WO2014172791A1

WO2014172791A1 - Fixed-film aeration apparatus and waste water treatment system

Info

Publication number: WO2014172791A1
Application number: PCT/CA2014/050393
Authority: WO
Inventors: Philip A. STREETS; Patrick Desmond KIELY
Original assignee: Clear Pod Inc.
Priority date: 2013-04-24
Filing date: 2014-04-24
Publication date: 2014-10-30

Abstract

Disclosed herein is a wastewater treatment system. The system has a tank having side walls, an inlet wall having an inlet, an outlet wall having an outlet, a floor and an upper surface. The tank has first and second baffles extending along the width of the tank which together with the inlet and outlets walls define first and second anaerobic zones within the tank. A fixed-film aeration apparatus is positioned between the baffles and defines an aerobic zone. Wastewater is directed by the baffles from the inlet through the first anaerobic zone, the aerobic zone, and the second anaerobic zone. Also disclosed is a fixed-film aeration apparatus that is configured for insertion through a standard septic system opening. An air line is coupled to a weighted base and delivers oxygen through an air dispersal mechanism to a plurality of stacked fixed-film media supports, thereby promoting metabolic activity of a fixed-film.

Description

FIXED-FILM AERATION APPARATUS AND WASTEWATER TREATMENT

SYSTEM

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. Provisional Patent

Application No. 61 /815,339, filed 04/24/2013, and U.S. Provisional Patent Application No. 61/847, 127, filed 07/ 17/2013, each of which is hereby incorporated by reference in its entirety. FIELD

The present disc losure relates generally to a fixed-film aeration apparatus and a wastewater treatment system, for example a septic system.

BACKGROUND

In rural areas of the developed world almost all domestic liquid waste is disposed of and partially treated using in-ground septic tank systems. In the U.S. and Canada approximately 25% of households have a septic system for treating w astewater. Standard septic system technology functions by settling sol ids from the wastewater stream in an anaerobic environment. Poorly functioning systems can introduce nitrogen, phosphorus, organic matter, and bacterial and viral pathogens into the surrounding area and groundwater, resulting in potential health hazards, and contamination of local water supplies.

Biological treatment of wastewater using bacteria, along with protozoa and microbes, has been shown to increase the efficiencies and effectiveness of wastewater treatment. The bacteria remove small organic carbon molecules by 'eating' them. As a result, the bacteria grow, and the wastewater is cleansed. The treated wastewater or effluent can then be discharged to receiving waters, such as a river or the sea.

The biological treatment of wastewater is typically divided into cither suspension growth methods or fixed-film growth methods. There arc three categories of fixed-film wastewater treatment processes: (i) submerged systems where the fixed-film is submerged in wastewater; (ii) trickle-bed systems in which the fixed-film is exposed to the atmosphere and wastewater is trickled over the film; and (i ii) a combination where the fixed-film is alternately submerged in wastewater and the atmosphere in a rotating biological contactor (RBC).

In submerged systems, a microbial biomass is attached to cither the surface of an immobile solid surface or to mobile solid particles suspended in the wastewater.

Submerged fixed film wastewater treatment systems can be operated under aerobic and anaerobic conditions with each mode of operation having specific impacts in terms of biomass and cell yield production, chemical oxygen demand (COD), ammonia, nitrite, nitrate, phosphate, and pathogenic bacterial species treatment.

While certain methods for treatment of wastewater are known, there remains a need for improved wastewater treatment systems and means for improving the function of existing septic tanks. In addition, there exists a need for low-cost, high-fidelity approach to measuring and relaying information to wastewater treatment system operators relating to the performance of a wastewater treatment system. SUMMARY

It is an object of the present disclosure to obviate or mitigate at least one disadvantage of previous fixed-film aeration apparatuses or wastewater treatment systems.

Disclosed herein is a wastewater treatment system comprising a tank having opposing first and second side walls, an inlet wall defining an inlet for receiving wastewater, an outlet wall defining an outlet for discharging treated wastewater, a floor and an upper surface. The first and second side walls and the inlet wall and the outlet wall connect the floor and the upper surface. The upper surface defines at least one opening, for accessing then tank when inserted in the ground.

The tank comprises a first baffle having an upper edge extending above the inlet and a lower edge extending below the inlet and above the floor. The first baffle extends between the first and second side walls along the entire width of the tank, and together with the inlet wal l the first baffle defines a first anaerobic zone in the wastewater treatment system. The tank comprises a second baffle that has an anchored end anchored to the floor of the tank and a free end projecting into the tank. The free end of the second baffle is positioned at a position higher than the lower edge of the first baffle. The second baffle is coupled to the first and second side walls and extends between the first and second side walls along the entire width of the tank. Together with the outlet wall, the second baffle defines a second anaerobic zone in the wastewater treatment system.

A fixed-film aeration apparatus is coupled to the first and second baffles, and is raised from the floor at a position above a level of accumulation of bio-solids in the tank. The fixed-film aeration apparatus comprises at least one fixed-film media support, and a base for supporting the at least one fixed-film media support. The fixed- film aeration apparatus further comprises an air line having an internal aeration connector, and an external oxygen source connector for coupling to an external oxygen source and an air dispersal mechanism coupled to the internal aeration connector. The air dispersal mechanism delivers oxygen to the at least one fixed-film media support. The fixed-film aeration apparatus defines an aerobic zone in the wastewater treatment system. The first and second baffles direct a flow of wastewater along a treatment path, the treatment path extending from the inlet through the first anaerobic zone, the aerobic zone, the second anaerobic zone and to the outlet.

The system may comprise at least one bio-electrochemical sensor for detecting the presence of wastewater constituents in the wastewater.

Also disclosed is a fixed-film aeration apparatus configured for insertion through a standard septic system opening. The fixed-film aeration apparatus comprises a base comprising a weighted portion, the weighted portion being configured to stabil ize the apparatus in an unanchored operating position during and after insertion. The apparatus further comprises a support member coupled to the base and an air line coupled to the base for delivering oxygen to a plurality of fixed-film media supports. The air line has an external oxygen source connector and an internal aeration connector, and an air dispersal mechanism is coupled to the internal aeration connector for delivering oxygen to the fixed - film media supports and promote the metabolic activity of a fixed-fil m on the fixed-film media supports. The plural ity of fixed-film media supports are vertically stacked on the base and supported by the support member.

Also disclosed is a method of controlling a wastewater treatment system, the method comprising: generating a potcntiostatic sweep across a bio-clectrochcmical sensor; measuring a current response of the bio-electrochemical sensor in response to the potcntiostatic sweep and comparing the measured current response to a threshold. In response to a determination that the measured current response is below the threshold, adjusting a wastewater treatment system operation parameter to increase the current response.

Also disclosed is an effluent filter for a wastewater system comprising a filter comprising a porous material, the filter for filtering solid material from the wastewater; and a bio-electrochemical sensor for sensing changes in conditions in the wastewater treatment system.

Other aspects and features of the present disclosure will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments in conjunction with the accompanying figures.

BRI EF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will now be described, by way of example only, with reference to the attached Figures, wherein:

Fig. 1 is an exploded perspective view of a fixed-film aeration apparatus according to an embodiment of the present disclosure;

Fig. 2 is a cross-sectional view of the embodiment of the fixed-film aeration apparatus shown in Figure 1 ;

Fig. 3 is a perspective view showing the positioning of air stones on a support tray, according to the embodiment shown in Figures 1 and 2;

Fig. 4 is a cross-section of a fixed-film aeration apparatus having a ballast tray according to an embodiment of the present disclosure;

Fig. 5 is a diagram showing a fixed-film aeration apparatus in a wastewater treatment tank according to an embodiment of the present disclosure;

Fig. 6 is a cross- sectional view of a wastewater treatment system according to an embodiment of the present disclosure comprising the fixed-film aeration apparatus shown in Figure 1 ;

Fig. 7 is a cross- sectional view of a wastewater treatment system according to an embodiment of the present disclosure;

Fig. 8 is a cross- sectional view of a bio-clcctrochcmical sensor according to an embodiment of the present disclosure;

Fig. 9 is a cross- sectional view of an effluent filter for a wastewater treatment system according to an embodiment of the present disclosure; Fig. 10 is a cross-sectional view of a wastewater treatment system according to an embodiment of the present disclosure showing the positioning of bio-clcctrodcs in the primary and secondary chambers and in the leech field;

Fig. 1 1 is a graphical representation of the BOD; concentration in wastewater that has been treated with the embodiment of the aeration apparatus shown in Figures 1 and 2 compared to wastewater treated with a standard septic system over a 3.5 month period; and

Fig. 12 is a graphical representation of the BOD₅ concentration in wastewater that has been treated with the embodiment of the aeration apparatus shown in Figures 1 and 2 compared to wastewater treated with a standard septic system over a period of 1 month.

