An upflow anaerobic granular bed microbial electrochemical reactor [UAGB-MER] for production of bio-h 2 from liquid waste / wastewater

Abstract

In the present invention, an integrated bio-electrochemical reactor system (BEC) has been developed for the production of bio-hydrogen from wastewater (domestic / municipal wastewater) and simultaneous treatment of wastewater respectively. The developed BEC system intrinsically couples the upflow anaerobic granular bed (UAGB) with microbial- electrochemical reactor (MER) together into an advance bio-reactor which employs biocatalyst to convert chemical energy stored in organics to electrical energy. Hence, the developed novel UAGB-MER technology aims towards the enhancement of the metabolic activity of electrochemically active biocatalyst by supplying organic / inorganic nutrients, electron acceptors, or donors, thus stimulating oxidation or reduction of contaminants for simultaneous remediation of water and clean bio-Hydrogen (green H2) production. The present invention also relates to a process for treatment of organic enriched wastewater to significantly reduce high concentrations of BOD and COD from effluent stream.

Description

[0001] An Upflow Anaerobic Granular Bed Microbial Electrochemical Reactor [UAGB-

[0002] MER] for Production of Bio-Hh from Liquid Waste / Wastew7ater

[0003] FIELD OF THE INVENTION

[0004] The present invention relates to an upflow anaerobic granular bed - microbial electrochemical reactor [UAGB-MER] for production of bio-H2 from liquid waste / wastewater. In particular, the present invention relates to an integrated bioelectrochemical reactor system (BEC) for production of bio-hydrogen from domestic / municipal wastewater. The developed system intrinsically couples the upflow anaerobic granular bed (UAGB) with microbial-electrochemical reactor, employing biocatalysts to convert chemical energy stored in biodegradable organic substrates to hydrogen. The present invention also relates to a process for extracting bio-H2 from wastewater which contains significant amount of biodegradable suspended solids (TSS) and high concentrations of BOD (biochemical oxygen demand) and COD (chemical oxygen demand) and enables the efficient removal of biodegradable TSS from wastewater. The modular reactor system of the present invention is useful for onsite bioHydrogen production and simultaneous wastewater treatment. The present invention shall help attain the 6thand 7thsustainable developmental goals of ‘Clean Water and Sanitation’ and ‘Affordable and Clean Energy’ respectively.

[0005] BACKGROUND OF THE INVENTION

[0006] Immense increase in universal demand for energy requirement has been observed in recent days. Depleting fossil fuel reserves, high-cost fluctuations, and consequential environmental effects have urged the need for alternative energy resources development. With reference to high efficiency, easy production, and pollution-free operation, biofuels are considered to be prospective and sustainable energy choice. Among various biofuels, bio-hydrogen has acquired greater attention owing to zero greenhouse gas emissions relative to other fuels.

[0007] In an era of increasing energy costs and environmental awareness, wastewater treatment industries need to look at alternative treatment options to reduce their net energy expenditure. It has been estimated that domestic wastewater alone may contain 17.8 kJ / g of chemical oxygen demand (COD) of energy. There is an increasingly urgent need to recover some of this energy, or at the very least not expend additional energy on treatment; the activated sludge process uses 2.5-7.2 kJ / g COD. Energy recovery could be achieved through innovative technologies by which one directly gets clean bio-energy (bio-hydrogen). The life cycle assessment has shown that the production of higher value products through the suite of integrated Bio-electrochemical systems (BES) may be the most viable solution.

[0008] Overall, in the world, the demand for energy is rapidly increasing. Furthermore, there are many countries which still depend on fossil fuel for energy generation but this source is not friendly to the environment due to a huge amount of CO2 generation during the conversion process. In addition, due to large number of manufacturing units and with exponential growth of population enormous amount of wastewater is generated which needs extensive energy and huge cost for recycling and treatment. Due to shortage of energy, water crisis and climate change globally, there is pressing need for providing new and sustainable energy resources. Further, there is a huge demand for generating energy from wastewater and reduce the operational costs. The wastewater bearing organic substances (pollutants) containing chemical energy can be converted into renewable energy using biocatalysts to produce Bio-FE and clean water simultaneously.

[0009] Hydrogen gas shows great promise as a non-polluting fuel. Also, to reduce carbon dioxide release in the environment hydrogen gas will need to be produced from renewable sources. Wastewaters have great potential for economical production of hydrogen. The technologies that remediate the pollutants can be divided into physicochemical and biological technologies. Physical technologies include washing by co-solvents, surfactants or reduction using chemical agents. The biological process utilizes the vast diversity of microbes to degrade organic / inorganic pollutants as a carbon energy source. These bio-electrochemical systems where carbon-rich waste is utilized as a substrate, release electrons (e ) and protons (H+) consequently generating bioelectricity. The process is inexpensive and assures the complete mineralization of pollutants.

[0010] In this regard, the bio-electrochemical cells (BEC) are gaining attention due to their possibility in overcoming the limitations associated with aerobic systems and the physicochemical processes. Bio-electrochemical systems (BESs) are characterized by the use of microorganisms for the generation of electricity by anodic and cathodic reactions within an electrochemical configuration, using the organic matter contained in the wastewater as a fuel source. The BESs have attracted interest in research, not only because of the worldwide trend in sustainable energy production, but also because these systems allow conducting other types of simultaneous operations to degrade organic matter and they also allow the bioremediation of polluted sites. Biological hydrogen production is also a promising technology for the future as it is considered a clean and renewable source and has the highest energy content per unit weight; 122-142 kJ / g, compared to any known fuel.

