AU2022201844B2 - Coagulation/Flocculation method - Google Patents

Abstract

The present invention relates to a method of removing suspended solids from untreated water originating from a well, comprising the steps of: (1) measuring the total suspended solids (TSS) content and flow rate of the untreated water; (2) treating the untreated water with a calculated dosage of a cationic flocculant and/or cationic coagulant based on the TSS content and flow rate of the untreated water, to produce cationic flocculant and/or coagulant-treated water comprising a floc or agglomerated component; (3) separating the floc or agglomerated component of the cationic flocculant and/or coagulant-treated water from a clarified water component of the cationic flocculant and/or coagulant-treated water; (4) treating the separated floc or agglomerated component with a calculated dosage of an anionic flocculant, to produce anionic flocculant treated water comprising a floc component; and (5) separating the floc component of the anionic flocculant-treated water from a clarified water component of the anionic flocculant-treated water. The present invention also relates to a system for removing suspended solids from untreated water originating from a well. 1/15 m 01 r~ - F 1 II L fiI zi 0 < < IF 1-7 000 I Owl Ij I CD Figure1I

Description

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TITLE Coagulation/Flocculation Method Field of the Invention

[0001] This invention relates to a method of, and system for, removing suspended solids from untreated water originating from a well, such as a coal seam gas well.

Background of the Invention

[0002] Coal seam gas (CSG) is a natural gas that is trapped in coal seams under pressure by groundwater. Large volumes of water are produced during the gas extraction process and are usually diverted to surface infrastructure treatment and processing plants. The well-originating water contains a mixture of salt, nutrients, heavy metals, organic compounds and suspended solids.

[0003] Typical in industry, mainly municipal waste, is the use of fluid sensing and automated chemical additive systems to clean water and separate impurities such as silt. Some systems add chemical to cause impurities to float allowing them to be skimmed off, other systems use flocculants to combine or group solids in order for them to settle and be pumped away. The impurities are then typically pumped into evaporation pits to further reduce the volume. Where an evaporation pit is not possible a drying system is utilised to reduce the volume. Drying systems typically include belt dryers, screw presses, evaporation bags etc.

[0004] A satisfactory method or system for removing suspended solids from untreated water originating from a well, particularly water from a CSG well, has yet to be devised.

Detailed Description of the Invention

[0005] The present invention relates to a method of, or system for, removing suspended solids from untreated water originating from a well, particularly water from a CSG well.

[0006] According to a first aspect of the present invention, there is provided a method of removing suspended solids from untreated water originating from a well, comprising the steps of:

[0007] (1) measuring the total suspended solids (TSS) content and flow rate of the untreated water;

[0008] (2) treating the untreated water with a calculated dosage of a cationic flocculant and/or cationic coagulant based on the TSS content and flow rate of the untreated water, to produce cationic flocculant and/or coagulant-treated water comprising a floc or agglomerated component;

[0009] (3) separating the floc or agglomerated component of the cationic flocculant and/or coagulant-treated water from a clarified water component of the cationic flocculant and/or coagulant-treated water;

[0010] (4) treating the separated floc or agglomerated component with a calculated dosage of an anionic flocculant, to produce anionic flocculant-treated water comprising a floc component; and

[0011] (5) separating the floc component of the anionic flocculant-treated water from a clarified water component of the anionic flocculant-treated water using a screw press separator.

[0012] According to an embodiment of the first aspect of the present invention, there is provided a method of removing suspended solids from untreated water originating from a well, comprising the steps of:

[0013] (1) measuring the total suspended solids (TSS) content and flow rate of the untreated water;

[0014] (2) treating the untreated water with a calculated dosage of a cationic flocculant based on the TSS content and flow rate of the untreated water, to produce cationic flocculant treated water comprising a floc component;

[0015] (3) separating the floc component of the cationic flocculant-treated water from a clarified water component of the cationic flocculant-treated water;

[0016] (4) treating the separated floc component with a calculated dosage of an anionic flocculant, to produce anionic flocculant-treated water comprising a more dense floc component; and

[0017] (5) separating the more dense floc component of the anionic flocculant-treated water from a clarified water component of the anionic flocculant-treated water.

[0018] Step (1) can be carried out in any suitable way. For example, a TSS meter can be used. Preferably, an inline TSS meter is used. The TSS meter can be operably connected to a programmable logic controller (PLC), microcontroller, human machine interface (HMI) or the like.

[0019] The TSS may be measured directly or indirectly. For example, the TSS may be measured indirectly by measuring the turbidity and then using this measurement to determine the TSS. In other embodiments, TSS may be measured ultrasonically, optically, or using microwaves. The TSS may be determined from measured turbidity (for example using an optical measurement), or slurry density (for example using an ultrasound measurement). An exemplary instrument for measuring slurry density using ultrasound may be available from Rhosonics. The TSS may be measured using microwaves. An exemplary instrument for measuring TSS using microwaves may be available from Cerlic.