DETAILED DESCRIPTION

Generally, the present disclosure provides a wastewater treatment system comprising a fixed-film aeration apparatus and a fixed film aeration apparatus.

Wastewater treatment systems may be, without limitation, any one of a residential septic system, a municipal wastewater treatment facility, an industrial wastewater treatment facil ity, a commercial wastewater treatment facility, an agricultural wastewater facility, (e.g. a lagoon) or a municipal wastewater lagoon.

The wastewater treatment system has a tank having side walls, an inlet wall having an inlet, an outlet wall having an outlet, a floor and an upper surface. The tank has first and second baffles extending along the width of the tank from the side walls. The first baffle and the inlet wall together define a first anaerobic zone in the wastewater treatment system, the second baffle and the outlet wall together define a second anaerobic zone in the wastewater treatment system. A fixed-film aeration apparatus is positioned between the baffles and defines an aerobic zone. Wastewater is directed by the baffles along a treatment path, the treatment path extending from the inlet through the first anaerobic zone, the aerobic zone, and the second anaerobic zone, and to the outlet.

Also disclosed herein is a fixed-film aeration apparatus that is configured for insertion through a standard septic system opening and may be easily incorporated into any existing water treatment system containing treatment units. An air line is coupled to a weighted base and delivers oxygen from an external source through an air dispersal mechanism to a plurality of stacked fixed-film media supports, thereby promoting metabolic activity of a fixed-film.

The tank comprises a first baffle having an upper edge coupled to the first and second side walls at a position above the inlet and a lower edge coupled to the first and second side walls at a position between the bottom of the tank and the inlet. The first baffle extends between the first and second side walls along the entire width of the tank, and together with the inlet wall the first baffle defines a first anaerobic zone in the wastewater treatment system. The tank comprises a second baffle that has an anchored end anchored to the floor of the tank and a free end projecting into the tank. The free end of the second baffle is positioned between the bottom of the tank and the outlet at a position higher than the lower edge of the first baffle. The second baffle is coupled to the first and second side walls and extends between the first and second side walls along the entire width of the tank. Together with the outlet wall, the second baffle defines a second anaerobic zone in the wastewater treatment system.

A fixed-film aeration apparatus is coupled to the first and second baffles, and is raised from the floor at a position above a level of accumulation of bio-solids in the tank. The fixed-film aeration apparatus comprises at least one fixed-film media support, and a base for supporting the at least one fixed-film media support. The fixed- film aeration apparatus further comprises an air line having an internal aeration connector, and an external oxygen source connector for coupl ing to an external oxygen source and an air dispersal mechanism coupled to the internal aeration connector. The air dispersal mechanism delivers oxygen to the at least one fixed-film media support. The fixed-film aeration apparatus defines an aerobic zone in the wastewater treatment system. The first and second baffles direct a flow of wastewater along a treatment path, the treatment path extending from the inlet through the first anaerobic zone, the aerobic zone, the second anaerobic zone and to the outlet. The upper edge of the first baffle may be anchored to the upper surface of the tank at a position closer to the inlet wall than the outlet wall. The base of the fixed-film aeration apparatus may comprise a tray for supporting the air dispersal mechanism. The tray may comprise raised side portions which engage with a bottom surface of the at least one fixed-film media support to restrict bio-solids from clogging the air dispersal mechanism. The air dispersal mechanism may comprise at least one air stone.

The wastewater treatment may further comprise at least one bio-clcctrochcmical sensor for detecting the presence of wastewater constituents in the wastewater. The detected constituents may comprise toxic chemicals. The at least one bio-electrochemical sensor may be positioned in the first or second anaerobic chamber, or outside the tank. The wastewater treatment system may be in fluid communication with a leech field and the at least one bio-electrochemical sensor may be positioned in the leech field. The wastewater treatment system may comprise an oxygen pump positioned externally to the tank and revcrsibly coupled to the oxygen source connector, for providing oxygen to the air line.

The wastewater treatment system may comprise an effluent filter, the effluent filter comprising a filter inlet for receiving wastewater to be filtered and a first chamber in fluid communication with the filter inlet. The first chamber comprises a porous material for filtering solid material from the wastewater and at least one bio-electrochemical sensor. The effluent filter comprises a filter outlet, in fluid communication with the first chamber, the filter outlet for discharging filtered wastewater from the filter. The porous material may comprise a conductive material for supporting the growth of exoelcctrogcnic bacteria. The first chamber may further comprise a plurality of electrode pairs coupled to the porous material, each electrode pair comprising an anode and a cathode, wherein the

exoelcctrogcnic bacteria are in proximity to the anode and release electrons to the anode. The released electrons flow from the anode to the cathode. A terminal electron acceptor may be electrically coupled to the cathode and receives the electrons from the cathode thereby generating an electrical output. A resistor may be electrically coupled to the terminal electron acceptor, and the output may be measured across the resistor using a data acquisition system. The electrical output of the resistor is indicative of a metabolic activity of the exoelcctrogcnic bacteria. The effluent filter may comprise a second chamber in fluid communication with the first chamber and the filter outlet, the second chamber housing an adsorptivc material for clarifying the filtered wastewater. The adsorptivc material may be activated carbon or bio-char granules, iron filings, zeolite, or ceramic.

Also disclosed is a fixed-film aeration apparatus configured for insertion through a standard septic system opening. The fixed-film aeration apparatus comprises a base comprising a weighted portion, the weighted portion being configured to stabilize the apparatus in an unanchorcd operating position during and after insertion. The apparatus further comprises a support member coupled to the base and an air line coupled to the base for delivering oxygen to a plurality of fixed-film media supports. The air line has an external oxygen source connector and an internal aeration connector, and an air dispersal mechanism is coupled to the internal aeration connector for delivering oxygen to the fixed- film media supports and promote the metabolic activity of a fixed-fil m on the fixed-film media supports. The plural ity of fixed-film media supports arc vertically stacked on the base and supported by the support member.

The fixed-film aeration apparatus may further comprise at least one leg connected to the base, the leg for raising the plurality of fixed-film media supports above a level of bio-sludge accumulation in a septic tank. The at least one leg may be collapsibly connected to the base allowing the at least one leg to move between a first, retracted position, for facilitating the insertion of the apparatus into a septic system, and a second operating position for supporting the apparatus. The at least one leg may be weighted or the weighted portion of the base may be a weighted ballast tray.

Each of the plurality of fixed-film media supports may comprise a substantially central passageway for receiving the air line and wherein the air line supports each of the plurality of fixed-film media supports in a position to receive oxygen from the air dispersal mechanism. The air dispersal mechanism may comprise at least one air stone.

The base may comprise a tray for supporting the air dispersal mechanism, the tray having raised sides which engage with a bottom surface of a lowermost fixed-film media support of the plurality of fixed-film media supports for restricting bio solids from clogging the air dispersal mechanism. The support member may be integral with the air line. The plurality of fixed-film media supports may be movable between a collapsed insertion position for insertion of the fixed-film media support into a small opening and an expanded, operating position wherein the fixed-film media support is fully expanded.

Also disclosed is a method of controlling a wastewater treatment system, the method comprising: generating a potcntiostatic sweep across a bio-clectrochcmical sensor; measuring a current response of the bio-clectrochcmical sensor in response to the potcntiostatic sweep and comparing the measured current response to a threshold. In response to a determination that the measured current response is below the threshold, adjusting a wastewater treatment system operation parameter to increase the current response. The parameter may comprise an oxygen concentration in the wastewater treatment system.

Also disclosed is a bio-elcctrochemical sensor for use in a wastewater treatment system. The bio-clectrical sensor comprises a support comprising a bio support material for supporting the growth of cxoclectro genie bacteria, and at least one electrode pair connected to the support. The at least one electrode pair comprise an anode and a cathode and the exoelectrogenic bacteria arc in proximity to the anode. The exoelectrogenic bacteria release electrons to the anode, which flow from the anode to the cathode. A terminal electron acceptor is electrically coupled to the cathode and receives the electrons from the cathode, generating an electrical output. A resistor is electrically coupled to the terminal electron acceptor, and the output is measured across the resistor using a data acquisition system. The output of the bio-elcctrochemical sensor is indicative of a metabolic activity of the exoelectrogenic bacteria.

