Patent Description:
The necessity of cost-efficient and reliable water and wastewater treatment processes has increased in order to meet more stringent environmental regulations and increased system reliability requirements; and, to allow operators to reduce costs associated with system operation and maintenance.

Bio-electrochemical systems are a technology that rely on bacteria that normally use insoluble metal deposits as electron sinks during anaerobic consumption of reduced substrates. By substituting an electrode pair (anode and cathode) for the metal deposits, electrical current can be collected or recorded as it passes through an external resistor. The metabolic activity and respective bioelectric current of these bio-electrochemical systems have been shown to vary according to wide ranging environmental alterations that include, water composition / chemistry (nutrient content, pH, redox state), temperature and recirculation / sheer.

Examples of bio-electrochemical sensors or fuel-cells suitable in wastewater treatment systems and using different types of bacteria are described in B. Ringeisen et al. (<NUM>), C. Chen et al. (<NUM>), <CIT>, <CIT>, V. Fedorovich et al. (<NUM>), X. Quan et al. (<NUM>) and M. Malki et al.

Improvements in detecting and reducing system imbalances in wastewater treatment systems are desirable.

One or more previous proposals consider that, for a bio-electrochemical system to perform its desired function, the anodic biofilm community of the system should be placed in an anaerobic liquid environment because the presence of oxygen in close proximity to the anodic microbial community has been demonstrated to have a negative impact on bio-electrochemical system activity. The presence of oxygen is thought to negatively impact the anodic communities by, for example: (<NUM>) facultative exo-electrogenic microbes preferentially utilizing oxygen as a terminal electron acceptor; (<NUM>) impairing and/or killing strict anaerobic microbes; or (<NUM>) a combination thereof. The requirement of the use of bio-electrochemical systems in an anaerobic environment has hindered the widespread adoption of bio-electrochemical systems in aerobic environments, for example, in water and wastewater treatment plants that comprise zones of aerobic, aerated, oxygenated, or partially oxygenated water or wastewater streams.

The present invention relates to a bio-electrochemical sensor as defined in the claims, as well as systems and methods comprising it, that are suitable for an oxygenated wastewater treatment system. The scope of the present invention is defined in the set of claims.

One or more advantages of the present invention may: (<NUM>) reduce the cost of operation; (<NUM>) decrease the amount of costly equipment; (<NUM>) increase efficiency and/or performance of wastewater treatment systems (<NUM>) increase accuracy and/or precision of measurements; (<NUM>) expand the locations of use in a wastewater treatment system; (<NUM>) reduce energy consumption; (<NUM>) reduce use of chemical addition and/or carbon addition; (<NUM>) increase the quality of the effluent; (<NUM>) reduce the amount of manual sampling; allow for larger flowrates to move through the systems; (<NUM>) increase the efficiency of food to mass ratios, recirculation rates, sludge wasting, and/or the mixed liquid suspended solids concentration; or (<NUM>) a combination thereof, in comparison to exo-electrogenic bacteria, sensors, methods and systems that require an anaerobic environment to operate desirably.

Embodiments of the present disclosure will now be described, by way of examples only, with reference to the attached Figures.

In the context of the present disclosure, the oxygenated environment refers to an aerobic, aerated, oxygenated, or partially oxygenated liquid environment or zone that has at least some dissolved oxygen. The oxygenated environment or zone may have from about <NUM>/L to about <NUM>/L of dissolved oxygen, for example, about <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; <NUM>/L; or the concentration is from one of the concentrations listed above to any other of the concentrations listed above, or any concentration therebetween. Optionally, the oxygenated environment or zone has from about <NUM>/L to about <NUM>/L of dissolved oxygen. Optionally, the oxygenated environment or zone has from about <NUM>/L to about <NUM>/L of dissolved oxygen.

In the context of the present disclosure, the water or wastewater treatment system is any system that converts water or wastewater into an effluent that can either be discharged, returned to a water cycle, or reused. The water or wastewater treatment process may comprise at least one oxygenated or zone, for example, in a chamber that receives influent water or wastewater coming into the water or wastewater treatment plant or facility, for example, a lift chamber, a primary clarifier, and/or a primary aeration chamber. Optionally, the at least one oxygenated environment or zone is a chamber that is discharging treated water or wastewater out of a water or wastewater treatment plant, for example, a water or wastewater chamber before and/or after the final disinfection step (e.g. UV, chlorination, ozone). Optionally, the at least one oxygenated environment or zone is a range of process tanks or chambers that are associated with biological nutrient removal (Nitrogen of Phosphorous removal). Optionally, the at least one oxygenated environment or zone is an equalization tank, a pumping station or wet well, a recirculation line, an aerobic digester, a sludge holding tank, primary, secondary, tertiary aeration chambers and/or tanks, a sequencing batch reactor which may cycle between multiple water or wastewater conditions including aerobic, or an anammox reactor.

Exo-electrogenic bacteria refers to bacteria that has the ability to transfer electrons extracellularly, and that is metabolically activatable by one or more agents in a wastewater treatment system. A skilled person would likely consider that exo-electrogenic bacteria in an oxygenated environment would preferentially transfer electrons extracellularly to the oxygenated environment rather than a proximate conductive surface. However, surprising, as described herein, the inventors discovered that: (<NUM>) modified exo-electrogenic bacteria that are: (A) selected functionally during their growth in an oxygenated environment; and/or (B) produced genetically by modifying, selecting, and/or incorporating cytochromes that preferentially transfer electrons extracellularly to a proximate conductive material; (<NUM>) providing a multi-layered microorganism biofilm on a conductive surface that allows for a syntrophic interaction between the layers such that the exterior layer(s) may shield oxygen and/or consume oxygen at a sufficient rate, to reduce or limit the amount of oxygen interacting with interior exo-electrogenic bacteria layer(s); or (<NUM>) a combination thereof, may be incorporated into a bio-electrochemical sensor for use in an oxygenated environment, as described in Examples <NUM> and <NUM>.

In the context of the present disclosure, it should be understood that reference to "microbe", "microorganism" or "bacteria" includes one or more bacterium. Typically, a wastewater treatment system will comprise more than one type of resident bacteria. The terms "microbe and "microorganism" are used interchangeably herein to describe the one or more resident bacterium in the wastewater treatment system. The terms "electrogenic" and "exo-electrogenic" bacteria are used interchangeably herein.

