Trickle filter system and method

Abstract

A trickling filter for treating wastewater and producing treated effluent includes a tank having an internal volume, a filter media mounted in the tank, a support beam supporting the filter media in the tank between a top surface of the filter media and a base of the tank without ventilation openings or sealable man way, a reservoir defined between the support beam and the base of the tank, and an extension wall extending above the top surface to block wind relative to the top surface.

Description

TITLE OF THE INVENTIONTrickle Filter System and MethodCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of U.S. Provisional Patent Application No. 63 / 528,722, filed July 25, 2023 and titled, “Trickle Filter System and Method,” the entire contents of which is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION

[0002] Trickling filter systems are designed to treat wastewater by exposing the wastewater to layers of microbial slime growing on a bed of media. Trickling filter systems are designed to treat domestic sewage and industrial wastewater, alone or in combination. Certain trickling filter systems for a combined sewer system treat a combination of rainwater runoff and domestic and / or industrial wastewater. The trickling filter systems are designed to remove organic pollutants and ammonia nitrogen from the wastewater stream through aerobic treatment by microorganisms in the slime layer in the bed of the trickling filter tank.

[0003] Existing trickling filter systems often become limited when ambient and wastewater temperatures are low, because temperatures of the wastewater in the trickling filter tank drives the bio-chemical processes used to treat the wastewater and these biochemical processes are diminished at relatively low temperatures. This effect may be particularly impactful in regions that are often subject to cold temperatures and during winter seasons the efficiency of the trickling filter system may be negatively impacted. Efficiency of the trickling filter system is also diminished by limited air or oxygen levels in the wastewater, which reduces the effectiveness of the bio-chemical processes used to treat the wastewater. It is desirable to design, construct and implement a trickling filter system that maintains desired temperatures and oxygen levels or aeration within the trickling filter tank to maintain efficient bio-chemical processes during treatment of the wastewater and to, therefore, more efficiently process the wastewater.BRIEF SUMMARY OF THE INVENTION

[0004] Briefly stated, a preferred embodiment of the present invention is directed to a trickling filter system for treating wastewater and producing treated effluent. The trickling filter system includes a tank having an internal volume, a filter media bed with a support beam supporting the filter media in the tank between a top surface of the filter media and a base of the tank, a reservoir defined between the support beam and the base of the tank and an extension wall extending above the top surface to block wind relative to the top surface. Wastewater is introduced to the top of the media bed through a distribution system, which can be a rotary distribution arm for circular tanks, a fixed nozzle distribution for rectangular tanks or other shapes for tanks having shapes other than circular and rectangular. Wastewater then trickles through the media bed, where the contaminated wastewater contacts microorganisms in the slime layer and ambient air, such that the wastewater is subjected to a bio-chemical treatment process. The treated wastewater is then collected in the bottom of the reservoir and discharged from the tank to a downstream treatment unit or otherwise out of the tank. The treated wastewater may alternatively be recirculated to the distribution system to pass through the media bed for additional treatment.

[0005] In another aspect, the preferred invention is directed to a trickling filter system for treating wastewater and producing treated effluent. The trickling filter includes a tank having an internal volume, a filter media mounted in the tank, a support beam supporting the filter media in the tank between a top surface of the filter media and a bottom of the tank, a reservoir defined between the support beam and the bottom of the tank and an extension wall extending above the top surface configured to block wind relative to the top surface.

[0006] In a further aspect, the preferred invention is directed to a trickling filter system for treating wastewater and producing treated effluent. The trickling filter includes a tank having an internal volume and defining a tank height, a filter media mounted in the tank, a support beam supporting the filter media in the tank, a reservoir defined between the support beam and a base of the tank, a distributor configured to introduce the wastewater onto the top surface and an extension wall extending above thetop surface and defining a clearance height. The filter media includes a top surface and defines a media bed depth. An underdrain height defined between a bottom of the tank and the support beam The media bed depth is approximately eighty-five to one hundred forty-three percent of the underdrain height.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0007] The foregoing summary, as well as the following detailed description of a preferred embodiment of the trickling filter system of the present application, will be better understood when read in conjunction with the appended drawings. For the purposes of illustrating the trickling filter system and method, there is shown in the drawings a preferred embodiment. It should be understood, however, that the application is not limited to the precise arrangements and instrumentalities shown. In the drawings:

[0008] Fig. 1 illustrates a top perspective, partial cross-sectional view of a trickling filter system in accordance with a preferred embodiment of the present invention.DETAILED DESCRIPTION OF THE INVENTION

[0009] Certain terminology is used in the following description for convenience only and is not limiting. Unless specifically set forth herein, the terms “a”, “an” and “the” are not limited to one element but instead should be read as meaning “at least one”. The words "right", "left", "lower" and "upper" designate directions in the drawings to which reference is made. The words "inwardly" or “distally” and "outwardly" or “proximally” refer to directions toward and away from, respectively, the components of the trickling filter system, or the geometric center of the preferred trickling filter system and related parts thereof. The terminology includes the above-listed words, derivatives thereof and words of similar import.

[0010] It should also be understood that the terms “about,” “approximately,” “generally,” “substantially” and like terms, used herein when referring to a dimension or characteristic of a component of the preferred invention, indicate that the described dimension / characteristic is not a strict boundary or parameter and does not exclude minor variations therefrom that are functionally the same or similar, as would be understood by one having ordinary skill in the art. At a minimum, such references that include anumerical parameter would include variations that, using mathematical and industrial principles accepted in the art (e.g., rounding, measurement or other systematic errors, manufacturing tolerances, etc.), would not vary the least significant digit.

[0011] Referring to Fig. 1, a high-rate nitrifying trickling filter or trickling filter system, generally designated 9, with enhanced passive aeration and natural heating (biothermal heating) includes a trickling filter tank 1 with filter media 2 therein, support beams or media support beams 3 supporting the filter media 2, supporting columns 4 supporting the support beams 3 and a distributor 5, which may be comprised of a rotating distribution arm or speed control distribution arm 5, to introduce wastewater into the tank 1. The support beams 3 support the filter media 2 in the tank 1 between a top surface 2c of the filter media 2 and a bottom lb of the tank 1. The tank 1 has an internal volume to hold the components of the trickling filter system 9 and for filtering the wastewater therein that generally flows from a top la of the tank 1 out of the distributor 5 to a bottom lb of the tank 1. The tank 1 defines a longitudinal axis 14 that extends preferably vertically from the top la of the tank 1 to the bottom lb of the tank 1. The wastewater flows generally under the force of gravity from the distributor 5 along the longitudinal axis 14 to the bottom lb of the tank 1, although the wastewater may flow in other directions in the tank 1, particularly under the influence of the filter media 2.

[0012] The filter media 2 is mounted in the tank 1 between the top la and the bottom lb. The wastewater is exposed to layers of microbial slime growing on the filter media 2 to treat the wastewater. The preferred filter media 2 may include a combination of cross flow media 2a and vertical flow filter media 2b, including two or three layers of cross flow media 2a positioned above a layer of vertical flow filter media 2b. The trickling filter system 9 is not limited to this first preferred arrangement of filter media 2, shown in Fig. 1, and may include alternative arrangements and numbers of layers of the filter media 2a, 2b, 2, depending on design requirements, designer preferences and other factors. For example, the filter media 2 may be comprised of all cross flow media 2a, all vertical flow filter media 2b or a combination of cross flow and vertical flow filter media 2a, 2b different than the arrangement of the filter media 2 shown in Fig. 1. The cross flow media 2a is configured to urge the wastewater to flow at an angle relative to the longitudinal axis 14 and the vertical flow filter media 2b is configured to urge or allowthe wastewater to flow generally parallel to the longitudinal axis 14. The cross flow and vertical flow media 2a, 2b may include surface features, such as roughness or microstructure to maximize surface area, create even liquid distribution, allow air circulation and provide drainage for biomass. The cross flow and vertical flow media 2a, 2b are preferably comprised of sheets assembled into packs that may be staked in the tank on the support beams 3. The filter media 2, 2a, 2b, when configured with both cross flow and vertical flow media 2a, 2b, is configured to urge the wastewater to flow in a combination of at an angle to the longitudinal axis and generally parallel to the longitudinal axis 14. The angle is preferably thirty to sixty degrees (30-60°) and may be forty-five degrees (45°). The wastewater may flow through the filter media 2 in the tank 1 in a cross flow direction, in a vertical-flow orientation or in a combination of directions for exposure to the filter media 2 and the bacteria or slime growing on the filter media 2.