Also disclosed is an effluent filter for a wastewater system comprising a filter comprising a porous material, the filter for filtering solid material from the wastewater; and a bio-clectrochcmical sensor for sensing changes in conditions in the wastewater treatment system. The porous material of the effluent filter may comprise a conductive material, wherein the bio-electrochemical sensor is integral with the filter.

Disclosed herein is the use of a bio-clectrochcmical sensor for detecting nutrient over-loading in a leech field associated with a wastewater treatment system or for detecting changed in hydraulic loading in a leech field associated with a wastewater treatment system. Also disclosed is a use of a bio-elcctrochemical sensor for detecting the presence of toxic chemicals in a wastewater treatment system. As used herein, the term "air" is meant to include any form of oxygen, ozone or combination thereof.

As used herein, the term "fixed-film" is used interchangeably with the term "fixed biofilm" and refers to a collection of microorganisms coupled together that grow on a fixed- film support. Bacteria used in fixed- films for the treatment of wastewater are known to a person of skill in the art, and may be found, for example in US Patent Application Publication No. 2013/0193068, which is incorporated by reference herein. Examples of the most frequently found prokaryotcs in biological wastewater treatment systems belong to the classes Alpha-, Beta-, and Gamma-proteobacteria, Bacteroides and Actinobacteria. This would include members of the genera Pseiidomonas, A!ca/igenes, Acinetobacter, Bacillus, Clostridia, Escherichia, Comamonas. and Aeromonas. The microorganisms populating the fixed-film may be adapted for growth in both aerobic and anaerobic environments, thereby allowing for the treatment of total carbon, nitrogen and phosphate concentrations from the wastewater The populations of microorganisms may be optimized to allow for successful nitrification and de-nitrification of the wastewater as required by specific wastewater compositions.

The term "Exoelectrogenic" bacteria is meant to include any bacteria that has the ability to transfer electrons to electrodes or to accept electrons from electrodes. Examples of bacteria identified with "exoelectrogenic" capabilities include members of the genera Pseiidomonas, Shewane!la, Geobacler, Paracoccus, Rhodopseudomonas, and Escherichia.

As used herein, the term "fixed-film media support" is used interchangeably with "media support" and refers to a support upon which one or more bacteria or

microorganism partially adhere or grow allowing for the growth and/or development of a fixed-film. The media support may comprise a plastic mesh material or polymeric material, including but not limited to, high density polyethylene (HDPE), poly-vinyl chloride (PVC), polydimethylsiloxane (PDMS), silicone, polyvinylidene fluoride (PVDF), polytetratluoroethylene (PTFE), poly-lactic acid (PLA), or nylon.

Other materials such as metals and natural materials (e.g., cotton) may be used to fonn the media support. For example, a media support may include a plurality of porous ceramic rocks. The rocks may be constrained to a mechanism to build a colony, with respect to each other, such that a plurality of passages are defined by the rocks. The media support may be chemically treated with an acid or base solution or with an organic compound, for example, acetone, to increase or decrease the hydrophobic! ty and/or to improve microbial attachment to the media support.

The media support may have additional fibers attached so as to increase the specific surface area of the media support. These fibers can be the same as the media support or can comprise different materials including but not limited to carbon, various plastics, natural fibers, ccllulosic fibers, metallic fibers. The fibrous material can be adhered to the media support using methods that include but arc not limited to cpoxics, solvents, glues or thermo-chemical bonding agents.

The media support may be combined with a material to increase the conductivity of the media. Exemplary conductive materials include, but arc not limited to, platinum, titanium, iron, stainless steel or carbon. The conductive material can be embedded in the media support or adhered to the surface of the substrate and may or may not be used as an electrode. The conductive material can be adhered to the media support using methods that include but are not limited to cpoxics, solvents, glues or thermo-chemical bonding agents. Increasing the conductivity of the media support increases the ability of the microbes to communicate and exchange electrons. This can be beneficial for enhanced biofilm formation as it can allow different populations to rapidly share reducing equivalents of differing energetic potential.

In another embodiment the media support may be combined with carbon based materials including biochar, activated carbon, or graphene. The carbon can be embedded in the media support or adhered to the surface of the media support. The carbon can be in either granular form, wherein the granule radius can range from a maximum of 2cm to the size of a single molecule. In the case of a single carbon molecule this may be deposited in a single layer typically referred to as a graphene layer or up to 10 cm thick, and deposited intermittently or in an even layer over the media. The carbon material may take the form of an aerogel. A carbon based aerogel is composed of particles with sizes in the nanometer range, covalcntly bonded together. Depending on the density the carbon, the aerogel may be electrically conductive and may or may not be used as an electrode.

The carbon can be adhered to the media support using methods that include but arc not limited to cpoxics, solvents, glues or thermo-chemical bonding agents. In another embodiment the media support is coated in polymer material chosen for the abil ity to trap, or treat specific contaminants including but not limited to endocrine disrupting compounds and volatile organic compounds. In one embodiment the media support is a polymer and the surface of the polymer may be chemically treated to imprint the molecular structure of a particular contaminant. The polymer may then be used to trap the same contaminant in a wastewater stream.

The fixed-film media support can be any shape. For example, the fixed-film media support may be planar, substantially cylindrical, substantially conical, substantially spherical, substantially rectangular, substantially square, substantially oval shaped, and/or irregularly shaped.

Embodiments of the fixed film aeration apparatus will now be described with reference to the figures. Figure 1 is an exploded view of an embodiment of a fixed-film aeration apparatus shown generally as 2. The apparatus has a base shown generally as 4 and an air dispersal mechanism which can include air stones. The base includes a tray 6 which supports a plurality of air diffusing air stones 8. In this embodiment there are four air stones, but any number of air stones may be used. In addition, any means of providing oxygen to the fixed-film media support is contemplated. The tray 6 is connected to base 4 and is supported by legs 10. A support member is coupled to the base. In Figure 1 , the support member is integral with air line 12,

Air is delivered from the external air source to the air stones 8 via an air line 12 which has an external oxygen source connector (not shown) for connecting to the external oxygen or air source (not shown). The external air source may be any suitable source that provides air, oxygen, ozone or any combination thereof such as an air pump, or any suitable source of compressed or pressurized air. The air line 12 passes through a central opening 14 in the tray 6 and connects to an air dispersal mechanism via air aeration connector 16. The air dispersal mechanism is meant to include any means of dispersing air from the air line 12 to the fixed-film media supports. The air dispersal mechanism may comprise a series of secondary air lines and connectors which couple with the air line 12 and direct air to the fixed-film media support. The air dispersal mechanism may include an air diffuser, such as an air stone for diffusing oxygen. A person of skill in the art would understand that any appropriate fine or coarse bubble diffuser may be used. For example, the air diffuser may comprise a rubber membrane or a ceramic clement. In the example shown in Figure 1 , the aeration connector 16 comprises a t-spl it connector which directs air in two secondary distribution lines 20, 22 towards the air stones 8. Once split, the two secondary distribution lines 20, 22 curve and travel upwards towards the four air stones 8 where two further T split connectors (not shown) create a total of four air distribution lines (not shown), each directed to an air stone. This configuration allows each air stone 8 to receive oxygen or air from the air line 12. Diffused oxygen from the air stones passes from the air stones 8 into the fixed-film media supports. Once the air line 12 is coupled to the aeration connector 16 the air line 12 cannot return through the opening 14 in the tray 6. This enables the airline 12 to be used to insert and remove the apparatus from the tank as the apparatus is supported by the air line.

Fixed-film media supports 24, 26, 28 arc vertically stacked on the base above the air stones 8 and each have a central opening sized to receive the air line 12. The air line 12 passes through the central opening of each of the fixed-film media supports 24, 26, 28 and serves to support and vertically integrate the fixed-fil m media supports. Diffused oxygen rises from the air stones 8 and passes through the fixed film media supports 24, 26, 28, promoting the growth of a fixed-film on the fixed-film media support.

