WO2018044153A1

WO2018044153A1 - Electrochemical system for recovery of components from a waste stream and method there for

Info

Publication number: WO2018044153A1
Application number: PCT/NL2017/050304
Authority: WO
Inventors: Philipp KUNTKE; Hubertus Victor Marie Hamelers; Tomas Hubertus Johannes Antonius Sleutels; Machiel Saakes; Cees Jan Nico Buisman
Original assignee: W&F Technologies B.V.
Priority date: 2016-08-29
Filing date: 2017-05-16
Publication date: 2018-03-08
Also published as: EP3504162A1; NL2017383B1

Abstract

The invention relates to an electrochemical system and method for recovery of components from a waste stream. The system according to the invention comprises a reactor that comprises: - an anode compartment with an anode; - a cathode compartment with a cathode; - a feed compartment that is provided between the anode and cathode compartments or is integrally provided with one of these compartments; - one or more ion-exchange membranes separating the anode and cathode compartments; - a recovery compartment configured for recovering components, wherein the recovery compartment is separated from one or more compartments with a hydrophobic membrane; and - a circuit connecting the anode and the cathode, the circuit comprising a power source for providing an electric current.

Description

ELECTROCHEMICAL SYSTEM FOR RECOVERY OF COMPONENTS FROM A WASTE STREAM AND METHOD THERE FOR

The invention relates to an electrochemical system for recovery of components from a waste stream. For example, the recovery of components relates to recovery of ammonia (NH₃) and/or ammonium (NH₄ ⁺) such that the system provides for ammonia and/or ammonium recovery from a waste stream. Waste stream may involve municipal waste water and industrial waste water, for example.

Conventional systems for recovering components involve the use of so-called strippers, for example for recovery of ammonia gas and/or ammonium solution. Such process is energy intensive and, furthermore, requires large amounts of chemicals.

Conventional bio-electrochemical systems strongly depend on the available organic matter (COD), have a relatively long start-up and adaptation period, are strongly temperature dependent, and show relatively low current densities.

Also, bio-electrochemical systems are known for recovery of nitrogen from an ammonium comprising fluid. Such recovery is described in WO 2013/105854, for example.

An objective of the present invention is to provide an electrochemical system for recovery of components from a waste stream that is more effective and more efficient as compared to conventional methods.

This object is achieved with the electrochemical system according to the invention, the system comprising a reactor that comprises:

- an anode compartment with an anode;

- a cathode compartment with a cathode;

- a feed compartment that is provided between the anode and cathode compartments; - one or more ion-exchange membranes separating the anode and cathode compartments;

- a recovery compartment configured for recovering components, wherein the recovery compartment is separated from one or more compartments with a hydrophobic membrane; and

- a circuit connecting the anode and the cathode, the circuit comprising a power source for providing an electric current.

The system according to the present invention comprises a number of compartments. In one of the presently preferred embodiments the system comprises at least four compartments, i.e. an anode compartment with at least one anode, a cathode compartment with at least one cathode, a feed compartment provided between the anode and cathode compartments that in use is provided with the waste stream, and a recovery compartment that is configured for recovering components. The anode(s) and cathode(s) are connected in a circuit, the circuit comprising a power source for providing an electric current.

The compartments are separated with one or more ion-exchange membranes, and the recovery compartment is being separated from one or more of the other compartments with an hydrophobic membrane.

The at least one ion exchange membrane separating the anode and cathode compartments is preferably one or more of the following: a cation exchange membrane (CEM), an anion exchange membrane (AEM), a bipolar exchange membrane (BEM) or a charge mosaic membrane (CMM). In one of the presently preferred embodiments according to the invention, the membrane separating the anode compartment from the cathode compartment comprises a CEM, since transfer of NH₄ ⁺ from the anode compartment is most efficient using a CEM. In one of the presently preferred embodiments the cathode and anode compartments are separated with one or more cation exchange membranes. This enables transport of the protons and ammonium between the different compartments. It will be understood that other configurations for the compartments are possible, and some examples of embodiments of the invention having another configuration will be discussed.

Waste streams may involve municipal waste waters and industrial waste waters, for example. This may involve ammonia and/or ammonium rich waste water streams such as the effluent of an anaerobic digester, urine treatment etc. Industrial waste waters may relate to waste waters from food processing, paper industry, and agriculture. It will be understood that also other waste water streams, preferably with a substantial amount of a component, such as ammonia and/or ammonium, can be treated in the electrochemical system according to the present invention.