The exo-electrogenic bacteria comprise one of more of Geobacter sulfurreducens, Geobacter metaloreducens, Pseudomonas aeruginosa, and Shewanella putrefaciens. The number and type of exo-electrogenic bacteria may depend on the type of oxygenated environment. Preferably, the exo-electrogenic bacteria comprises or consists of Geobacter sulfurreducens.

Respiring to an electrically conductive surface refers to any process in which exo-electrogenic bacteria transfer an electron extracellularly to an electrically conductive surface rather than to its oxygenated environment. The exo-electrogenic bacteria may respire to the electrically conductive surface with a tendency of about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, greater than the tendency of the exo-electrogenic bacteria to respire to their oxygenated environment. Respiring to the oxygenated environment refers to exo-electrogenic bacteria transferring at least one electron, extracellularly, to oxygen dissolved in the aerobic, aerated, oxygenated, or partially oxygenated environment. The exo-electrogenic bacteria's aerobic, aerated, oxygenated, or partially oxygenated environment refers to the exo-electrogenic bacteria being in fluid communication with the oxygenated environment. Optionally, the exo-electrogenic bacteria are fully immersed in their oxygenated environment.

In the context of the present disclosure, "immersed" within or into an environment refers to sinking at least a portion of the exo-electrogenic bacteria into the environment, for example, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, or the percentage is from any one of the percentages listed above to any other of the percentages listed above, or any percentage therebetween, of the surface area of the exo-electrogenic bacteria is immersed into the liquid environment. Optionally, the exo-electrogenic bacteria is coupled to a bio-electrochemical sensor that is immersed wholly or partially within an oxygenated environment.

Producing exo-electrogenic bacteria refers to a process of generating or growing bacteria from a seed sample. The seed sample may be obtained from stock or a previously selected exo-electrogenic bacteria that is able to respire to an electrically conductive surface in an oxygenated environment. The exo-electrogenic bacteria that respires to electrically conductive surface in an oxygenated environment may be selected functionally and/or produced genetically.

Selected functionally during their growth in an oxygenated, or environment refers to controlling the growth parameters of exo-electrogenic bacteria that results in exo-electrogenic bacteria with the ability to respire to an electrically conductive surface in an oxygenated environment. Optionally, exo-electrogenic bacteria are added to an oxygenated mixture comprising feed solution, monitored for biological activity, and viable exo-electrogenic bacteria are selected.

In the context of the present disclosure, feed solution is any liquid mixture that contains sufficient materials to cause exo-electrogenic to grow while being biologically active. The feed solution may comprise NaHCO<NUM>, casein hydrolysate, meat extract, urea, NaCl, CaCl<NUM>, MgSO<NUM>. <NUM><NUM>O, and sodium acetate. Optionally, the concentration of the components of the feed solution are adjusted so that the final BOD measured for the solution is from about <NUM>/L to about <NUM>,<NUM>/L. Optionally, the concentration of NaHCO<NUM> is from about <NUM>/L to about <NUM>/L, for example, about <NUM>/L. Optionally, the concentration of casein hydrolysate is from about <NUM>/L to about <NUM>/L, for example, about <NUM>/L. Optionally, the concentration of the meat extract is from about <NUM>/L to about <NUM>/L, for example, about <NUM>/L. Optionally, the concentration of urea is from about <NUM>/L to about <NUM>/L, for example, about <NUM>/L. Optionally, the concentration of the NaCl is from about <NUM>/L to about <NUM>,<NUM>/L, for example, about <NUM>/L. Optionally, the concentration of the CaCl<NUM> is from about <NUM>/L to about <NUM>,<NUM>/L, for example, about <NUM>/L. Optionally, the concentration of the MgSO<NUM>. <NUM><NUM>O is from about <NUM>/L to about <NUM>/L, for example, about <NUM>/L. Optionally, the concentration of sodium acetate is about <NUM>/L.

Biologically active refers to any reaction between the exo-electrogenic bacteria and at least one more agents in an oxygenated environment that causes at least one electron to transfer extracellularly from the exo-electrogenic bacteria, wherein, the at least one electron transfers extracellularly from the exo-electrogenic bacteria to a proximate conductive material, for example, an electrically conductive surface. Biological activity may be monitored by, for example: (<NUM>) measuring the amount of ATP in the exo-electrogenic bacteria; (<NUM>) measuring the transfer of electrons extracellularly from the exo-electrogenic bacteria to the proximate conductive material; (<NUM>) measuring byproducts and/or the degradation of substrates of the exo-electrogenic bacteria; or (<NUM>) a combination thereof.

The one or more agents is any component in an oxygenated environment that interacts with, and affects the ability of, the exo-electrogenic bacteria to transfer an electron extracellularly. The one or more agents may be oxygen, organic matter, a toxic agent, or a combination thereof. The organic matter may be an organic carbon compound. An organic carbon compound is any molecule comprising carbon and hydrogen that metabolically activates the exo-electrogenic bacteria. Optionally, the organic carbon compound is a volatile fatty acid, organic acid, complex organic compound, methanol, ethanol, acetate, acetic acid, glycerol, molasses sugar water, MicroC™, or a combination thereof. Optionally, the toxic agent is a cleaning agent, for example, sodium hypochlorite, peracetic acid, citric acid, or a combination thereof. Optionally, the toxic agent is an inhibitor compound, for example, ammonia, heavy metals, arsenic, sulfur, temperature, salinity, phenols, cyanides, thiocyanate, p-cresol, pesticides, acids, quaternary ammonium compounds, or a combination thereof.

The conductive material or electrically conductive surface may be any material that serves as a channel or medium for electrical current. Optionally, the electrically conductive surface is made of carbon fiber, activated carbon, graphene, stainless steel, platinum, palladium, iron, carbon paper, carbon graphite, titanium, mixed metal oxides, copper, brass, silver, or a combination thereof, or any material suitable for use as an electrode. Optionally, the electrically conductive surface is an anode of an electrode pair. Current measured from the electrode pair may be correlated with the biological activity of the exo-electrogenic bacteria.

