Nitrification Rates in a Reversed-Flow, Spouted-Bed, Bioreactor Applied to Recirculating Aquaculture Systems
The effects of media selection and organic loading on nitrification rates in a reversed-flow, three-phase, spouted-bed, bioreactor with draft-tube (A-1 Aquaculture Continuous-Cleaning Multifunctional Biofilter or CCMB) were studied. Experiments were conducted on three identical recirculating aquaculture systems (RAS) each having a CCMB unit with a unique plastic pelletized media and operated over five successive trials with varying components and operating conditions. Based upon organic loading, three of the five trials were grouped into two organic loading regimes of approximately 91 mg/L COD and 149 mg/L COD. Comparing nitrification rates against the three media types by organic loading showed that media selection had a significant (p<0.05) impact on nitrification performance. At both levels of organic loading, the nitrification rates of Media 1 outperformed Media 2 and Media 3. The differences between the Media 1 rates and those of Media 2 and Media 3 were greater at the lower organic loading than at the higher loading, for nitratation than for nitritation, and for areal comparisons than for volumetric comparisons. Comparing nitritation and nitratation rates against organic loading for each media type showed that organic loading had little impact on nitrification. A barely significant (p<0.05) difference between nitrification rates at the two organic loadings was observed only for Media 1 nitratation, where the nitratation rate was greater at the lower organic loading. Throughout all five trials, the CCMB demonstrated the ability to successfully nitrify over organic levels ranging from 13.5 to 205.3 mg/L COD and without showing any signs of biofouling or other problems associated with traditional fixed-film nitrification systems. Media 1 achieved the highest mean nitrification rates during all trials with an average concentration-normalized volumetric nitritation rate of 223 g TAN/day-m3 (0.0139 lb TAN/day-ft3) and maximum of 254 g TAN/day-m3 (0.0159 lb TAN/day-ft3) observed during Trial 5, which had both the highest organic loading and flow rates of all trials.
Advisor:Caye Drapcho; Steven Hall; Ralph Portier
School:Louisiana State University in Shreveport
School Location:USA - Louisiana
Source Type:Master's Thesis
Keywords:biological and agricultural engineering
Date of Publication:11/04/2002