In the case of component recovery, for example ammonia and/or ammonium recovery, involving the system according to the present invention, the term "ammonium" will be understood as NH₄ ⁺ ions, and "ammonia" will be understood as NH₃ (for example in the gas phase (g) or in solution (aq)). The term "nitrogen recovery" will be understood as the recovery of a nitrogen comprising compound, such as ammonium (NH₄ ⁺) and/or ammonia (NH₃) and/or nitrogen (N₂).

As an example, in use, some of the cations are transported from the anode to the cathode, for example protons (H⁺). For example, protons are produced in the anode compartment due to an oxidation reaction and pass through the membrane(s) to the cathode compartment.

Transport of cations other than H⁺ and NH₄ ⁺ will lead to an increase in the pH of the liquid in the cathode compartment, which will influence the equilibrium between ammonium and ammonia (NH₄ ⁺ + OH <— > NH₃ + H₂0) resulting in a higher ammonia concentration once the pH is higher than the pKa of ammonia (pKa = 9.25).

In one of the presently preferred embodiments water is reduced to hydrogen gas at the cathode, and hydrogen is oxidized at the anode. This achieves a stable operation of the electrochemical system according to this embodiment of the invention. Furthermore, the rate of recovery of the component can be controlled with a current. As a further advantage the anodic and cathodic reactions require a low power input as energy can be recycled for the recovery for ammonia from various types of waste water, for example. Therefore, losses in the system determine the required energy input.

Below, the cathode reaction (hydrogen evolution reaction) and the anode reaction

(hydrogen oxidation reaction) are included

Cathode reaction - Hydrogen evolution reaction (HER)

2H₂0 + 2e 20H + H₂

Anode reaction - Hydrogen oxidation reaction (HOR)

H₂ 2H⁺ + 2e In this embodiment of the invention, the electrochemical system is used for recovery of ammonia via using a gas permeable hydrophobic membrane, which is preferably integrated in the cathode compartment or in an additional compartment.

More specifically, the hydrophobic membrane separates the recovery compartment from one or more of the other compartments.

The use of the gas permeable hydrophobic membrane allows an effective ammonia recovery as compared to conventional ammonia stripping that is highly dependent on temperature and requires large volumes of gas flow involving a relatively high energy requirement.

Next, as an example, some of the characteristic elements of one of the presently preferred embodiments of the invention will be described in more detail. This presently preferred electrochemical system is provided with at least four compartments that are separated by different membranes allowing different operational conditions and enabling a selective recovery of ammonia, for example. The anode compartment comprises an anode. Preferably, the anode compartment comprises a so-called membrane electrode assembly (MEA) comprising an electrode, for example carbon black with platinum, and a Nafion proton/cation exchange membrane

(PEM/CEM). In the anode compartment the hydrogen (gas) is oxidized. The protons that are the result of the oxidation process are transported over the CEM/PEM (of the MEA) that separates the anode compartment from the feed compartment. The feed compartment is filled with waste water/feed water in a continuous or batch wise operation. Ammonia that is present in the feed water is protonated to ammonium involving the reaction:

NH₃ + H⁺ -> NH₄ ⁺. Ammonium is transported over a further CEM, for example a Nafion membrane, to the cathode compartment wherein the ammonium is deprotonated to ammonia involving the hydroxyl ions produced in the HER. The hydrogen (gas) produced in a cathode compartment is transported externally. The dissolved ammonia is transported over the gas permeable hydrophobic membrane, allowing transmembrane chemisorption (TMCS) to the recovery compartment that comprises an acid. In the recovery compartment ammonia is protonated in the presence of acid/protons to ammonium. Examples of suitable acids are: H₃P0₄, H₂S0₄, HC1, HN0₃, H₂C0₃. The

concentration of the acid in the recovery compartment influences the maximum NH₄ ⁺ concentration that is achieved in the recovery compartment. It will be understood that other configurations according to the invention can be envisaged and the illustrated reactions and components depend on the conditions and components to be recovered.

For example, in one of the presently preferred embodiments the anode of the

electrochemical system of the invention comprises a bio-anode. Providing the anode as a bio-anode results in a so-called bio-electrochemical system where electroactive microorganisms catalyse the anodic reaction and thereby improve the overall energy efficiency. The electroactive

microorganisms at the anode preferably oxidize organic substrate from wastewater (e.g. sugars, fatty acids, organic acids, etc.). This results in a more efficient oxidation at the anode. The bio- anode potential may lower the voltage which has to be applied across the anode and cathode. This may decrease the power consumption of the system resulting in an efficient operation.