The exo-electrogenic bacteria may be proximate to the conductive material or electrically conductive surface, for example, from about <NUM> to about <NUM> away from the conductive material or electrically conductive surface. Optionally, the exo-electrogenic bacteria transfers electrons to the conductive material or electrically conductive surface via at least one mediator compound located in the environment surrounding the conductive material or electrically conductive surface. Optionally, the exo-electrogenic bacteria is coupled directly to the conductive material or electrically conductive surface, for example, the exo-electrogenic bacteria is grown on the conductive material or electrically conductive surface. Alternatively, the exo-electrogenic bacteria is coupled to the conductive material or electrically conductive surface by means of an intervening electrical linker, for example, a wire.

Monitoring the biological activity may comprise steps of monitoring biological activity for a set period of time, for example, from about <NUM> minutes to about <NUM> weeks. Optionally, following the set period of monitoring time, the oxygenated, or mixture is replaced with new, oxygenated mixture. This cycle of monitoring and replacement may be repeated for a total time of from about <NUM> hour to about <NUM> months. Following the cycle, metabolically active exo-electrogenic bacteria may be selected. Optionally, the oxygenated mixture is provided to the exo-electrogenic bacteria as a continuous feed.

Genetically producing exo-electrogenic bacteria that respires to a conductive surface or electrically conductive surface in an oxygenated environment may comprise steps that: modify at least one cytochrome that enables at least one electron to transfer extracellularly to the conductive material or electrically conductive surface and not to the oxygenated environment; add at least one cytochrome that enables at least one electron to transfer extracellularly to the conductive material or electrically conductive surface and not to the oxygenated environment; select for at least one cytochrome that enables at least one electron to transfer extracellularly to the conductive material or electrically conductive surface; or a combination thereof.

Providing a multi-layered microorganism bacteria biofilm on a conductive surface refers to growing a sufficient thickness of microorganisms to shield oxygen from interacting with interior exo-electrogenic bacteria layers. The microorganisms are exo-electrogenic bacteria. The thickness of the microorganism layer(s) is sufficient to modify the mass transport limitations of oxygen through the layers of the microorganisms and is from about <NUM> to about <NUM> from the conductive surface. Allowing for a syntrophic interaction between the layers refers to a more exterior layer of microorganisms consuming oxygen and decreasing the amount of oxygen that interacts with a more interior layer of microorganisms and/or exo-electrogenic bacteria.

The present disclosure also provides a cell or reactor cell for removing oxygen from an oxygenated wastewater stream for measuring the amount of one or more agents in a wastewater treatment system, the cell being connectable in fluid communication upstream of a bio-electrochemical sensor. The cell comprises: an enclosure having an outer wall defining a passageway therethrough; a support structure, couplable to the enclosure and in fluid communication with the passageway, the support structure couplable to de-oxygenating biomass. Optionally, the bio-electrochemical sensor is the bio-electrochemical sensor according to the present disclosure. Alternatively, the bio-electrochemical sensor may be a sensor that functions in an anaerobic environment.

A skilled person would likely consider that current produced by a bio-electrochemical sensor in an oxygenated environment would not accurately and/or imprecisely correlate with the metabolic activity of resident microbes because the exo-electrogenic bacteria would preferentially transfer electrons to the oxygenated environment rather than a proximate conductive material or electrically conductive surface. As described herein, the inventors discovered that a cell that removes oxygen from the oxygenated environment upsteam of the bio-electrochemical sensor results in the bio-electrochemical sensor producing a current that more accurately and more precisely correlates with the metabolic activity of resident microbes as compared to using the bio-electrochemical sensors without the cell, as described in Example <NUM>.

The passageway may be any size provided that the oxygenated environment is able to pass therethrough. The enclosure may be made of any material provided that the enclosure is able to withstand the oxygenated environment passing therethrough. The enclosure may be made of a plastic material, metallic material, glass material, resin, epoxy, fiberglass, or a combination thereof. Optionally, the plastic material is HDPE, PVC, or silicon. Optionally, the metallic material is stainless steel or copper. The support structure may be any material that is couplable to the de-oxygenating biomass. Optionally, the de-oxygenating biomass is grown directly on the support structure. Alternatively, the de-oxygenating biomass may be connected to the support structure by way of an intervening linker. The support structure may be made of a plastic material, metallic material, glass material, carbon-based material, or a combination thereof. Optionally, the plastic material is HDPE, PVC, or silicon. Optionally, the metallic material is stainless steel or copper. Optionally, the carbon-based material is carbon mesh or activated carbon.

The de-oxygenating biomass may be grown on the surface of the support structure or the surface of the enclosure. In some examples according to the present disclosure, the de-oxygenating biomass is suspended in the cell without the requirement of a support structure.

The de-oxygenating biomass is any mass of organisms that have the ability to remove oxygen by consumption from their environment. Optionally, the de-oxygenating biomass is active bacterial biofilm comprised of a mixed microbial community. The mixed microbial community may be facultative and able to be metabolically active in the presence of oxygen or in low or no oxygen environments.

The rate at which the oxygenated environment is moved through the cell may vary provided that the de-oxygenating biomass is able to consume at least about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, or <NUM>% of the oxygen in the oxygenated environment. The flow rate of the oxygenated environment may be adjusted to increase or decrease the amount of oxygen consumption in the oxygenated environment. Optionally, the oxygenated environment is a wastewater treatment plant stream.

Optionally, the length of the cell is extended to increase the amount of oxygen consumption by the de-oxygenating biomass. Alternatively, additional cells can be positioned in series to increase the amount of oxygen consumption by the de-oxygenating biomass.

The presently disclosed exo-electrogenic bacteria are incorporated into a bio-electrochemical sensor to monitor metabolic activity of a population of exo-electrogenic bacteria in response to one or more agents in an oxygenated environment. The present disclosure provides a bio-electrochemical sensor for monitoring metabolic activity of a population of exo-electrogenic bacteria in response to one or more agents in oxygenated wastewater in a wastewater treatment system. The sensor comprises: at least one electrode pair comprising an anode and a cathode, the anode in electrical communication with the exo-electrogenic bacteria for receiving electrons therefrom; a current sensor for measuring electron flow between the anode and the cathode and producing an electrical output that correlates with metabolic activity of the exo-electrogenic bacteria; and a power source in electrical communication with the electrode pair for delivering a voltage across the electrode pair. The exo-electrogenic bacteria is the exo-electrogenic bacteria as presently disclosed, and the anode of the bio-electrochemical sensor is the conductive material or electrically conductive surface.