[0011] Reference may be made to Wu, T., et. al. (2013). Hydrogen production with effluent from an anaerobic baffled reactor (ABR) using a single-chamber microbial electrolysis cell (MEC), International Journal of Hydrogen Energy 38 (25), 11117-11123, which discloses orthogonal experiments to operate the four-compartment ABR [anaerobic baffled reactor] with a hydraulic retention time (HRT) of 24 h, influent COD - 4600 mg / L, temperature - 35 °C, with pH - 7, C / N - 44, and 2-bromoethanesulfonate (BES) concentration - 20 mmol / L to achieve the high acetic acid accumulation in effluent. The single-chamber membrane less MEC with carbon cloth as anode and Ni-catalyst stainless steel as cathode (liquid volume *4 85 mL) fed with the ABR effluent with applied voltage of 0.6 V and electric conductivity of 7.45 mS / cm, achieved 99.0 ± 0.3% total COD removal efficiency, 1.31 ± 0.04 m3H2 / m3.d hydrogen production, 2.78 ± 0.11 mLH2 / mg COD hydrogen yield and 138.63 ± 3.11% electrical energy efficiency. However, researchers used sludge as a feedstock for bio-hydrogen (biogas) production. Gas composition of produced biogas was not discussed in the document. In the present innovation wastewater was used as a feedstock for bio-hydrogen production involving non-catalyzed graphite as bio-anode and SS mesh as cathode without coating with metals like gold, platinum, nickel, etc. Present innovation does not involve any metal catalyst in the reactor to avoid heavy metal contamination in the discharge effluent and generation of secondary pollutant which make the process sustainable.

[0012] Reference may be made to Babu et. al., 2013. Bio-electrolytic conversion of acidogenic effluents to biohydrogen: An integration strategy for higher substrate conversion and product recovery. Bioresource Technology, 133, 322-331 that demonstrates the feasibility of integrating Microbial electrolysis cell (MEC) process with darkfermentation process for additional hydrogen recovery as well as substrate degradation. MEC was employed in order to utilize the residual organic fraction present in the acidogenic effluents of dark fermentation process as substrate for hydrogen production with input of small elec, current. MEC was operated at volatile fatty acids (VFA) concentration of 3000 mg / 1 under different poised potentials (0.2, 0.5, 0.6, 0.8 and 1.0 V) using anaerobic consortia as biocatalyst. Maximum hydrogen production rate (HPR), cumulative hydrogen production (CHP) (0.53 mmol / h and 3.6 mmol), dehydrogenase activity (1.65 pg / mL) and VFA utilization (49.8%) was recorded at 0.6 V. Microbial diversity analysis using denaturing gradient gel electrophoresis confirmed the presence of y-proteobacteria (50%), Bacilli (25%) and Clostridia (25%). However, the drawbacks associated with this document are that two-stage process was used which involve batch fermentation in the first stage and MEC operation in the second stage. Present innovation involves a continuous bio-electrochemical flow reactor in a single cell configuration.

[0013] Various biohydrogen-producing methods from organic wastes are reported. Dark fermentation is the process of fermentative conversion of the organic substrate to biohydrogen by using microorganisms in the absence of light. Limitation of this process are lower biohydrogen yield, hydrogenase inhibition due to presence of O2 and the augmentation of H2 pressure turn the process thermodynamically unfavourable. In microbial electrolysis process the microbial conversation of organic material happed into hydrogen and methane by applying an electric current. Major limitation of the process is low production of the H2 when the electrode power densities are low and energy efficiency is negatively influenced by a high applied voltage. Photo- fermentation is process refers to the fermentative conversion of organic substrate to hydrogen by employing photosynthetic microorganisms via biochemical reactions. Limitations of the process are slow production rate of H2, the produced O2 inhibits the nitrogenase, pretreatment requirements of the substrate and height implementation costs. Another process is Direct biophotolysis. It’s the process that breaks down the molecules of water into H2 and O2 in presence of light by photoautotrophic microalgae. Drawback of this process includes the high light intensity requirement, concurrently generation of H2 and O2 and the latter negatively affects the whole system and lower photochemical efficiency.

[0014] Major problem in hydrogen production from wastewater is the presence of contaminants, such as organic substances and impurities, which can affect the efficiency of electrolysis process. Membrane fouling and cost is also a serious issue in electrolysis that restricts its application in hydrogen production. Energy-intensive electrolysis processes contribute to the high cost of green hydrogen.

[0015] Therefore, keeping in view the drawbacks of the hitherto reported prior art, the inventors of the present invention realized that there exists a dire need to provide a microbial reactor for producing hydrogen from wastewater through an advanced bio-electro chemical process for simultaneous production of green hydrogen and treated water while improving the overall efficiency of hydrogen production, via an innovative, membrane less single cell reactor contributing to low process and operating cost coupled to a solar driven sustainable process; in order to maximise resource utilisation, improve wastewater treatment procedures, produce clean energy, and support environmental sustainability, thereby being in line with the overarching objectives of shifting to a more efficient and circular economy.

[0016] OBJECTIVES OF THE INVENTION

[0017] The main objective of the present invention is therefore to provide an integrated bioelectrochemical reactor system (BEC) for production of bio-hydrogen from domestic / municipal wastewater which obviates the drawbacks of the hitherto reported prior art.

