WO2022211651A1

WO2022211651A1 - Systems, devices, and processes for nano-biotreatment of contaminated water

Info

Publication number: WO2022211651A1
Application number: PCT/QA2022/050006
Authority: WO
Inventors: Muftah H. El-Naas; Riham SURKATTI
Original assignee: Qatar University; Qatar Foundation For Education, Science And Community Development
Priority date: 2021-04-02
Filing date: 2022-04-01
Publication date: 2022-10-06

Abstract

Wastewater, such as a gas-to-liquids (GTL) process water, contains a wide range of organic pollutants that required effective treatment before being introduced to the environment. An environmental friendly treatment process was developed to remove organic pollutants presents in the water. The treatment process includes a pre-treatment and a biological treatment. The application of this process resulted in high organic removal and achieved a high COD reduction. The treatment process can lead to the production of a treated wastewater such as GTL process water with suitable characterization for safe discharge or reuse.

Description

TITLE

SYSTEMS, DEVICES, AND PROCESSES FOR NANO-BIOTREATMENT OF

CONTAMINATED WATER

CROSS REFERENCE TO RELATED APPLICATIONS The present application claims priority to Provisional Patent Application No. 63/170,055, filed on April 2, 2021, the entire contents of which are being incorporated herein by reference.

BACKGROUND

[0001] The present disclosure generally relates to systems, devices, and processes for treatment of water, specifically contaminated water or wastewater, such as gas-to-liquids (GTL) process water.

[0002] GTL process water contains a wide range of organic pollutants that require effective treatment before being introduced to the environment. There are many problems and issues associated with existing GTL process water and its treatment.

[0003] For example, the major limitations of the current activated sludge (AS) process include low degradation rates, long residence time and high rate of sludge generation, making it inefficient for the treatment of large amounts of process water. High cost and large footprint are required for the current GTL process water treatment plants, since they usually use multiple treatment steps.

SUMMARY

[0004] In a general embodiment, the present disclosure provides a process of treating water, the process comprising providing a raw feed water; pre-treating the raw feed water to remove volatile organic compounds (VOC) to obtain a stripped water; adjusting a pH of the stripped water; and bio-treatment of the stripped water comprising contacting the stripped water with nano-biocatalyst particles to remove organic pollutants to obtain a bio-treated water.

[0005] In an embodiment, the raw feed water has a pH of 4 or lower.

[0006] In an embodiment, the pH of the stripped water is adjusted to about 5 to about 7. [0007] In an embodiment, the raw feed water comprises a gas-to-liquids (GTL) process water.

[0008] In an embodiment, the raw feed water comprises organic compounds with COD ranging from 7000 to 10000 mg/1.

[0009] In an embodiment, the VOC comprise alcohols and volatile fatty acids (VFA).

[0010] In an embodiment, the pre-treating of the raw feed water comprises contacting the raw feed water with inert particles configured to absorb the volatile organic compounds, the inert particles moving in the raw feed water.

[0011] In an embodiment, the pre-treating of the raw feed water further comprises introducing air into the raw feed water causing the moving of the inert particles in the raw feed water.

[0012] In an embodiment, bacteria immobilized on the nano-biocatalyst particles degrade organic pollutants in the stripped water through aerobic degradation.

[0013] In an embodiment, the nano-biocatalyst particles comprise Ti02 nanoparticles in a polyvinyl alcohol (PVA) gel matrix.

[0014] In an embodiment, the process further comprises bio-treatment of the bio treated water by contacting the bio-treated water with additional nano-biocatalyst particles.

[0015] In an embodiment, the process results in more than 90% COD reduction from the raw feed water.

[0016] In an embodiment, the pre-treating of the raw feed water is conducted for about 5 hours to about 24 hours.

[0017] In an embodiment, the bio-treatment of the stripped water is conducted for about 24 hours to about 48 hours.