[0013] The treated wastewater filters into a reservoir 6 below the support beams 3 and flows out of the tank 1 through a discharge channel or effluent trough 7 for further treatment or discharge. The reservoir 6 is defined between the support beam 3 and the bottom lb of the tank 1. An effluent pipe 10 is positioned downstream of the reservoir 6 in the flow of the wastewater. The effluent is the wastewater or other liquid, partially or completely treated, flowing from the reservoir 6. The influent is the wastewater or other liquid flowing into the trickle filter system 9.

[0014] The tank 1 has the internal volume and defines a tank height HT. The preferred tank 1 includes an extension wall 8 that extends above the top surface 2c of the filter media 2, preferably by a clearance height or extension wall height He of approximately a minimum of six feet (6 ft) or one and eighty-three hundredths meters (1.83 m) above the top surface 2c of the filter media 2 to reduce heat loss in the wastewater, although the clearance height He is not so limited. The clearance height He may be nearly any dimension that extends above the top of the media 2 to limit heat loss in the trickling filter system 9 through wind or convection heat loss. The trickling filter system 9 is also configured to promote air circulation through the filter media 2 and to improve oxygen transfer and, consequently, to increase biofilm treatment capacity. The extension wall 8 provides a block for wind, as the extension wall 8 blocks or diminishes the movement of air at the top surface 2c of the filter media 2 and near the distributor 5 to limit or reducedforced conduction between the air and the wastewater during use. As a non-limiting example, the clearance height He may be approximately six feet (6 ft) or one and eighty- three hundredths meters (1.83 m) and the tank height HT may be approximately twenty feet (20 ft) or six and ten hundredths meters (6.10 m).

[0015] The innovative nitrifying fdter or preferred trickling filter system 9 also preferably incorporates an elevated underdrain / media support system, including the support beams 3, the supporting columns 4, the reservoir 6, the shallow media bed 2 and the speed control distribution arm 5 that can consistently achieve a concentration of ammonia-nitrogen in a trickling filter effluent pipe 10 from the trickling filter system 9 of one and one-half milligrams per Liter (1.5 mg / L) or less when the filter influent temperature is less than forty-five degrees Fahrenheit (45°F) or approximately seven and twenty-two hundredths degrees Centigrade (7.22°C). The underdrain / media support system is positioned within a reservoir or underdrain space 6 below the media support beams 3 and above the base of the tank 1. The underdrain / media support system, including the support beams 3, the columns 4 and the reservoir 6 in this preferred trickling filter system 9 has an underdrain height Hu that is in the range of five to seven feet (5-7 ft) or one and fifty -two hundredths to two and thirteen hundredths meters (1.52- 2.13 m) and the filter media 2 has a media bed depth HM of approximately eighty -five to one hundred forty-three percent (85% -143%) of the underdrain height Hu. In the preferred embodiment, the media bed depth HM is approximately four to ten feet (4-10 ft) or one and twenty -two hundredths to three and five hundredths meters (1.22-3.05 m). The underdrain height Hu may assist with the circulation of air in the wastewater and increase biofilm treatment capacity. The preferred underdrain height Hu is approximately five to seven feet (5-7 ft) or one and fifty -two hundredths to two and thirteen hundredths meters (1.52-2.13 m), and the media bed depth HM is preferably in the approximate range of eighty-five to one hundred forty -three percent (0.85 X Hu - 1.43 X Hu) of the underdrain height Hu. This preferred design allows improved air circulation through the media bed 2. The underdrain height Hu is preferably defined between the bottom lb of the tank 1 and the support beam 3. The media depth Hm may be defined by the filter media 2. A ratio of the media depth Hm and the underdrain height Hu may be eighty-five to one hundred forty-three percent. The preferred trickling filter system 9 has a relatively shallow filtermedia 2 with the media bed depth HM being approximately six to ten feet (6-10 ft) or one and eighty -three hundredths to three and five hundredths meters (1.83-3.05 m), a relatively tall underdrain wherein the underdrain height Hu is approximately five to seven feet (5-7 ft) or one and fifty-two hundredths to two and thirteen hundredths meters (1.52- 2.13 m) and the relatively tall clearance height He of approximately six feet (6 ft) or one and eighty -three hundredths meters (1.83 m), as many prior art trickling filter systems have no or limited wall height extending above the filter media.