[0018] Another objective of the present invention is to provide a bio-H2 producing system that intrinsically couples the upflow anaerobic granular bed (UAGB) with microbial- electrochemical reactor, employing biocatalysts to convert chemical energy stored in biodegradable organic substrates to hydrogen.

[0019] Still another objective of the present invention is to provide eco-friendly and sustainable bio-electrochemical process for production of clean energy (green-H2) and simultaneous remediation of wastewater.

[0020] Yet another objective of the present invention is to provide a bio-electrochemical (UAGB-MER) reactor for hydrogen production from sewage / municipal wastewater liquid waste. Still another objective of the present invention is to provide a renewable energy based (solar) system that is modular, scalable, and is low carbon footprint for operation.

[0021] Yet another objective of the present invention is to provide a renewable energy based integrated process for the treatment of organic-rich wastewater which is capable of recovering resources from wastewater to produce bio-hydrogen and clean water.

[0022] Still another objective of the present invention is to provide a modular system for onsite and on demand bio-hydrogen production utilizing high strength wastewater (high COD) from various sources.

[0023] Yet another objective of the present invention is to provide a membrane less electrode module to support hydrogen producing microbial growth on the electrode surface.

[0024] Still another objective of the present invention is to provide a bio-catalyst for enhance bio-hydrogen production from wastewater.

[0025] SUMMARY OF THE INVENTION

[0026] The present invention provides an integrated bio-electrochemical reactor system (BEC) for production of bio-hydrogen from domestic / municipal wastewater. The developed system intrinsically couples the upflow anaerobic granular bed (UAGB) with microbial- electrochemical reactor (MER), employing biocatalysts to convert chemical energy stored in biodegradable organic substrates to hydrogen. The developed UAGB-MER system is intrinsically coupled the anaerobic degradation with microbial-electrochemical process together into a next generation bioreactor which employs biocatalyst to convert chemical energy stored in organics to hydrogen. The developed system aims towards the enhancement of the metabolic activity of electrochemically active biocatalyst by supplying organic / inorganic nutrients, electron acceptors, or donors, which felicitate the electro-hydrogenises in a membrane less single cell reactor for bio-Hydrogen (green H2) production.

[0027] Accordingly, the present invention integrates a bio-electrochemical reactor with anaerobic microbial processes in a single device. It provides a UAGB-MER Reactor for the production of bio-hydrogen (bio-EE) from liquid waste or wastewater, offering a sustainable, modular, and scalable treatment system for simultaneous bio-hydrogen production and wastewater remediation.

[0028] In an embodiment, the present invention provides an upflow anaerobic granular bed - microbial electrochemical reactor [UAGB-MER] system (100) for production of bio-IU from liquid waste / wastewater containing biodegradable solids comprising: a) a vertically oriented elongated vessel compartmentalised into a bottom chamber (7B), middle chamber (7 A) and top chamber (7T), each chamber being connected through a flange with gasket (22); b) a nozzle (20) establishing fluid communication between the bottom chamber (7B) and the outside of the feed vessel for input of wastewater into the reactor (7); c) a nozzle (36) establishing fluid communication between the liquid retention space of the top chamber (7T) with the outside of the vessel for discharge of treated wastewater from the vessel, arranged so as to retain a level of liquid within the top chamber (7T); d) a nozzle (35) for discharge of gas from the gas retention space of the top chamber (7T).

[0029] In another embodiment, the present invention provides a reactor system (100), wherein the UAGB-MER reactor (7) comprising a cylindrical column with a hemispherical lower / bottom section (7B), middle section (7 A) and top section (7T) fixed by manifold; a particulate filter bed (29) confined inside the middle section (7A); wherein the lower section (7B) being provided with a dished bottom on which is provided feed inlet nozzle (6) for input of the feed wastewater by means of a pump (5); wherein the electrode module (24, 25) being fixed at the bottom of the reactor; connected to a pump (5) for continuously feeding the reactor with wastewater from an inlet port (6) placed at the bottom of the column, the effluent port (14) being located at upper part of the reactor; a gas solids separator (32) being mounted on top of the reactor; an overflow weir allowing liquid to overflow from the reactor through an outlet nozzle (36); a gas outlet nozzle (35) connecting the gas collection chamber with a constant pressure gas reservoir; further equipped with a feed vessel / tank (2), pump (5), UAGB-MER reactor (7), gas flow meter (15), gas separation unit (17), bio-hydrogen storage vessel (18), valves, pH sensor (9), ORP sensor (10) and solar PV unit (19); coupled to a gas-liquid-solid separator (32) at the top of the reactor (7T), reaction zone at the middle of the reactor (7A) and placement of electrode module (24, 25) at the bottom compartment of the reactor (7B).

[0030] In still another embodiment, the present invention provides a reactor system (100), wherein the said top of the middle chamber (7 A) contains a packing media module (29) to prevent the washing out of biomass or sludge granules and enable biofilm formation.

[0031] In yet another embodiment, the present invention provides a reactor system (100), wherein the said top chamber (7T) further comprising a gas-liquid-solid (GLS) separator (32) to enable disengagement of gas, settling of sludge and the overflow of clarified liquid from the reactor.

[0032] In still another embodiment, the present invention provides a reactor system (100), wherein a single cell / chamber, membrane less continuous anaerobic -bio-electro chemical reactor for bio-hydrogen production.

[0033] In yet another embodiment, the present invention provides a reactor system (100), wherein it comprises a modular electrode assembly supporting the growth of exo- electrogenic H2 producing micro-organisms and is configured to maximize surface contact with wastewater, providing enhanced microbial biofilm growth and efficient bioelectrochemical reactions for bio-hydrogen production.

