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Table 3. Continuous removal of nonylphenol from synthetic medium and spiked secondary effluent in the two stage membrane bioreactor (Méndez-Hernandez et al. 2015).

Table 3 Continuous removal of nonylphenol from synthetic medium and spiked secondary effluent in the two stage membrane bioreactor (Méndez-Hernandez et al. 2015).

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Table 1. Examples of enzymatic systems using oxidative enzymes applied for the removal of pollutants from wastewaters. CSTR: continuous stirred tank reactor. CLEAs: cross-linked enzyme aggregates. Peroxidases are produced by a variety of source including microorganisms, plants and animals (Guzil et al. 2014). The extracellular enzymes produced by white rot fungi, namely, lignin peroxidase (LIP), man ganese peroxidase (MnP) and versatile peroxidase (VP have been successfully applied for the removal of « wide range of environmental pollutants in batch anc continuous systems (Table 1).
Table 1. Examples of enzymatic systems using oxidative enzymes applied for the removal of pollutants from wastewaters. CSTR: continuous stirred tank reactor. CLEAs: cross-linked enzyme aggregates. Peroxidases are produced by a variety of source including microorganisms, plants and animals (Guzil et al. 2014). The extracellular enzymes produced by white rot fungi, namely, lignin peroxidase (LIP), man ganese peroxidase (MnP) and versatile peroxidase (VP have been successfully applied for the removal of « wide range of environmental pollutants in batch anc continuous systems (Table 1).
Figure 1. Generic schemes of the catalytic cycle of (A) peroxidases as reported by Wesenberg et al. (2003) and (B) laccase involv- ing the reduction of dioxygen and the concomitant oxidation of substrate molecules (at the T1 copper site) to the corresponding radicals (adapted from Riva 2006). S: substrate molecule; S°: oxidized substrate. Laccases contain four copper atoms (belonging to three types: T1, T2 or T3) per monomer located at the catalytic site. T1 (one Cu atom) acts as the primary electron acceptor site where the enzyme catalyzes the oxidation of the substrate. T2 (one Cu atom) forms a Horseradish peroxidases (HRP) have also been pro- posed for pollution control (Auriol et al. 2006; Mao et al. 2013). This enzyme is suitable for wastewater treatment because it retains its activity over a broad range of pH and temperature (Duran and Esposito 2000). Other plant peroxidases, such as soybean perox- idase or bitter gourd peroxidase, were also effective for removal of phenolic compounds and dyes (Caza et al. 1999; Akhtar et al. 2005; Akhtar and Husain 2006; Bodalo et al. 2008).
Figure 1. Generic schemes of the catalytic cycle of (A) peroxidases as reported by Wesenberg et al. (2003) and (B) laccase involv- ing the reduction of dioxygen and the concomitant oxidation of substrate molecules (at the T1 copper site) to the corresponding radicals (adapted from Riva 2006). S: substrate molecule; S°: oxidized substrate. Laccases contain four copper atoms (belonging to three types: T1, T2 or T3) per monomer located at the catalytic site. T1 (one Cu atom) acts as the primary electron acceptor site where the enzyme catalyzes the oxidation of the substrate. T2 (one Cu atom) forms a Horseradish peroxidases (HRP) have also been pro- posed for pollution control (Auriol et al. 2006; Mao et al. 2013). This enzyme is suitable for wastewater treatment because it retains its activity over a broad range of pH and temperature (Duran and Esposito 2000). Other plant peroxidases, such as soybean perox- idase or bitter gourd peroxidase, were also effective for removal of phenolic compounds and dyes (Caza et al. 1999; Akhtar et al. 2005; Akhtar and Husain 2006; Bodalo et al. 2008).
Figure 2. Schematic representation of main configurations of enzymatic reactors using a membrane to retain the enzyme in the system: (A) CSTR coupled to an external membrane or (B) containing a submerged membrane, to separate the enzyme from the effluent; and (C) enzymatic membrane reactor using a membrane as support for the biocatalyst. In the second configuration, the biocatalyst is sus- pended in solution and compartmentalized by a mem- brane in the reactor vessel (Giorno and Drioli 2000) (Figure 2(B)). This system can be used with free (Nguyen et al. 2014b) or insolubilized enzyme, Two-stages mem brane reactor. This approach con- sists of separating the catalytic cycle of the enzyme from the degrada ion process of the target compound. Therefore, it is only valid for those processes where the enzyme can perform the oxidation of the target compound indirectly. In this configuration, the oxidiz- ing agent is enzymatically produced in a first vessel and then is used removal of the Majcherczyk and laccase mediator in a second tank to perform the target compound. In this regard, Johannes (2000) took advantage of systems to evaluate the two-stage concept. This was based on a compartment system with a membrane physically separating the enzyme
Figure 2. Schematic representation of main configurations of enzymatic reactors using a membrane to retain the enzyme in the system: (A) CSTR coupled to an external membrane or (B) containing a submerged membrane, to separate the enzyme from the effluent; and (C) enzymatic membrane reactor using a membrane as support for the biocatalyst. In the second configuration, the biocatalyst is sus- pended in solution and compartmentalized by a mem- brane in the reactor vessel (Giorno and Drioli 2000) (Figure 2(B)). This system can be used with free (Nguyen et al. 2014b) or insolubilized enzyme, Two-stages mem brane reactor. This approach con- sists of separating the catalytic cycle of the enzyme from the degrada ion process of the target compound. Therefore, it is only valid for those processes where the enzyme can perform the oxidation of the target compound indirectly. In this configuration, the oxidiz- ing agent is enzymatically produced in a first vessel and then is used removal of the Majcherczyk and laccase mediator in a second tank to perform the target compound. In this regard, Johannes (2000) took advantage of systems to evaluate the two-stage concept. This was based on a compartment system with a membrane physically separating the enzyme
Figure 3. (A) One-stage enzymatic membrane reactor for the treatment of secondary effluents by free laccase. (B) Two-stage membrane bioreactor for the removal of nonylphenol by Mn?*—malonate complex. Selection of the technology based on the target pollutant A valve located at the end of the membrane module was used to control both the membrane permeate and the recycling flow rates.