[0016] In the preferred embodiment, a ratio of the media bed depth HM and the underdrain height Hu is eighty-five to one hundred forty-three percent. This ratio is configured to increase passive aeration capacity and improve aerobic treatment performance of the trickling filter system 9. This ration of the media bed depth H and the underdrain height Hu is designed to facilitate exposure of the wastewater to the filter media 2 and aeration in the reservoir 6.

[0017] The filter media 2 is preferably comprised of sheets constructed of fill sheet material that is comprised of a polymeric material. The polymeric material of the fill sheets material is preferably constructed of a polyvinyl chloride (“PVC”), polypropylene (“PP”), polyethene (“PE”) or other synthetic material structured sheet media 2, fill packs or assemblies of the structured sheet media 2 or other synthetic media installed to provide surface or an area for bacteria to grow and sustain bio-chemical reactions. The filter media 2 may alternatively be comprised of a non-self-supported random media that facilitates slime or bacteria growth and flow of the wastewater therethrough. The biochemical reactions convert ammonia-nitrogen in the wastewater to nitrate nitrogen. The filter media 2 may also be comprised of random media or other self-support media, such as web-structured media, without significantly impacting the design, configuration and / or function of the preferred trickling filter system 9. The first preferred embodiment of the filter media 2 is comprised of a self-supported media bed. The filter media 2 may be comprised of a self-support media bed other than structured sheet with synthetic material (e.g., hair curl web-structure media).

[0018] Underdrain containment may be fully enclosed within the tank 1 without ventilation openings, or with ventilation openings or a ventilation port 11 that can be fully sealed to reduce airflow circulation through the openings or ventilation port 11. Thetank 1 may, accordingly, exclude ventilation openings, such as the ventilation port 1 1, proximate the support beam 3 or anywhere therein. The tank 1 is, thereby, configured to improve airflow circulation through open flutes in the filter media 2 and promote biochemical reactions of the wastewater flowing through the filter media 2. In the preferred embodiment, the tank 1 includes the selectively sealable ventilation port 11 positioned at a side of the tank 1 proximate the support beam 3 that is selectively sealable to allow or prevent exposure of the wastewater to the ambient air. The sealable ventilation ports 11 are preferred to capture and retain the bio-thermal process within the wastewater in the tank 1 and to retain heat from warmer wastewater streams or heat from exothermic reactions within the tank 1. A control box 13 with a gate valve may be connected to the trickling filter effluent pipe 10 to control the outflow of the treated effluent from the reservoir 6. The trickling filter system 9 may include the ventilation port 11 in the tank 1 that opens into the reservoir 6. The heat from a residual, which is described in greater detail below, may be configured to warm ambient air flowing into the reservoir 6. The tank 1 may also include the ventilation port 11 to increase airflow into the reservoir, which may assist with chemical reactions occurring in the tank. The ventilation port 11 may be closed during operation, particularly in cold conditions or in cold climates, to prevent the cold air from impacting the chemical reactions within the tank 1 and to maintain temperature with in the tank 1.

[0019] The design features the combination of a tall underdrain / media support system with the extension wall 8 and the shallow media bed or filter media 2 that promotes air circulation through the filter media 2 and consequently, increases oxygen transfer to the wastewater that trickles through filter media 2 improves the performance of the preferred trickling filter system 9 described herein. The enclosed underdrain containment reduces the possibility of air short-circuiting through the ventilation openings or port 11, which may occur in the conventional trickling filters with underdrain openings or ventilation ports. The enclosed underdrain containment also limits contact between or exposure of wastewater / bacteria with cold ambient air outside of the trickling filter system 9. Limiting exposure of the wastewater and bacteria on the filter media 2 with the cold ambient air reduces heat loss, which can negatively impact the bio-chemical treatment processes that occur in the preferred trickling filter system 9.

[0020] As a result, the dissolved oxygen (“DO”) concentration in the effluent pipe 10 of the preferred trickling filter system 9 is higher than the dissolved oxygen (“DO”) in the effluent of a conventional trickling filter. It is observed that DO concentration in the effluent pipe 10 of the preferred trickling filter system 9 is close to saturation or over saturation.

