Mobile carrier for water treatment

Abstract

A migrating biofilm carrier for intensifying the treatment of wastewater including a biopolymer including an organic polymer, a fill material, and a densifying material. Also disclosed is a method of acclimating a migrating biofilm carrier for treatment of wastewater including charging the carrier into an acclimation tank, charging a conditioning agent into the acclimation tank, and subjecting the carrier and conditioning agent to aerobic, anerobic, and / or anoxic conditions to provide an acclimated carrier wherein the acclimated carrier has a biofilm disposed on the carrier.

Description

MOBILE CARRIER FOR WATER TREATMENTCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Application No. 63 / 515,698, filed on July 26, 2023, which is incorporated herein by reference in its entirety.BACKGROUNDField of the Invention

[0002] The present invention is directed to methods of wastewater treatment employing a migrating biofilm carrier, and more particularly to methods for the treatment of wastewater with an injection molded / extruded, acclimated, organic-filled biocomposite for use as a migrating carrier.Brief Description of the Related Art

[0003] In addition to traditional phase separating treatment, biological treatment of wastewater provides a complementary water treatment process. In biological treatment, wastewater is subjected to microorganisms. The microorganisms can reduce different types of pollutants present in the wastewater and reduce the biochemical oxygen demand of the water. For example, activated sludge processes use aeration and microorganisms to biologically oxidize contaminants.

[0004] As wastewater treatment faces increasingly stringent effluent guidelines and increased influent flows due to rising populations and water usage, there remains a need for materials and methods to intensify biological wastewater treatment processes.SUMMARY OF THE DISCLOSURE

[0005] In an embodiment, a migrating biofilm carrier for intensifying the treatment of wastewater including a biopolymer including an organic polymer, a fill material, and a densifying material.100061 In another embodiment, a method of acclimating a carrier for treatment of wastewater including charging the carrier into an acclimation tank where the carrier includes a biopolymer, a fill material, and a densifying agent. Charging a conditioning agent into the acclimation tank and subjecting the carrier and the conditioning agent to aerobic, anaerobic, and / or anoxic conditions to provide an acclimated carrier wherein the acclimated carrier has a biofilm disposed on the carrier.

[0007] The above described and other features are exemplified by the following detailed description.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Referring now to the figures, which are exemplary embodiments, and wherein the like elements are numbered alike.

[0009] FIG. 1 is a schematic cross-sectional view of an embodiment of a migrating biofilm carrier;

[0010] FIG. 2 is a schematic cross-sectional view of an embodiment of a migrating biofilm carrier;

[0011] FIG. 3 is a graph illustrating biochemical oxygen demand (milligrams per milliliter, mg / mL) versus days for Example 1 ;

[0012] FIG. 4 is a graph illustrating ammonia concentration (mg / mL) versus days for Example 1 ;

[0013] FIG. 5 is a graph illustrating Total Kjeldahl Nitrogen (TKN) concentration (mg / mL) versus days for Example 1 ; and

[0014] FIG. 6 is a graph illustrating total nitrogen concentration (mg / mL) versus days for Example 1.DETAILED DESCRIPTION

[0015] Disclosed herein is a migrating biofilm carrier (hereinafter carrier) for intensifying the treatment of wastewater. The carrier serves as a scaffolding for biofilm attachment, biofilm growth, and biofilm transport during wastewater treatment. The carrier facilitates the transport of biofilm within a zone (e.g., an acclimation tank or a bioreactor) of a wastewater treatment system and throughout a wastewater treatment system. The carrier includes a biopolymer, a fill material, and a densifying agent. The densifying agent can modulate the specific gravity of the carrier. The combination of the biopolymer, the fill material, and the densifying agent can be extruded together to provide a selected surface area, density and / or porosity.

[0016] Methods to use the carrier are also disclosed. The carriers can be acclimated for microbial attachment via exposure to influent contaminants, return activated sludge, waste activated sludge, bioaugmentation, and / or biostimulation. During the acclimation of the carriers, biofilm growth can be optimized to provide a concentration suitable for carbon nutrients and nitrogen and phosphorus constituents removal. After disposition of the biofilmon the carrier, the biofilm can be contacted with wastewater to reduce different types of pollutants present in the wastewater. In this manner, biofilm disposed on a carrier can be used to intensify a wastewater treatment process for predictability, consistency, and throughput.

[0017] “And / or,” includes any and all combinations of the one or more of the associated listed items.

[0018] “Activated sludge,” as used herein, is defined as an aerated sludge that contains flocculent culture of microorganisms developed under aeration conditions.

[0019] “Bioaugmentation,” as used herein, is defined as the addition of microbial strains and / or carbon nutrients to wastewater.

[0020] “Biofilm,” as used herein, is defined as at least two microorganisms that are disposed on a surface.

