solvating agent . 
Meaning of the word marked with <WSD> tags:  put into service; make work or employ for a particular purpose or for its inherent or natural purpose