[0034] In still another embodiment, the present invention provides a reactor system (100), wherein the modular electrode assembly comprises modified graphite as the bio-anode and stainless steel mesh as the cathode each providing a conducive surface for biofilm formation.

[0035] In yet another embodiment, the present invention provides a reactor system (100), wherein the re-circulation loop is equipped with a pump and valves, allowing for the redistribution of liquid within the reactor to maintain optimal flow rates and enhance contact with the electrode surfaces.

[0036] In still another embodiment, the present invention provides a reactor system (100), wherein the middle chamber (7 A) contains a packed filter bed (29) that retains progressively finer suspended solids, promoting efficient separation of solid and liquid phase and degradation of organic matter.

[0037] In yet another embodiment, the present invention provides a reactor system (100), wherein the gas separation unit (17) comprises a multi-stage purification system to remove contaminants, allowing for the collection of bio -hydrogen with high purity levels.

[0038] In still another embodiment, the present invention provides a reactor system (100), further comprising a solar photovoltaic (PV) unit (19) connected to the DC power supply, providing renewable energy to sustain the bio-electrochemical reactions.

[0039] In a further embodiment, the present invention provides a process for the generation of bio-hydrogen using the developed reactor system (100), wherein the steps comprising anaerobic degradation followed by electro-hydrogenesis which produces in-situ anode respiring exoelectrogenic bacteria that facilitate the transfer of the generated electrons to the cathode, where they react with protons at cathode, thus enhancing the biohydrogen energy evolution.

[0040] In another embodiment, the present invention provides a process for the generation of bio-hydrogen using the developed reactor system, wherein the yield of bio-tk is 20.54 mol tk / kg of COD and 81.21 to 106 g / kg feedstock respectively; COD removal is 83 %.

[0041] In still another embodiment of the invention, the reactor system (100) comprises three compartments: a bottom chamber (7B) for wastewater intake, a middle chamber (7 A) for biofilm formation and filtration, and a top chamber (7T) for gas-liquid-solid separation.

[0042] In yet another embodiment of the invention, the modular electrode assembly includes a modified graphite bio-anode and stainless steel (SS) mesh cathode, providing a conducive surface for efficient bio-electrochemical reactions.

[0043] In still another embodiment, the invention incorporates a packing media module in the middle chamber to prevent the washout of biomass or sludge granules while supporting microbial biofilm growth.

[0044] In yet another embodiment, the reactor features a gas-liquid-solid (GLS) separator (32) to enable the disengagement of gas, settling of sludge, and overflow of treated water. In still another embodiment, the invention utilizes a solar photovoltaic (PV) unit (19) for renewable energy, making the system environmentally friendly and energy efficient.

[0045] In yet another embodiment, the invention supports temperature regulation using a circulating water bath to optimize microbial activity for bio-hydrogen production.

[0046] In still another embodiment, the reactor enables re-circulation of wastewater using pumps and valves, ensuring optimal flow rates and enhanced interaction with microbial biofilms.

[0047] In yet another embodiment, the invention incorporates a multi-stage filter bed to trap and degrade suspended solids, promoting effective separation of organic matter.

[0048] In still another embodiment, the invention integrates a gas purification system for the removal of impurities, allowing the collection of bio -hydrogen with high purity levels.

[0049] In yet another embodiment, the present invention provides a compact, modular design, reducing operational costs and complexity for industrial and municipal wastewater treatment applications.

[0050] BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0051] In the drawings accompanying the specification;

[0052] Figure 1 represents process flow diagram of bio-electrochemical (BEC) process; wherein 1 represent wastewater feed line; 2 represent feeding tank; 3 represent dosing vessel; 4 represent mixing manifold; 5 represent pump; 6 represent reactor feed line; 7 represent UAGB-MER reactor; 8 represent circulating water bath; 9 represent pH sensor; 10 represent ORP sensor; 11 represent online data monitoring system; 12 represent treated water tank; 13 represent recirculating loop; 14 represent treated water outlet from GLS; 15 represent gas flow meter; 16 represent pressure sensor; 17 represent gas separation unit; 18 represent bio-Hydrogen storage vessel; 19 represent solar PV unit.

[0053] Figure 2 represents a fully functional laboratory realization of a UAGB-MER (Up flow Anaerobic Granular Bed coupled with Microbial-Electrochemical Reactor) reactor constructed using stainless steel (SS). Figure 3 represents bottom section (7B) of UAGB-MER reactor where 20 represent reactor inlet nozzle, 21 represent reactor bottom compartment; 22 represent flange with gasket; 24 represent electrode; 25 represent electrode module.

[0054] Figure 4 represents middle section (7 A) of UAGB-MER reactor where 23 circulating water bath inlet; 26 represent restrain clamp of filter module, 27 represent lower ss mesh of filter module; 28 represent upper ss mesh of filter module; 29 represent poly propylene packing media; 31 represent connecting flange with gasket.

[0055] Figure 5 represents top section (7T) of UAGB-MER reactor where 32 represent gas- liquid-solid (GLS) disengagement module, 33 represent discharge effluent nozzle, 34 represent overflow weir, 35 represent gas outlet nozzle, 36 represent discharge effluent nozzle, 37 represent liquid level in GLS module.

[0056] Figure 6 represents a fully functional laboratory realization of another configuration of UAGB-MER reactor.

