Nabin Chowdhury

Load maximization of a liquid–solid circulating fluidized bed bioreactor for nitrogen removal from synthetic municipal wastewater

A novel liquid-solid circulating fluidized bed bioreactor (LSCFB) configured with anoxic and aerobic columns and lava rock as the biofilm carrier was used to treat synthetic municipal wastewater. Four different empty bed contact times (EBCTs) of 0.82, 0.65, 0.55, and 0.44 h were examined to optimize nutrient removal capability of the system. The LSCFB demonstrated tertiary effluent quality organic and nitrogen removal efficiencies. Effluent characteristics of the LSCFB were soluble biological oxygen demand (SBOD)10 mg l(-1) and total nitrogen (TN)<10 mg l(-1) at organic loading rate (OLR) of 5.3 kg m(-3)d(-1) and nitrogen loading rate of 0.54 kg Nm(-3)d(-1). Remarkably low yields of 0.14, 0.17, 0.19, and 0.21 g VSS g(-1)COD were observed at OLR of 2.6, 3.2, 4.1 and 5.3 kg COD m(-3)d(-1), where increment of biomass growth and detachment rate were also experienced with increasing OLR. However the system demonstrated only 30% phosphorus removal, and mass balances along the anoxic and aerobic columns showed biological phosphorus removal in the system. Organic mass balance showed that approximately 40% of the influent COD was utilized in the anoxic column and the remaining COD was oxidized in the aerobic column. The system is very efficient in nitrification-denitrification, with more than 90% nitrification of ammonium and overall nitrogen removal in the LSCFB was 70+/-11% even at an EBCT of 0.44 h.

Biological nutrient removal from leachate using a pilot liquid–solid circulating fluidized bed bioreactor (LSCFB)

Biological treatment of landfill leachate is a concern due to toxicity, high ammonia, low biodegradable organic matter concentrations, and low carbon-to-nitrogen ratio. To study the reliability and commercial viability of leachate treatment using an integrated liquid-solid circulating fluidized bed bioreactor (LSCFB), a pilot-scale LSCFB was established at the Adelaide Pollution Control Plant, London, Ontario, Canada. Anoxic and aerobic columns were used to optimize carbon and nutrient removal capability from leachate using 600 microm lava rock with a total porosity of 61%, at empty bed contact times (EBCTs) of 0.55, 0.49, and 0.41 d. The LSCFB achieved COD, nitrogen, and phosphorus removal efficiencies of 85%, 80%, and 70%, respectively at a low carbon-to-nitrogen ratio of 3:1 and nutrients loading rates of 2.15 kg COD/(m(3) d), 0.70 kg N/(m(3) d), and 0.014 kg P/(m(3) d), as compared with 60-77% COD and 70-79% nitrogen removal efficiencies achieved by upflow anaerobic sludge blanket (UASB) and moving bed bioreactor (MBBR), respectively. The LSCFB effluent characterized by <or=35 mg SBOD/L, <35 mg NH(4)-N/L, <1.0 mg PO(4)-P/L, and 37 mg VSS/L can easily meet sewer by-law requirements. Remarkably low yields of 0.13, 0.15, and 0.16 g VSS/g COD were observed at long biological solids retention times (SRTs) of 31, 38 and 44 d.

Pilot-scale experience with biological nutrient removal and biomass yield reduction in a liquid-solid circulating fluidized bed bioreactor.

A pilot-scale liquid-solid circulating fluidized bed (LSCFB) bioreactor was developed at the Adelaide Pollution Control Plant, London, Ontario, Canada, to study its commercial viability for biological nutrient removal. Lava rock particles of 600 microm were used as a biomass carrier media. The LSCFB removed approximately 90% organic, 80% nitrogen, and 70% phosphorus at loading rates of 4.12 kg COD/m3 x d, 0.26 kg N/m3 x d, and 0.052 kg P/m3 x d, and an empty bed contact time of 1.5 hours. Effluent characterized by < 1.0 mg NH4-N/L, < 5.0 mg NO3-N/ L, < 1.0 mg PO4-P/L, < 10 mg TN/L, < 10 mg SBOD/L, and 10 to 15 mg volatile suspended solids (VSS)/L can easily meet the criteria for nonpotable reuse of treated wastewater. The system removed nutrients without using any chemicals, and the secondary clarifier removed suspended solids removal without chemicals. A significant reduction (approximately 75%) in biomass yield to 0.12 to 0.16 g VSS/g chemical oxygen demand (COD) was observed, primarily because of long biological solids retention time (SRT) of 20 to 39 days and a combination of anoxic and aerobic COD consumption.

Effect of Dynamic Loading on Biological Nutrient Removal in a Pilot-Scale Liquid-Solid Circulating Fluidized Bed Bioreactor

A pilot-scale liquid-solid circulating fluidized bed (LSCFB) bioreactor was employed for biological nutrient removal from municipal wastewater at the Adelaide Pollution Control Plant, London, Ontario, Canada. Lava rock particles of 600 μm were used as a biomass carrier media. The system generated effluent characterized by <1.0 mg NH4 —N/L , <6.0 mg NO3 —N/L , <1.0 mg PO4 —P/L , <10 mg TN/L, and <10 mg SBOD/L at an influent flow of 5  m3 /d , without adding any chemicals for phosphorus removal and secondary clarification for suspended solids removal. The impact of the dynamic loading on the LSCFB effluent quality and its nutrient removal efficiencies were monitored by simulating wet weather condition at a maximum peaking factor of 3 for 4 h. The achievability of effluent characteristics of 1.1 mg NH4 —N/L , 4.6 mg NO3 —N/L , 37 mg COD/L, and 0.5 mg PO4 —P/L after 24 h of the dynamic loading emphasize the favorable response of the LSCFB to the dynamic loadings and the sustainability of performance without l...

A novel fluidized bed respirometric technique for determination of in situ biofilm kinetics.

A respirometric approach has been developed to determine heterotrophic biofilm kinetics using fluidized bioparticles – particles with attached biomass. Lava rock particles of 600 μ m were used as a biomass carrier medium. The modified respirometer successfully estimates in situ biofilm kinetics of the bioparticles collected from a pilot-scale liquid–solid circulating fluidized bed (LSCFB) bioreactor. The observed maximum specific growth rates (μmax) of 3.69±0.44 d−1 and biomass yields (Y H ) of 0.36±0.03 g COD/g COD in the fluidized bed respirometers were significantly different from the μmax of 5.57–5.72 d−1 and Y H of 0.54–0.59 g COD/g COD observed in the conventional respirometric tests for bioparticles and detached biomass. The higher Monod half-saturation coefficient (K S ) of 186–219 mg COD/L observed in the fluidized bed respirometers relative to the 49–58 mg COD/L in the conventional respirometers reveals the presence of mass transfer resistance in the LSCFB despite fluidization. Significantly reduced yields in the fluidized bed respirometers and the estimated maintenance coefficient of 1.16 d−1 for the particulate biofilm in the LSCFB clearly emphasize that a substantial amount of substrate was utilized for cell maintenance at the low food to microorganism (S/X) ratio of 0.5 g COD/g VSS.