[0021] Previous studies have suggested that the ammonia-nitrogen removal rate is a function of bulk liquid DO in a submerged biofilm reactor (Rusten, et al., 2006). As ammonia-nitrogen is removed from the wastewater through the oxidation process (i.e., nitrification), a higher DO concentration will result in a higher nitrification rate.

[0022] This preferred design of the trickling filter system 9 also features heat loss prevention and natural heating effect that reduces the impact of relatively low wastewater temperatures or relatively low ambient temperature to the nitrifying activities in the trickling filter system 9. Nitrification rate reduces as temperature drops and may cease when wastewater temperature is below forty-one degrees Fahrenheit (41 °F) or approximately five degrees Centigrade (5°C). In this design of the preferred trickling filter system 9, heat loss through the ventilation openings 11 is reduced, at least in part because the underdrain space or reservoir 6 is enclosed. Heat generated through the biological activities in the area of the filter media 2 can be retained in the large, enclosed underdrain space 6 and used to warm incoming cold wastewater and air from the distribution arm 5 or other wastewater introduction system or device. It has been observed that a high level of nitrification occurs at an ambient temperature of as low as negative two degrees Fahrenheit (-2 °F) or approximately negative eighteen and nine tenths degrees Centigrade (-18.9°C) and when the extension wall 8 is positioned at the clearance height He of approximately six feet (6 ft) or one and eighty-three hundredths meters (1.83 m) above the top surface 12 of media 2, for example. Heat retained in the underdrain space 6 improves the high nitrification rate of the wastewater in the area of the filter media 2.

[0023] Another heat loss prevention feature of this preferred trickling filter system 9 is the extension wall 8 that acts as a wind wall. The extension wall 8 preferably extends at the clearance height He approximately six feet (6 ft) or one and eighty -three hundredths meters (1.83 m) or more above the top of the filter media 2 or the top surface 12. Thewind wall or extension wall 8 reduces heat loss during windy days and limits possibility that the wastewater flow from the distribution arm 5 freezes on the distribution arm 5 and / or at the surface of the wastewater in the trickling filter tank 1.

[0024] Another process feature of the preferred trickling filter system 9 is that a minimum residual alkalinity of one hundred fifty to two hundred milligrams per Liter (150-200 mg / L) of calcium carbonate (CaCCh) is desired to enhance nitrification in the trickling filter system 9 of the treated effluent. Nitrifying one milligram per Liter (1 mg / L) of ammonia-nitrogen to nitrate nitrogen consumes seven and fourteen hundredths milligrams per Liter (7.14 mg / L) of alkalinity as calcium carbonate (CaCCh). Alkalinity balance is preferably calculated to optimize nitrification performance and alkalinity addition may be encouraged to balance the alkalinity.

[0025] It is a further feature of the preferred trickling filter system 9 that the polyvinylchloride (“PVC”) or polypropylene (“PP”) structured sheet media 2 or other synthetic or polymeric media can be comprised of a cross flow or a combination of the cross flow media 2a and the vertical flow media 2b that provides a non-linear flow path through the filter media 2. Urging the wastewater to take a non-linear flow path through the media 2 or nearly any circuitous route as the wastewater flows from the top of the tank 1, to the bottom of the tank 1 and out the effluent trough 7 improves contact and / or prolongs contact of the wastewater, air, and bacteria.

[0026] A further feature of this preferred trickling filter system 9 is that the design can also be used to improve organic pollutants oxidation ( / .<?., biochemical oxygen demand and chemical oxygen demand (“BOD / COD”) removal) and, therefore, the application of this preferred trickling filter system 9 is not limited to nitrification, but can be extended to BOD roughing, BOD removal and combined BOD removal and nitrification in the trickling filter system 9.

[0027] Another advantage of this preferred trickling filter system 9 is that the energy consumption of the enhanced passive aeration system is significantly lower than that of the active aeration systems (such as mechanical aeration, or diffused aeration) in activated sludge processes.

[0028] These features and advantages provide an innovative design for the preferred trickling filter system 9 by combining a tall, enclosed underdrain, reservoir or underdrainspace 6 having the underdrain height Hu with the extension wall 8 defining the clearance height He in conjunction with a shallow structured sheet media 2 having the bed depth HM with extended containment, and the speed control distribution 5. This design helps creating a favorable environment for bacteria growth and chemical interaction with the wastewater (heterotrophs for BOD removal and autotrophs for nitrification) in the trickling filter tank 1. A microbiology study revealed that the nitrifier colonies in the biofilm of the preferred trickling filter system 9 were denser and more well-organized compared to the microorganisms’ colonies in a conventional trickling filter biofilm. The biological treatment capacity and efficiency of this trickling filter system 9 is improved when compared to conventional trickling filters. Attached Tables 1 and 2 represent conditions and average DO concentration for a single month collected at an experimental plant and in a prior art system with rock media in a winter season in the US Northeast.