[0018] In another general embodiment, the present disclosure provides a system for water treatment, the system comprising: a feeding tank containing a raw feed water and configured to feed the raw feed water to a stripping column; the stripping column fluidly connected to the feeding tank and containing inert particles configured to remove volatile organic compounds (VOC), the stripping column comprising an inlet configured for receiving the raw feed water from the feeding tank, and the stripping column further comprising an outlet configured for a stripped water to exit the stripping column; a neutralization tank configured to receive the stripped water from the stripping column and a pH adjusting agent; and a bioreactor containing nano-biocatalyst particles and configured to receive the stripped water from the neutralization tank and to allow the stripped water to contact the nano-biocatalyst particles to remove organic pollutants to obtain a bio-treated water.

[0019] An advantage of the present disclosure is to provide systems, devices, and processes that help manage the disposal of contaminated water or wastewater, even highly contaminated water, such as GTL process water, to be reused for other purposes, such as irrigation, or to be disposed of safely into the environment.

[0020] Another advantage of the present disclosure is to provide systems, devices, and processes that allow the treatment of water, specifically contaminated water or wastewater, such as GTL process water, and consequently, solve one of the major environmental and economic issues related to the oil and gas industries.

[0021] Yet another advantage of the present disclosure is to provides an environmental friendlily and cost effective process for the treatment of wastewater.

[0022] Still another advantage of the present disclosure is to provide an effective nanoparticle-based biocatalyst that has high mechanical strength, durability and performance in the treatment of wastewater while having less residence time.

[0023] An additional advantage of the present disclosure is to provide systems, devices, and processes for effective treatment of huge amount of wastewater. The load on the desalination plants is a main source of water supply in certain regions of the world. The effective treatment of huge amount of wastewater will facilitate the use of an alternative water supply in the several industrial sectors and can also be used for irrigation applications. This will have an immense influence on the water supply in the industrial sector and, subsequently, the water security.

[0024] A further advantage of the present disclosure is that application of an immobilized bacteria will overcome the challenges related to the current activated sludge systems utilized in wastewater water treatment plants.

[0025] Yet a further advantage of the present disclosure is that the combination of the nanotechnology and biological activity prepares durable and strong nano-biocatalyst to be used for cell immobilization and applied as biofdm in a moving bed reactor.

[0026] Still another advantage of the present disclosure is achieving high COD reduction, such as more than about 90%, using different arrangements of stripping and biotreatment units. [0027] An additional advantage of the present disclosure is reducing the cost of the treatment process through stripping at low temperatures compared to the currently used distillation column.

[0028] Yet an additional advantage of the present disclosure is that the disclosed process and system can replace the application of the activated sludge system that requires complicated sludge processing. Using immobilized bacteria will enhance the biological treatment efficiency by increasing the tolerance of biomass towards a high COD content and the sudden change in the operation conditions, such as pH and temperature, during the treatment process.

[0029] Additional features and advantages are described in, and will be apparent from, the following Detailed Description and the Figures.

BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 shows a non-limiting example of a water treatment system according to the present disclosure.

[0031] Figure 2 is a SEM image of a non-limiting example of an immobilization matrix for the biomass, specifically, a PVA/Ti02 hydrogel with 10wt% PVA and 0.1% Ti02, according to the present disclosure.

[0032] Figure 3 shows the COD and TOC reduction% after each treatment step in a non-limiting example of a three-step treatment system according to the present disclosure.

[0033] Figure 4 shows the cumulative COD reduction% of a GTL process water during each treatment unit in a non-limiting example according to the present disclosure.

DETAILED DESCRIPTION

[0034] All percentages are by weight of the total weight of the composition unless expressed otherwise. Similarly, all ratios are by weight unless expressed otherwise. When reference is made to the pH, values correspond to pH measured at 25 °C with standard equipment. As used herein, "about," "approximately" and "substantially" are understood to refer to numbers in a range of numerals, for example the range of -10% to +10% of the referenced number, preferably -5% to +5% of the referenced number, more preferably -1% to +1% of the referenced number, most preferably -0.1% to +0.1% of the referenced number. [0035] Furthermore, all numerical ranges herein should be understood to include all integers, whole or fractions, within the range. Moreover, these numerical ranges should be construed as providing support for a claim directed to any number or subset of numbers in that range. For example, a disclosure of from 1 to 10 should be construed as supporting a range of from 1 to 8, from 3 to 7, from 1 to 9, from 3.6 to 4.6, from 3.5 to 9.9, and so forth.

