Esa S. Melin

High-rate bioremediation of chlorophenol-contaminated groundwater at low temperatures.

Aerobic luidized-bed treatment was employed for psychrotrophic bioremediation of chlorophenol-contaminated groundwater. Laboratory-scale, continuous-low reactors were inoculated with nonacclimated activated sludge, the groundwater was amended with inorganic nutrients and a phosphate buffer, and continuous groundwater feed was started at 14-17 o C. Chlorophenol concentrations (in mg/L) in groundwater were as follows: 7-11 for 2,4,6-trichlorophenol, 32-36 for 2,3,4,6-tetrachlorophenol, and 1.8-2.3 for pentachlorophenol. After the startup period, the treatment temperature was gradually decreased to the ambient groundwater temperature (7 o C) and further to 4 o C

Effects of temperature on chlorophenol biodegradation kinetics in fluidized-bed reactors with different biomass carriers

Abstract Groundwater contaminants including 2,4,6-trichlorophenol (TCP), 2,3,4,6-tetrachlorophenol (TeCP), and pentachlorophenol (PCP) were mineralized in three aerobic fluidized-bed reactors (FBRs) employing sand, volcanite, and diatomaceous earth as biomass carriers. The effect of temperature on chlorophenol degradation kinetics was studied in FBR batch tests at temperatures ranging from 4 to 16.5°C. TCP and TeCP degradation was modeled using the Michaelis-Menten kinetics. Specific maximum degradation rates for TCP and TeCP varied with temperature from 0.46 × 10 −3 to 31 × 10 −3 mg mgVS −1 h −1 and K s varied from zero to 7.1 mg l −1 . Degradation of PCP was affected by the presence of TCP and TeCP and followed competitive inhibition kinetics. Specific degradation rates for PCP degradation varied with temperature from 0.24 × 10 −3 to 1.7 × 10 −3 mg mgVS −1 h −1 and were always lower than for other chlorophenols. The Arrhenius equation described the temperature effects on biodegradation of chlorophenols. The activation energies (kJ mol −1 ) for TCP and TeCP varied from 126 to 194, and for PCP from 59 to 130. In the studied temperature range, a 10°C decrease in temperature generally resulted in over seven times slower degradation rates. The volcanite reactor had the highest and the sand reactor the lowest biomass accumulation.

Degradation of 4-chlorophenol in denitrifying fluidized-bed process

Abstract Chlorophenol degradation by dissimilatory nitrate reduction was studied in an anoxic fluidized‐bed reactor. 4‐Chlorophenol (4‐CP) served as a carbon source for denitrification although both 4‐CP and nitrate removals remained incomplete (23–82 and 9–60%, respectively) at 5 h hydraulic retention time. Under varying experimental conditions, 1.9–2.5 mg 4‐CP was degraded and dechlorinated per 1 mg NO3‐N reduced. This is higher than the theoretical 4‐CP/NO3‐N ratio of 1.8 and the difference is likely due to aerobic degradation in the presence of trace concentrations of oxygen. The mass balance based on inorganic chloride release and disappearance of the parent compound gave further evidence of chlorophenol degradation in the system.

Continuous ethanol production from glucose using Saccharomyces cerevisiae immobilized on fluidized microcarriers

Abstract The feasibildty was explored of employing biofluidized bed (BFB) technology based on immobilized Saccharomyces cerevisiae for continuous ethanol production from glucose. Long-term, steady and effective performance of ethanol production and glucose utilization is achievable in the BFB reactor when porous microcarriers are used to immobilize and retain yeast cells. More than two- thirds of the total reactor yeast cell mass was immobilized. Zero-order kinetics for ethanol production and glucose utilization existed at bulk liquid glucose concentrations greater than 1 g L −1 . Ethanol inhibition of yeast cells was absent at bulk liquid ethanol concentrations as high as 78 g L −1 .

Biodegradation of PAH Mixtures by a Marine Sediment Enrichment

Abstract Aerobic polycyclic aromatic hydrocarbon (PAH) degrading bacteria were enriched from creosote contaminated marine sediments (Puget Sound, Washington, USA) using a continuous-flow fluidized-bed reactor. Artificial seawater media and a mixture of seven 2 to 3-ring PAHs were used as enrichment substrates. The biodegradability of PAH mixtures by the enrichment was determined in batch vial assays. The tested PAH mixtures included alkyl substituted naphthalenes, phenanthrene, anthracene, fluoranthene, and pyrene. Co-occurring PAHs significantly affected the degradation rates of individual compounds. Degradation was generally slower in mixtures than with individual compounds indicating competition. Degradation of some recalcitrant PAHs, on the other hand, was enhanced in mixtures. Phenanthrene degraded rapidly but pyrene degradation was insignificant when present alone. In pyrene-phenanthrene mixtures, pyrene was nearly completely removed indicating enzyme induction or cometabolism.