Rapid sand filtration is a purely physical drinking water purification method. Rapid sand filters (RSF) provide rapid and efficient removal of relatively large suspended particles. Two types of RSF are typically used: rapid gravity and rapid pressure sand filters. For the provision of safe drinking water, RSFs require adequate pre-treatment (usually coagulation-flocculation) and post-treatment (usually disinfection with chlorine).
with great suddenness the car in front stopped abruptly, and we almost hit it Synonyms short, suddenlyRelated Words surprisingly, unexpectedly; directly, immediately, incontinently, instantaneously, instantly, promptly, pronto, right, right away, right off, straightaway; fast, full-tilt, posthaste, quick, quickly, rapidly, readily, snappily, ...
interchange, substitute, replace, exchange - put in the place of another; switch seemingly equivalent items; the con artist replaced the original with a fake Rembrandt; substitute regular milk with fat-free milk; synonyms can be interchanged without a changing the context's meaning 8. shift - move sideways or in an unsteady way; The ship careened out of control