The positioning of the fixed-film supports above the air stones results in the generation of a dispersal zone wherein the dissolved oxygen concentration is at a minimum of approximately 0.5 mg/L and under standard conditions below the threshold of 7mg/L. This dissolved oxygen concentration is ideal for the growth of aerobic bacteria that form the fixed-film. The tray 6 and the media supports 24, 26, 28 arc positioned so as to maximize the Standard Oxygen Transfer Efficiency (SOTE) for the wastewater treatment system. The SOTE can be defined as the % oxygen delivered to the wastewater treatment system. By stacking the fixed-film media supports, the surface area can be maximized, allowing for increased attachment and growth of bacteria and increased biofilm development and metabol ic activity, thereby increasing the rate of wastewater contaminant (Biological Oxygen Demand, Chemical Oxygen Demand, Total suspended Solids) oxidation. In an example embodiment, the fixed film media support is porous both vertically and laterally, resulting in n on -oxygen a ted wastewater being drawn into the fixed film media support. Drawing the contaminated wastewater from the surrounding water, the apparatus generates simultaneous anaerobic and aerobic zones in a single tank of a wastewater treatment system allowing for enhanced nutrient cycling and improved treatment of the wastewater without having to provide separate tanks for anaerobic and aerobic conditions. Retention ring 30 is positioned around the air line and is sized to engage the air line 12 so as to retain the fixed-film media supports 24, 26, 28 in position above the air stones or air dispersal mechanism.

When the apparatus 2 is positioned in a wastewater treatment system, the legs 10 raise the tray 6 and the air dispersal mechanism above the level in a tank where bio-solid materials would accumulate. A typical bio-solids layer is from I - 10 inches in thickness from the bottom of the tank depending on the nutrient loading and the frequency of pumping of the tank. The legs can be designed to be any height between 1 and 24 inches when in an extended position. For example, the legs may be 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, 14 , 15, 16, 17, 1 8, 19, 20, 21 , 22 23 or 24 inches. In an embodiment the legs arc designed to be 8 inches in height and arc designed to handle bio-solids that build up around the apparatus. By "handling" bio-solids it is meant that the bio-solids are allowed to settle to the bottom of the tank and the oxygen may be del ivered to the contaminants solubilizcd in the wastewater stream. This is advantageous compared to known aeration devices that are designed to aerate the entire tank, as these aerations devices result in mixing of bio-solids in the wastewater stream.

The legs 10 arc weighted so as to allow the apparatus 2 to maintain an upright position when the apparatus is installed in a wastewater treatment system and when the system is at least partially filled with wastewater. The weighted legs allow the apparatus to be inserted into a system when the system is full of water. This is advantageous as the system does not have to be drained in order for the apparatus to be installed, thereby saving time, effort and cost. Additionally, the weighted legs contribute to the ability of the apparatus 2 to be inserted via a standard septic system opening and to operate in an unanchorcd position, in contrast to known approaches in which a similar apparatus must be anchored to the base of the system when the system is drained.

The tray 6 is designed with an outer raised edge 32 that has a height greater than the height of the air stones 8, The raised edge 32 is connected to a substantially horizontal edge 34 that engages the undcrsurfacc of the lowermost fixed-film media clement 24 thereby forming a seal between the tray 6 and the fixed film media element 24 and inhibiting the accumulation of bio-solids on the air-stoncs 8.

The fixed-film aeration apparatus 2 may be inserted through a standard opening in a septic tank by gradually lowering the apparatus by feeding the air line 12 into the tank, In an embodiment, the height of the apparatus may be adjusted, for instance to raise the apparatus above the level where bio-solid materials accumulate in the tank by securing the air line and suspending the apparatus at the desired height. In the case where the fixed- film aeration apparatus is to be removed from the septic system, for instance for cleaning, repair or replacement, the apparatus may be hoisted from the septic system by retrieving the air line. Thus, the air line 12 allows the apparatus to be hoisted in or out of a septic tank and supports the weight of the apparatus during the insertion and removal of the apparatus. The air line 12 may be any required length, allowing the apparatus to be introduced into any portion of the wastewater treatment system.

The fixed-film aeration apparatus may include any number of individual fixed - film media supports. In some instances, one or more media supports arc removably coupled to the aeration apparatus to allow easy removal for cleaning or replacement of the fixed film media support.

In an alternative embodiment the legs 10 may be pivotally connected to the base so that they can move from an operational position to a retracted position which allows the legs to pass through a narrow opening.

Figure 2 is a cross-sectional view of the embodiment of the fixed-film aeration device shown in Figure 1 which more clearly shows the connection between the air l ine 12 and the air stones 8. As described above, air line 12 ends in a aeration connector 16 which directs air in two secondary distribution lines 20, 22 towards the air stones 8. In this embodiment the support member is a support tube 32 and is connected to the base and houses air line 12. Similarly to the air line 12, support tube 32 passes through an opening 33 in the central portion 14 of the tray 6. Support tube 32 functions to protect the air line 12 and to support the fixed film media supports 24, 26, 28 in a vertical orientation above the air-stones 8 and tray 6. In some embodiments, the a connection may be provided at the top of the central support tube to ease assembly/production - performs in exactly the same way though.

The positioning of the air stones 8 on the tray 6 is clearly seen in Figure 3. In certain embodiments, the fixed-film aeration apparatus may be assembled in the septic tank. The base 2 comprising the legs 10, the tray 6 and the air stones 8, (as shown in

Figure 3) supported by the air line 12 and, optionally, the support tube 32, may be lowered into the tank until the base is in the desired position. The base may be supported by the legs 10 or may be suspended by anchoring the air line 12 at the desired position. Fixed- film media supports may then be inserted onto the air line 12 by passing the air line through the central opening in the fixed- film media supports and allowing them to fall into position on the tray 6. As in other embodiments, this allows the stacking of a plurality of fixed-film media supports in a vertical orientation, maximizing the ability of oxygen to be diffused to the fixed-film media supports and consumed by fixed film microbial populations.

In some embodiments, the apparatus may comprise a plurality of interconnected support members, each interconnected support member supporting at least one fixed-film media support. The at least one fixed film media support may be a vertical stack of fixed- film media supports. When more than one support member is present, the air dispersal mechanism may comprise additional splitters or lines and additional air stones to direct and diffuse oxygen to the fixed-film media supports. In this embodiment, the central support member may comprise a plural ity of articulated legs connected to a plurality of support members that fold to be in an insertion position, for insertion into a septic tank, and expand to an operating position when positioned in the tank. Each of the plurality of support members comprises a base to allow stacking of at least one fixed-film media supports. When more than one fixed-film media support is stacked, the support members retain the fixed-film media supports in a substantially vertical position, A central support member is connected to the base and houses an air line. The air line may connect to an air dispersal mechanism that delivers air to each of the stacks of the fixed-film media supports. Each base may comprise an air stone to allow the diffusion of air from the air line to the vertical stack of fixed-film media supports.

Figure 4 shows an embodiment of the fixed-film aeration apparatus in which a the tray 6 for supporting air stones 8 comprises a ballast tray 34. The ballast tray 34 is weighted in order to provide stability to the apparatus during and after insertion of the apparatus into a wastewater treatment system. In this embodiment, the tray 6 and the legs 10 arc molded as a single piece.

In an embodiment the support member comprises a net that can be inserted through a standard sized opening of a septic wastewater treatment system. Sections of fixed-film media support, sized to fit through the opening of the tank arc subsequently added to the net. Any number of sections of fixed-film media support may be added and is restricted only by the size of the net. The fixed-film media supports may be stacked vertically in the net. An air line that is conncctablc to an air source is fed through an opening in a septic tank system and is incorporated into a base portion of the net. An air dispersal mechanism such as an air stone may be incorporated into the base portion of the net and connected to the air line to diffuse oxygen to the fixed-film media supports. The air dispersal mechanism may be positioned below the sections of fixed-film media support. The base may be weighted to secure the apparatus in a specific location. To add structural support and to stabilize the system, the base of the net material can be integrated with a structural footing or legs that may be weighted and stabilize the apparatus in the wastewater treatment system during insertion and operation. In an example embodiment, the top of the net includes a hoist cable or rope that, if required, would be used to pull the apparatus back out of the wastewater treatment system. In an embodiment, the hoist cable is incorporated with the air line using ties or a surrounding tube material to form an integrated tubular support member. In another embodiment, the air line may itself be used to raise and lower the apparatus. The hoist cable, air line or legs can be used to elevate the apparatus above any accumulating bio-solid material.

