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, ...
The road ended in an abrupt (= sudden and very steep) slope down to the sea. The car juddered and came to an abrupt halt in the middle of the road. There was an abrupt change in her attitude towards me when she heard that I was Alan's girlfriend. The party came to rather an abrupt ending when Tom's parents came home. There was an abrupt fall in our sales figures following the bad publicity.