[0057] Figure 7 represents electrode module of another configuration of UAGB-MER reactor were 38 represent electrode; 39 represent reactor bottom plate; 40 represent connecting flange with gasket; 41 represent electrode module.

[0058] Figure 8 represents middle section of another configuration of UAGB-MER reactor where 46 represent lamella separator, 43 represent sampling nozzle, 44 represent effluent nozzle, 45 represent recirculation loop nozzle.

[0059] Figure 9 represents top section of another configuration of UAGB-MER reactor where 47 represent gas outlet nozzle.

[0060] LIST OF ALL THE ABBREVAITIONS USED

[0061] DETAILED DESCRIPTION OF THE INVENTION

[0062] The invention is explained with respect to the drawing accompanying this specification. In the drawings many details pertaining to fabrication not bearing upon points of novelty are omitted in the interest of descriptive clarity. Functionally equivalent components are given identical reference numbers in the various drawings. These components are explained in detail for the first occurrence only for sake of brevity.

[0063] In an aspect, the present invention provides an upflow anaerobic granular bed reactor advanced bio-electro chemical process for simultaneous production of green hydrogen and treated water from wastewater, while improving the overall efficiency of hydrogen production, wherein an innovative, membrane less single cell reactor contributes to low process and operating cost coupled to a solar driven sustainable process. The developed Microbial-bio-electrochemical reactor intrinsically couples the anaerobic degradation with microbial-electrochemical process together into a next generation bioreactor which employs biocatalysts to convert chemical energy stored in organics to hydrogen energy. The developed system aims towards the enhancement of the metabolic activity of electrochemically active biocatalyst by supplying organic / inorganic nutrients, electron acceptors, or donors, which facilitate electro-hydrogenesis in a membrane less single cell reactor for bio-Hydrogen (green H2) production. The present invention also relates to a process for extracting bio-H2 energy from wastewater which contains significant amount of biodegradable suspended solids (TSS) and high concentrations of BOD (biochemical oxygen demand) and COD (chemical oxygen demand) and enables the efficient removal of biodegradable TSS from wastewater.

[0064] A series of experiments were conducted to obtain optimised process conditions as mentioned below:

[0065] • System pH: 5

[0066] • Temperature: 40 °C

[0067] • ORP: 159 mV

[0068] • Nutrients concentration: 32.44 g / 1 • Nutrients pH: 7

[0069] • Biocatalyst / feed ratio: 1:3

[0070] • Applied voltage: 0.9 V

[0071] • Electrode type: modified graphite as bio-anode and SS mesh as cathode.

[0072] • Micro-organism: in-situ developed exoelectrogenic micro-organism classified under Bacillus species.

[0073] In another aspect, the present invention provides an integrated upflow anaerobic granular bed - microbial electrochemical reactor (UAGB-MER) for the production of biohydrogen from wastewater (domestic / municipal wastewater) with simultaneous treatment of wastewater. The UAGB-MER consists of a plexi glass column (9 cm of internal diameter (ID) and 66 cm height) with a flat bottom (4.6 cm in ID and 5.2 cm height). The top of the UAGB-MER is sealed for maintaining an anoxic environment and gas-liquid- solid separator. For fluidizing, a recirculation flow is drawn from the top section using a peristaltic pump. The medium is fed downwards with an elbow that drives the flow to the vertex of the conical bottom, resulting in a rising flow of fluid through the column. The total working volume of the reactor is 3.24 L. Electrode module is fixed at the bottom of the reactor. Modified graphite rod is used as bio-anode and SS mesh is used as cathode. The UAGB-MER is operated as a two-electrode membrane less bio-electrochemical cell. A peristaltic pump (Watson and Marlow) is used for continuously feeding the reactor with wastewater from an inlet port placed at the bottom of the column. The effluent port is located at upper part of the reactor. The hydraulic retention time (HRT) in the UAGB- MER is of 4-5 hr.

[0074] The process operating conditions are as mentioned below:

[0075] • System pH: 5

[0076] • Temperature: 30-35 °C

[0077] • ORP: 125.8 mV

[0078] • Nutrients concentration: 31.67 g / 1

[0079] • Biocatalyst / feed ratio: 1:3

[0080] • Applied voltage: 1 V

[0081] • Electrode type: modified graphite as bio-anode and SS mesh as cathode.

[0082] • HRT: 4-5 hr.

[0083] • Micro-organism: in-situ developed exoelectrogenic micro-organism classified under Bacillus species. In still another aspect, the present invention provides a UAGB-MER reactor [Up flow Anaerobic Granular Bed with Microbial-Electrochemical Reactor] comprising a cylindrical column with a hemispherical bottom section (7B), middle section (7 A) and top section (7T). The top of the UAGB-MER is sealed for maintaining an anoxic environment and gas-liquid-solid (GLS) separator. For up-flow, a recirculation flow is drawn from the top section using a pump. The medium is fed downwards with an elbow that drives the flow to the vertex of the conical bottom, resulting in a rising flow of fluid through the column. Electrode module (24) is fixed at the bottom of the reactor. Modified graphite rod is used as bio-anode and stainless- steel mesh is used as cathode. The UAGB- MER is operated as a two-electrode membrane less bio-electrochemical cell. A pump is used for continuously feeding the reactor with wastewater from an inlet port placed at the bottom of the column. The effluent port is located at upper part of the reactor.

