Regeneration of spent dialysate using a membrane bioreactor

A membrane bioreactor (MBR) system using Sporosarcina pasteurii for the removal of urea from spent dialysate was investigated. Work entailed the identification of growth conditions for S. pasteurii in batch, continuous, and MBR formats to understand nutritional requirements, growth parameters, and ultimately, clearance of urea. During the preliminary studies, a method for growing S. pasteurii in spent dialysate was developed. S. pasteurii lag phase decreased from 150h to a few hours when 1% (w/w) yeast extract and 10% of acclimated inoculum source were used. Acclimated S. pasteurii used as working stock has a lifetime of up to 15h at 30°C. The kinetic parameters of S. pasteurii in spent dialysate were studied using a batch reactor and a chemostat. During the batch reactor tests, S. pasteurii growth could be modeled with Blackman's equation for glucose concentration lower than 2g/L. The maximum specific growth rate for S. pasteurii was 0.113h-1. When grown in chemostat, S. pasteurii growth exceeded the predicted maximum dilution rate based on preliminary batch values.; Urea removal as high as 90% could be achieved during the membrane bioreactor studies. Dilution rates as high as approximately 20 times the expected critical dilution rate could be realized, and large solid retention times did not affect membrane flux. The polysulfone membrane with a molecular weight cut off of 10,000 produced a flux as high as 20L/m2h. Glucose consumption was negligible during the MBR runs. Finally, a preliminary economic analysis of a MBR system used to degrade urea was completed. The analysis showed a return on investment of 115% when a dialysis clinic uses regenerated spent dialysate with S. pasteurii in a MBR system.