[0036] As used herein and in the appended claims, the singular form of a word includes the plural, unless the context clearly dictates otherwise. Thus, the references "a," "an" and "the" are generally inclusive of the plurals of the respective terms. For example, reference to "an ingredient" or "a method" includes a plurality of such "ingredients" or "methods." The term "and/or" used in the context of "X and/or Y" should be interpreted as "X," or “Y,” or "X andY."

[0037] Similarly, the words "comprise," "comprises," and "comprising" are to be interpreted inclusively rather than exclusively. Likewise, the terms "include," "including" and "or" should all be construed to be inclusive, unless such a construction is clearly prohibited from the context. However, the embodiments provided by the present disclosure may lack any element that is not specifically disclosed herein. Thus, a disclosure of an embodiment defined using the term "comprising" is also a disclosure of embodiments "consisting essentially of and "consisting of the disclosed components. Where used herein, the term "example," particularly when followed by a listing of terms, is merely exemplary and illustrative, and should not be deemed to be exclusive or comprehensive. Any embodiment disclosed herein can be combined with any other embodiment disclosed herein unless explicitly indicated otherwise.

[0038] The present disclosure provides an efficient process for the treatment of GTL process water. The system may implement a multi-stage treatment process that includes pre treatment and main treatment processes. The process may include two treatment steps: stripping and nanoparticles-based biological treatment. In an embodiment, the process may consist of these two treatment steps.

[0039] The process may utilize a system including specially designed stripping and biotreatment units. The pretreatment is carried out using air stripping in a moving bed column, followed by biological treatment in a moving bed bio-reactor. The treatment process can be operated under several arrangements of stripping and biological units. These units may have the same or different volume and dimensions. The stripping unit may house inert particles to facilitate mixing and to remove the volatile organics. The biotreatment unit may contain a nanoparticles-based biocatalyst that contain active bacteria for the biodegradation of the remaining organic contaminants.

[0040] The bioreactor may have a special type of nano-biocatalyst prepared by bacterial immobilization into a matrix embedded with nanoparticles. The biocatalyst may be prepared by the immobilization of a biomass and Ti02 nanoparticles on cost effective materials, such as polyvinyl alcohol (PVA) polymer. The nano-biocatalyst may comprise a suitable bacterial immobilized into a PVA gel matrix embedded with Ti02 nanoparticles. The nanoparticles may be utilized to increase the durability and mechanical strength of the PVA matrix and consequently ensure stable, long-term performance of the system. The immobilization matrix is porous, durable and has high mechanical stability. The bacterial strain may be isolated from the GTL process water and then used for the treatment of the same GTL process water.

[0041] The application of the nano-based biocatalyst can be applied in any bioreactor, in order to improve the bioreactor stability and the biodegradation performance. Additionally, the biological reactor in the present disclosure can be applied to and/or replace a conventional activated sludge system.

[0042] A neutralization tank may be placed between the two units to adjust the water pH and provide the necessary nutrients supply for the bioreactors. The treatment process may include one stripping unit followed by biotreatment.

[0043] The process and system may include a combination of any numbers of the stripping unit and the biotreatment unit depending on the target water quality.

[0044] The process and system include a continuous combination of one or more stripping columns and one or more moving bed reactors. The one or more bioreactors can be arranged in one, two or three reactors in series. Increasing the number of bioreactors will enhance the overall treatment efficiency.

[0045] The system, device, and process can be used in the treatment of any industrial wastewater that contains alcohols, ketones, fatty acids and/or other aliphatic hydrocarbons. The system, device, and process can be used to remove a wide range of organics pollutants, such as alcohols, ketones, esters and volatile fatty acids. Combinations of the treatment steps, devices and/or systems according to the present disclosure can be operated for the reduction of a high COD content from wastewater. The treatment process, device, and system can be utilized for the treatment of wastewater other than a GTL process water, such as refinery, textile and/or pharmaceutical wastewater, which usually may have a high COD content and contain a wide range of organic pollutants.

[0046] The disclosed process has fewer steps compared to the conventional GTL process water treatment and has the ability to achieve at least about 90% COD removal by reducing the concentrations of various organics, including alcohols, ketones and fatty acids.