[0084] In yet another aspect, the present invention provides a modular UAGB-MER reactor system (100) that intrinsically couples the upflow anaerobic granular bed (UAGB) system with microbial-electrochemical reactor (MER) together into an advance bio-reactor unit. Figure 1 represents the developed bio-electrochemical (BEC) process as a whole. BEC process is equipped with a feed vessel / tank (2), pump (5), UAGB-MER reactor (7), gas flow meter (15), gas separation unit (17), bio-hydrogen storage vessel (18), valves, pH sensor (9), ORP sensor (10) and solar PV unit (19).

[0085] Figure 2 represents a fully functional laboratory realization of a single chamber UAGB- MER reactor (7) constructed using stainless steel (SS). UAGB-MER reactor is a cylindrical column of 100 mm internal diameter. The reactor vessel (7) is partitioned into bottom section (7B), middle section (7 A) and top section (7T), fixed by manifold. In actual construction of this laboratory realization of the invention, the reactor, is clamped together in leak tight manner using flange with gasket (22). The lower section 7B, is provided with a dished bottom on which is provided feed inlet nozzle (6), for input of the feed wastewater by means of a pump. Electrode module (24, 25) is attached with the bottom section. The cell works at a closed-circuit voltage, using an external resistance and DC power supply. DC power supply unit is connected with a solar PV unit (19). Modified graphite is used as bio-anode and SS mesh is used as cathode. Reactor middle section (7A) is an elongated annular cylindrical unit made of SS. Temperature of the reactor is controlled by a circulating water bath attached with the reactor.

[0086] A gas solids separator (32), made of steel is mounted on top of the reactor. The gas Solids Separator has an outer shell, shaped as an inverted frustum of a cone which is jointed in a leak tight manner to the walls of the upper chamber (7T), at its top. An overflow weir, allows liquid to overflow from the reactor vessel into a circumferential collection launder, and thereafter can be taken out of the reactor through an outlet nozzle (36). A cylindrical SS vessel (7 A), with open top and bottom is mounted below the Gas-Solid-Separator, by a fixing means, such that its cylindrical wall projects inside and off the sloping side walls of the gas-solid-separator. A gas outlet nozzle (35) connects fluidly the gas collection chamber with a constant pressure gas reservoir. A particulate filter bed (29) made of polystyrene beads is confined inside the middle section (7 A). The operation of the invention is explained below with respect to the laboratory scale model represented in Figure 2 and 6. The operation of the subsequent manifestations follows similar principles and has been omitted, except where there are significant differences.

[0087] The reactor is filled with deoxygenated water. The reactor is provided with sufficient quantity of acclimatised seed sludge (i.e., anaerobic microbial sludge), which may have granular or flocculant settling characteristics. This forms a sludge bed in the lower chamber and a sludge bed in medium chamber. The continuous pumping of wastewater (arrow) containing suspended organic matter is commenced through reactor inlet nozzle. As pumping proceeds, liquor fills in bottom (7B) and middle chamber (7 A) passing through the electrode module and, permeates through the filter bed (29), and enters into top chamber (7T) through GLS (32). Filtration action at the filter bed (29) retains suspended particles in the wastewater passing through the bed. Some part of soluble matter in the wastewater is converted to bio-hydrogen and carbon dioxide by electrohydrogenesis in presence of microbial action in the reactor. The produced gas is collected in gas space which exits through the nozzle to a constant pressure gas storage tank. Produced gas from the reactor again passes through the gas separation unit (17) to remove impurities and is finally stored in SS vessel. A continuous liquid overflow over weir at top chamber (7T) is also set up. Alternately, an overflow outlet is provided in the upper chamber, so that treated effluent overflows from the top chamber and flows out from exit nozzle (36) and stored in a vessel (12).

[0088] Figure 6 represents another fully functional laboratory realization of a single chamber UAGB-MER reactor constructed using poly acrylic sheet. UAGB-MER reactor is a cylindrical column of 90 mm internal diameter. The reactor is partitioned into bottom section (B), middle section (M) and top section (T), fixed by manifold. In actual construction of this laboratory realization of the invention, the reactor, is clamped together in leak tight manner using flange with gasket. The lower section B, is provided with a flat plate bottom on which is provided feed inlet nozzle (42), for input of the feed wastewater by means of a pump. Electrode module (41) is attached with the bottom section. A lamella screen (46) is attached at top of the middle section (M) for solid-liquid separation. Top section is used a gas holder with gas outlet nozzle (47). The cell works at a closed-circuit voltage, using an external resistance and DC power supply. DC power supply unit is connected with solar PV unit. Modified graphite is used as bio-anode and SS mesh is used as cathode.

[0089] In a further aspect, the instant invention provides a membrane less single cell UAGB- MER reactor, where there are several intermediate stages between the bottom stage and the top stage. The passage of liquid from bottom to top passes through electrode module and filter bed at intermediate stage. This enables very high efficiency of suspended solids and dissolved organic matter removal. The filter beds may be constructed so as to retain coarse suspended matter at the succeeding stage retailing progressively finer solids. Moreover, growth of biofilm and microbial consortia attached with electrode surface accelerates the degradation of suspended solid and dissolved organic matter. This is easily accomplished by elctro-hydrogenesis and choice of the filter media and in particular the particle size of filter media. Those in the art will acknowledge the extreme difficulty in filtration separation of wastewater containing large sized to fine sized suspended solids organic matter and will readily appreciate advantages of the UAGB-MER reactor of this invention which is not only able to separate but also to degrade the separated matter and produce bio-hydrogen, in a single, compact and energy efficient device.

