A METHOD FOR THE TREATMENT OF OILFIELD PRODUCED WATER (OFPW)

Abstract

ABSTRACT A METHOD FOR THE TREATMENT OF OILFIELD PRODUCED WATER (OFPW) A method for the treatment of water produced from oilfields (OFPW) includes an initial pretreatment stage that involves gravity separation, sand filtration, and aeration using a centrifuge to facilitate sedimentation, resulting in a first intermediate of treated water. This is followed by a membrane treatment stage, where the first intermediate water from the pretreatment phase undergoes membrane treatment processes, specifically microfiltration, ultrafiltration, and nanofiltration. FIG.1

Specification

Description:FIELD OF THE INVENTION
The present invention pertains to Water Treatment and Management, specifically focusing on water produced from oilfield operations (OFPW).

BACKGROUND OF THE INVENTION
Produced water management has long been a significant challenge in the oil and gas industry due to the high levels of pollutants such as oil, grease, heavy metals, and other contaminants. Traditional water treatment techniques often fall short in meeting stringent environmental regulations and are sometimes costly to implement. With the growing emphasis on sustainability and environmental responsibility, there is a critical need for innovative solutions that balance efficacy with cost-effectiveness.

There is a necessity to create a comprehensive filtration method that can effectively remove larger contaminants while also tackling the issue of smaller, persistent particles. In particular, a viable technique for the efficient removal of oil and various hydrocarbons on an industrial scale is essential, as it would improve overall water quality and uphold environmental standards.

OBJECTS OF THE INVENTION
The object of the present invention is to provide the oil industry with a practical, economically viable method for produced water treatment, ultimately contributing to more sustainable industrial practices.
SUMMARY OF THE INVENTION
The present invention provides a method for treating oilfield-produced water (OFPW) encompasses a comprehensive two-stage approach, initiating with a pretreatment stage (PT) that employs gravity separation (GS), sand filtration (SF), and Aeration with Centrifuge (AwC). The pretreatment stage (PT) facilitates sedimentation, resulting in an initial intermediate of treated water by enabling the separation of components based on their density-where denser sediments settle and lighter crude oil floats for removal through decantation.

Subsequently, the membrane treatment (MT) stage applies microfiltration (MIF), ultrafiltration (UF), and nanofiltration (NF) techniques to the first intermediate water. The microfiltration (MIF) employs a polyacrylonitrile membrane, while the ultrafiltration (UF), and nanofiltration (NF) membranes are crafted from polysulfone, with defined pore sizes for effective filtration. This systematic method ensures the reduction of contaminants, promoting both aerobic biodegradation and high-quality water recovery.

BRIEF DESCRIPTION OF THE FIGURES
FIG.1 is a block diagram illustrating the method of oilfield-produced water (OFPW) treatment, incorporating various methodologies, namely gravity separation (GS), soil filtration (SF), Aeration with Centrifuge (AwC), and membrane technology (MT).

FIG.2 is a block diagram illustrating the modeling of Preliminary Treatment Stage of oilfield-produced water (OFPW).

FIG.3 is a block diagram illustrating the modeling of Hollow Fiber Membrane Module (HFMM) Stage of oilfield-produced water (OFPW).

DETAILED DESCRIPTION OF THE INVENTION
The present invention addresses the management of untreated oilfield produced water (OFPW) through a thorough treatment strategy that initiates with pretreatment (PT). This initial stage includes Gravity Separation (GS), Sand Filtration (SF), and Aeration with Centrifuge (AwC), which work together to eliminate larger particles and dissolved substances. After PT, Membrane Technology (MT) is utilized, incorporating Microfiltration (MiF), Ultrafiltration (UF), and Nanofiltration (NF). This layered approach significantly improves water quality, ensuring that oilfield produced water (OFPW) is properly treated for safe reuse or environmentally sound discharge.

The present invention addresses existing limitations in filtration methodologies by integrating both preliminary and advanced treatment techniques to enhance overall efficacy. Initial processes, including gravity separation and sand filtration, demonstrate significant effectiveness in the removal of larger contaminants. In conjunction, advanced membrane filtration technologies exhibit considerable capability in targeting smaller, persistent particles, particularly those comprising oil and hydrocarbons, at the nanometer scale. This dual approach is designed to provide a comprehensive solution for improved filtration outcomes.