[0029] Referring to Tables 1 and 2, the preferred trickling filter system 9 may be configured to produce treated effluent having a dissolved oxygen (“DO”) that is typically increased by two to four milligrams per Liter (2-4 mg / L) as compared to DO in a conventional trickling filter treated effluent. Referring specifically to Table 2, due to the unique design of improved natural ventilation of the trickling filter system 9, the passive aeration in the trickling filter system 9 may be more efficient than that in a conventional trickling filter. Based on Tests 1 and 2 and a comparison of a similarly situated prior art system having rock media results in a DO that is over two to over three milligrams per Liter (>2 mg / L - >3 mg / L) on average. Specifically, as indicated in Table 2, the DO of effluent of the conventional or prior art trickling filter is eight milligrams per Liter (8 mg / L) and the DO of effluent of a prototype preferred trickling filter 9 is ten and twenty- six milligrams per Liter to eleven and seventy-five milligrams per Liter (10.26 - 11.75 mg / L) or greater than two to three milligrams per Liter (2-3 mg / L) compared to the DO in the conventional or prior art trickling filter treated effluent.TABLE 11Data represents experimental plan data collected during a thirty-one day period in the winter season in the US Northeast.TABLE 21Data represents experimental plant data collected during a thirty-one day period in the winter season in the US Northeast2Prior Art System data represents plant data with rock media collected during a thirty- one day period in the winter season in the US Northeast.

[0030] The preferred trickling filter system 9 may incorporate an alkalinity supplement that is configured to be added to the trickling filter system 9, the wastewater in the tank 1 or the effluent to maintain a residual alkalinity of one hundred fifty to two hundred milligrams per Liter (150-200 mg / L) to boost nitrification activities. The alkalinity supplement may be comprised of calcium carbonate (CaCO3) or another substance or compound to control alkalinity in the trickling filter system 9. The alkalinity supplement is not limited to being comprised of calcium carbonate (CaCO3) and may be comprised of sodium bicarbonate, lime or other related substances or compounds. The dosage of the alkalinity supplement is preferably calculated based on an equivalent to calcium carbonate but may be otherwise dosed based on designer or operator preferences or requirements. The alkalinity supplement is preferably utilized because the nitrification process in the trickling filter system 9 consumes alkalinity. In order to convert one milligram per Liter (1 mg / L) of ammonium -nitrogen to nitrate nitrogen, seven and fourteen hundredths milligrams per Liter (7.14 mg / L) of alkalinity as CaCCh isconsumed. Alkalinity in wastewater can vary throughout the day and the trickling filter system 9 has limited buffering of alkalinity concentrations due to relatively short contact times. A high concentration of residual alkalinity in the effluent is, therefore, preferred in order to maximize the nitrification capacity of the trickling filter system 9.

[0031] The trickling filter system 9 may include a residual retained in the reservoir 6. The residual may be configured to produce a bio-thermal process, thereby providing heat and warming the wastewater flowing from the filter media 2 into the reservoir 6. The heat improves the chemical reactions in the trickle filter system 9 to improve the efficiency of the system 9. Composting of wastewater residual is a bio-thermal aerobic process that decomposes the organic portion of the residuals. The composting process reduces the organic material in the residual by approximately twenty-five percent (25%). During composting the heat generated by the decomposition of the organic portion of the residuals reduces the moisture content of the residual, stabilizes the residual and renders the residual harmless by transforming it into a usable biosolid to warm incoming wastewater and airflow under cold climate conditions.

[0032] The underdrain height Hu creates a relatively large space with temperature differences in a base of the tank 1, which promotes air circulation through the filter media 2, as the pressure drop through the shallow filter media 2 is limited, and the air flow may pass through the entire filter media 2. The combination of underdrain height Hu and the media bed depth Hm is designed to increase passive aeration capacity and, therefore, improve the aerobic treatment performance of the trickling filter system 9.