[0021] “Biostimulation,” as used herein, is defined as the addition of nitrogen and phosphorus constituents to wastewater.

[0022] “Contaminated water,” as used herein, is defined as water with at least one contaminant. Untreated wastewater and contaminated water are used interchangeably herein.

[0023] “Effective surface area,” as used herein, is defined as the surface area useable for biofilm attachment.

[0024] “Return activated sludge,” as used herein, is defined as settled activated sludge that is collected in a selector and returned to the bioreactor to mix with incoming untreated wastewater.

[0025] “Solids retention time,” as used herein, is defined as the time the solid fraction of the wastewater spends in the wastewater treatment system.

[0026] “Waste activated sludge,” as used herein, is defined as sludge removed from the wastewater treatment process. The waste activated sludge contains excess biomass or cell mass and is removed to maintain the biological balance of the wastewater treatment system and / or achieve a specific solids retention time.

[0027] The migrating biofilm carrier serves as a scaffolding surface for microorganisms. The carrier can transport the biofilm through a wastewater treatment system. The movement of the carrier through a wastewater treatment system is based on the density and settling properties of the carrier. Biofilm disposed on the carrier serves to intensify the biological wastewater treatment process by improving settleability, carbon nutrient and phosphorus and nitrogen constituent removal.

[0028] As shown in FIG. 1, the carrier 100 can include a biopolymer 101 , a fillmaterial 103, and a densifying agent 102. The carrier can be compostable and / or biodegradable. The carrier can be injection molded or extruded. As shown in FIG. 1, the carrier 100 can bein a core-shell format, where the biopolymer 101 partially or fully encapsulates a core of a fill material 103 and a densifying agent 102. In an aspect, the biopolymer 101, the fill material 103, and the densifying agent 102 can be in a mixed format as shown in FIG. 2, such as uniformly distributed throughout the carrier. The biopolymer 101, the fill material 103, and the densifying agent 102 may be distributed throughout the carrier in a homogenous or heterogenous manner. When the materials are distributed in a heterogenous matter, the biopolymer 101, the fill material 103, and the densifying agent 102 may be distributed in layers or in concentration gradients in the carrier 100. The distributed mixed format of the biopolymer 101, the fill material 103, and the densifying agent 102 throughout the carrier 100 may be formed by co-extrusion of a mixture of the biopolymer 101, the fill material 103, and the densifying agent 102. The carrier 100 can be nonabsorbent, neutrally charged, and / or inert. The molding and / or extrusion of the mobile carrier 100 can provide an irregular surface with dimpling, porosity, and the like. The irregular surface can facilitate the attachment of biofilm to the carrier, protect biofilm growth, increase the total and effective surface area, and provide differentiating redox zones on the carrier. For example, the outermost surface of the carrier may be exposed to different redox conditions than an interior covered surface area of the carrier 100. The carrier 100 can be fully manufactured to a predetermined size, density, and / or surface area. The controlled physical and chemical characteristics of the carrier 100 can improve the consistency and predictability wastewater treatment process.

[0029] The carrier 100 can be a three-dimensional shape with a length, a width, and a height of about 500 micrometers to about 3 millimeters. In some embodiments, the carrier 100 is roughly spherical with a diameter of about 500 micrometers to about 3 millimeters. The overall surface area of the carrier 100 can be about 0.02 square meters per gram (m2 / g) to about 5 m2 / g. The specific gravity of the carrier 100 can be about 1 to about 5.

[0030] The core of the carrier 100 may contain the fill material 103. The fill material 103 can be an organic material and / or a recycled material. Suitable fill materials include cellulose, lignocellulose, moss, algae, mollusk shells. The fill material 103 can be about 5 weight percent (wt %) to about 95 wt %, about 10 wt % to about 75 wt%, or about 25 wt % to about 50 wt % of the total weight the carrier 100.

[0031] The biopolymer 101 of the carrier 100 may be an organic polymer, disposed primarily on the exterior of the fill material 103 and the densifying agent 102 or thebiopolymer 101 may be homogeneously or heterogeneously mixed with fill material 103 and densifying agent 102. The biopolymer 101 can be molded or extruded with the fill material 103 and the densifying agent 102. The biopolymerlOl can be structured to provide a porous surface of the carrier 100.

[0032] Suitable biopolymers include polylactic acid (PL A), polypropylene (PP), high density polyethylene (HDPE), acrylonitrile butadiene styrene (ABS), low density polyethylene (LLDPE), high impact polystyrene (HIPS), or combinations thereof. In some embodiments, the biopolymers can be biodegradable. Examples of suitable biodegradable polymers are polylactic-glycolic acid (PLGA), poly-caprolactone (PCL), copolymers of polylactic-glycolic acid and poly-caprolactone (PCL-PLGA copolymer), polyhydroxy- butyrate-valerate (PHBV), polyorthoester (POE), polyethylene oxide-butylene terephthalate (PEO-PBTP), poly-D,L-lactic acid-p-dioxanone-polyelhylene glycol block copolymer (PLA- DX-PEG), or the like, or combinations comprising at least one of the foregoing biodegradable polymers.