The comprehensive model that integrates pretreatment (PT) and Membrane Technology (MT) methods has been meticulously developed to enhance treatment efficiency while simultaneously reducing operational costs. This innovative approach effectively addresses the shortcomings of traditional techniques and complies with stringent environmental standards. By improving water quality and offering a scalable solution, the model is particularly advantageous for oil fields worldwide, especially those subject to increasingly rigorous disposal regulations and environmental oversight.

FIG.1 is a block diagram illustrating the modelling of oilfield-produced water (OFPW) treatment, incorporating various methodologies, namely Gravity separation (GS), Sand filtration (SF), Aeration with Centrifuge (AwC), and membrane technology (MT). Each treatment method is depicted as an integral component of the overall system, highlighting their respective roles in enhancing the efficacy of oilfield-produced water (OFPW) management. This schematic serves as a foundational reference for understanding the interconnected processes involved in the treatment of produced water in oilfield operations.
The present invention provides a multifaceted treatment methodology aimed at augmenting the efficiency of contaminant removal, as illustrated in FIG.1.
This methodology is composed of four sequential stages:

Gravity Separation (GS),
Sand Filtration (SF),
Aeration with Centrifuge (AwC), and
Membrane Technology (MT).

Initially, Gravity Separation (GS), leverages density differences to segregate oil and solids from wastewater, thereby simplifying its composition and facilitating further treatment. Sand Filtration (SF), SF subsequently employs granular materials to extract fine particulates, enhancing water clarity. The third stage, Aeration with Centrifuge (AwC), integrates aeration to effectively remove dissolved gases and volatile organic compounds, while the centrifuge enhances separation based on density and size.

Lastly, Membrane Technology (MT) implements advanced filtration techniques to eliminate residual impurities, ensuring that the treated water complies with stringent regulatory standards for safe discharge or reuse.
the innovative treatment method for oilfield-produced water (OFPW) defined herein represents a holistic and systematic approach to water management in oilfields. By targeting specific contaminants at each stage of the process, the methodology not only enhances the efficacy of contaminant removal but also contributes to the sustainable utilization of water resources in an industry characterized by substantial environmental impacts.

the Aeration with Centrifuge (AwC) allows aerobic biodegradation of both organic and inorganic matter, and the gases formed during organic decomposition are removed and oxidised Fe and Mn to form precipitates; the microfiltration (MIF) membrane is composed of polyacrylonitrile (pan), and the ultrafiltration (UF) and nanofiltration (NF) membranes are made from polysulfone (PS).

In some embodiment of the present invention, Gravity separation of oilfield-produced water (OFPW) is conducted by allowing the fluid to sit undisturbed for a period of 24 hours. This technique relies on the natural density differences between the water and the various associated contaminants, facilitating the settling of oils and solids. During this time, denser particles gradually descend to the bottom, forming a sludge layer, while lighter hydrocarbons rise to the surface. The clear water that remains in the middle can then be effectively extracted for further treatment or disposal, thereby enhancing the efficiency of the overall separation process.

In some embodiment of the present invention, the sand filtration process consists of sand particle size 0.044 - 0.062mm, sandstone particle size 0.044 -0.062 mm and charcoal particle size 0.125 - 0.149 mm, arranged in that order from top to bottom for the effective treatment of oilfield-produced water.

In some embodiment of the present invention, the Aeration with Centrifuge (AwC) method facilitates the removal of contaminants from sand-filtered water by promoting aerobic biodegradation of organic and inorganic substances.

In some embodiment of the present invention, the Membrane Technology (MT) process involves the pretreatment (PT) stage of treated water undergoing sequential filtration through a Hollow Fiber Membrane Module (HFMM). This procedure utilizes microfiltration (MIF), followed by ultrafiltration (UF), and concludes with nanofiltration (NF) membranes. Each filtration stage is designed to progressively remove contaminants, thereby enhancing the quality of the treated water.
In some embodiment of the present invention, the microfiltration (MIF)is composed of Polyacrylonitrile (PAN) with an average pore diameter of 200nm.
In some embodiment of the present invention, the ultrafiltration (UF), and nanofiltration (NF)membranes are composed of Polysulfone (PS) with pore diameter 12.9 and 1.04 respectively.

Example
The untreated oilfield produced water (OFPW) undergoes Pretreatment Treatment (PT), which includes Gravity Separation (GS), Sand Filtration (SF), and Aeration with Centrifuge (AwC). This initial phase is succeeded by Membrane Technology (MT), consisting of Microfiltration (MiF), Ultrafiltration (UF), and Nanofiltration (NF).