In the embodiment shown generally in Figure 5, the fixed-film media support is collapsibly connected to the support member, so that the apparatus may be collapsed or folded into an insertion position (shown generally as 37), allowing the fixed-film media support to be inserted into wastewater treatment systems with small openings. One example implementation of this arrangement is in the retrofitting of a single home septic system having an opening designed for sludge removal as small as 6" in diameter. In this embodiment, the fixed-film media support is a flexible mesh material, or a polymer netting material that could be easily expanded into an operating position wherein the fixed-film media support is fully expanded. Connectors join the fixed-film media support to a moveable hollow column comprising an internal shaft. When the apparatus is positioned in the wastewater treatment system, the moveable hollow column is moved to an operating position, wherein the fixed-film media support is expanded to its final size. When it is required to remove the apparatus from the wastewater treatment system, the moveable hollow column is placed in the up position, resulting in a compression of the media support and aeration volume allowing for removal or insertion. In another embodiment the fixed-film elements may be divided into smaller units and assembled with a base and support member in a septic tank. In this embodiment, the support member may comprise netting material and may be made of flexible hooped sections. This structure may be flexed to fit into the tank and springs and open to create a defined structure and volume. The smaller sections of media support arc subsequently added into the internalized structure. Air lines and/or air stones may be incorporated into the base of the netting material allowing for oxygen diffusion throughout the fixed-film media supports. Weight and leg features may be added to the structure to add structural integrity, to assist in insertion of the apparatus or to elevate the apparatus above any accumulating bio-solid materials.

Figure 6 shows a fixed-film aeration apparatus 2 according to an embodiment shown in Figure 1 positioned within a standard septic tank 40. The wastewater flows from the primary chamber 44 into a secondary chamber 48 and passes through an effluent filter 50 before passing through outlet 52 to a leech field, a river bed or other suitable wastewater dispersal means. The primary and secondary chambers 44, 48 arc separated by baffles 51 , 54 which are connected to the side walls (not shown) of the septic tank. The wastewater treatment system is designed so that each of the chambers 44, 48 can be accessed through ports 56, 58 having covers 60, 62, The covers 60, 62 comprise openings 64 to allow passage of the air line 12 and a support member housing the air line, if present. The air line 12 connects at an external end portion via an external oxygen source connector to an oxygen pump 62.

The fixed-film aeration apparatus 2 is positioned in the primary chamber 44 of the system and may be inserted and removed through the port 56 by lifting or lowering the air line 12. The fixed-film aeration apparatus 2 comprises legs 10 that raise the apparatus above the sludge layer 46, allowing the settling of biological material in the tank, while continuing to promote the separation of sol ids and liquids (typically known as clarification). The fixed-film aeration apparatus allows for the generation of aerobic and anaerobic zones in the same chamber which results in a significant reduction of the organic content of the septic system effluent (BOD₅ and TSS). As seen in described later in Example 1, septic systems with a fixed-film aeration device positioned therein show enhanced performance when compared to standard septic technology. In the embodiment shown in Figure 6, two chambers are shown and the apparatus is positioned in the primary chamber. In another embodiment, the fixed-Film aeration apparatus may be positioned in cither the primary or the secondary chamber or any additional chamber if the wastewater treatment system comprises additional chambers.

Figure 7 is a diagram depicting an embodiment of a wastewater treatment system, shown generally as 65 in which a fixed-film aeration apparatus 2 is integrated into the system. Septic tank 68 has opposing first and second side walls (not shown), an inlet wall 70 an outlet wall 72 connecting a floor 74 and an upper surface 76. Wastewater enters through an inlet 42 positioned on the inlet wall 70 and enters a first anaerobic zone 78 where bio-solids accumulate in a sludge layer 46. A scum layer (not shown) develops above the water level.

The fixed film aeration apparatus 2 is coupled to first 80 and second 82 baffles which support the apparatus 2 in a raised or suspended position above the bottom surface 74 of the tank at a position that is above a level of accumulation of bio-solids in the tank. The first baffle 80 has an upper edge 84 coupled to the first and second side walls at a position above the inlet 42 and a lower edge 86 coupled to the first and second side walls at a height that is between the floor of the tank 74 and the inlet 42. The first baffle 80 is coupled to the first and second side walls and extends between the first and second side walls across the entire width of the tank. In figure 7, the first baffle is anchored to the upper surface 76 of the tank along the width of the tank. However, the first baffle docs not need to be anchored to the upper surface and the upper edge may be coupled to the side walls at any position above the inlet so that a flow of wastewater is directed from the inlet downwards and under the lower edge of the first baffle. In an embodiment, the upper edge 84 of the first baffle 80 extends below the inlet 42 and the lower edge 86 extends below the inlet 42 and above the floor 74.

The fixed fi lm aeration apparatus 2 has an air line 12 connected at one end to an external oxygen pump 62 and at the other end to an air dispersal mechanism (not shown) that provides air to air stones 8. Oxygen from the air line 12 is diffused within the fixed- film media support 24 to promote the growth of aerobic bacteria in the fixed film and to further remove organic contaminants from the wastewater. The fixed-film aeration apparatus defines an oxygenated (or aerobic) zone within the wastewater treatment system. The second baffle 82 has an anchored end 88 connected to the floor 74 of the 76 and a free end 90 that projects upwardly from the floor 74 into the tank in a substantially perpendicular direction to a position or height between the floor the tank and the outlet 52 and. The free end 90 of the second baffle is positioned higher than the lower edge 86 of the first baffle. The free end 90 of the second baffle is positioned so that water exiting the fixed film aeration apparatus can pass over the free end 90 of the second baffle and enter a second anaerobic zone 92. Second baffle 82 is coupled to the first and second side walls and extends the between the first and second side walls the entire width of the tank.

The first baffle 70 is suspended above the sludge layer 46, directing the flow wastewater under the fixed film aeration apparatus 2. In this embodiment, the fixed-film aeration apparatus is positioned so that the bottom surface 78 of the apparatus is 12-24 inches from the bottom of the tank and well above the sludge layer 46.

The first baffle 80 and the inlet wall 70 define the first anaerobic zone. The second baffle 82 and the outlet wall 72 define a second anaerobic zone. The first and second baffles direct the flow of wastewater through the system. The positioning of the baffles forces the liquid to flow along a treatment path in a serpentine manner through different zones of wastewater treatment. Wastewater enters through inlet 42 into the first anaerobic zone 78 allowing for the decomposition of organ ic matter by anaerobic bacteria.

Wastewater in the first anaerobic zone 78 is forced to move downward and is subsequently required to move vertically through the aerobic zone defined by the fixed fi lm aeration apparatus 2. The wastewater exiting the fixed-film aeration apparatus 2 then passes over the second baffle 82 and is forced to move downward through the second anaerobic zone 92 for further purification. Wastewater may be passed through effluent filter 50, before exiting the secondary chamber via outlet 52. The purpose of the serpentine pathway is to promote settling of bio-solid material and enhance treatment of soluble wastewater contaminants. The resultant wastewater stream thereby has significantly reduced soluble and insoluble contaminants exiting the wastewater treatment system. The wastewater stream undergoes the simultaneous functions of clarification and aeration while passing through the wastewater treatment system. By alternating anaerobic and aerobic zones of treatment the treatment of carbon and nitrogen based contaminants may be increased.

In another embodiment, the wastewater treatment system may include at least one bio-electrochemical sensor, as will be described in further detail herein. Bio- electrochemical sensors (or bioclcctrical systems, BES) rely on bacteria that normally use insoluble metal deposits as electron sinks during anaerobic consumption of reduced substrates. By substituting an electrode 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 sensors has been identified to vary according to wide ranging environmental alterations that include, water composition and chemistry (nutrient content, pH, redox state), temperature and recirculation and sheer forces. This ability enables these sensors to function as direct biological sensors for parameters that affect their performance.

Once transferred to the anode, the electrons flow to the cathode where they participate in the reduction of the terminal electron acceptor. Bio-clcctrochcmical sensor performance can vary according to a number of chemical parameters input to the device including electron donor concentration, temperature, pH, salinity, and redox state. While perturbations to voltage or current output may have negative impacts in some applications, this property also allows bio-electrochemical sensors to function as biological sensors for parameters that affect their performance.