In the context of the present disclosure, the bio-electrochemical sensor is any sensor that can, with a voltage input, monitor the metabolic activity of microbes in oxygenated wastewater in a wastewater treatment system in real time, and provide an electrical output that correlates with the metabolic activity. Optionally, the bio-electrochemical sensor is a microbial electrolysis cell.

Without being bound by theory, bio-electrochemical sensors according to the present disclosure produce a substantially constant current under constant oxygenated environmental conditions. This may be, for example, referred to as a steady-state current. Once steady-state is reached in the oxygenated environment, a deviation indicates an impact on the metabolic activity of the resident microbes. For example, when a toxic component is introduced into an oxygenated environment, the oxygenated, or environment is imbalanced, and the metabolic activity of the microorganism community in the oxygenated environment can be impacted, resulting in a deviation from a reference current or steady-state current. A system operator will be able to determine a threshold deviation or threshold current at which an action is needed.

A skilled person would likely consider that current produced by a bio-electrochemical sensor in an oxygenated environment would not accurately and/or imprecisely correlate with the metabolic activity of resident microbes because electrons produced by the exo-electrogenic bacteria would preferentially transfer to the oxygenated environment rather than a proximate conductive surface. However, the inventors discovered that: (<NUM>) modified exo-electrogenic bacteria that are: (A) selected functionally during their growth in an oxygenated environment; and/or (B) produced genetically by modifying, selecting, and/or incorporating cytochromes that preferentially transfer electrons extracellularly to a proximate conductive material; (<NUM>) providing a multi-layered microorganism biofilm on a conductive surface that allows for a syntrophic interaction between the layers such that the exterior layer(s) may shield oxygen and/or consume oxygen at a sufficient rate, to reduce or limit the amount of oxygen interacting with interior exo-electrogenic bacteria layer(s); or (<NUM>) a combination thereof, may be incorporated into a bio-electrochemical sensor used for monitoring and/or controlling one or more agents in an oxygenated environment, as described in Examples <NUM> and <NUM>.

The bio-electrochemical sensor comprises at least one electrode pair comprising an anode and a cathode. The anode of the one electrode pair is in direct electrical communication with exo-electrogenic bacteria, for example, the exo-electrogenic bacteria may be attached to, grown on, or otherwise electrically coupled with, the anode. At least one layer of microorganisms may be grown on or otherwise coupled to the exo-electrogenic bacteria.

The current sensor is any sensor that measures electron flow between the anode and the cathode, and produces an electrical output. Optionally, the current sensor comprises a terminal electron acceptor in electrical communication with the cathode for receiving electrons therefrom, and a resistor in electrical communication with the electrode pair, where electrical current is measured across the resistor. The resistor may operate in the range of from about <NUM> Ohm to about <NUM>,<NUM> Ohms, for example, <NUM> Ohm, <NUM> Ohms, <NUM> Ohms, <NUM> Ohms, <NUM> Ohms, <NUM> Ohms, <NUM> Ohms, <NUM> Ohms, <NUM> Ohms, <NUM> Ohms, <NUM> Ohms, <NUM> Ohms, <NUM> Ohms, <NUM> Ohms, <NUM> Ohms, <NUM> Ohms, <NUM>,<NUM> Ohms, <NUM>,<NUM> Ohms, <NUM>,<NUM> Ohms, <NUM>,<NUM> Ohms, <NUM>,<NUM> Ohms; or the electrical resistance is between any one of the electrical resistances listed above to any other of the electrical resistances listed above, or any electrical resistance therebetween. Optionally, the resistor is a low-Ohm resistor (about <NUM> Ohms). Measuring an electrical output across the resistor refers to measuring the change in electrical potential before and after the resistor.

The power source may be any power-emitting instrument that applies a voltage across the electrode pair of the bio-electrochemical sensor. The applied voltage may be from about <NUM> V to about <NUM> V, for example, about <NUM> V; <NUM> V, <NUM> V, <NUM> V, <NUM> V, <NUM> V, <NUM> V, <NUM> V, <NUM> V, <NUM> V, <NUM> V, <NUM> V, <NUM> V, <NUM> V, <NUM> V; or the voltage is between any one of the voltages listed above to any other of the voltages listed above, or any voltage therebetween. Optionally, the applied voltage is from about <NUM> V to about <NUM> V. Without being bound by theory, the applied voltage to the bio-electrochemical sensor may allow the sensor to utilize a non-oxygen terminal electron acceptor, for example, H+ or CO<NUM>. In the context of the present disclosure, a terminal electron acceptor refers to any component that receives or accepts an electron. Optionally, the terminal electron accepter is any conductive material that allows for an electrochemical reduction reaction, for example, the reduction of H+ as a terminal electron acceptor in the production of hydrogen gas.

As used herein, the phrase "oxygen terminal electron acceptors" refers to use of the compound dioxygen (i.e., O<NUM>) as a terminal electron acceptor. In contrast, the phrase "non-oxygen terminal electron acceptors" refers to terminal electron acceptors that are not dioxygen (i.e., O<NUM>); however, this is not meant to exclude terminal electron acceptors that may be comprised of oxygen atoms, such as but not limited to CO<NUM>, etc..

The presently disclosed bio-electrochemical sensors may be incorporated into systems for monitoring and/or controlling one or more agents in an oxygenated environment. The present invention provides a system for monitoring one or more agents in oxygenated wastewater in a wastewater treatment system. The system comprises: a bio-electrochemical sensor for monitoring metabolic activity of a population of exo-electrogenic bacteria and providing an electrical output corresponding with the metabolic activity, the bio-electrochemical sensor comprising an electrode pair and a power source for delivering a voltage across the electrode pair; and an electrical output analyzer for analyzing the electrical output and correlating the electrical output with the one or more agents in the wastewater treatment system. The exo-electrogenic bacteria is the exo-electrogenic bacteria as presently disclosed. The present invention also provides a system for controlling the delivery of one or more agents in oxygenated wastewater in a wastewater treatment system. The system comprises: a bio-electrochemical sensor for monitoring metabolic activity of a population of exo-electrogenic bacteria and providing an electrical output correlating with the metabolic activity, the bio-electrochemical sensor comprising an electrode pair and a power source for delivering a voltage across the electrode pair; an electrical output analyzer for analyzing the electrical output and providing a signal to a controller; and a pump operably coupled to the controller for controlling the delivery of the one or more agents in response to the signal. The exo-electrogenic bacteria is the exo-electrogenic bacteria as presently disclosed. The electrode pair comprises an anode and a cathode, the anode in electrical communication with the exo-electrogenic bacteria for receiving electrons therefrom. The bio-electrochemical sensor further comprises a current sensor for measuring electron flow between the anode and the cathode and producing an electrical output that correlates with metabolic activity of the exo-electrogenic bacteria.