Example 1: Pretreatment Treatment (PT):
Referring to FIG.2, The Gravity Separation (GS) method serves as an effective primary treatment for oilfield produced water (OFPW), utilizing a 1L cylinder characterized by a diameter of 80 mm and a height of 320 mm, with a processing duration of 24 hours. This technique exploits the density differences among three distinct components within the OFPW; denser sediments inevitably settle at the bottom, while lighter crude oil ascends to the surface via flotation. Following this separation, the crude oil is extracted through decantation. The resultant treated OFPW is subsequently subjected to the Sand Filtration (SF) method for further purification.
The combined Sand Filtration (SF) system is structured with a stratified arrangement of filtration media, wherein sand particles ranging from 0.044 to 0.062 mm in size serve as the uppermost layer. Beneath this, sandstone particles of identical dimensions (0.044 to 0.062 mm) are positioned, providing an additional filtration mechanism. At the base, a layer of charcoal with a larger particle size of 0.125 to 0.149 mm completes the configuration. This arrangement is designed to enhance the overall efficacy of the filtration process by utilizing the distinct properties of each material.
Table 1: SF Composition from top to bottom
S.No ASTM Particle size (mm) Aggregate name (Wentworth class) Experimental sample
1 325 - 230 0.044 - 0.062 Coarse silt Brahmaputra sand
2 325 - 230 0.044 - 0.062 Coarse silt Reservoir Sandstone
3 120 - 100 0.125 - 0.149 Fine sand Decolorizing powder activated charcoal

The treated oilfield produced water (OFPW) from sand filtration (SF)is subsequently processed using the Advanced Treatment method, which includes Aeration followed by Centrifugation Aeration with Centrifuge (AwC).

Sand Filtration (SF) treated oilfield produced water (OFPW) undergoes natural aeration in a 1L beaker before being subjected to centrifugation at 1500 rpm for 15 minutes using an Electra lab centrifuge. This process constitutes the final stage of Preliminary Treatment (PT) water, which is comprised of 90% liquid, with the remaining 10% consisting of sediment that is safely discarded for further treatment. The aeration technique facilitates the aerobic biodegradation of organic and inorganic contaminants, while simultaneously allowing for the oxidation of iron and manganese, resulting in the formation of precipitates. Centrifugation effectively separates solids from the SF treated water based on various physical properties such as size, shape, density, and viscosity, making it a highly efficient method for sludge concentration. Notably, the Aeration followed by Centrifugation (AwC) method is advantageous due to its simplicity, lack of chemical requirements, cost-effectiveness, and the ease with which well-stabilized sludge can be removed from the Preliminary Treatment (PT) water.
Table 2: Aeration with Centrifuge (AwC) and its functions


Function Aeration with Centrifuge (AwC)
Aeration Centrifuge
Aerobic biodegradation of OC and IEA of OFPW Removal of sediments by settling

II. Membrane Technology (MT) Stage:
The Pretreatment (PT) stage water, obtained in the previous Pretreatment (PT) stage, undergoes advanced purification via a Hollow Fiber Membrane Module (HFMM), employing Microfiltration (MiF), Ultrafiltration (UF), and Nanofiltration (NF) membranes in a sequential manner. This multi-stage filtration process effectively enhances water quality by removing particulate matter, pathogens, and dissolved contaminants, thereby ensuring the delivery of treated water that meets stringent regulatory standards for various applications. The integration of these membrane technologies illustrates a robust approach to water treatment, promoting both efficiency and sustainability in resource management.
Figure 2 defines the configuration of the HFMM system, which incorporates a Feed Tank specifically designated for the treatment of Pretreated (PT) water. The treatment process commences with Pretreated (PT) water being drawn by a booster pump and subsequently conveyed to the Membrane Module (MM) through a 6 mm polyurethane tube, securely connected to a Perspex flange.
A set of pressure gauges, calibrated to measure between 0 and 60 psi, is positioned on both the upstream and downstream sides of the module to ensure effective monitoring of the system's performance. A ¾ inch stainless steel needle valve on the retentate line enables accurate control of pressure and flow rates within the membrane module (MM). Additionally, a rotameter with a range of 0 to 50 L/hr is utilized to measure the Retentate Stream (RS), which is then recycled back to the feed tank. A bypass line, featuring a ½ inch stainless steel bypass valve, connects the booster pump to the feed tank. Concurrently, the permeate, which consists of filter treated water, is directed through a 5 mm polyurethane pipe into the permeate collector.