The exoelectrogenic biofilm that develops on the anode of different bio- electrochemical sensors reflects the different processes required to convert specific substrates into electrical current. Community profiles generated for a wide range of substrates indicate a hierarchical community structure with certain microbes hydrolyzing and fcmicnting complex organics, and others using these by-products for current generation. The wealth of community profiling data indicates microbes with high 16S rRNA sequence similarity to microbes of the genera Geobacter, Shewcmella,

Pseiidomonas, Paracoccus, Escherichia, Rhodopseiidamonas represent a large proportion of most exoelectrogenic biofi lms. Complex carbohydrates result in communities dominated by bacteria capable of fermentation, such as Clostridium (cellulose) and Rhodopseudomonas (glucose). Characterization of microbial populations fed a variety of these fermentation products indicates the complex interactions between microbes competing for direct clectrogencsis and those looking to ferment substrates. The syn trophic interactions that are at play in this complex ecosystem allow for the rapid and complete conversion of complex wastewater streams into valuable by-products. An embodiment of a bio-clectrochemical sensor to be used in a wastewater treatment system is shown in Figure 8. In the example embodiment shown in Figure 8, each bio-clcctrochcmical sensor contains six electrode pairs 94, with each electrode pair having an anode and a cathode. The electrode pairs arc separated by a porous bio-support material 96 such as granular activated carbon or biochar or any material that supports the growth of bacteria. The bio-clcctrochcmical sensor may have a casing enclosing the sensor and has a wastewater inlet 98 for receiving influent and a wastewater outlet 99 for receiving effluent. Exoclcctrogcnic bacteria from the wastewater attach to the porous bio- support material 96 and grow in proximity to the anode, releasing electrons to the anode. The released electrons flow from the anode to the cathode of each pair of electrodes. Anode electrodes consist of corrosion resistant mesh {such as titanium or stainless steel 316) with the cathode electrode consisting of stainless steel 316 mesh. Voltage (E) is measured across an external 1 Ω resistor using a multimeter data acquisition system (Keithley 2700; Keithley, United States) to calculate the current ( I = E/R) and power (P = I E), where R is external resistance.

The electrode pairs 94 are connected to one or more power sources 100 that are used to maintain a set voltage difference to each electrode pair 94 under a steady state mode of operation. Wastewater influent enters into the filter via inlet 98 and passes through or along each electrode pair. The wastewater inlet or outlet may be adjusted to restrict the flow of wastewater through the sensor. Alternatively the flow can be determined by connecting a flow meter in-line with the sensor.

Polarization and power density curve values are attained for bio-clcctrochcmical sensors producing a maximum stable voltage by generating a potentiostatic sweep - changing the external voltage across each electrode pair using Potcntiostat 101. In this embodiment, the sensor platform (or support) is 20 cm in length and 5 cm in diameter. However, a person of skill in the art would understand that other suitably sized bio- electrochemical sensors may be designed, with more or fewer electrode pairs. A person of skill in the art would also understand that the electrodes may be orientated vertically within the sensor and the wastewater would move through the bio-clcctrochcmical sensor perpendicularly to the electrodes.

Data analysis software developed using Matlab allows for real-time visualization of current output (A/m² electrode surface). Current and power densities were normalized to the anode projected surface area (Aan). Internal resistance (R_JN I ) was calculated from the slope of polarization curves. Coulombic efficiency (CE), defined as the percentage of electrons recovered as current in one batch cycle versus the total available electrons from the initial input substrate (e.g. 8 c-/mol acetate), was calculated as previously described (Lalaurette E, Thammannagowda S, Mohaghcghi A, Maness PC, Logan BE, 2009,

Hydrogen production from cellulose in a two-stage process combining fermentation and clcctrohydro genesis, Int J Hydrogen Energy 34:6201-6210).

These bio-clcctrochcmical sensors can be incorporated in a plurality of locations in the wastewater treatment system allowing for the characterization of microbial metabolic rate and viability throughout the system.

Figure 9 shows an embodiment of septic system effluent filter 50. The septic system effluent filter 50 has a first chamber 102 comprising a porous material, shown in Figure 9 as a series of porous sheets 104 which restrict the flow of insoluble organics out of the septic system, thereby removing suspended sol ids from the wastewater. Any form of porous material that removes suspended solids may be used in the filter. In addition, the porous material may support the growth of fixed film bacterial communities that oxidize soluble wastewater organics as it passes past the material, thereby reducing the transport of soluble organics. The porous sheets may be composed of polymer sheets, however, a person of skill in the art would understand that there are many materials that arc suitable for use in the filter. In this embodiment, wastewater flows from the first chamber 102 into a second chamber 106 which houses adsorptive material 108 used to further clarify the wastewater and remove further contaminants (e.g. phosphate, ammonia, BOD, contaminants of emerging concern (CECs). The adsorptive material in the second chamber may include sachets of activated carbon, bio-char granules, iron filings, zeolite, ceramic or any material that can act to filter or precipitate contaminants from a waste water stream. A coupl ing portion 109 allows the filter to be coupled to an outlet of a septic system.

In an embodiment the septic system effluent filter 50 comprises a bio- clcctrochcmical sensor, such as the bio-clcctrochcmical sensor shown in Figure 8. The bio-clcctrochcmical electrode pairs, forming the bio-clcctrochcmical sensor described in Figure 8 may be located in series in the porous sheets 104 of the effluent filter 50. In an embodiment, the electrodes are embedded into the porous sheets 104 and can be orientated in such a way (in parallel to the flow of wastewater) that they do not restrict the flow of wastewater through the filter.

In a further embodiment, the porous sheets 104 arc made from a conductive material, for example, stainless steel, and arc used to support the growth of bio- electrochemical microbial communities. Thus, the bio-electrochemical sensors can be integrated directly into the filter material i .e. by replacing the polymer filter with a conductive material. In such an embodiment, the porous material performs the dual function of sensing and filtering. The conductive material has the dual function of filtering suspended solid materials and allowing exoelectrogenic bacterial communities to convert soluble organics present in the waste stream into a bio-clectrochemical signal.

The passage of wastewater through the filter generates gradients in solution nutrients, including but not limited to volatile fatty acids (acetic acid, formic acid, lactic acid, butyric acid, propionate), Chemical Oxygen Demand, and Biological Oxygen Demand. This gradient is such that when potcntiomctric sweeps of the bio-electrodcs take place, differences in nutrient concentrations can become limiting at certain electrodes resulting in concentrations being quantified or estimated. Thus, the concentration gradient through the filter is represented by a differential bio-electrochemical response in the sequential anode-cathode pairs. This response can be used to control system aeration or can be used to alter system recirculation or flow rate through the system.

Figure 10 shows the positioning of bio-clectrochemical sensors 110, 1 12, 114,

116, 118, 120 in a wastewater treatment system having a fixed-film aeration apparatus 2. By integrating data produced directly from exoelectrogenic communities, full-scale control in wastewater treatment systems may be effected using in situ bio-clectrochemical sensors and/or a combination of bio-clectrochemical sensors and nutrient sensors. The bio-electrochcmical sensors allow for real-time communication between wastewater treatment biofilms and the operational control of the wastewater treatment system.

Examples of processes that bio-electrochemical sensors may be used to evaluate include estimating the metabolic activity of a fixed-film, measuring the presence of toxic compounds, characterizing BOD concentration. Power source 100 is coupled to the bio- electrochemical sensors 110, 112, 114, 116, 118, 120.

Bio-electrochcmical sensors may be incorporated in a plurality of locations in the system allowing for the characterization of microbial metabol ic rate and viability throughout the wastewater treatment system. For example, the electrodes may be placed in the primary chamber 44, or the secondary chamber 48, or both. In addition, bio- clcctrochcmical sensors may be placed in primarily anaerobic or aerobic zones. In addition or alternatively, the sensors may be located in the leech field 122, allowing for prediction of system failure. Bio-electrochemical response from microbial communities present in a leech field would be demonstrative of excessive nutrient load reaching the lccch-ficld and could be used as an early warning of system failure. Instances of failure in metabolic viability or metabolic activity could include instances where toxic chemicals (such as cleaning detergents) are present in the reactor, instances where temperature in the system fluctuates from mean operational temperatures, instances where heavy metals accumulate in the reactor, instances where the internal pH in the reactor fluctuated from mean operational parameters.

A bio-electrochemical sensor produces a constant current under constant conditions. However, when a toxic component impacts the anodic microbial community, the bacteria can be impacted resulting in a decrease in current densities generated by the community. The bio-electrochemical sensor can therefore be used as a sensor for toxic components in wastewater streams. Typically, when characterizing the electrochemical characteristics of an anode community cells are typically characterized by shifting the external resistance on the system and polarization curves are generated. Generally these polarization curves arc carried out by starting with a high external resistance and with gradual step- wise reductions. This is typically followed by increasing current densities through the system until additional losses in the system (incl. Ohmic, Mass transfer etc.) impact system performance. Recent studies using polarization data have successfully modelled the impact that toxic components have an effect on the electrochemical ly active bacteria in the cell (Stein, Hamelers, and Buisman, The effect of different control mechanisms on the sensitivity and recovery time of a microbial fuel cell based biosensor 2012, Sensors and Actuators). Butler Volmer Monod (BVM) models were used to describe the polarization curves of the BES under nontoxic and toxic conditions. It was possible to properly fit BVM models using linear regression techniques to the polarization curves and to distinguish between different types of kinetic inhibitions (Stein ct al. On-line detection of toxic components using microbial fuel cell-based biosensor, Journal of Process Control, 2012, 22, 1 755- 1 761 ). The switch between aerobic and anaerobic modes of operation can be controlled by bacterial metabolic response generated by bio-elcctrochcmical sensors powered by an external power source. In this case cxoclcctrogcnic biofilms grown on anode or cathode electrodes can be used to determine metabolic activity and microbial viability in the wastewater treatment system allowing for the control of system aeration. To estimate the metabolic activity of a fixed-film, the conversion of soluble organics present in the wastewater stream into electrical current is calculated and compared to that of a stable cxoclcctrogcnic anode community. Bench-scale calibration of stable bio-clcctrochcmical sensors in domestic wastewater in an optimized synthetic wastewater stream may be carried out with Coulombic efficiencies {% electrons transferred into electrical current) correlated to reductions in Chemical Oxygen Demand (COD) to determine a threshold level. The switch between modes of operation may be regulated in response to a determination that a measured current response is below the threshold. The response can be used to change a waste water treatment parameter to raise the response to the threshold value. In this example, the waste water treatment parameter is an oxygen concentration in the wastewater treatment system.