Figure 3. (A) One-stage enzymatic membrane reactor for the treatment of secondary effluents by free laccase. (B) Two-stage membrane bioreactor for the removal of nonylphenol by Mn?*—malonate complex. Selection of the technology based on the target pollutant A valve located at the end of the membrane module was used to control both the membrane permeate and the recycling flow rates.
able 2. Removal efficiency of target pollutants under different operational conditions in the polymeric and ceramic membrane reactors
able 2. Removal efficiency of target pollutants under different operational conditions in the polymeric and ceramic membrane reactors
Operatea In Similar Way than the polymeric one (Figure 3(A)) with slight differences in the working vol ume (1.5L versus 2L), and recycling feed/flow ratic (Table 2). Furthermore, oxygenation was not per formed, since it did not exert a positive effect on BPA removal (Arca-Ramos et al. 2015b). In experiments 5-8 the ceramic membrane reactor was applied for the continuous treatment of BPA from buffer solution a various BPA addition rates (Table 2). The removal per centage of BPA was above 93% for all the evaluatec experiments; nonetheless, the reduction in the feec addition rate enhanced the removal percentage o BPA, and almost complete conversion was achievec for 7.5 ug/(L-h). The effect of real matrix on the cata lytic action of laccase was evaluated (experiment 9 Table 2), and the performance of the reactors operatec with buffer solution (pH 6) and filtered secondary effluent (pH~7.2) is depicted in Figure 4(A) and (B) respectively. In the experiment with buffer solution laccase activity remained stable and almost complete transformation of BPA was observed along the oper ation of the reactor. In contrast, in the operation witk real wastewater, a gradual drop in the activity wa: observed after 22h of operation and a pulse of laccase was required to return the enzymatic activity to value: around 1000 U/L. Despite the real matrix affected the removal yield of BPA, it remained still high, arounc 95%. The retention of colloidal organic matter by the nanofiltration membrane and its subsequent accumu lation in the reactor vessel may be behind the drop ir both laccase activity and removal efficiency. This phe nomenon was not evidenced during the operation o the CSTR coupled to the polymeric membrane (Llore et al. 2013c), probably because of its higher pore size The implementation of a periodic backwash coulc solve clogging and fouling problems caused by accu mulation and adsorption of polymers, proteins or bio films on the membrane surface. In the two-ctagqe cvctam the catalvtic cvcle ic canp.
Operatea In Similar Way than the polymeric one (Figure 3(A)) with slight differences in the working vol ume (1.5L versus 2L), and recycling feed/flow ratic (Table 2). Furthermore, oxygenation was not per formed, since it did not exert a positive effect on BPA removal (Arca-Ramos et al. 2015b). In experiments 5-8 the ceramic membrane reactor was applied for the continuous treatment of BPA from buffer solution a various BPA addition rates (Table 2). The removal per centage of BPA was above 93% for all the evaluatec experiments; nonetheless, the reduction in the feec addition rate enhanced the removal percentage o BPA, and almost complete conversion was achievec for 7.5 ug/(L-h). The effect of real matrix on the cata lytic action of laccase was evaluated (experiment 9 Table 2), and the performance of the reactors operatec with buffer solution (pH 6) and filtered secondary effluent (pH~7.2) is depicted in Figure 4(A) and (B) respectively. In the experiment with buffer solution laccase activity remained stable and almost complete transformation of BPA was observed along the oper ation of the reactor. In contrast, in the operation witk real wastewater, a gradual drop in the activity wa: observed after 22h of operation and a pulse of laccase was required to return the enzymatic activity to value: around 1000 U/L. Despite the real matrix affected the removal yield of BPA, it remained still high, arounc 95%. The retention of colloidal organic matter by the nanofiltration membrane and its subsequent accumu lation in the reactor vessel may be behind the drop ir both laccase activity and removal efficiency. This phe nomenon was not evidenced during the operation o the CSTR coupled to the polymeric membrane (Llore et al. 2013c), probably because of its higher pore size The implementation of a periodic backwash coulc solve clogging and fouling problems caused by accu mulation and adsorption of polymers, proteins or bio films on the membrane surface. In the two-ctagqe cvctam the catalvtic cvcle ic canp.
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