Table 3: List of membranes used in HFMM
SN Membrane Composition Molecular weight cut-off (MWCO) (kDa) Membrane surface area
(cm2) Average pore diameter (nm) OD of the membrane
(cm) ID of the membrane
(cm) Length of the membrane
(cm)
1 MiF Polyacrylonitrile (PAN) - 107 200 2.6 2 16
2 UF Polysulfone (PS) 70 12.9
3 NF 0.7 1.04

Ten(10) untreated oilfield produced water samples are subjected to the treatment process outlined in the present invention. The results are detailed in the following section.
The analysis presents the results of physicochemical parameters (PP) and the concentrations of inorganic elements and anions (IEA) from ten untreated oilfield produced water (OFPW) samples.
Table 4: Results of physicochemical parameters (PP) 10 untreated oilfield produced water (OFPW) samples
Parameters Units *CPCB limit Untreated Oilfield Produced Water (OFPW) Samples
S1 S2 S3 S4 S5 S6 S7 S8 S9 S10
Temperature oC 40 (max) 25.1 25.2 24.8 25.0 24.9 25.1 25.0 24.9 24.8 25.0
pH - 6.5-8.5 6.80 7.15 6.97 7.07 7.71 7.80 7.38 7.39 7.33 7.90
Turbidity NTU 10 (max) 82 85 75 56 66 54 51 68 65 59
EC mS/cm 40 (max) 16.85 15.9 13.50 14.80 11.98 13.50 10.19 10.46 11.90 9.77
Salinity
ppm 600 (max) 6890 6750 6610 6520 5740 4850 3860 3280 3380 2940
TDS 2100 (max) 9770 9540 7830 8580 6940 8100 5910 6270 6900 5660
DO 6 (min) 5.3 5.8 6.8 7.9 6.3 7.2 8.0 7.5 6.8 7.1
TSS 100 (max) 326 305 280 258 220 268 293 226 205 185
TS 2200 (max) 10096 9845 8110 8838 7160 8368 6203 6496 7105 5845
O&G 10 (max) 2200 2000 1800 1500 1200 1000 920 750 540 620
Alkalinity 600 (max) 275 267 217 188 252 207 180 190 162 154
Hardness 600 (max) 480 430 320 354 340 309 315 298 264 285
BOD5 30 (max) 51.68 39.52 40.53 44.58 48.64 37.49 28.37 35.47 38.51 30.4
* Central Pollution Control Board: CPCB

Table 5: Results of inorganic elements and anions (IEA) of 10 untreated oilfield produced water (OFPW) samples

Parameters Units *CPCB limit
Untreated Oilfield Produced Water (OFPW) Samples
S1 S2 S3 S4 S5 S6 S7 S8 S9 S10
Na ppm 100 (max) 152.8 178.5 102.5 148.7 130.6 95.8 115 90.2 84.7 81.3
K 20 (max) 15.5 12.3 9.5 10.8 8.7 7.7 8.3 6.5 5.2 4.9
Ca 200 (max) 198 185 148 157 168 146 149 131 120 126
Li 0.7 (max) 1.21 1.28 1.15 1.03 1.19 0.86 0.95 0.72 0.54 0.6
Mg 100 (max) 9.57 10.23 7.85 8.23 8.92 6.21 6.56 5.72 4.56 4.98
Sr 0.1 (max) 4.89 4.79 4.15 4.21 4.45 3.56 3.8 3.72 3.05 2.97
Fe 1 (max) 0.45 0.48 0.37 0.41 0.35 0.29 0.38 0.28 0.23 0.21
Zn 2 (max) 1.29 1.22 0.95 1.09 0.89 0.63 0.67 0.61 0.52 0.55
Pb 0.1 (max) 0.78 0.76 0.65 0.58 0.56 0.61 0.52 0.53 0.44 0.47
Mn 2 (max) 0.132 0.127 0.075 0.092 0.081 0.056 0.066 0.064 0.034 0.037
As 0.05 (max) 0.0054 0.0051 0.0042 0.0046 0.0048 0.0039 0.0035 0.0029 0.0017 0.002
F 1.5 (max) 8.7 8.4 7.2 7.9 7.5 5.3 6.2 6.5 4.5 4.9
Cr 1 (max) - - - - - - - - - -
Cu 0.2 (max) - - - - - - - - - -
Mo 0.1 (max) - - - - - - - - - -
Ni 3 (max) - - - - - - - - - -
Cl^- 1000 (max) 115 113 91 77 108 88 74 79 69 64
HCO_3^- 200 (max) 185 177 147 128 172 137 120 130 112 104
〖CO〗_3^(2-) 200 (max) 90 90 70 60 80 70 60 60 50 50
SO_4^(2-) 100 (max) 48 42 38 35 39 35 34 33 27 29
* Central Pollution Control Board: CPCB