Additionally, the recycled hydrogen from the cathode may provide an easily accessible electron donor for the electro active microorganism either directly (hydrogen oxidation) or indirectly by a stepwise conversion to other organic substrate (e.g. volatile fatty acids) followed by their oxidation.

The use of different compartments enables the use of different conditions in the compartments to optimize the desired reactions. For example, in the anode compartment hydrogen (gas) is supplied with a pH in the feed compartment of about 6. In one of the presently preferred embodiments the waste water comprises urine. In the cathode compartment the pH may be much higher, for example about 10, while the pH in the acid compartment preferably is below 6. It will be understood that depending on the actual components that are involved in the electrochemical system according to the invention the specific operational conditions can be different.

In one of the alternative embodiments of the present invention the feed compartment is integrated with one of the other compartments. Most preferably, in such embodiment the feed compartment is integrated with the cathode compartment. For example, in such embodiment an N- rich stream is directly added to the cathode compartment and ammonia can be extracted near the cathode using hydrophobic (TMCS) membrane(s) provided between an integrated cathode/feed compartment and a recovery compartment. It will be understood that also other embodiments having different configurations for the compartments are possible according to the invention. In general, in the anode compartment an oxidation/anodic reaction takes place, for example H₂ is oxidized to H⁺. In a feed compartment, for example ammonia is acidified, preferably with adding feed water comprising NH₃ and wherein ammonia is protonated. In a concentrate compartment, for example NH₄ ⁺ is concentrated and deprotonated by OH (preferably formed at the cathode) to NH₃. Preferably, the concentrate compartment is combined with one of the other compartments and comprises a TMCS membrane to selectively remove NH₃. In a cathode compartment the reduction reaction takes place and H₂/OH is formed, for example. Preferably, H₂ is recycled to the anode and OH is used to deprotonate NH₄ ⁺. In a recovery compartment, for example NH₃ is recovered from the

concentration compartment as HN₄ ⁺ in an acid solution. Alternatively, ammonium could be recovered/extracted from the concentrate compartment as a gas. It will be understood that some of the compartments can be combined.

For example, a four compartment embodiment will be discussed in detail relating to the setup shown in figure 1 having an anode compartment, a feed compartment, a cathode with concentrate compartment, and a recovery compartment.

A five compartment embodiment can also be envisaged, for example involving two concentrate sub-compartments between the feed and recovery compartments and between the recovery and cathode compartments, and having an anode compartment. In such embodiment the anode compartment is separated from the feed compartment with a MEA, the feed compartment is separated from the concentration compartment with a CEM, the concentrate compartment is separated from the cathode compartment with an AEM, and the concentrate compartment is separated from the recovery compartment with a TMCS membrane.

As a further example, a three compartment embodiment may comprise an anode compartment that is separated from a combined feed-concentrate-cathode compartment with a MEA, and wherein the combined compartment is separated from the recovery membrane with a TMCS membrane that preferably is in close proximity to the cathode.

In a presently preferred embodiment according to the invention the electrochemical system further comprises a recycling system connecting an outlet of the cathode compartment to an inlet of the anode compartment to enable recycling or recirculation of H₂.

By recycling a component from the cathode compartment to the anode compartment an active and efficient recovery can be achieved. The component that is recycled supplies a reactant to the anode compartment and extracts a gas produced in the cathode compartment. More preferably, this component comprises H₂. It is shown that this enables an effective recovery of components, especially ammonia from a waste flow such as urine, by recycling hydrogen over the system, preferably between the cathode and the anode compartment. In such system, the recovery can be performed without requiring an external supply of a reactant involving a substantially high amount of energy.

Recycling of H₂ enables effective and efficient recovery of components, such as NH₃. Preferably, the recycling in an embodiment of the system according to the present invention relates to internal recycling of H₂ in the system. The reactions in the system involving H₂ lower the required energy input of the system. This increases the energy efficiency of the system. Especially, an embodiment of the invention making use of the recycling of H₂ and the hydrophobic membrane in a (electrochemical/bioelectrochernical) cell/system enables an efficient recovery process.

This recirculation of hydrogen allows for a theoretical cell voltage of 0 Volts, as oxidation and reduction occur at the same electrode potentials. Therefore, the actual cell voltage is determined only by the losses originating from anode and cathode overpotentials, membrane potential and transport losses. This is an exceptional advantage compared to other ammonia recovery systems.