Combining this with estimated bacterial cell dimensions and calculated biofilm thickness, the predicted metabol ic flux through each bacterial cell can be calculated. Using optimized performance parameters and potentiostatic sweeps, an envelope for performance for the electrode surface will be generated and correlated with the current densities generated by consumption of volatile fatty acids (acetic acid, ethanol) and Chemical Oxygen Demand (COD). A bio-clectrochcmical sensor can then be integrated to a waste stream and used to estimate metabolic activity of an adjacent surface area by correlating current density to previously generated calibration curves. Alternatively the electrode pairs can be placed in the leech-field of a wastewater treatment system and used to predict the presence of soluble wastewater organics. The presence of soluble wastewater organics (BOD, COD) in the leech field would be an indication of system over-loading and could be used as an indication of system failure (as described above).

As wastewater flows through a bio-electrochemical sensor a COD and BOD gradient will develop. By combining this concentration gradient with a polarization characterization of each biofilm, the concentrations at the influent of the sensor can be accurately determined. The sensor is designed so that BOD concentrations becoming limiting in the sensor across at least one of the 5 electrode pairs - the polarization curve and associated drop in external resistance on the anode electrode will result in increased current densities and metabolic flux through each electrode pair. The bio-clcctrochcmical sensors disclosed herein arc ideal for process control as they allow for real-time monitoring where rapid feedback is essential .

The bio-clcctric response can be combined with information generated from additional sensors to include flow, temperature, conductivity, or dissolved oxygen to give the wastewater operator information relevant to the microbial metabolic activity and the water chemistry. For example, by combining data from a flow meter with the bio- electrochemical sensor response generated through a wastewater filter where BOD concentrations become limiting, the concentration of BOD in the wastewater stream may be extrapolated. By integrating the bio-electrochemical response with a thermocouple, the response can also be used to predict the impact of temperature changes on metabolic activity. By monitoring the bio-electrochemical response, the sensor can be used as a predictor of conditions that are unsuitable for microbial metabolic activity. This information can be used to automate the wastewater treatment process and control by turning pumps on or off, changing temperature, opening or closing valves or adding chemicals, for example.

hi an embodiment, the bio-electrochemical sensors may be adapted for the removal of nutrients, including but not l imited to nitrogen compounds, phosphate and endocrine disrupting compounds.

Example 1

A fixed-film aeration apparatus was designed in the general configuration shown in Figures 1 to 3, and was evaluated for septic system wastewater treatment. The apparatus used in the Example has the following dimensions: 36"(h) x 18" (1) x 18¹' (w). The base has a diameter of 1 8 inches.

Project Summary

The study was carried out to characterize the performance of a standard septic system incorporating a fixed-film aeration apparatus as described in Figure I in a system as shown in Figure 5. The study was carried out over a 2.5 month period and demonstrated BODs effluent concentrations significantly lower than those typically reported for standard septic system technology. System Install and Operation

The fixed-film aeration apparatus was operated and characterized over a 2.5 month period from August to October. The septic system consisted of a 5,700 L septic tank with a single internal baffle. The septic tank used was a two-component polyethylene tank, 4 ft deep with 20 inch openings at cither end (WEDCO WP-5700). The tank was fed 900 L of domestic wastewater per day, equating to the typical waste produced by an average household (3.3 persons, 273 L/pcrson/day)). Average values for septic tank effluent quality were taken from recent comprehensive studies, characterizing 200 standard septic systems (Charles et al., 2013) and guideline values provided by the US EPA (EPA, 1992). Wastewater samples from the influent and effluent of the system were taken every two weeks and characterized for pH, BOD₅ (mg/L), TSS (mg/L), TKN (mg/L), P0₄-(mg/L).

Table 1 outlines the Influent and effluent wastewater characteristics over a 3.5 month period for the tested system.

Table 1

Table 2 outlines the design guidelines and recorded average values previously recorded for standard septic systems.

Tabic 2

BODs: Figure 1 1 and Figure 12 show BOD₅ concentrations characterized for the septic system comprising the fixed-film aeration apparatus compared to a standard septic system technology. Figure 11 shows the influent BOD5 concentration over a 3.5 month period. There was significant variation in the influent BOD₅ concentrations (361 - 183 mg/L) recorded over the 3.5 month operational period for the system. BOD₅ data demonstrated steadily dropping concentrations in the effluent stream from a starting point of 253 mg/L to a lowest concentration of 46 mg/L.

In Figure 12, the data was compiled from the final month of pcrfonnancc. When averaged over the last month of operation (Oct 1 st - Oct 3 1 st) the BODj removal rate was calculated to be 78% with an average effluent concentration of 62 mg/ L. The most recent literature states that the average septic system effluent has a BOD₅ concentration of 224 mg/L, thereby containing 360% more when compared to a septic system comprising the fixed-film aeration apparatus (Figure 12). The recommended soil organic loading rates proposed by the US EPA for standard septic systems is 150 mg/L BOD₅ which is 240% higher when compared to a septic system comprising the fixed-film aeration apparatus.

TSS : An average concentration of 64 mg/L was recorded throughout the study, translating to a 78% removal rate. No noticeable patterns emerged throughout the study for changing TSS concentrations in the system effluent with a range of (48— 100 mg/L).

TKN-NI: No noticeable pattern emerged for the effluent stream with concentrations ranging from 40.2 - 47.7 mg/L. The average effluent concentration (44.3 mg/L) was shown to be 15% lower than the influent (52.0 mg/L).

OPO₄-: Effluent phosphate concentrations in the system effluent were relatively stable ranging from 4.10 to 5.42 mg/L. Average total phosphorous has been recorded at 6.0 ± 1.3 mg/L.

pH: The pH for the effluent stream (6.63) was consistently lower than that of the influent (7.41 ), indicating anaerobic, acidogenic processes occurring in the reactor.

This study was carried out over a 3.5 month period and demonstrated BOD₃ effluent concentrations significantly lower than those typically reported for standard septic system technology, with the final month of operation demonstrating 78% removal and an average effluent of 62 mg/L. The average TSS concentration of 64 mg/L recorded through-out the study, translating to a 78% removal rate. By significantly reducing the organic content of the septic system effluent ( BOD5 and TSS) the septic system comprising the fixed-film aeration apparatus shows enhanced performance with respect to standard septic technology and could be used to increase the efficiency of undcrpcrforming or failing systems.

In the preceding description, for purposes of explanation, numerous details arc set forth in order to provide a thorough understanding of the embodiments. However, it will be apparent to one skilled in the art that these specific details arc not required. The above- described embodiments arc intended to be examples only. Alterations, modifications and variations can be effected to the particular embodiments by those of skill in the art without departing from the scope, which is defined solely by the claims appended hereto.

All of the references cited herein arc herein incorporated by reference.

