MD80 CREW RPTS ENCOUNTERING SEVERE TURB AT FL320 INJURING 2 FLT ATTENDANTS AND 1 PAX.

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NORMAL TKOF AND CLB TO FL320. WE LEVELED OFF AND ESTABLISHED CRUISE OF MACH .76 AND WAS HEADED FOR ABC VOR. WE HAD SEEN NO SIGNIFICANT WX UNTIL CLOSE TO ZZZ. IT WAS E AND S OF ABC. WE ASKED FOR A DEV TO THE W FOR A LITTLE MORE ROOM. TURNED ON SEATBELT SIGN JUST AS A PRECAUTION ABOUT 7-8 MINS BEFORE WE HIT THE TURB. WE WERE ABOUT 10-15 MI N AND W OF ABC. WE HIT A COUPLE OF SMALL BUMPS. I GOT ON THE PA; TOLD THE FLT ATTENDANTS TO PICK UP AND TAKE THEIR SEATS. NOT MORE THAN 15-20 SECONDS LATER; GOT HIT WITH SEVERE TURB NOT LASTING MORE THAN 10-15 SECONDS. RPTED IT TO ZZZ CTR. ALT GAIN OR LOST NOT MORE THAN 150 FT. AFTER CLR OF TURB; CALLED TO BACK OF ACFT TO FIND OUT ABOUT DAMAGE/INJURY TO ANYONE. INFORMED THE #2 FLT ATTENDANT WAS BLEEDING FROM HER NOSE AND MOUTH. THE #4 HAD HIT HEAD AND WAS BLEEDING FROM THE NOSE. ONE PAX; WHO WAS IN THE AFT LAVATORY WITH THE SEATBELT SIGN ON; HAD HIT HER HEAD AND WAS BLEEDING. I DECLARED AN EMER AND REQUESTED CLRNC BACK TO ZZZ AND TO HAVE MEDICAL EQUIP AND PERSONNEL MEET US AT THE GATE. I DIDN'T SUSPECT ANY DAMAGE TO THE ACFT; NO ABNORMAL CTL INPUTS WERE NEEDED. CTR GAVE US VECTORS TO ZZZ ON THE GND IN ABOUT 15 MINS. LNDG WT WAS 130000 LBS. TAXIED TO GATE; MET BY GND PERSONNEL AND MEDICAL. THERE WERE NO PREVIOUS RPTS OF TURB ON OUR RTE OF FLT.