Table 6: Results of physicochemical parameters (PP) 10 treated oilfield produced water (OFPW) samples
Parameters Units *CPCB limit S1 S2 S3 S4 S5 S6 S7 S8 S9 S10
pH 6.5-8.5 7.12 7.36 7.19 7.27 7.83 7.88 7.5 7.49 7.44 7.85
Turbidity
NTU 10 (max) 7.8 8.3 8.7 7.5 8.1 7 0 7.2 0 0
EC mS/cm 40 (max) 15.2 14.5 11.7 13.1 10.7 12 9.4 9.5 10.4 8.9
Salinity







ppm






600 (max) 520 540 480 490 410 380 360 310 320 330
TDS 2100 (max) 1940 1860 1650 1820 1520 1560 1490 1500 1510 1410
DO 6 (min) 8.6 7.4 8 8.3 8.5 7.7 6.9 7.8 7.9 7.4
TSS 100 (max) 80 72 55 50 48 50 82 45 32 30
TS 2200 (max) 2020 1932 1705 1870 1568 1610 1572 1545 1542 1440
O&G 10 (max) 10 10 10 0 0 0 0 0 0 0
Alkalinity 600 (max) 232 225 174 142 198 161 129 146 121 115
Hardness 600 (max) 378 351 266 295 286 256 264 245 212 236
BOD5 30 (max) 27.36 23.31 24.32 25.33 26.35 24.32 22.29 25.33 25.33 24.32
* Central Pollution Control Board: CPCB


Table 7: Results of inorganic elements and anions (IEA) of 10 treated OFPW samples

Parameters Units *CPCB limit S1 S2 S3 S4 S5 S6 S7 S8 S9 S10
Na
ppm 100 (max) 91.5 82.6 67.5 88.4 79.6 59.8 75.8 57.6 51.2 49.5
K 20 (max) 11.6 8.5 5.8 7.2 5.4 4.9 5.5 3.9 3.4 3.1
Ca 200 (max) 165 149 116 125 136 115 117 100 88 92
Li 0.7 (max) 0.59 0.61 0.52 0.51 0.59 0.46 0.49 0.38 0.32 0.30
Mg 100 (max) 9.12 9.93 7.52 7.69 8.18 5.76 5.98 4.85 3.86 4.43
Sr 0.1 (max) 0.1 0.1 0 0 0 0 0 0 0 0
Fe 1 (max) 0.28 0.3 0.21 0.25 0.14 0.1 0.2 0.11 0.08 0.05
Zn 2 (max) 1.02 0.98 0.7 0.78 0.65 0.41 0.42 0.38 0.29 0.31
Pb 0.1 (max) 0.1 0.08 0.1 0.07 0 0 0 0 0 0
Mn 2 (max) 0.081 0.095 0.015 0.062 0.048 0 0 0 0 0
As 0.05 (max) 0.0022 0.0018 0 0 0 0 0 0 0 0
F 1.5 (max) 1.15 1.02 0.49 1.08 0.97 0.56 0.78 0.89 0.25 0.38
Cl^- 1000 (max) 96 93 75 61 85 69 52 57 49 47
HCO_3^- 200 (max) 174 151 130 90 138 105 89 96 85 69
〖CO〗_3^(2-) 200 (max) 58 74 44 52 60 56 40 50 36 46
SO_4^(2-) 100 (max) 33 30 25 21 23 21 18 20 17 19
* Central Pollution Control Board: CPCB

