Keywords: centrate, fixed-, film enhanced suspended growth, nitrification, sequencing batch reactors, SBR, dewatering, anaerobically digested sludge, zero-, order kinetics, ammonia removal, biomass
Nitrification of centrate from dewatering of anaerobically digested sludge
Nitrification of anaerobically digested sludge centrate was studied in bench-scale suspended growth and fixed film enhanced suspended growth systems at temperatures of 10.5-28.5°C and pH values of 6.0-9.1. Nitrification followed zero-order kinetics in both systems, and ammonia removals in excess of 99% were observed. The temperature dependency of the suspended growth nitrification rate observed under not fully acclimated biomass conditions at pH between 6.8 and 8.5, was expressed as kT = k20θT-20where k20 and θ were found to be 0.34 mg NH3-N/MLVSS-d and 1.033, respectively. The nitrification rate in the fixed film enhanced suspended growth system involving styrofoam pads ranged from 0.11 to 0.13 mg NH3-N/mg MLVSS-d at temperatures of 21.5-25°C and pH values of 7.8-8.6. The process contained suspended solids in the range of 10-20 mg/l.