[0033] In some embodiments, the biopolymer 101 can include a mixture of biopolymers of about 5 wt % to about 30 wt % of the total weight of the biopolymer 101. The biopolymer 101 can be about 1 wt % to about 99 wt %, 2 wt % to 75 wt %, 5 wt % to about 30 wt %, or about 2 wt % to about 15 wt % of the total weight the carrier 100.

[0034] The densifying agent 102 can be organic or inorganic compounds. In some embodiments, the densifying agent 102 can include organic compounds with a hydroxyl functionality to increase hydrogen bonding in the filler core of the carrier. Suitable densifying agents include calcium salts, iron salts, granular activated carbon, and the like, and combinations thereof. In some embodiments, the densifying agent 102 may include metals (e.g., iron) or Group II salts, such as a calcium salt, a strontium salt, a barium salt, or a combination thereof. For example, the densifying agent 102 may be calcium carbonate, ferric chloride, barium chloride, iron, or the like. In an embodiment, the densifying agent 102 may be comprise 2, 3, or 4 organic or inorganic compounds. For example, when the densifying agent 102 comprises two organic or inorganic compounds, the two organic or inorganic compounds may be present in a 1: 1 ratio, a 1 :2 ratio, a 1 :3 ratio, a 1 :4 ratio, or the like. The densifying agent 102 can be about 0.2 wt % to about 75 wt %, 2 wt % to about 60 wt %, about 5 wt % to about 50 wt %, or about 10 wt % to about 25 wt % of the total weight the carrier 100.

[0035] A biofilm biomass is disposed on the migrating biofilm carrier 100 during and / or prior to wastewater treatment. The biofilm biomass includes microorganisms such asbacteria and protozoa. The biofilm biomass can be a single or heterogeneous species. The species of microorganism for the biofilm biomass are selected based on the composition of the incoming contaminated water, the redox conditions of the bioreactor, and the solids retention time (SRT). The biofilm biomass serves to biodegrade the constituents, such as phosphorus and nitrogen containing chemicals and nutrients, such as carbonaceous materials, contained in the contaminated water. Proper species selection and concentration of the biofilm biomass improves nutrient carbon removal, reduces suspended fine solids, and reduces total suspended solids.

[0036] The application of the biofilm disposed on the carrier to contaminated water increases the efficiency and throughput of the wastewater treatment. Use of the composition saves time, decreases treatment costs, and increases the treatment capacity of the system.

[0037] A method of acclimating the carrier for treatment of wastewater can include acclimating the carrier 100 in an acclimation tank. The carrier 100 can be charged into an acclimation tank and treated to one or more of a combination of redox conditions, such as aerobic, anaerobic, and / or anoxic. In the acclimation tank, the carrier 100 may be treated to one or more of a combination of redox conditions for 1 hour, 12 hours, 1 day, or 7 days to provide an acclimated carrier. Within the acclimation tank, the carrier 100 can be treated with untreated wastewater influent, return activated sludge, waste activated sludge, bioaugmentation, and / or biostimulation. The selected treatment or combination of treatments of the carrier within the acclimation tank facilitates the growth of biofilm on the carrier acclimated to the treatment conditions. Conditioning agents can be charged into the acclimation tank in combination with the carrier. Conditioning agents can include seed microorganisms. The seed microorganisms can be contained in the untreated wastewater influent, return activated sludge, waste activated sludge, bioaugmentation, and / or biostimulation. In some embodiments, the seed microorganisms can include a nitrifier, a denitrifier, methanogens, gram-negative bacteria, heterotrophic bacteria, or combinations thereof.

[0038] A method of wastewater treatment can include charging a carrier 100 into a wastewater treatment system. In some embodiments, the carrier 100 is acclimated prior to charging of the carrier into the wastewater treatment system. After contact with wastewater in the wastewater treatment system or after acclimation of the carrier 100, biofilm is disposed on the carrier. The carrier with biofilm disposed thereon can be transported throughout the wastewater treatment system. As the acclimated carrier migrates through the wastewater treatment system, the biofilm disposed on the carrier is contacted with wastewater. Thebiofilm disposed on the carrier reduces carbon nutrients and nitrogen and phosphorus constituents contained in the wastewater to provide treated wastewater. The biofilm disposed on the carrier serves to intensify the wastewater treatment process by increasing predictability, consistency, and throughput.