The electrical output analyzer provides a signal to a controller, which in turn controls the delivery of one or more agents into the oxygenated environment via a pump. The controller is any processor in communication with the bio-electrochemical sensor that accepts a signal from the electrical output analyzer and relays the signal to a pump.

The presently disclosed exo-electrogenic sensors may also be used in methods of monitoring and/or controlling a population of exo-electrogenic bacteria in response to one or more agents in an oxygenated environment. The present invention also provides a method of monitoring one or more agents in oxygenated wastewater in a wastewater treatment system. The method comprises: applying power to a bio-electrochemical sensor; measuring an electrical output of the bio-electrochemical sensor and correlating the output with metabolic activity of exo-electrogenic bacteria present in the system; and correlating the electrical output with the one or more agents in the wastewater treatment system. The exo-electrogenic bacteria is the exo-electrogenic bacteria as presently disclosed. The present invention also provides a method of controlling the delivery of one or more agents in oxygenated wastewater in a wastewater treatment system. The method comprises: applying power to a bio-electrochemical sensor; measuring an electrical output of the bio-electrochemical sensor and correlating the output with metabolic activity of exo-electrogenic bacteria present in the system; delivering the one or more agents into the system; monitoring a change in the electrical output in response to the one or more agents; and adjusting the delivery of the one or more agents in response to a change in the electrical output. The exo-electrogenic bacteria is the exo-electrogenic bacteria as presently disclosed.

The herein described systems and methods may initiate, increase, decrease, or discontinue the delivery of one or more agents into an oxygenated environment in response to a signal produced as a result of a change in electric output when the electric output meets or exceeds a threshold. The one or more agents may negatively impact the exo-electrogenic bacteria resulting in a decrease in metabolic activity and a decrease in measured current. Alternatively, the one or more agents may positively impact the exo-electrogenic bacteria resulting in an increase in metabolic activity and an increase in measured current.

The herein described electrical output analyzer is able to analyze the electrical output from the bio-electrochemical sensor and provide a signal, when appropriate, to cause an adjustment in the oxygenated environment. Optionally, the signal is provided when the electrical output meets a threshold output, or deviates from a reference output.

A threshold output is an output (such as a current measurement) at which the oxygenated environment parameters are no longer at levels acceptable for the continuing operation or function. As would be known by one of skill in the art, determining what is considered an acceptable parameter level(s) for the operation or function of the oxygenated environment will be dependent on, or determined by the specific type of oxygenated environment. The threshold current or other output may represent a deviation from a reference operating electrical output of, for example, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>%, about <NUM>% deviation, or the percentage is from any one of the percentages listed above to any other of the percentages listed above. The reference operating output may, for example, be a baseline or steady-state current. A skilled person, such as a manufacturer or an operator, will be able to determine acceptable levels of deviation. The threshold current may be pre-determined, for example, from previous methods; known values in the art; or a value determined using alternative methods known to a skilled person. Optionally, the threshold is determined relative to the current generated from the metabolic activity of the exo-electrogenic bacteria under standard operating conditions, for example, temperature, oxygen levels, pH, pressure, or a combination thereof.

The deviation may be measured over time; and, a threshold may be set based on one or both of the deviation and time. The deviation may be measured over a period of about <NUM> second to about <NUM> hours, for example, about <NUM> second, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM>,<NUM> seconds, <NUM>,<NUM> seconds; or the time is from any one of the times listed above to any other of the times listed above, or any time therebetween. In some examples according to the present disclosure, the measurement is initiated about <NUM> seconds after the addition of one or more agents, and the oxygenated environment is monitored for a deviation for about <NUM> hour thereafter. In some examples according to the present disclosure, a threshold deviation may be a deviation of greater than about <NUM>% from the reference operating electrical output over about <NUM> hours from the introduction of one or more agents into the wastewater treatment system. The deviation may be measured in less than about <NUM> seconds, about <NUM> seconds, about <NUM> seconds, about <NUM> second, or the time is from any one of the times listed above to any other of the times listed above, after the introduction of one or more agents or condition. The impact of the one or more agents may be visualized by the operator, or signaled by a system if it has an impact on the bio-electrochemical sensor. This variation or deviation in output from the bio-electrochemical sensor may be used to discontinue or control the addition of the one or more agents. The amount of time after the introduction of one or more agents or condition in which a change in current can be measured will depend on various factors, for example, components in the oxygenated environment, volumetric size of the oxygenated environment, the type and amount of exo-electrogenic bacteria, or a combination thereof.

The herein described systems and methods may be used to adjust the amount, type, or combination thereof of one or more agents delivered into an oxygenated environment. Once it is determined that the measured current has reached the determined threshold, a signal is sent to a pump that controls the delivery of the one or more agents into the oxygenated environment, which in turn decreases or discontinues the delivery of the one or more agents. Once it is determined that the measured current is within an acceptable range or within the threshold output, a further signal may be sent to a pump to increase or commence the delivery of the one or more agents.

An operator may affect an adjustment on the system in response to signals provided by the bio-electrochemical sensors, systems, and methods as presently disclosed. Optionally, a processor running an algorithm and in communication with the presently disclosed bio-electrochemical sensors and systems predicts imbalances on the oxygenated environment based on the electrical output provided by the herein described systems and bio-electrochemical sensors, and adjusts the oxygenated environment in response to the prediction. Optionally, the processor is a predictive learning machine.

