Removal of xenobiotics in a two phase sequencing batch reactor: kinetics and modelling

The objectives of the paper are to verify the potentialities of a sequential two phase partitioning bioreactor in degrading xenobiotics and to evaluate the kinetic parameters for modelling the system. The target compound investigated was the 4-nitrophenol. Preliminary tests were carried out to define the solvent most appropriate for the compound. Among the three investigated solvents 1-undecanol, 2-undecanon and oleyl alcohol, the 2-undecanon was chosen because of the higher partition coefficient of 30 and the negligible formation of emulsions. Moreover, the tested solvent showed satisfactory "biocompatibility" characteristics for the biomass with minor effects on the intrinsic kinetics. Parallel batch kinetic tests were then performed with the conventional one phase and the two phase systems. In the two phase system the biomass is exposed for all the time to 4NP concentrations that are significantly lower if compared to the conventional system and, for the highest concentration (450 mg/l) in the two phase system a reduction of the reaction time is observed depending on the biomass concentration. Kinetic parameters were also evaluated in both cases by fitting of the experimental data with a modified form of the Haldane equation

4-Nitrophenol biodegradation in a sequencing batch reactor operating with aerobic-anoxic cycles

The study regards 4-nitrophenol removal performed in a lab-scale sequential batch reactor with an integrated aerobic-anoxic cycle. The purpose of the study was to examine the kinetics of 4-nitrophenol biological oxidation and denitrification in order to test the feasibility of the proposed technological solution for xenobiotic removal. The results obtained show that high removal efficiency of 4-nitrophenol is easily achieved when the compound is fed into the reactor as the sole carbon source. Residual concentrations of 4-nitrophenol and nitrous/nitric nitrogen in the effluent lower than 1 mg L -1 were observed in the range of applied feed concentration (200-320 mg L -1). Low concentrations of dissolved oxygen (≤2 mg L -1) in the feed and aerobic phases lead to appreciable simultaneous denitrification. As regards the denitrification process, while no carbon-limiting effects were observed at COD/N ratios ≥ 3, a significant decrease in the rate of denitrification is detected for COD/N ratios ≤ 2. The denitrification rate obtained in tests with no external carbon addition proved very low and unsuitable for practical application. A model of the denitrification process taking into account both the limiting effect of nitrogen and carbonaceous substrate has been proposed and applied for experimental data correlation. © 2005 American Chemical Society

4-nitrophenol biodegradation in a sequencing batch reactor: kinetic study and effect of filling time

Biodegradation kinetics of 4-nitrophenol (4NP) was investigated in a lab-scale sequencing batch reactor fed with the compound as the sole carbon source. The experimental results showed that complete 4NP removal can be easily achieved with acclimatized biomass, even if an inhibition kinetics is observed; furthermore, an improvement in the removal kinetics is obtained if the substrate concentration peak, reached in the reactor at the end of the filling time, is maintained to quite a low value. Both long feed phase and high biomass concentration are effective in reducing the substrate concentration peak and then improving the process efficiency. Kinetic test data are well correlated by the Haldane equation, with a saturation constant K-s and an inhibition constant K-I, of 17.6 and 30.7 (mg l(-1) 4NP), respectively, whereas the maximum removal rate was in the range of 3.3-8.4 (mg 4NP mg VSS-1 d(-1)) depending on the substrate concentration peak reached in the reaction phase. (C) 2003 Elsevier Ltd. All rights reserved

2,4-Dichlorophenol removal in a solid-liquid two phase partitioning bioreactor (TPPB): Kinetics of absorption, desorption and biodegradation

The applicability of a sequencing batch two phase partitioning bioreactor (TPPB) to the biodegradation of a highly toxic compound, 2,4-dichlorophenol (DCP) (EC50 = 2.3-40 mg L-1) was investigated. A kinetic study of the individual process steps (DCP absorption into the polymer, desorption and biodegradation) was performed and, based on favourable absorption/desorption characteristics (DCP diffusivity of 6.6 x 10(-8) cm(2) s(-1)), the commercial polymer Tone P787 (Dow Chemical), was utilized as the sequestering phase for TPPB operation. Batch kinetic biodegradation tests were performed in both single-and two-phase modes, and the Haldane equation kinetic parameters were estimated (k = 1.3 x 10(-2) mgDCP mgVSS(-1) h(-1), K-I = 35 mgDCP L-1 and K-s = 18 mgDCP L-1), confirming the highly toxic nature of DCP. Consistent with these findings, operation of the single-phase system showed that for an initial DCP concentration of 130 mg L-1 the biomass was completely inhibited and DCP was not degraded, while the two-phase system achieved near-complete DCP removal. In sequencing batch mode the TPPB had a removal efficiency of 91% within 500 min for a feed of 320 mg L-1, which exceeds the highest concentration previously degraded. These results have confirmed the effectiveness of the use of small amounts (5%, v/v) of inexpensive commercial polymers as the partitioning phase in TPPB reactors for the treatment of a highly toxic substrate at influent loads that are prohibitive for conventional single-phase operation, and suggest that similar detoxification of wastewater influents is achievable for other target cytotoxic substrates

Solid-liquid two-phase partitioning bioreactors (TPPBs) operated with waste polymers. Case study: 2,4-dichlorophenol biodegradation with used automobile tires as the partitioning phase

Used automobile tire pieces were tested for their suitability as the sequestering phase in a two-phase partitioning bioreactor to treat 2,4-dichlorophenol (DCP). Abiotic sorption tests and equilibrium partitioning tests confirmed that tire "crumble" possesses very favourable properties for this application with DCP diffusivity (4. 8 × 10-8 cm2/s) and partition coefficient (31) values comparable to those of commercially available polymers. Biodegradation tests further validated the effectiveness of using waste tires to detoxify a DCP solution, and allow for enhanced biodegradation compared to conventional single-phase operation. These results establish the potential of using a low-cost waste material to assist in the bioremediation of a toxic aqueous contaminant. © 2012 Springer Science+Business Media B.V