Ammonia recovery systems which rely on bioelectrochemical systems (Microbial Electrolysis Cells), which oxidize an organic matter at the anode and reduce water at the cathode, require a theoretical cell voltage higher than 0.12 Volts. Additionally, losses from anode and cathode overpotentials, membrane potential and transport losses will further increase the cell voltage.

Ammonia recovery systems which rely on water electrolysis (i.e. Electrochemical systems), require a theoretical cell voltage of 1.23 Volts. Additionally, losses from anode and cathode overpotentials, membrane potential and transport losses will further increase the cell voltage.

In a further preferred embodiment according to the present invention the electrochemical system further comprises a concentrate/intermediate compartment between the feed and cathode compartments with the concentrate compartment comprising one or more separating ion exchange membranes.

By providing an additional compartment further differences to the operational conditions can be achieved to enable a selective recovery of a component such as ammonium. In one of the presently preferred embodiments of the invention, the concentrate compartment is provided between the feed compartment and the cathode compartment. In this concentrate compartment further reactions can be performed. For example, in the concentrate compartment ammonium is deprotonated to ammonia due to the hydroxyl produced during the hydrogen evolution reaction or cathode reaction in the cathode compartment. In this embodiment the concentrate compartment is separated from the cathode compartment by an anion exchange membrane, for example. The dissolved ammonia is transported over the gas permeable hydrophobic membrane to the acid that is provided in the recovery compartment. In the cathode compartment hydrogen is produced and removed from the cathode compartment. Preferably, the hydrogen that is produced is recycled to the anode compartment with the recycling system. In the recovery compartment ammonia is protonated, preferably in accordance with the process described in relation to the embodiment with at least four compartments.

In a presently preferred embodiment the recovery compartment is positioned adjacent the concentrate compartment with a hydrophobic membrane separating the concentrate compartment from the recovery compartment. Preferably, the concentrate compartment is positioned between the feed and cathode compartments. It was shown that such configuration of compartments and membranes provides an effective and efficient recovery of components.

In such preferred embodiment, dependent of the type of membranes, different ions are being transported between the compartments. For example, through the anion exchange membrane (AEM) this mostly involves OH that is transferred from cathode to concentrate compartment. The cathode pH is relatively high at this stage due to cations, mostly NH₄ ⁺ and other metal ions (Na⁺, K⁺, Mg²⁺, Ca²⁺), that may lead to a pH increase in the intermediate or cathode compartment. Once there is an equilibrium between the concentration of ions in anode compartment liquid and cathode compartment liquid the charge transport through the cation exchange membrane (CEM) will substantially/exclusively involve NH₄ ⁺ and H⁺ as NH₄ ⁺ + OH— > NH₃ + H₂0, and ammonia is removed involving the TMCS (hydrophobic membrane) and H⁺ + OH— > H₂0. At this point the pH of the concentrate should be stable and be defined by the buffer capacity and the most dominate species in the concentrate compartment which should be above 9.25 (pKa of ammonia = 9.25. This illustrates an exemplary operation with the system according to the present invention.

In a presently preferred embodiment according to the present invention the hydrophobic membrane is positioned adjacent to a separating ion-exchange membrane.

By positioning the hydrophobic membrane close to a separating ion-exchange membrane the flow channel provides at an optimal location for optimal ion concentrations, for example a location having a relatively high OH concentration and highest pH. This renders the

electrochemical system according to the invention even more effective.

Preferably, the hydrophobic membrane is integrated with a separating ion-exchange membrane. This further improves the efficiency of the hydrophobic membrane and provides an effective means to assemble the reactor according to the present invention involving ion-exchange membranes and at least one hydrophobic membrane.

In one of the preferred embodiments the (gas permeable) hydrophobic membrane is provided as a number of tubular elements from a hydrophobic membrane material. Preferably, the tubular elements are shaped as hollow fiber flow channels, tubular members or straw like channels. The tubular elements can optionally be bundled. It will be understood that other designs for the hydrophobic membrane can also be envisaged in accordance with the present invention. The use of a flow channel defining hydrophobic membrane enables gas extraction from the compartment and/or reactant supply. It is shown that this significantly improves the overall efficiency of the reactions that take place in the electrochemical system according to the present invention. Therefore, the efficiency of such system is improved due to the use of one or more flow channels defining hydrophobic membranes.

In a further preferred embodiment according to the present invention, the electrochemical system further comprises a fuel cell or engine configured for generating electricity with gasses removed from the reactor.