The present disclosed systems may incorporate a presently disclosed bio-electrochemical sensor in close proximity to a portion of the wastewater treatment tank where the wastewater enters the tank, for example when monitoring and/or controlling one or more agents entering the tank from upstream sources is preferable. The present disclosed systems may also incorporate a presently disclosed bio-electrochemical sensor in close proximity to a portion of the wastewater treatment tank where the water exits the tank, for example when monitoring one or more agents that are exiting the tank is preferable. More than one bio-electrochemical sensor may be positioned within a wastewater treatment tank, for example when monitoring one or more agents at different locations within the tank is preferable. Optionally, one bio-electrochemical sensor is positioned in close proximity to a portion of the wastewater treatment tank where the wastewater enters the tank, and one bio-electrochemical sensor is positioned in close proximity to a portion of the wastewater treatment tank where the water exits the tank, for example when: (<NUM>) monitoring a change in the amount of the one or more agents in the tank; (<NUM>) monitoring the movement of the one or more agents in the tank; or (<NUM>) a combination there of, is preferable.

The present invention further provides a method of monitoring the viability of microorganisms in an oxygenated environment. Generally, the method comprises providing exo-electrogenic bacteria in the oxygenated environment. The current generated from the metabolic activity of the exo-electrogenic bacteria is measured and compared to a reference current of a viable amount of the microorganisms. If the measured current is above or below the set threshold current, an adjustment is needed. A viable amount of the microorganisms is a sufficient amount of microorganisms for the oxygenated environment to operate. The presently disclosed bio-electrochemical sensors may be used in the method of monitoring the viability of microorganisms in a wastewater treatment system. The exo-electrogenic bacteria is the exo-electrogenic bacteria as presently disclosed.

The present disclosure also provides a use of a bio-electrochemical sensor as presently disclosed in the methods and/or systems as presently disclosed.

Operating the herein described bio-electrochemical sensors, systems and methods in an oxygenated environment may: (<NUM>) decrease the amount of costly equipment; (<NUM>) increase the efficiency of the wastewater treatment system; (<NUM>) increase accuracy of the correlation of the electrical output and the metabolic activity of the exo-electrogenic bacteria; or (<NUM>) a combination thereof, in comparison to previously proposed bio-electrochemical sensors, systems and methods that preferably operate in oxygenated environments.

As noted above, the present invention provides a bio-electrochemical sensor for performing the above described methods, as well as for being incorporated into the above described systems. An exemplary sensor configuration is shown in <FIG>. The sensor (<NUM>) generally comprises: an electrode pair comprising an anode (<NUM>) and a cathode (<NUM>), the anode (<NUM>) in electrical communication with the exo-electrogenic bacteria (<NUM>) for receiving electrons therefrom; a resistor (<NUM>) electrically coupled to the electrode pair, the electrical current being measured across the resistor (<NUM>); a power source (<NUM>) in electrical communication with the electrode pair for delivering voltage across the electrode pair; and a terminal electron acceptor (not shown) for receiving electrons from the cathode. Changes in electrical output may be used to optimize wastewater treatment system performance, for example, to determine optional delivery of one or more agents to the system. A change in electrical output may be measured against a set threshold to determine when an adjustment is needed.

As noted above, the present disclosure provides a cell for removing oxygen from an aerated wastewater stream for measuring the amount of one or more agents in a wastewater treatment system, the cell being connectable in fluid communication upstream of a bio-electrochemical sensor. An exemplary cell is shown in <FIG>. The cell (<NUM>) comprises an enclosure (<NUM>) having an outer wall defining a passageway therethrough (arrows); a support structure (<NUM>), couplable to the enclosure (<NUM>) and in fluid communication with the passageway (arrows), the support structure (<NUM>) couplable to de-oxygenating biomass.

Duplicate bio-electrochemical sensors according to the present invention were installed in a water (comparative) or wastewater (invention) plant effluent channel immediately before UV lights to monitor effluent water or wastewater and two sensors were installed at the influent of the water or wastewater treatment plant (in the effluent of the primary clarifier) to monitor the impact of incoming water or wastewater. The plant is a typical water or wastewater treatment plant, with screens, primary clarifiers, activated sludge basins, secondary clarification, UV disinfection and anaerobic digestion. The plant is primarily responsible for treating organics and TSS.

For effluent monitoring, the probes were tied together to confirm reliability of the data and test two bio-electrochemical sensors in parallel. The bio-electrochemical sensors were hung into the water or wastewater stream using two wire supports. The bio-electrochemical sensors hung in a swing like application, which allowed the sensors to swing in the channel but not wrap around each other.

The operator had the ability to easily pull the effluent bio-electrochemical sensors up and shake off algae. The operator may scrape algae off the weirs manually on a regular basis because as the algae flows through the system, it may get caught on the bio-electrochemical sensors and the UV lights. This equipment is cleaned after the weirs are scraped. To accommodate the cleaning of algae off the bio-electrochemical sensors, the stainless steel cable was extended to connect to each probe and the side of the grate. Instead of connecting to the grate on each side, the wires ran through the grate and attached the two ends on the top center of the grate with a cable clamp. The operator can grab the wire on top of the grate, shake off any algae and drop it back in the channel.

The bio-electrochemical sensors were installed right before a large gate valve. To ensure the probes could not be hit by the closing valve, a third cable was added, tied around both of the bio-electrochemical sensors, short enough to prevent the bio-electrochemical sensors from hitting the gate in high flow situations. This wire was secured to the grate by creating a loop in the wire with a cable clamp and secured to the grate using a carabiner.

The dissolved oxygen in the effluent water or wastewater stream varied from <NUM>/L to <NUM>/L. The bio-electrochemical sensors were installed and information from the bio-electrochemical sensors was collected using an online dashboard. Data was collected from the bio-electrochemical sensors and BOD measurements were collected from the water or wastewater and correlated with output from the bio-electrochemical sensors. The bio-electrochemical sensors data is illustrated in <FIG> and <FIG>.

The data collected demonstrated that the effluent bio-electrochemical sensors output is reproducible for the two bio-electrochemical sensors installed in the water or wastewater effluent stream. The range for the output was from <NUM> - <NUM>µA with a daily pattern emerging and the highest peaks in performance identified at <NUM>:<NUM> pm each day. The daily fluctuations in output from the biology is a direct measure of increased biological activity at this time and correlates with increased biological demand in the water or wastewater at this time.

BOD correlations were performed on the influent and effluent samples by plant operators. The sensor's output is that of Microbial Electron Transfer (MET). MET is specifically the measurement of electrons transferred across the resistor (or current), which is placed between the anode and cathode pairing. Plotting of this combined data shows that the sensors (MET) value at these time points predicts the BOD with an R<NUM> of <NUM>. BOD sampling events of influent showed an average of <NUM>/L, with a range of <NUM>-<NUM>/L.