EXAMPLES

[0047] Example 1 : A non-limiting example of a water treatment system according to the present disclosure

[0048] A water treatment system according to the present disclosure may include or consist of two main columns and three tanks (Figure 1). In this example, a feeding tank (1) contains a raw feed water, such as a raw GTL process water without any modification or adjustment. The feeding tank (1) may be 20-liter or any other suitable and/or desired capacity. The raw feed water, such as the raw GTL process water, may be highly acidic, for example, with a pH of 4.0 or lower, 3.0 or lower, or 2.0 or lower. The raw feed water, such as the raw GTL process water, may include a large amount of organic compounds, with COD ranging from about 7000 to about 10000 mg/1.

[0049] A cylindrical column may be used as a stripping unit or column (3) for pre treatment of the raw feed water, such as the raw GTL process water. The cylindrical column may be 3-liter or any other suitable and/or desired capacity. The stripping column (3) may contain inert particles as a moving material (4). The inert particles may be polymeric spherically shaped with an average diameter less than 1 mm, such as 0.9, 0.8 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or 0.1 mm. The use of the inert particles enhances mass transfer in the system and maximizes the removal of volatile organic compounds (VOC).

[0050] The raw feed water, such as the raw GTL process water, may be fed through the bottom of the stripping column (3) using a peristaltic pump (2) that introduces the water at a fixed liquid flow rate, such as 0.3 L/h or any other suitable and/or desired rate. Air may be supplied to the stripping column (3) by an air compressor (5) and introduced to the column (3) through a nozzle at the bottom of the column (3). The introduced air, together with the movement of the inert particles, allows the completion of the stripping process. The column (3) may be provided with a water jacket to maintain the water temperature at a set value. [0051] The treated/stripped water may leave the stripping column (3) via a tube at the top of the column. The VOC-rich-air may be collected in a condenser (not shown) to separate alcohols and volatile fatty acids (VFA) from the GTL process water.

[0052] The stripped water may then be collected in a neutralization tank (6). A pH adjusting agent, such as NaOH, in a form of powders and/or pellets, may be added to the stripped water in the neutralization tank (6) to adjust the pH of the stripped water to about 5 to about 7. Mineral nutrients may also be added to the stripped water to maintain the biological treatment conditions.

[0053] Following the neutralization tank, the stripped water may be sent to the bioreactor (7) that includes the nano-biocatalyst (8) as moving particles. In this step, the bacteria immobilized on the nano-biocatalyst particles degrade the rest of organic pollutants in the water through aerobic degradation. Air may be introduced to the bioreactor to maintain aerobic conditions and also to ensure the movement of the biocatalyst in the bioreactor for effective contact between the bacteria and the contaminants in the water in the bioreactor.

[0054] Example 2: A non-limiting example of preparation of the nano-biocatalyst according to the present disclosure

[0055] In this non-limiting example, a PVA gel was prepared and reinforced using Ti02 nanoparticles. The gel matrix was tested for its mechanical strength and porous structure. The effect of the amount of Ή02 nanoparticles added to the PVA gel matrix was investigated. The results showed that, the reinforcement of the PVA gel using Ti02 nanoparticles resulted in an improvement in its mechanical properties.

[0056] Compared to the pure PVA, increasing the Ti02 content from 0.1 to 1 wt% or more enhanced the compression strength of the PVA/Ti02 by 50% to 150% or more. The resulted PVA/Ti02 gel with at least 1.0 wt% Ti02 is durable and has high stability that allows it application in the biological reactor for a long period of time.

[0057] Example 3: A non-limiting example of GTL process water treatment according to the present disclosure

[0058] In this non-limiting example, the GTL process water is acidic and characterized with its high COD content ranging from 7000 to 10,000 mg/1. The water treatment process was used for the removal of a wide range of organic pollutants from GTL process water. [0059] The process was operated in the continuous mode using the stripping and biological treatment units. Both units were operated at a residence time of 12h, to ensure enough time for the stripping process and to improve the contact between biomass and organic pollutants in the bioreactor. The organics concentration was evaluated using COD and TOC analysis at several time intervals in each treatment step. The volatile organic compounds in the GTL process water were removed by the stripping unit. The removed volatile organics may be collected through a condensation system and sent to one or more separation units to separate several short chain alcohols for other industrial applications.