Claims

WHAT IS CLAIMED IS:

1. A wastewater treatment system comprising:

a tank having opposing first and second side walls, an inlet wall defining an inlet for receiving wastewater, an outlet wall defining an outlet for discharging treated wastewater, a floor and an upper surface, the first and second side walls and the inlet wall and the outlet wall connecting the floor and the upper surface, the upper surface defining at least one opening, the tank comprising:

a first baffle having an upper edge extending above the inlet and a lower edge extending below the inlet and above the floor, the first baffle extending between the first and second side walls along the entire width of the tank, wherein the first baffle and the inlet wall together define a first anaerobic zone in the wastewater treatment system;

a second baffle having an anchored end anchored to the floor of the tank and a free end projecting into the tank, the free end being positioned at a position higher than the lower edge of the first baffle, the second baffle being coupled to the first and second side walls and extending between the first and second side walls along the entire width of the tank and wherein the second baffle and the outlet wall together define a second anaerobic zone in the wastewater treatment system;

a fixed-film aeration apparatus coupled to the first and second baffles, and raised from the floor at a position above a level of accumulation of bio-solids in the tank, the fixed-film aeration apparatus comprising:

at least one fixed-film media support;

a base for supporting the at least one fixed-film media support;

an air line comprising an internal aeration connector, and an external oxygen source connector for coupling to an external oxygen source; and,

an air dispersal mechanism coupled to the internal aeration connector, the air dispersal mechanism for delivering oxygen to the at least one fixed-film media support, wherein the fixed-film aeration apparatus defines an aerobic zone in the wastewater treatment system; and

wherein the first and second baffles direct a flow of wastewater along a treatment path, the treatment path extending from the inlet through the first anaerobic zone, the aerobic zone, the second anaerobic zone and to the outlet.

2. The wastewater treatment system according to claim 1 , wherein the upper edge of the first baffle is anchored to the upper surface of the tank at a position closer to the inlet wall than the outlet wall.

3. The wastewater treatment system according to claim 1 or 2, wherein the base comprises a tray for supporting the air dispersal mechanism.

4. The wastewater treatment system according to any one of claims 1 to 3, wherein the tray comprises raised side portions which engage with a bottom surface of the at least one fixed-film media support to restrict bio-solids from clogging the air dispersal mechanism.

5. The wastewater treatment system according to any one of claims 1 to 4, wherein the air dispersal mechanism comprises at least one air stone.

6. The wastewater treatment system according to any one of claims 1 to 5, further comprising at least one bio-electrochemical sensor for detecting the presence of wastewater constituents in the wastewater.

7. The wastewater treatment system according to claim 6, wherein the at least one bio-electrochemical sensor is positioned in the first or second anaerobic chamber.

8. The wastewater treatment system according to claim 6, wherein the at least one bio-electrochemical sensor is positioned outside the tank.

9. The wastewater treatment system according to claim 6, wherein the tank is in fluid communication with a leech field and the at least one bio-clcctrochcmical sensor is positioned in the leech field.

10. The wastewater treatment system according to claim 6, wherein the detected wastewater constituents comprise toxic chemicals.

1 1 . The wastewater treatment system according to any one of claims 1 to 10, further comprising an oxygen pump positioned externally to the tank and rcvcrsibly coupled to the oxygen source connector, for providing oxygen to the air line.

12. The wastewater treatment system according to any one of claims 6 to 1 1 further comprising an effluent filter, the effluent filter comprising:

a filter inlet for receiving wastewater to be filtered;

a first chamber in fluid communication with the filter inlet, the first chamber comprising:

a porous material for filtering solid material from the wastewater: and the at least one bio-electrochemical sensor; and

a filter outlet, in fluid communication with the first chamber, the filter outlet for discharging filtered wastewater from the filter.

13. The wastewater treatment system according to claim 12, wherein

the porous material comprises a conductive material for supporting the growth of exoelectrogenic bacteria, and

the first chamber further comprises:

a plurality of electrode pairs coupled to the porous material, each electrode pair comprising an anode and a cathode, wherein the exoelectrogenic bacteria are in proximity to the anode and release electrons to the anode, the released electrons flowing from the anode to the cathode;

a terminal electron acceptor electrically coupled to the cathode for receiving the electrons from the cathode and for generating an electrical output; and a resistor electrically coupled to the terminal electron acceptor, wherein the electrical output is measured across the resistor using a data acquisition system,

wherein the electrical output of the resistor is indicative of a metabolic activity of the cxoclcctrogcnic bacteria.

14. The wastewater treatment system according to claim 12 or 13, wherein the effluent filter comprises a second chamber in fluid communication with the first chamber and the filter outlet, the second chamber housing an adsorptivc material for clarifying the filtered wastewater.

15. The wastewater treatment system according to claim 14, wherein the adsorptivc material is activated carbon, bio-char granules, iron filings, zeolite, or a ceramic.

16. A fixed-fil m aeration apparatus configured for insertion through a standard septic system opening, comprising:

a base comprising a weighted portion, the weighted portion configured to stabilize the apparatus in an unanchored operating position during and after insertion;

a support member coupled to the base;

an air line coupled to the base for delivering oxygen, the air line having an external oxygen source connector and an internal aeration connector;

an air dispersal mechanism coupled to the internal aeration connector;

a plurality of fixed-film media supports vertically stacked on the base and supported by the support member,

the air dispersal mechanism for delivering oxygen to the plurality of fixed-film media supports and promoting the metabolic activity of a fixed-film on the plurality of fixed-film media supports.

17. The fixed-film aeration apparatus according to claim 16, further comprising at least one leg connected to the base, the leg for raising the plurality of fixed-film media supports above a level of bio-sludge accumulation in a septic tank.

18. The fixed- film aeration apparatus according to claim 17, wherein the at least one leg is eoUapsibly connected to the base allowing the at least one leg to move between a first, retracted position, for facilitating the insertion of the apparatus into a septic system, and a second operating position for supporting the apparatus and raising the plurality of fixed- film media supports above a level of bio-sludge accumulation in the tank.

19. The fixed- film aeration apparatus according to claim 17 or 18, wherein the at least one leg is weighted.

20. The fixed-film aeration apparatus according to claim 16, wherein the weighted portion of the base is a weighted ballast tray.

21 . The fixed- film aeration apparatus according to any one of claims 1 6 to 20, wherein each of the plurality of fixed-film media supports comprises a substantially central passageway for receiving the air line and wherein the air line supports each of the plural ity of fixed-film media supports in a position to receive oxygen from the air dispersal mechanism.

22. The fixed-film aeration apparatus according to any one of claims 1 6 to 21 , wherein the air dispersal mechanism comprises at least one air stone.

23. The fixed- film aeration apparatus according to any one of claims 16 to 22, wherein the base comprises a tray for supporting the air dispersal mechanism, the tray having raised sides which engage with a bottom surface of a lowemiost fixed-film media support of the plurality of fixed-film media supports for restricting bio solids from clogging the air dispersal mechanism.

24. The fixed-film aeration apparatus according to any one of claims 16 to 23, wherein the support member is integral with the air line.

25. The fixed-film aeration apparatus according to any one of claims 16 to 24, wherein the plurality of fixed-film media supports are movable between a collapsed insertion position for insertion of the fixed-film media support into a small opening and an expanded, operating position wherein the fixed-film media support is fully expanded.

26. A method of controlling a wastewater treatment system, the method comprising: generating a potentiostatic sweep across a bio-electrochemical sensor;

measuring a current response of the bio-clcctrochcmical sensor in response to the potcntiostatic sweep;

comparing the measured current response to a threshold; and

in response to a determination that the measured current response is below the threshold, adjusting a wastewater treatment system operation parameter to increase the current response.

27. The method of claim 26, wherein the wastewater treatment system operation parameter comprises an oxygen concentration in the wastewater treatment system.

28. A bio-electrochemical sensor for use in a wastewater treatment system, the sensor comprising:

a support comprising a bio support material for supporting the growth of exoelectrogcnic bacteria;

at least one electrode pair connected to the support, the at least one electrode pair comprising an anode and a cathode,

wherein the exoelectrogcnic bacteria arc in proximity to the anode and release electrons to the anode, the released electrons flowing from the anode to the cathode; and a terminal electron acceptor electrically coupled to the cathode for receiving the electrons from the cathode and for generating an electrical output; and

a resistor electrically coupled to the terminal electron acceptor, wherein the output is measured across the resistor, using a data acquisition system,

wherein the output of the bio-clcctrochcmical sensor is indicative of a metabolic activity of the exoelectrogcnic bacteria.

29. An effluent filter for a wastewater system comprising: a filter comprising a porous material, the filter for filtering solid material from the wastewater; and

a bio-clcctrochcmical sensor for sensing changes in conditions in the wastewater treatment system.

30. The effluent filter according to claim 29, wherein the porous material comprises a conductive material and the bio-clcctrochcmical sensor is integral with the filter.

3 1 . Use of a bio-electrochemical sensor for detecting nutrient over-loading in a leech field associated with a wastewater treatment system.

32. Use of a bio-electrochemical sensor for detecting changed in hydraulic loading in a leech field associated with a wastewater treatment system.

33. Use of a bio-electrochemical sensor for detecting the presence of toxic chemicals in a wastewater treatment system.