Key daily and weekly patterns were identified through a statistical analysis of the sensor data generated on the influent and effluent sensors.

An analysis of the daily influent cycle was performed. The night-time period between 5PM to 8AM showed the lowest activity, with highest influent activity occurring typically at noon.

Using this daily and weekly data, the operator can gain additional understanding of the changing demands (i.e. organic loading or toxic impacts) on the system. This allows the operator to understand logical times and days for maintenance down times (during low flow/low stress times), and better understand the stress on the system.

Using this data, additional organic loads (revenue generating) could be taken in to the facility. The sensor could be used to predict optimal times to receive these flows.

Precipitation has a pronounced effect on the water or wastewater treatment plant. Typically there is a <NUM>-<NUM> hour delay from the start time of a precipitation event to having an impact on the water or wastewater plant. These events can cause large changes in MET entering the system, decreasing the water or wastewater concentration by as much as <NUM>%.

Bio-electrochemical sensors according to the present invention were installed at different tie-in locations of a water (comparative) or wastewater (invention) plant. The water or wastewater treatment plant consists of screening, an activated sludge aeration basin/primary treatment tank, secondary clarification, UV disinfection, aerobic sludge digestion, sludge holding tank, and UV disinfection.

Influent sensor installation location: The bio-electrochemical sensor was installed in a channel that received raw water or wastewater entering the plant. The bio-electrochemical sensor was lowered into a trough that received the influent water or wastewater just after a series of screens and prior to the primary treatment tank. The bio-electrochemical sensor was totally submerged in water or wastewater and received flow from a pumping station.

Effluent sensor installation location: The bio-electrochemical sensor was installed in an effluent channel prior to the final effluent weir. The bio-electrochemical sensor was hung from an existing angle iron bracket in the channel. The bio-electrochemical sensor was secured using a stainless steel wire and stainless steel wire clamps. It hung approximately <NUM>' below the water level. This water level was approximately <NUM>" above the bottom of the V notch weir. The bio-electrochemical sensor was unable to dry out in this location even at low water levels. The bio-electrochemical sensor support wire was positioned away from the wall of the tank, away from dead spots, where there is visible flow.

The dissolved oxygen in the water or wastewater streams was maintained at a range of <NUM> and <NUM>/L dO using a variable frequency drive blower. The bio-electrochemical sensors were installed and information from the bio-electrochemical sensors was collected using an online dashboard. Data was collected from the sensor and BOD measurements were collected from the water or wastewater and correlated with output from the bio-electrochemical sensors. BES data collected is illustrated in <FIG> and <FIG>.

The data collected demonstrated that the bio-electrochemical sensor output to be significantly higher for the influent water or wastewater stream when compared to the bio-electrochemical sensor located in the effluent stream. The range for the steady state influent water or wastewater was <NUM> - <NUM>µA whereas the effluent water or wastewater was more variable in output and ranged from <NUM> - <NUM>µA. This variation in output from the bio-electrochemical sensors is reflective of the microbial metabolic activity and the presence of lower concentrations of biological oxygen demand or bio-available carbon in the effluent stream when compared to the influent water or wastewater.

Aeration Basin location: The bio-electrochemical sensor was installed directly into the activated sludge aeration basin. It was done so by connecting the sensor to a PVC pipe and lowering down into the basin. The system was installed in an attempt to contact a representative sample of the solution.

The aeration basin data output showed an interesting variation in microbial activity in the biology. The output was primarily between <NUM>-<NUM>µA. Trending in the location showed that there was diurnal variation of at least +/- <NUM>µA. Highest microbial activity at ~6am, with lowest activity between 1pm-3pm.

Sludge holding tank location: The bio-electrochemical sensor was installed into the sludge holding tank. It was done so by connecting the sensor to a PVC pipe and lowering down into the basin. The system was installed in an attempt to contact a representative sample of the solution.

The sludge holding data output showed a relatively low level of output. A sample was collected and brought into the lab to confirm that the output was very low. This may have been due to the fact that biological activity and compounds were limited at this location as the biology in this system would have removed most soluble organic compounds at this time.

Observations: Analysis of the influent data showed that the nighttime period between 1am-3am showed the lowest organic strength, with highest influent concentration occurring between 11am-3pm (see <FIG>). From reviewing at several months of data, the highest amount of stress for the facility appeared to be during the summer months (early June to mid-August), coinciding with additional summer loading the facility sees due to its seasonal location.

Weekly trend data of the effluent showed diuranal effluent variation, with maximum MET typically between 11am and 3pm. Minimum concentrations tended to occur between 1am-3am. The weekends had the lowest concentration (see <FIG>).

To protect bio-electrochemical sensor biological communities according to the present invention from the potential negative impact of oxygen, the inventors tested and validated the application of a cell (putrification cell) for the removal of oxygen from a water or wastewater stream. The test apparatus to validate the putrification cell is illustrated in <FIG>.

Influent water or wastewater is collected in a holding tank and can be spared to remove oxygen or can be aerated. This test system was developed to validate a putrifcation cell could function to remove oxygen from an aerated water or wastewater stream prior to it reaching a bio-electrochemical sensor surface according to the present disclosure.

Methodology: A synthetic water or wastewater containing <NUM>/l sodium acetate trihydrate and BOD pillows as a water or wastewater condition (according to dilution ratios for the BOD dilution method) was mixed as a large batch in a <NUM> gallon pail. The synthetic water or wastewater was then deoxygenated by bubbling nitrogen through it until the dissolved oxygen measured below <NUM>/l. The experiment was split into <NUM> phases to determine the impact of the putrification cell.

Phase <NUM>: The sample, having been deoxygenated, was sent directly from the pail into the bio-electrochemical sensor. (Putrification cell was flushed with <NUM> litre of water prior to being connected to the sensor).

Phase <NUM>: The sample, having been deoxygenated, was sent through the putrification cell prior to the bio-electrochemical sensor.

Phase <NUM>: The sample, now continually aerated, was sent through the putrification cell.

Phase <NUM>: Finally, the system was turned off, still with the contents of the probe stirring but no fresh media entering the cell.

Results: Phase <NUM>: Anaerobic water or wastewater was sent direct to the bio-electrochemical sensor and not through the putrification cell.