[0033] It will be appreciated by those skilled in the art that changes could be made to the preferred embodiment described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiment disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.

Claims

CLAIMSI / We claim:

1. A trickling filter system for treating wastewater and producing treated effluent, the trickling filter comprising: a tank having an internal volume; a filter media mounted in the tank; a support beam supporting the filter media in the tank between a top surface of the filter media and a bottom of the tank; a reservoir defined between the support beam and the bottom of the tank; and an extension wall extending above the top surface configured to block wind relative to the top surface.

2. The trickling filter system of claim 1, wherein the tank excludes ventilation openings in the tank proximate the support beam, the tank thereby being configured to improve airflow circulation through open flutes in the filter media and promote biochemical reactions of the wastewater flowing through the filter media.

3. The trickling filter system of claim 1, wherein an underdrain height is defined between a bottom of the tank and the support beam, the underdrain height being approximately five to seven feet (5-7 ft), the filter media defining a media bed depth, the media bed depth being approximately four to ten feet (6-10 ft).

4. The trickling filter system of claim 1, wherein an underdrain height is defined between a bottom of the tank and the support beam, a media bed depth defined by the filter media, a ratio of the media bed depth and the underdrain height being eighty -five to one hundred forty-three percent and configured to increase passive aeration capacity and improve aerobic treatment performance.

5. The trickling filter system of claim 1, further comprising: an alkalinity supplement configured for introduction into the wastewater in the tank, the alkalinity supplement configured to maintain a residual alkalinity of onehundred fifty to two hundred milligrams per Liter (150-200 mg / L) to boost nitrification activity.

6. The trickling filter system of claim 1, further comprising: an effluent pipe downstream of the reservoir, the trickling filter system configured to have a dissolved oxygen of one and one-half milligrams per Liter or less when a filter influent temperature is less than forty-five degrees Fahrenheit.

7. The trickling filter system of claim 1, wherein the extension wall extends at least six feet (6 ft) above a top surface of the filter media.

8. The trickling filter system of claim 1, wherein a residual is retained in the reservoir, the residual configured to produce a bio-thermal process, thereby providing heat and warming the wastewater flowing from the filter media into the reservoir.

9. The trickling filter system of claim 7, further comprising: a ventilation port in the tank opening into the reservoir.

10. The trickling filter system of claim 1, wherein the filter media includes cross flow media and the tank defines a longitudinal axis, the cross flow media configured to urge the wastewater to flow at an angle relative to the longitudinal axis.

11. The trickling filter system of claim 1, wherein the filter media includes a vertical flow media and the tank defines a longitudinal axis, the vertical flow media configured to urge the wastewater to flow generally parallel to the longitudinal axis.

12. The trickling filter system of claim 1, wherein the filter media includes a cross flow media and a vertical flow media, the tank defining a longitudinal axis, the cross flow and vertical flow media stacked in the tank, the filter media configured to urge the wastewater to flow in a combination of at an angle relative to the longitudinal axis and generally parallel to the longitudinal axis.

13. The trickling filter system of claim 1, wherein the filter media is comprised of sheets constructed of a fill sheet material.

14. The trickling filter system of claim 13, wherein the fill sheet material is comprised of a polymeric material.

15. The trickling filter system of claim 14, wherein the polymeric material is selected from the group consisting of polyvinyl chloride, polypropylene and polyethene.

16. The trickling filter system of claim 1, wherein the filter media is comprised of non-self-support random media.

17. The trickling filter system of claim 1, wherein the filter media is comprised of a self-supported media bed.

18. A trickling filter system for treating wastewater and producing treated effluent, the trickling filter comprising: a tank having an internal volume and defining a tank height; a filter media mounted in the tank, the filter media including a top surface, the filter media defining a media bed depth; a support beam supporting the filter media in the tank, an underdrain height defined between a bottom of the tank and the support beam; a reservoir defined between the support beam and a base of the tank; a distributor configured to introduce the wastewater onto the top surface; and an extension wall extending above the top surface and defining a clearance height, the media bed depth being approximately eighty -five to one hundred forty -three percent of the underdrain height.

19. The trickling filter system of claim 18, wherein the clearance height is approximately six feet and the tank height is approximately twenty feet.

20. The trickling filter system of claim 18, wherein the filter media includes cross flow media.

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