By generating electricity using hydrogen fuel and/or using ammonia as fuel in a solid oxide fuel cell (SOFC), for example, electricity can be generated to further improve the overall energy efficiency of the electrochemical system according to the present invention. This may even result in a stand-alone application that can be operated in remote areas.

The invention relates to a method for recovery of components from a waste stream, the method comprising the steps of:

- providing an electrochemical system in one of the embodiments described earlier in this application;

- supplying a waste stream to the system;

- supplying a reactant to and/or extracting a gas from the reactor; and

- operating the reactor.

The method provides the same effects and advantages as those described for the electrochemical system.

In one of the presently preferred embodiments of the method according to the invention the recovery of components involves recovery of ammonia. For example, the method treats urine that comprises several organic compounds and having an ammonium-nitrogen concentration as high as 10 g/1 or higher, for example. Also other ammonium comprising fluids can be treated. Furthermore, energy can be gained from the process, and the organic material and ammonia and/or ammonium can be removed from the (waste water) fluid. Alternatively, and in addition thereto, electrical energy can be generated.

In one of the presently preferred embodiments of the invention, H₂ is recycled. More specifically, H₂ is recycled between the cathode and anode compartment(s). This provides an effective removal of components such as ammonium.

In experiments it was shown that an effective ammonia removal and/or recovery is possible, especially from concentrated streams, such as urine. The method and system achieve high recovery rates at low power inputs as compared to conventional nitrogen removal processes.

Furthermore, results showed that the electrochemical system with the hydrophobic membrane and recycling system can be used advantageously. Features from one or more of the preferred embodiments of the electrochemical system and/or method that were described earlier can also be applied in the electrochemical system with hydrophobic membrane and recovery system.

Further advantages, features and details of the invention are elucidated on the basis of preferred embodiments thereof, wherein reference is made to the accompanying drawings, in which:

- figure 1 shows a reactor with an electrochemical system according to the invention; and

- figure 2 shows an alternative embodiment of an electrochemical system according to the invention.

Electrochemical system 2 (figure 1) comprises reactor 4. In the illustrated embodiment reactor 4 comprises four compartments. Anode compartment 6 comprises anode 8. Furthermore, anode compartment 6 comprises inlet 10, recycling inlet 12 and outlet 14. Feed compartment 16 is separated from anode compartment 6 with cation exchange membrane 18. Cation exchange membrane 18 enables transfer of protons, or other cations, from anode compartment 6 to feed compartment 16. Feed compartment 16 is provided with inlet 20 and outlet 22 enabling a continuous or batch wise supply of waste water. The flow of cations 24 from anode compartment 6 is received in feed compartment 16. Cathode compartment 26 is separated from feed compartment 16 by cation exchange membrane 28. Cation exchange membrane 28 may enable transfer 30 of ammonium to cathode compartment 26. Cathode compartment 26 comprises cathode 32. Cathode 32 and anode 8 are connected in circuit 34. Cathode compartment 26 further comprises inlet 36, outlet 38 and recycling outlet 40. In the illustrated embodiment recycling system 42 connects recycling outlet 40 with recycling inlet 12 involving a tube or pipe.

Recovery compartment 44 is separated from cathode compartment by hydrophobic membrane 46. Recovery compartment 44 is further provided with inlet 48 and outlet 50.

Alternatively, electrochemical system 102 (figure 2) also comprises reactor 104 that is provided with anode compartment 106 with anode 108 and having inlets 110, 112 and outlet 114. Feed compartment 116 is separated by cation exchange membrane 118 from anode compartment 106 and comprises inlet 120 and outlet 122. Intermediate compartment 124 is separated from feed compartment 116 with cation exchange membrane 126. Intermediate compartment 124 further comprises inlet 128 and outlet 130. Cathode compartment 132 comprises cathode 134 and is separated from intermediate compartment 124 by anion exchange membrane 136. Cathode 134 and anode 108 are connected in circuit 138. Cathode compartment 132 comprises inlet 140, outlet 142 and recycling outlet 144 that is connected by recycling system 146 to recycling inlet 112 of anode compartment 106. In the illustrated embodiment recovery compartment 148 is separated from intermediate compartment 124 by hydrophobic membrane 150. Recovery compartment 148 comprises inlet 152 and outlet 154.