Phase <NUM>: After being in this state for over <NUM> hours, the system was reconfigured and the putrification cell was put in-line before the bio-electrochemical sensor. A noticeable increase in the signal occurred, however, throughout the <NUM> hours the putrification cell was attached a measurable increase in the signal was apparent, as illustrated in <FIG>. It appears that the putrification cell itself is contributing to the signal and generating additional substrate for the bio-electrochemical sensor's biology to consume.

Phase <NUM>: The configuration of the system was not changed, but the pail with the synthetic water or wastewater was aerated. This did not appear to have a material impact on the signal and suggest that the aeration of a sample (at least with a significant BOD) is not of concern to impacting the measurement. The putrification cell is demonstrated to limit any negative impact of oxygen being present in the up-front influent holding tank.

Phase <NUM>: Finally, the pump was turned off while stirring was maintained and the signal decreased modestly (<NUM> uA) to the same conditions as when a flow through sample was provided without going through the putrification cell.

The development of anodic microbial communities that are tolerant to oxygen yet continue to utilize the electrode surface for respiration is counter intuitive to the current scientific consensus on how specifically microbial electrolysis cells are thought to operate.

The following procedure for inoculating exo-electrogenic microbial biofilm in a micro-aerobic or aerobic environment has allowed the inventors to select for microbial communities that retain a unique functionality. The ability for bacterial communities to respire to an electrode surface of a bio-electrochemical sensor (specifically of a microbial electrolysis cell) while in the presence of oxygenated water or wastewater.

The procedure does not involve any aspects of sparging water or wastewater streams for the exclusion of oxygen from the inoculation process. Original water or wastewater seed samples are collected typically from aerated zones of a water or wastewater treatment plant. During cell inoculation, there is no sparging of feed water or wastewater or of seed inoculum. Furthermore, an air-tight seal on the sensor inoculation cells is not required.

Table <NUM> Adapted synthetic water or wastewater recipe (Peel & Nyberg <NUM>) used as the inoculation and feed for the SENTRY inoculation cells with the addition of sodium acetate and making a 25x <NUM> stock solution.

Bio-electrochemcial sensors according to the present invention were installed at three different tie-in locations of a water (comparative) or wastewater (invention) plant on October <NUM>, <NUM>: one located in a primary clarifier of the water or wastewater plant, one located just before biological nutrient reactors of the water or wastewater plant, and one located at an effluent of the water or wastewater plant.

Primary clarifier installation location: The bio-electrochemical sensor was installed on a moving bridge primary clarifier, which rotated approximately once per hour. It was connected to the moving bridge via PVC pipe and sensed the water or wastewater strength variation.

Prior to biological nutrient removal reactors: The bio-electrochemical sensors was installed just prior to entering the biological nutrient removal reactors.

Effluent sensor location: The bio-electrochemical sensor was installed at the effluent of the bioreactors.

Relevant information gained: The sensor correlated well with TCOD/fCOD/TBOD5 with r2 ranging from <NUM>-<NUM>, when the data was combined the r2 additionally increased.

<FIG>, <FIG>, and <FIG> illustrate the measurement results from the influent and effluent sampling. The sensor identified days of the week with the highest organic strength in the influent (Wednesday-Friday) and a time of the day (after 5pm). The lowest organic strength in the influent occurred on Monday (as well as the weekend), with lowest activity around noon.

Four major events occurred at the facility during this time, with the primary cause of disturbance due to rainfall in the region and additional material being brought into the system.

The SENTRY system was installed at a Water Treatment Plant. The herein described sensors were used to monitor the biological activity of the water at two key locations at the facility. The facility is using the sensors to help flag abnormal biological activity and abnormal water constituents entering their facility (raw water intake) and leaving the water treatment process - granular activated carbon contactor (GACC). The incoming raw water, which is drawn in from a lake source to the treatment plant, is considered aerobic with a dissolved oxygen concentration in the range of <NUM> - <NUM>/L. The lake is part of the local watershed and impacted by rain events, runoff, seasonal variation and point and non-point discharges from the region, including upstream water or wastewater treatment facilities.

Installation location: Sensor <NUM> was installed at the raw water intake of the plant. Sensor <NUM> was installed on the effluent of granular activated carbon contactor (GACC) reactor.

Results: The sensors showed a high level of response to the fluctuations in the water quality in both the Raw Water Intake and the granular activated carbon contactor effluent. A web-based alert system was set in place to flag and email operators at the plant during large fluctuations outside of a specific controlled range. This allows operations staff to take additional samples during imbalance events to further track the change in conditions. Five alert events were tracked during the trial time period. The sensors were able to pick up water or wastewater bypass events from the upstream water or wastewater treatment plant, showing abnormal spikes in both sensor locations.

Initial correlations were drawn with the organic compounds tested by OCWA (TOC/COD/DOC). Correlations were strongest with TOC (R<NUM> of <NUM>-<NUM>) and DOC (R<NUM> of <NUM>), showing the value of the sensor as a real-time estimate on biologically available carbon in the system.

The information that the SENTRY probe provides is unique as it provides data both on the relative organic strength as well as biological response to known and unknown events. Typically, a separate, expensive and complicated sensor would be provided for BOD estimations and there is no probe available to receive instant updates to biological process upsets (ATP test kits are an example of a technology which is a snapshot of the biological health, but they are one-off events and are expensive to run per event).

Claim 1:
A bio-electrochemical sensor for monitoring metabolic activity of a population of exo-electrogenic bacteria in response to one or more agents in oxygenated wastewater in a wastewater treatment system, the sensor comprising:
at least one electrode pair comprising an anode and a cathode, the anode in electrical communication with the exo-electrogenic bacteria for receiving electrons therefrom, wherein the exo-electrogenic bacteria are formed into a multi-layered biofilm on the anode, said biofilm having a thickness of from about <NUM> to about <NUM>, and wherein the exo-electrogenic bacteria comprises one or more of Geobacter sulfurreducens, Geobacter metaloreducens, Pseudomonas aeruginosa and Shewanella putrefaciens;
a current sensor for measuring electron flow between the anode and the cathode and producing an electrical output that correlates with metabolic activity of the exo-electrogenic bacteria; and
a power source in electrical communication with the electrode pair for delivering a voltage across the electrode pair.