[0020] The method may comprise measuring another physical or chemical property of the untreated water. The another physical or chemical property of the untreated water may comprise: pH, conductivity, concentration of suspended solids, total mass flow of solids, fluid density and temperature. The calculated dosage of the cationic flocculant and/or cationic coagulant may be affected by the measured another physical or chemical property of the untreated water. The method may also comprise adding a further agent based on the measured another physical or chemical property of the untreated water. For example, a pH adjusting agent (such as an acid or base) may be added based on the measured pH. Similarly, a temperature adjusting apparatus (such as a heater or a cooler) may be used to heat or cool the untreated liquid based on the measured temperature.

[0021] The method can comprise the step of conveying the untreated water to the TSS meter or flow meter. This can be achieved in any suitable way. For example, a pump can be used to convey the untreated water to the TSS meter or flow meter. The pump can be operably connected to a programmable logic controller (PLC), microcontroller, human machine interface (HMI) or the like.

[0022] Step (1) comprises the step of measuring the flow rate of the untreated water and this can be achieved in any suitable way. For example, a flow meter, preferably an inline flow meter, can be used. The flow meter can be operably connected to a programmable logic controller (PLC), microcontroller, human machine interface (HMI) or the like.

[0023] The method can comprise the step of degassing the untreated water prior to step (1) to produce degassed untreated water.

[0024] Degassing can be carried out in any suitable way. For example, a degasser can be used. Degassing can comprise the step of separating the gas from the untreated water within an impingement separator of the degasser. The degasser can comprise a settling or collection compartment for containing the degassed untreated water. The degasser can be as described in PCT/AU2011/000899 filed 15 July 2011, the entire contents of which are incorporated herein by reference.

[0025] The method can comprise the step of conveying the untreated water from the well to the degasser. This can be achieved in any suitable way. For example, a pump can be used to directly or indirectly convey the untreated water from the well to the degasser unit.

[0026] The method can comprise the step of storing the untreated water or degassed water prior to step (1). This can be achieved in any suitable way. Any suitable type of storage tank or container can be used to store the untreated water or degassed water.

[0027] The method can comprise the step of conveying the untreated water from the storage tank or container to the TSS meter or flow meter. This can be achieved in any suitable way. For example, a pump can be used to convey the untreated water from the storage tank or container to the TSS meter or flow meter. The pump can be operably connected to a programmable logic controller (PLC), microcontroller, human machine interface (HMI) or the like.

[0028] Step (2) can be carried out in any suitable way. The dosage of cationic flocculant and/or cationic coagulant based on the TSS content and water flow rate can be calculated in any suitable way. In some embodiments, the dosage is calculated by reference to a predetermined stoichiometric relationship between the cationic flocculant and/or cationic coagulant and TSS content. In some embodiments, the dosage is automatically calculated. In some embodiments, the dosage of cationic flocculant and/or cationic coagulant is automatically calculated and adjusted based on the TSS content and water flow rate.

[0029] For Step (2), a cationic flocculant and/or cationic coagulant dosing system comprising a cationic flocculant and/or cationic coagulant can be used. In one embodiment, the amount of cationic flocculant and/or coagulant is automatically dosed. The cationic flocculant and/or cationic coagulant dosing system can comprise a programmable logic controller (PLC), microcontroller, human machine interface (HMI) or the like for automatically calculating and adjusting the dosage of the cationic flocculant and/or cationic coagulant based on the TSS content and water flow rate. In some embodiments, a PLC, microcontroller, human machine interface (HMI) or the like utilises a reading from a TSS meter and flow meter to determine the correct dosage rate of the cationic flocculant and/or cationic coagulant and then controls at least one operably connected dosing pump (eg. peristaltic dosing pump).

[0030] Step (2) can have a cationic flocculant and/or cationic coagulant dosing point at which point the cationic flocculant and/or cationic coagulant mixes with the untreated water or degassed water.

[0031] The cationic flocculant and/or cationic coagulant dosing system can comprise a cationic flocculant and/or cationic coagulant reservoir, container or tank containing the cationic flocculant and/or cationic coagulant. Any suitable type can be used.

[0032] The method of step (2) can comprise thoroughly mixing the cationic flocculant and/or cationic coagulant with the untreated water. This can be achieved in any suitable way. The cationic flocculant and/or cationic coagulant dosing system can, for example, comprise an inline static mixer, inline dynamic mixer or a pump (such as a progressive cavity pump (PCP)). The mixer or pump can be operably connected to a programmable logic controller (PLC), microcontroller, human machine interface (HMI) or the like.

[0033] The cationic flocculant and/or cationic coagulant dosing system can comprise at least one, but preferably two, dosing pumps (eg. peristaltic dosing pumps) for pumping cationic flocculant and/or cationic coagulant from the flocculant reservoir, container or tank to the inline static mixer, inline dynamic mixer or a PCP at the cationic flocculant and/or cationic coagulant dosing point. The at least one pump can be operably connected to the PLC, microcontroller, human machine interface (HMI) or the like for regulating the at least one pump and thereby adjusting the dosage of the cationic flocculant and/or cationic coagulant.

