EMPLOYEE WAS EMPTYING THE NEUTRALIZER TANK PUTTING WATER/CARBON IN 3 1/2 GALLON BUCKETS WHILE PICKING UP THE BUCKETS HE TWISTED CAUSING A LOWER LUMBAR SPRAIN. THE EMPLOYEE DID NOT SEEK MEDICAL ATTENTION UNTIL 11-4. HE WAS RE-EVALUATED 11-7. AT THIS TIME THE DOCTOR RECOMMENDED LIGHT DUTY WORK.