[0060] After the stripping step, residual organics was removed using the biological treatment unit. The biological treatment was carried out using the immobilized bacteria in the PVA/Ti02matrix as the nano-based biocatalyst. The immobilized bacteria allowed the degradation of the residual organics present in the stripped GTL process water.

[0061] GTL process water treatment can be applied using several numbers of stripping units and biological reactors. The treatment of GTL process water was tested continuously using one and two stripping columns, as pre-treatment step. Results showed that there was no significant change in the COD content by utilizing one or two stripping columns. In contrast, increasing the number of the bioreactors resulted in more COD reduction and improved the efficiency of the overall treatment. The operation conditions of a tested treatment process consisting of a stripper-bioreactor-bioreactor system are presented in Table 1.

[0062] Table 1 : Parameters and conditions of a treatment process using a stripping- bioreactor-bioreactor system

[0063] Continuous treatment of GTL process water through a stripping-bioreactor system was evaluated for three days (72 hours), in order to ensure the steady state of the organic concentration. The removal of organic pollutants from the GTL process water was described by the COD and TOC content. The results showed that the reduction of COD through the stripping column was very fast in the first 5 hours or so. However, the COD content was slightly further reduced within the first day (24 hours), and no more reduction was observed after this period.

[0064] During the biological treatment, the removal of organic pollutants was very high in the first day (24 hours). However, the organics’ removal was only slightly increased within the second day, and there was no further reduction after about 48 hours. Although the biological treatment can be very slow and may need a long residence time, this treatment step resulted in high COD reduction regardless the initial COD concentration (e.g., about 4000 mg/1 or more).

[0065] The COD and TOC reduction percentages were evaluated at study state values, after each treatment step (Figure 3). In this example, the stripping unit resulted in COD and TOC reduction of about 43% and about 38%, respectively. However, the first bioreactor resulted in about 60% COD and TOC reductions, and the application of the second bioreactor allowed the removal of the residual organics from the GLT process water and caused about 80% COD and TOC reductions.

[0066] In order to understand the performance of the full treatment process, the cumulative COD reduction was evaluated at several time intervals through each treatment unit. As shown in Figure 4, the stripping process was very fast and achieved more than about 43% COD reduction. The biotreatment of the stripped water resulted in about 80% cumulative COD reduction in the second day and reduced the COD content to about 1500 mg/1. Furthermore, the addition of the second biological reactor resulted in a high removal of the organics and achieved an overall COD reduction of about 90%. These results showed that this treatment system is effective for the GTL process water treatment and resulted in a treated water with a low organics concentration.

[0067] GC-MS analysis of the raw GTL process water (7000-10000 mg/1 COD), the stripped water, and the treated water after the final bio-treatment step were analyzed (Table 2). Clearly, the GTL process water contains number of alcohols, ketones, volatile fatty acids, ester, and other aliphatic.

[0068] The above results showed that more than about 40% COD reduction was obtained by the stripping unit, and the resulted water contains around 4000 mg/1 COD content. This reduction is related to the removal of most VFA, such as propenoic and butanoic acids, esters including methyl and ethyl ester, and alcohols, such as heptanol and decanol derivatives, in addition to most of the short chain alcohols. This is directly related to the nature of the stripping process as a fast physical treatment method that is applied to remove volatile organics from wastewater.

[0069] After the biological treatment, all ketones and the remaining acids (e.g., acetoacetic acid) were removed from the GTL process water, in addition to most of the alcohols except hexanol, octanol and decanol. This resulted in treated water that has a COD content of less than about 600 mg/1.

[0070] Table 2: Qualitative analysis for GTL process water before and after biological treatment using isolated strains: (D) Detected; (ND) Non-Detected.