[0090] EXAMPLES The following examples are given by way of illustration only and therefore should not be construed to limit the scope of the present invention in any manner.

[0091] Example 1: Bio-hydrogen production from domestic wastewater

[0092] Feedstock used: CSIR-NIIST, Thiruvananthapuram, India canteen wastewater

[0093] Procedure: A modular, UAGB-MER reactor for bio-hydrogen production was fabricated based on the present invention. The reactor consisted of an SS cylindrical column with 10 cm inner diameter, 90 cm in height, and a working volume of 10 1. Reactor was operated in continuous flow under anaerobic conditions, at a temperature of 35 °C and at a pH 5-6. The reactor was operated with a hydraulic retention time (HRT) of 7-10 hr. Modified graphite was used as bio-anode and SS mesh was used as cathode. Reactor is worked as a single cell microbial bio-electrochemical hydrogen generator. The cell worked at a closed-circuit voltage, using an external resistance of 100 Q. Reactor was operated with and applied voltage of 0.5- 1.0 V through a DC power supply which is connected with the solar PV system.

[0094] H2-producing bio-catalyst was prepared from the activated sludge obtained from a wastewater treatment plant (8°27'32.62"N and 76°56T5.08"E) located at Valiyathura, Paruthikuzhy Rd, Thiruvananthapuram, Kerala 695026. Liquid bio-catalyst was prepared by cyclic treatment of acid-alkali, thermal and sonication steps.

[0095] First step involves filtration, where the collected seed sludge was passed through 200 pm sieve to removing the larger particle that present in the sludge and a series of steps were followed for enrichment with specific microorganisms tolerant to a low pH environment (3-4). Following filtration, the pH of the sludge sample was measured using a pH meter and the pH was maintained using HC1 and NaOH (0.1 N). Subsequently, the pH-adjusted sludge sample was transferred to a sealed container to maintain anaerobic conditions and incubated at 35°C for 4-5 days to encourage microbial growth in the second steps. During this period, microorganisms adapted to the pH range of 3-4 proliferate and become enriched in the sludge sample, which was vital for subsequent treatment processes. Additionally, to further enrich the seed sludge for specific bacterial populations, a multi- step approach involving heat shock and, optionally, acid shock may be employed. The heat shock involves exposing the sludge to high temperatures (around 103 °C) for a short duration to selectively suppress non-spore forming methanogenic bacteria, allowing spore-forming acidogenic bacteria to thrive. In the third step ultra-sonication was also done for 15 minutes to enhance the microbial activity and promote a more efficient conversion of organic matter into bio hydrogen during the subsequent process. Ultra sonication generates waves that travel through a medium, forming bubbles that collapse and produce highly active radicals, shear forces, and intense temperatures and pressures. Regulating the input energy during inoculum helps suppress methanogens and safeguards hydrogen-producing micro-organism (i.e., bacteria).

[0096] Prior to start-up, reactor was inoculated with wastewater and bio-catalyst in the ratio of 3:1 and adjusting the overall pH of 5 and adding certain inhibitors (2- bromoethanesulfonate) to selectively inhibit methanogenesis without significantly affecting hydrogen producing bacteria. Biofilms rich in H2-producing microorganism were grown on the electrode surface at batch mode before the reactor was switched to a continuous mode. In-situ exoelectrogenic micro-organism grows on the electrode surface identified as Bacillus sp. The effluent of the reactor went to a gas-liquid separator, where the gaseous (bio-hydrogen) and treated effluent were collected separately. The performance data of UAGB-MER reactor is summarized in Table 1.

[0097] Result: Long-term operation (over 80 days) of the UAGB-MER reactor was conducted. The cumulative bio-H2 produced around 22 lit, with an average hydrogen (H2) content of 87.54%, and carbon di oxide (CO2) 7.26% and methane (CH4) 5.2%.

[0098] Table 1: Performance details of a UAGB-MER reactor The above example illustrates a system that can treat wastewater with COD of ~ 2000mg / l. The invention synergistically coupled the water and green energy systems which is demonstrated by the production of hydrogen from wastewater resulting in a more sustainable and integrated process of resource management.

[0099] Example 2: Effect of organic loading rate on bio-hydrogen production

[0100] Feedstock used: CSIR-NIIST canteen wastewater

[0101] Procedure: Similar experimental procedure and process condition was followed.

[0102] Prior to start-up, reactor was inoculated with wastewater and bio-catalyst in the ratio of 3:1 and adjusting the overall pH of 5 and adding certain inhibitors (2- bromoethanesulfonate) to selectively inhibit methanogenesis without significantly affecting hydrogen producing bacteria. Biofilms rich in H2-producing microorganism were grown on the electrode surface at batch mode before the reactor was switched to a continuous mode. In-situ exoelectrogenic micro-organism grows on the electrode surface identified as Bacillus sp. The effluent of the reactor went to a gas-liquid separator, where the gaseous (bio-hydrogen) and treated effluent were collected separately. The performance data of UAGB-MER reactor with varying OLR is summarized in Table 2.

[0103] Result: Detailed experimentation was performed with varying OLR ranging from 0.5-30 kg / m3.d. It was observed that both cumulative production and bio- H2 yield increases with increase in OLR. In-situ exoelectrogenic activity of biofilm developed on the electrode surface was confirmed by chromaamperometry which was observed as 3.22 mA / cm2. The average hydrogen (H2) content in gas produced was 95.92%. Total energy efficiency of the process was 81.9%. Electrical energy recovery by the process is 73.1%. Average power density of the process is 11 KW / m3.