Analytical findings of untreated and treated oilfield produced water compared with central pollution control board (CPCB) compliance
The management of produced water, particularly in oilfields, poses significant environmental challenges due to its inherent contamination. This essay explores the comparative analytical findings of untreated oilfield produced water (OFPW) and treated oilfield produced water (OFPW), in relation to compliance with the standards set by the Central Pollution Control Board (CPCB). The results demonstrate the efficacy of the employed treatment processes in effectively removing contaminants, inorganic materials, and anions from the water.
Untreated oilfield produced water (OFPW) often contains high concentrations of various pollutants, including heavy metals, hydrocarbons, and salinity, which can adversely affect terrestrial and aquatic ecosystems. In contrast, analytical data derived from treated OPW indicates a marked reduction in these harmful constituents. The treatment process employed not only adheres to the CPCB's stringent guidelines but also mitigates the risks associated with untreated discharges into surrounding environments.
The efficacy of the treatment process is underscored by a substantial decrease in the levels of total dissolved solids (TDS), chemical oxygen demand (COD), and specific heavy metals. Additionally, the concentration of anions, such as chloride and sulfate, is significantly reduced, ensuring that the treated water meets the permissible limits set forth by the CPCB. These findings validate the treatment methodology as a reliable means of rendering OPW suitable for potential reuse or safe discharge.
The analytical findings underscore the effectiveness of the treatment processes applied to oilfield produced water (OFPW). The substantial compliance with CPCB standards illustrates a successful approach to managing produced water, highlighting the potential for this technology to contribute to sustainable oilfield operations. As environmental regulations become increasingly stringent, the adoption of such effective treatment solutions will be paramount in minimizing the ecological footprint of the oil and gas industry.
The efficacy of processes of the present invention is further validated through UV-VIS spectrophotometry, wherein the absorbance levels of OFPW samples are recorded both prior to and after completion of the water treatment process. The absorbance details listed in the below table.
Table 8: Results of the UV-VIS absorbance for the treatment models
SN Samples Untreated OFPW treated OFPW
1 S1 2.63 0.38
2 S2 3.33 0.59
3 S3 2.91 0.41
4 S4 2.81 0.35
5 S5 3.81 0.54
6 S6 2.56 0.26
7 S7 2.42 0.21
8 S8 2.37 0.18
9 S9 2.43 0.23
10 S10 2.12 0.15

The treated oilfield produced water (OFPW) demonstrates significantly lower absorbance values, indicative of the effective treatment process employed. This reduction in absorbance not only highlights the efficacy of the purification method but also emphasizes the resultant water's suitability for potential reuse. Such outcomes underscore the importance of advanced treatment technologies in addressing environmental concerns associated with oilfield operations.
, Claims:We claim:

1. A method for treating oilfield-produced water comprising:
a pretreatment (PT) stage, wherein gravity separation (GS), sand filtration (SF), and aeration with centrifuge (AwC) to process oilfield-produced water via sedimentation, yielding a first intermediate of treated water; and
a membrane technology (MT)stage, wherein the first intermediate water obtained in the Pretreatment stage, is subjected to membrane treatment (MT), which includes microfiltration (MIF), ultrafiltration (UF), and nanofiltration (NF).

characterized in that, the gravity separation is a sedimentation process to remove components based on their density difference and sediments which are denser than oilfield-produced water settles at the bottom, while due to the floatation process the crude oil being lighter than oilfield-produced water floats at the top and the crude oil is removed from oilfield-produced water by the process of decantation;
the sand filtration consists of sand particles, sandstone particles and charcoal particles from top to bottom respectively;
the aeration with centrifuge allows aerobic biodegradation of both organic and inorganic matter, and the gases formed during organic decomposition are removed and oxidised Fe and Mn to form precipitates; the microfiltration (MIF) membrane is composed of polyacrylonitrile (pan), and the ultrafiltration (UF) and nanofiltration (NF) membranes are made from polysulfone (PS).

2. The method for treating oilfield-produced water as claimed claim 1, wherein the gravity separation Gravity separation of oilfield-produced water (OFPW) is conducted by allowing the water sample to sit undisturbed for a period of 24 hours.

3. The method for treating oilfield-produced water as claimed claim1, wherein the sand filtration process consists of sand particle size 0.044 - 0.062mm, sandstone particle size 0.044 -0.062 mm and charcoal particle size 0.125 - 0.149 mm, arranged in that order from top to bottom for the effective treatment of oilfield-produced water.

4. The method for treating oilfield-produced water as claimed claim 1, wherein the aeration with a centrifuge method facilitates the removal of contaminants from sand-filtered water by promoting aerobic biodegradation of organic and inorganic substances.

5. The method for treating oilfield-produced water as a claimed claim 1, wherein the membrane treatment involves the first intermediate of treated water is treating with Hollow Fiber Membrane Module (HFMM) by microfiltration (MIF), ultrafiltration (UF), and nanofiltration (NF)membranes consecutively.
6. The method for treating oilfield-produced water as claimed in claim 5, wherein the microfiltration (MIF)is composed of Polyacrylonitrile (PAN) with an average pore diameter of 200nm.

7. The method for treating oilfield-produced water as claimed in claim 5, wherein the ultrafiltration (UF), and nanofiltration (NF)membranes are composed of Polysulfone (PS) with pore diameter 12.9 and 1.04 respectively.

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