Non-stripped GTL Stripped GTL Treated GTL

Containment

Water Water Water

Short Chain Alcohol

Methanol D D ND

Ethanol D D ND

Propanol D D ND

Butanol D D ND

Long Chain Alcohol

3-Hexanol D D ND

2.5-dimethyl-2-Hexanol D D D

4-methyl-3-Heptanol D D ND Heptanol D ND ND 2-Octanol D D D

2-butyl- 1 -Octanol D ND ND

2.6-dimethyl-2-Octanol D D ND

3-hexadecanol D D ND

2-Methyl-2-decanol D D D

3-Tetradecanol D ND ND 2-Pentadecanol D ND ND 1-Nonadecanol D D ND

5 , 9-dimethyl- 1 -decanol D D ND Fatty Acids 2-Propenoic acid D ND ND Butanoic acid D ND ND Acetoacetic acid D D ND

Ketones

5 -methoxy-2-Pentanone D D ND methyl ketone D D ND Esters

1,1-dimethy ethyl ester D ND ND methyl ester D ND ND

Ethyl ester D ND ND

Others

4-hydroxy- D ND ND

Cyclohexanemethanol

1 -ethoxy-Hexane D ND ND

[0071] It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.

Claims

CLAIMS The invention is claimed as follows:

1. A process of treating water, the process comprising: providing a raw feed water; pre-treating the raw feed water to remove volatile organic compounds (VOC) to obtain a stripped water; adjusting a pH of the stripped water; and bio-treatment of the stripped water comprising contacting the stripped water with nano-biocatalyst particles to remove organic pollutants to obtain a bio-treated water.

2. The process of claim 1, wherein the raw feed water has a pH of 4 or lower.

3. The process of claim 1, wherein the pH of the stripped water is adjusted to about 5 to about 7.

4. The process of claim 1, wherein the raw feed water comprises a gas-to- liquids (GTL) process water.

5. The process of claim 1, wherein the raw feed water comprises organic compounds with COD ranging from 7000 to 10000 mg/1.

6. The process of claim 1, wherein the VOC comprise alcohols and volatile fatty acids (VFA).

7. The process of claim 1, wherein the pre-treating of the raw feed water comprises contacting the raw feed water with inert particles configured to absorb the volatile organic compounds, the inert particles moving in the raw feed water.

8. The process of claim 7, wherein the pre-treating of the raw feed water further comprises introducing air into the raw feed water causing the moving of the inert particles in the raw feed water.

9. The process of claim 1, wherein bacteria immobilized on the nano biocatalyst particles degrade organic pollutants in the stripped water through aerobic degradation.

10. The process of claim 1, wherein the nano-biocatalyst particles comprise Ti02 nanoparticles in a polyvinyl alcohol (PVA) gel matrix.

11. The process of claim 1 further comprising bio-treatment of the bio treated water by contacting the bio-treated water with additional nano-biocatalyst particles.

12. The process of claim 1 resulting in more than 90% COD reduction from the raw feed water.

13. The process of claim 1, wherein the pre-treating of the raw feed water is conducted for about 5 hours to about 24 hours.

14. The process of claim 1, wherein the bio-treatment of the stripped water is conducted for about 24 hours to about 48 hours.

15. A system for water treatment, the system comprising : a feeding tank containing a raw feed water and configured to feed the raw feed water to a stripping column; the stripping column fluidly connected to the feeding tank and containing inert particles configured to remove volatile organic compounds (VOC), the stripping column comprising an inlet configured for receiving the raw feed water from the feeding tank, and the stripping column further comprising an outlet configured for a stripped water to exit the stripping column; a neutralization tank configured to receive the stripped water from the stripping column and a pH adjusting agent; and a bioreactor containing nano-biocatalyst particles and configured to receive the stripped water from the neutralization tank and to allow the stripped water to contact the nano-biocatalyst particles to remove organic pollutants to obtain a bio-treated water.

16. The system of claim 15 further comprising a condenser configured to collect a VOC-rich-air from the stripping column.

17. The system of claim 15 further comprising an additional bioreactor containing additional nano-biocatalyst particles, and the additional bioreactor is configured to receive the bio-treated water from the bioreactor and to allow the bio treated water to contact the additional nano-biocatalyst particles to remove additional organic pollutants.

18. The system of claim 15, wherein the raw feed water comprises a gas- to-liquids (GTL) process water.

19. The system of claim 15, wherein the nano-biocatalyst particles comprise Ti02 nanoparticles in a polyvinyl alcohol (PVA) gel matrix.

20. The system of claim 15, wherein the nano-biocatalyst particles comprise bacteria immobilized on the nano-biocatalyst particles.