Experiments with the first illustrated embodiment have shown that it is possible to recover nitrogen from a waste flow. In experiments the following conditions were applied: current supply of 20 mA (to compensate for undesired leakage of hydrogen), feed flow 0.4 ml/min, current density about 16.5-17 A/m², feed compartment conductivity in mS/cm in the range of 8-8.5 and cathode compartment conductivity in mS/cm in the range of 30-33.5, pH of the feed compartment is between 6 and 7 and pH of the cathode compartment is between 9-10. The so-called areal resistance in Dm² is between 0.09-0.10. Results indicate an N-removal percentage of about 90% and an N-recovery in the range of 80-90%.

In further experiments with a urine as waste water or waste flow, it was shown that high Total Ammonia Nitrogen (TAN) recovery can be achieved with the system and method according to the present invention that outperforms other systems at similar conditions (i.e. current density and TAN loading). As a further effect, in the experiments the production of adsorbable organohalogens (AOX) in the system of the present invention is limited. As an even further effect, considering that the effluent of the H₂ recycling electrochemical system (HRES) of the present invention is to a large extent depleted of the TAN (in the experiments >73%), and the effluent still contains considerable concentrations of organic carbon, the effluent could be an interesting feed stream for anaerobic biological systems, such as a bioelectrochemical system (BES), to recover energy. In addition, the experiments showed a relatively low energy demand as compared to other TAN recovery systems.

Especially recycling H₂ over electrochemical system 2, 102 provides effective results as compared to conventional electrochemical cells. Also, when the system according to the present invention is combined with the described recycling and is compared to conventional

electrochemical cells a high removal rate in relation to the applied current density is achieved. This provides an effective performance of system 2, 102.

The present invention is by no means limited to the above described preferred

embodiments thereof. The rights sought are defined by the following claims within the scope of which many modifications can be envisaged. For example, the electrochemical system 2, 102 can be operated batch wise or continuously with a waste stream that may comprise ammonium such as urine.

Claims

1. Electrochemical system for recovery of components from a waste stream, the system comprising a reactor that comprises:

- an anode compartment with an anode;

- a cathode compartment with a cathode;

- a feed compartment that is provided between the anode and cathode compartments or is integrally provided with one of these compartments;

- one or more ion-exchange membranes separating the anode and cathode compartments; - a recovery compartment configured for recovering components, wherein the recovery compartment is separated from one or more compartments with a hydrophobic membrane; and

2. Electrochemical system according to claim 1 , further comprising a recycling system connecting an outlet of the cathode compartment to an inlet of the anode compartment enabling recycling of H₂.

3. Electrochemical system according to claim 1 or 2, wherein the anode compartment comprises a membrane electrode assembly.

4. Electrochemical system according to claim 1, 2 or 3, wherein the anode comprises a bio- anode.

5. Electrochemical system according to one of the foregoing claims, wherein the one or more ion-exchange membrane separating the feed and cathode compartments comprise cation and anion exchange membranes.

6. Electrochemical system according to one or more of the foregoing claims, wherein the feed compartment comprises an inlet and an outlet for a feed flow and/or waste flow.

7. Electrochemical system according to one or more of the foregoing claims, wherein the recovery compartment comprises an acid.

8. Electrochemical system according to claim 7, wherein the acid is one or more of the following: H₃P0₄, H₂S0₄, HC1, HN0₃, H₂C0₃.

9. Electrochemical system according to one or more of the foregoing claims, further comprising an intermediate compartment between the feed and cathode compartments, the concentrate/intermediate compartment comprising one or more separating ion-exchange membranes.

10. Electrochemical system according to claim 9, wherein the hydrophobic membrane separates the concentrate/intermediate compartment from the recovery compartment.

11. Electrochemical system according to one or more of the foregoing claims, wherein the gas permeable hydrophobic membrane is positioned adjacent to a separating ion-exchange membrane and/or is integrated with a separating ion-exchange membrane.

12. Electrochemical system according to one or more of the foregoing claims, wherein the anode and/or cathode is integrated with the hydrophobic membrane.

13. Electrochemical system according to one or more of the foregoing claims, wherein the gas permeable hydrophobic membrane defines a flow channel.

14. Electrochemical system according to one or more of the foregoing claims, further comprising a fuel cell or engine configured for generating electricity with gasses removed from the reactor.

15. Method for recovery of components from a waste stream, comprising the steps of:

- providing an electrochemical system according to one or more of the foregoing claims;

- supplying a waste stream to the system;

- supplying a reactant to and/or extracting a gas from the reactor; and

- operating the reactor.

16. Method according to claim 15, wherein supplying a reactant and extracting a gas comprises the step of recycling H₂.

17. Method according to claim 15 or 16, wherein the recovery of the components involves recovering of ammonia and/or ammonium.