[0039] Hereinafter, the disclosure will be described in more detail with the following Examples, but the technical scope of the disclosure is not limited thereto.EXAMPLES

[0040] Measurements of various water quality variables were collected in accordance with the Standard Methods for the Examination of Water and Wastewater from different wastewater treatment systems. Details for the water quality variables sampled are listed in Table 1.Table 1. Water Quality Variable AbbreviationsExample 1. Performance of a Wastewater System with Gravimetric Sludge Selection and a Biofilm Carrier System

[0041] Multiple wastewater quality variables were assessed for a Modified Ludzack- Ettinger (MLE) Process Wastewater Treatment System with a flow of 1.7 million gallons per day fitted with a particle size selector posterior to a Gravimetric Sludge Selection System (i.e., a clarifier and so forth). Daily measurements over a 6-month period are shown in FIGS. 2 to 5 for influent and effluent samples. As shown in FIGS. 2 to 5, the system effectively decreased the Biological Oxygen Demand (BOD), Ammonia Concentration(NH3), Total Kjeldahl Nitrogen (TKN), and Total Nitrogen (TN) from the influent to the effluent.

[0042] On Day 115, a Biofilm Carrier System comprising the disclosed carrier 100 was installed in the Wastewater Treatment System. The average values of the ammonia, TKN, and TN of the effluent decreased after installation of the Biofilm Carrier System and the variation in the data also decreased (i.e., decreased standard deviation), see Table 2. Accordingly, application of the disclosed carrier 100 to a wastewater treatment system can provide improved process consistency and efficiency.Table 2. Average Nitrogen Concentrations

[0043] While the disclosure has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes can be made and equivalents can be substituted for elements thereof without departing from the scope of the disclosure. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the disclosure without departing from essential scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this disclosure, but that the disclosure will include all embodiments falling within the scope of the appended claims.

Claims

CLAIMSWhat is claimed is:

1. A migrating biofilm carrier for intensifying the treatment of wastewater comprising: a biopolymer comprising an organic polymer; a fill material; and a densifying material.

2. The migrating biofilm carrier of claim 1 , wherein the migrating biofilm carrier is a three-dimensional shape with a length, a width, and a height of about 500 micrometers to about 3 millimeters.

3. The migrating biofilm carrier of claim 1 , wherein the migrating biofilm carrier has an overall surface area of about 0.02 square meters per gram to about 5 square meters per gram.

4. The migrating biofilm carrier of claim 1 , wherein the migrating biofilm carrier has a specific gravity of about 1 to about 5.

5. The migrating biofilm carrier of claim 1 , wherein the biopolymer is polylactic acid, polypropylene, polyethylene, acrylonitrile butadiene styrene, low density polyethylene, high impact polystyrene, polylactic-glycolic acid, poly-caprolactone, copolymers of polylactic-glycolic acid and poly-caprolactone, polyhydroxy-butyrate-valerate, polyorthoester, polyethylene oxide-butylene terephthalate, poly-D,L-lactic acid-p-dioxanone- polyethylene glycol block copolymer, or combinations thereof.

6. The migrating biofilm carrier of claim 1 , wherein the biopolymer is about 1 weight percent to about 99 weight percent of the total weight of the migrating biofilm carrier.

7. The migrating biofilm carrier of claim 1 , wherein the fill material is cellulose, lignocellulose, moss, algae, mollusk shells, or combinations thereof.

8. The migrating biofilm carrier of claim 1, wherein the fill material is about 5 weight percent to about 95 weight percent of the total weight of the migrating biofilm carrier.

9. The migrating biofilm carrier of claim 1 , wherein the densifying material is a metal, a Group II metal salt, an iron salt, granular activated carbon, or a combination thereof.

10. The migrating biofilm carrier of claim 1 , wherein the densifying material is about 0.2 weight percent to about 75 weight percent of the total weight of the migrating biofilm carrier.

11. A method of acclimating a carrier for treatment of wastewater comprising: charging the carrier into an acclimation tank, wherein the carrier comprises abiopolymer, a fill material, and a densifying agent; charging a conditioning agent into the acclimation tank; and subjecting the carrier and conditioning agent to aerobic, anerobic, and / or anoxic conditions to provide an acclimated carrier wherein the acclimated carrier has a biofilm disposed on the carrier.

12. The method of claim 11, wherein the conditioning agent is a seed microorganism.

13. The method of claim 12, wherein the seed microorganism is in untreated wastewater influent, return activated sludge, and / or waste activated sludge.

14. The method of claim 12, wherein the seed microorganism is a nitrifier, a denitrifier, a methanogen, gram-negative bacteria, heterotrophic bacteria, or a combination thereof.

15. The method of claim 11, further comprising charging the acclimated carrier into a wastewater treatment system.

16. The method of claim 15, wherein the acclimated carrier is transported throughout the wastewater treatment system.

17. The method of claim 16, wherein the biofilm disposed on the carrier is contacted with wastewater to provide treated wastewater with reduced carbon nutrients and nitrogen and phosphorus constituents.

Images