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The response of a continuous two-phase partitioning bioreactor (C-TPPB) operated with polymeric tubing treating hypersaline wastewater was investigated under dynamic load conditions of step, ramp and impulse inputs of the influent flow rate. Tests were performed with synthetic wastewater consisting of NaCl (100 g L −1 ) and 2,4-dimethylphenol (DMP) (∼1200 mg L −1 ) to simulate the organic fraction. A biomass specifically acclimatized to the compound was utilized in the tests. The experimental system provides separation of the toxic wastewater flowing inside the polymeric tubing (coiled in the bioreactor) from the microbial culture present in the bulk bioreactor phase with the polymer providing permeability to the organic molecules as well as a barrier to salt transport. These features allowed achieving high performance even in the most severe loading conditions. Removal efficiencies >96% were obtained for DMP under all investigated load conditions (i.e. for influent salt and organic loads up to six times the base case load). A DMP mass balance at the end of the dynamic tests showed that 88% of the removed DMP was biodegraded and only 8% was retained into the polymer tubing itself. No significant variation of the DMP concentration in the bioreactor was observed in all cases thus demonstrating the complete removal of the transferred substrate and the effective performance of the biomass, which was not affected by the applied dynamic loads. A comparative analysis of C-TPPB results with the performance data of the classical technologies commonly applied for saline wastewater treatment has been performed to evaluate the system applicability. [ABSTRACT FROM AUTHOR]

This work describes the application of a solid-liquid two-phase partitioning bioreactor (TPPB) for the removal of colour from a real textile wastewater containing reactive azo-dyes. Four polymers were tested over the pH range of 4–9 to select the most effective absorbant to be used as the partitioning phase in the TPPB. The best results were obtained with Hytrel 8206 at pH 4 achieving ~ 70% colour removal, based on the dominant wavelength, in the first 5 h of contact time, and 84% after 24 h. Wastewater treatment was undertaken in a solid-liquid TPPB operated with Hytrel 8206 in sequential anaerobic-aerobic configuration. The reaction time of 23 h was equally distributed between the anaerobic and aerobic phases and, to favour colour uptake, the pH was controlled at 4.5 in the first 4 h of the anaerobic phase, and then increased to 7.5. Colour removal (for the dominant wavelength, 536 nm) increased from 70 to 85% by modifying the bioreactor operation from single-phase to TPPB mode. Based on COD measurements nearly complete biodegradation of the intermediates produced in the anaerobic phase was obtained, both in the single-phase and two-phase mode, with better performance of the TPPB system reaching 75% COD Dye removal. [ABSTRACT FROM AUTHOR]

This paper proposes a dynamic model simulating the performance of a fed batch system operated as solid–liquid two-phase partitioning bioreactor, with polymer beads as the sequestering phase, applied to the removal of xenobiotic compounds from concentrated aqueous streams, in which substrate inhibition is significant. The model takes into account substrate mass transfer into, and within, the solid particles. Outputs of the models are xenobiotic concentrations in the liquid and solid phases and the concentration profile within the solid polymer beads. Sensitivity analyses have been performed on the influent concentration and on the main operating parameters, which can be modified to control the process performance (i.e. polymer/feed ratio, reaction and loading times). With an inhibitory substrate, the selected duration of the reaction period exhibits a critical value which determines the transition from high to low efficiency of the bioreactor. Application examples are provided for a target compound, 4-nitrophenol, previously investigated in TPPBs with an immiscible organic solvent, while Hytrel 8206 has been considered as the polymer partitioning phase. The proposed model has been shown to be a powerful tool to predict suitable operating conditions for TPPB systems treating inhibitory substrates. [ABSTRACT FROM AUTHOR]

The applicability of a sequencing batch two phase partitioning bioreactor (TPPB) to the biodegradation of a highly toxic compound, 2,4-dichlorophenol (DCP) (EC50 =2.3–40mgL−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 6.6×10−8 cm2 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 =1.3×10−2 mgDCPmgVSS−1 h−1, K I =35mgDCPL−1 and K s =18mgDCPL−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 130mgL−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 500min for a feed of 320mgL−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. [ABSTRACT FROM AUTHOR]

