Aerobic 4-nitrophenol degradation by microorganisms fixed in a continuously working aerated solid-bed reactor

Abstract

Studies of microbial purification of a model waste water containing 4-nitrophenol were carried out in a continuously working aerobic solid-bed reactor. The main emphasis was on the dynamic behaviour of the system after a sudden change in cultivation conditions and on the steady state performance of the reactor as a function of the pollution load. A change from ammonium-free to ammonium-containing medium hardly influenced the nitrophenol degradation. The reactor responded differently to an increase in pollutant load, which was brought about by increasing either the 4-nitrophenol content or the flow of the waste water. Up to a load of 270 mg l-1 h-1 the pollutant was stably and almost completely degraded. At a higher load, only a partial 4-nitrophenol degradation took place. A mathematical model was derived to describe the processes that occurred in the reactor. By segregation into two compartments--the aqueous phase and the biofilm--account was taken of the fact that the pollutant is carried into the biofilm by diffusion and is degraded there. The observed relations between the pollutant load, the pollutant concentration in the outlet of the reactor and the reactor performance agreed with the simulated process behaviour. As the model simulation showed, the incomplete pollutant degradation at a higher reactor load was caused by oxygen limitation.

Batch Biodegradation of Para-Nitrophenol Using Arthrobacter chlorophenolicus A6

“…The value of the kinetic parameter K i signifies the degree of resistance of the microorganism to toxic effects of PNP and, in general, a larger K i value reveals that the biomass is highly resistant to inhibition by its substrate. The K i value of the actinomycetes in the present study (128 mg l −1 ) was found higher than the value obtained for 4-CP degradation by R. erythropolis M1 and for PNP degradation using mixed culture [31,35,36] indicating good tolerance of A. chlorophenolicus A6 towards growth and degradation of PNP in treating contaminated wastewater. A high resistance of A. chlorophenolicus A6 as observed from the estimated K i value may be due to the production of micro colonies during its growth in culture media.…”

“…Half saturation constant (K s ) in the model is a measure of affinity between biomass and substrate [32] and the value (60.15 mg l −1 ) estimated in the study is found to correlate well with those found in literature on PNP and phenol degradation by mixed cultures [33,34]. The model parameter value is also found to be greater than the K s value of 13.33 mg l −1 obtained by Bhatti et al [35] and Ray et al [36] for the degradation of PNP using a mixed culture which indicates a high affinity of A. chlorophenolicus A6 towards the substrate. The value of the kinetic parameter K i signifies the degree of resistance of the microorganism to toxic effects of PNP and, in general, a larger K i value reveals that the biomass is highly resistant to inhibition by its substrate.…”

Rapid Establishment of p-Nitrophenol Biodegradation in Acetate-Fed Aerobic Granular Sludge

“…However, studies on PNP removal from bioreactors are relatively limited due to its acute toxicity on bacterial cells [16,17]. Immobilization strategies were reported to avoid PNP's acute toxicity and thereby achieve high degradation rates [16,18]. Yi et al [18] have shown that preconditioning of activated sludge with PNP is necessary for the cultivation of PNP-degrading aerobic microbial granules.…”

“…Biodegradation of p-nitrophenol (PNP) by various bacterial cultures is known, and catabolic pathways are fairly well understood [15]. However, studies on PNP removal from bioreactors are relatively limited due to its acute toxicity on bacterial cells [16,17]. Immobilization strategies were reported to avoid PNP's acute toxicity and thereby achieve high degradation rates [16,18].…”

Biodegradability of 3-Methyl-4-Nitrophenol by 4-Nitrophenol-Degrading Bacteria

“…Because 4NP is water-soluble, it affects humans as well as aquatic organisms through surface, ground, and drinking waters. The biodegradation of 4NP in soils, sludges, pure cultures, and bioreactors has been extensively studied [3][4][5][6] . As a result, some 4NP degradation pathways have been identified [7][8][9][10][11] and practical bioremediation using a 4NP-degrading bacterium has been initiated in India to remove soil contamination 12) .…”