[0104] Table 2: Effect of organic loading rate (OLR)

[0105] ADVANTAGES OF THE INVENTION

[0106] • The developed UAGB-MER reactor converts chemical energy stored in organics to bio-H2 energy and simultaneous produce treated water. • The developed system is a next generation bio-electrochemical reactor which combines anaerobic granular bed coupled bio-electrochemical reactor.

[0107] • The developed UAGB-MER reactor is a two-electrode membrane less bioelectrochemical single cell reactor.

[0108] • Developed BEC Process is low operating and maintenance cost. • It is a renewable energy based-solar driven sustainable process.

[0109] • It is a modular and scalable unit suitable for onsite bio-H2 generation and simultaneous treatment of wastewater.

[0110] • The developed UAGB-MER reactor converts 85-90% of the inlet COD into bio- H2.

Claims

We Claim:

1. An upflow anaerobic granular bed - microbial electrochemical reactor [UAGB- MER] system (100) for production of bio-tk from liquid waste / wastewater containing biodegradable solids comprising: a) a vertically oriented elongated vessel compartmentalised into a bottom chamber (7B), middle chamber (7A) and top chamber (7T), each chamber being connected through a flange with gasket (22); b) a nozzle (20) establishing fluid communication between the bottom chamber (7B) and the outside of the feed vessel for input of wastewater into the reactor (7); c) a nozzle (36) establishing fluid communication between the liquid retention space of the top chamber (7T) with the outside of the vessel for discharge of treated wastewater from the vessel, arranged so as to retain a level of liquid within the top chamber (7T); d) a nozzle (35) for discharge of gas from the gas retention space of the top chamber (7T).

2. The reactor system (100) as claimed in claim 1, wherein the UAGB-MER reactor (7) comprising a cylindrical column with a hemispherical lower / bottom section (7B), middle section (7 A) and top section (7T) fixed by manifold; a particulate filter bed (29) confined inside the middle section (7A); wherein the lower section (7B) being provided with a dished bottom on which is provided feed inlet nozzle (6) for input of the feed wastewater by means of a pump (5); wherein the electrode module (24, 25) being fixed at the bottom of the reactor; connected to a pump (5) for continuously feeding the reactor with wastewater from an inlet port (6) placed at the bottom of the column, the effluent port (14) being located at upper part of the reactor; a gas solids separator (32) being mounted on top of the reactor; an overflow weir allowing liquid to overflow from the reactor through an outlet nozzle (36); a gas outlet nozzle (35) connecting the gas collection chamber with a constant pressure gas reservoir; further equipped with a feed vessel / tank (2), pump (5), UAGB-MER reactor (7), gas flow meter (15), gas separation unit (17), bio-hydrogen storage vessel (18), valves, pH sensor (9), ORP sensor (10) and solar PV unit (19); coupled to a gas-liquid-solid separator (32) at the top of the reactor (7T), reaction zone at the middle of the reactor (7 A) and placement of electrode module (24, 25) at the bottom compartment of the reactor (7B).

3. The reactor system (100) as claimed in claim 1, wherein the said top of the middle chamber (7 A) contains a packing media module (29) to prevent the washing out of biomass or sludge granules and enable biofilm formation.

4. The reactor system (100) as claimed in claim 1, wherein the said top chamber (7T) further comprising a gas-liquid-solid (GLS) separator (32) to enable disengagement of gas, settling of sludge and the overflow of clarified liquid from the reactor (7).

5. The reactor system (100) as claimed in claim 1, being a single cell / chamber, membrane less continuous anaerobic -bio-electro chemical reactor for bio-hydrogen production.

6. The reactor system (100) as claimed in claim 1, wherein it comprises a modular electrode assembly supporting the growth of exo-electrogenic H2 producing microorganisms and is configured to maximize surface contact with wastewater, providing enhanced microbial biofilm growth and efficient bio-electrochemical reactions for bio-hydrogen production.

7. The reactor system (100) as claimed in claim 1, wherein the modular electrode assembly comprises modified graphite as the bio-anode and stainless steel mesh as the cathode each providing a conducive surface for biofilm formation.

8. The reactor system (100) as claimed in claim 1, wherein the re-circulation loop is equipped with a pump and valves, allowing for the redistribution of liquid within the reactor to maintain optimal flow rates and enhance contact with the electrode surfaces.

9. The reactor system (100) as claimed in claim 1, wherein the middle chamber (7 A) contains a packed filter bed (29) that retains progressively finer suspended solids, promoting efficient separation of solid and liquid phase and degradation of organic matter.

10. The reactor system (100) as claimed in claim 1, wherein the gas separation unit (17) comprises a multi-stage purification system to remove contaminants, allowing for the collection of bio -hydrogen with high purity levels.

11. The reactor system (100) as claimed in claim 1, further comprising a solar photovoltaic (PV) unit (19) connected to the DC power supply, providing renewable energy to sustain the bio-electrochemical reactions.

12. A process for the generation of bio-hydrogen using the reactor system (100) as claimed in claim 1, wherein the steps comprising anaerobic degradation followed by electro-hydrogenesis which produces in- situ anode respiring exoelectrogenic bacteria that facilitate the transfer of the generated electrons to the cathode, where they react with protons at cathode, thus enhancing the biohydrogen energy evolution.

13. The process as claimed in claim 12, wherein the yield of bio-tk is 20.54 mol tk / kg of COD and 81.21 to 106 g / kg feedstock respectively; COD removal is 83 %.

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