Sequential anaerobic–aerobic digestion was applied to waste activated sludge (WAS) of a full scale wastewater treatment plant. The study was performed with the objective of testing the sequential digestion process on WAS, which is characterized by worse digestibility in comparison with the mixed sludge. Process performance was evaluated in terms of biogas production, volatile solids (VS) and COD reduction, and patterns of biopolymers (proteins and polysaccharides) in the subsequent digestion stages. VS removal efficiency of 40%, in the anaerobic phase, and an additional removal of 26%, in the aerobic one, were observed. For total COD removal efficiencies of 35% and 25% for anaerobic and aerobic stage respectively, were obtained. Kinetics of VS degradation process was analyzed by assuming a first order equation with respect to VS concentration. Evaluated kinetic parameters were 0.44±0.20d−1 and 0.25±0.15d−1 for the anaerobic stage and aerobic stage, respectively. With regard to biopolymers, in the anaerobic phase the content of proteins and polysaccharides increased to 50% and 69%, respectively, whereas in the subsequent aerobic phase, a decrease of 71% for proteins and 67% for polysaccharides was observed. The average specific biogas production 0.74m3/(kgVS destroyed), was in the range of values reported in the specialized literature for conventional anaerobic mesophilic WAS digestion. [ABSTRACT FROM AUTHOR]

The toxicity of four xenobiotic compounds 3,5-dichlorophenol, formaldehyde, 4-nitrophenol and dichloromethane, representative of industrial wastewater contaminants was evaluated by a simple respirometric procedure set up on the basis of OECD Method 209 and by the Microtox® bioassay. Very good reproducibility was observed for both methods, the variation coefficients being in the range of 2–10% for the respirometric procedure and 6–15% for Microtox®, values that can be considered very good for a biological method. Comparison of EC50 data obtained with the two methods shows that in both cases 3,5-dichlorophenol is more toxic than other compounds investigated and dichloromethane has a very low toxicity value. Intermediate EC50 values were found for the two other chemicals, formaldehyde and 4-nitrophenol. Moreover, the Microtox® EC50 values are generally lower (except for dichloromethane) than the respirometric ones: these differences could be explained by the fact that the Microtox® method uses a pure culture of marine species and, therefore, should not necessarily be expected to behave like a community of activated sludge bacteria.In conclusion, both methods can be usefully applied for toxicity detection in wastewater treatment plants but it is advisable to take into account that Microtox® is more sensitive than respirometry in estimating the acute toxicity effect on the biomass operating in the plant. [Copyright &y& Elsevier]

A continuous two-phase partitioning bioreactor has been tested for treating a synthetic leather tannery wastewater with the objective of achieving effective removal of the organic load and complete chromium separation. The bioreactor was operated with 5.5 m of Hytrel 8206 polymeric tubing fed with a synthetic tannery wastewater consisting of 4-chlorophenol (concentration in the range of 1000–2500 mg L −1 ) and potassium dichromate (100 mg L −1 as Cr (VI)), and immersed in a 4 L bioreactor containing the microbial culture acclimatized to the compound. This configuration prevents the direct contact between the toxic wastewater and the microorganisms themselves, and provides the gradual organic substrate delivery through the tubing walls. Abiotic partition and mass transfer tests were performed to investigate the transport of dichromate and 4-chlorophenol across the tubing into the bulk phase of the bioreactor. No appreciable mass transfer of dichromate was detected. During biotic testing, the influent organic load in tubing has been varied in the range of 19–94 mg h −1 and the hydraulic retention time from 3 to 6 h. Achieved biological removal efficiencies were in the range of 89–95% for the highest applied loads. Process kinetics (which included consideration of both mass transfer and biological rates) were evaluated, and it was found that the increased load did not result in any decrease in 4-chlorophenol removal rate. This work has shown that the continuous two-phase partitioning bioreactor has significant potential in enhancing the biological treatment of tannery wastewater, which is a typical representative of industrial “hostile” wastewater. [ABSTRACT FROM AUTHOR]