The pebbles are big it should be removed through bar screening not by grit and sand removal!!!! 
BTW in grit and sand removal grit and sand is not removed!!!

IT IS REMOVED IN THE SAND AND GRIT REMOVAL AND NOT IN BAR SCREEN AS BAR SCREEN IS NOT THAT MUCH FINE THAT IT REMOVES THE PEBBLES . IT REMOVES ONLY THINGS LIKE PLASTICS , CARDBOARDS ETC.