[0034] In one embodiment, the cationic flocculant and/or cationic coagulant is a cationic flocculant. In another embodiment, the cationic flocculant and/or cationic coagulant is a cationic coagulant. A cationic coagulant may have at least some properties of a cationic flocculant. A cationic flocculant may have at least some properties of a cationic coagulant.

[0035] As used herein, the term "coagulant" refers to an agent for destabilising a colloidal suspension by virtue of its charge density. Coagulation may occur by the agent neutralising the charge in the untreated water. In one embodiment, the agent is a polymer of a molecular weight of from around 20,000 to 1 million. The polymer may be adsorbed onto part of the surface of the colloidal particles to thereby result in coagulation.

[0036] As used herein the term "flocculant" refers to an agent for destabilising a colloidal suspension by bonding between colloidal particles. The flocculant may be a polymer. The flocculant may have a molecular weight of greater than 1 million.

[0037] In one embodiment, the cationic flocculant and/or cationic coagulant has a charge density of from 1% to 100%, especially from 1% to 10%, from 10% to 40%, from 40% to 80% or from 80% to 100%. The cationic flocculant and/or cationic coagulant may have a charge density of from 1% to 20% or from 1% to 25%; or from 20% to 40% or from 25% to 40% or from 20% to 45% or from 25% to 45%; or greater than 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 8 0 %.

[0038] In one embodiment, the cationic flocculant and/or cationic coagulant has a molecular weight of from 10,000 or 20,000 to 1 million g/mol, or from 1 million to 3 million g/mol, or from 3 million to 6 million g/mol, or from 10 million to 15 million g/mol, or more than 15 million g/mol.

[0039] The cationic flocculant and/or cationic coagulant may be a polymer or copolymer. The polymer may be a block polymer or a random polymer.

[0040] The cationic coagulant and/or cationic flocculant may be or comprise a polyacrylamide, a polyacrylate, an acrylamide-dimethylaminoethyl acrylate copolymer, a polyamine, a polyethyleneimine, polyamidoamine or a polyethylene oxide.

[0041] Any suitable type or types of cationic flocculant and/or coagulant can be used (eg. a mixture of different flocculants). The cationic flocculant and/or coagulant can be a polyelectrolyte flocculant and/or coagulant. The cationic flocculant and/or coagulant can be a cationic polymer. Preferably, the cationic flocculant and/or coagulant is polydiallyldimethylammonium chloride (also known as polyDADMAC; polyDDA; polyquaternium-6; CAS No. 26062-79-3; and 'CW304' as used herein). Examples of cationic flocculants and/or coagulants include FL4526 and FL4440 available from SNF Australia.

[0042] Any suitable dosage of cationic flocculant and/or coagulant can be used. For example, the dosage range can be from about 0.0003 ml/L of neat (undiluted) cationic flocculant and/or coagulant (eg. polyDADMAC)per 1 g/L TSS, to about 0.0006 ml/L of neat cationic flocculant and/or coagulant (eg. polyDADMAC) per 1 g/L TSS. This range includes all values between 0.0003 and 0.0006. Preferably, the dosage is about 0.0004 ml/L of the cationic flocculant and/or coagulant (eg. polyDADMAC) per 1 g/L TSS.

[0043] In one embodiment, the cationic flocculant and/or coagulant can be used in combination with aluminium chlorohydrate (also known as ACH or aluminium chloride hydroxide). Examples of ACH include FLB4431AC, FLB4450AC, and FLB4418AC available from SNF Australia. ACH can also be used independently as a cationic flocculant and/or coagulant depending on the water to be treated. The cationic flocculant and/or coagulant may be, for example, a combination of ACH and polyDADMAC. An exemplary such combination is 1104c available from Water Floc Pty Ltd (Australia).

[0044] The method can comprise the step of conveying the cationic flocculant and/or coagulant-treated water from the cationic flocculant and/or coagulant dosage point for separation in step (3). This can be achieved in any suitable way. For example, a pump can be used to convey the cationic flocculant and/or coagulant-treated water for separation in step (3). The pump can be operably connected to a programmable logic controller (PLC), microcontroller, human machine interface (HMI) or the like.

[0045] Step (3) can be carried out in any suitable way. Separation can comprise the floc or agglomerated component settling under the influence of gravity.

[0046] For step (3) a separator/clarifier can be used. Any suitable type of separator/clarifier can be used. For example, a lamella separator can be used to separate different components of the cationic flocculant and/or coagulant-treated water. The clarifier can comprise an inlet for cationic flocculant and/or coagulant-treated water. The clarifier can comprise a clarifying tank having a top and a bottom. The clarifying tank can contain settling plates extending within the clarifying tank. The clarifier can comprise one or more outlets at a bottom of the clarifying tank. The clarifier can comprise one or more clarified water outlets located at the top of the clarifying tank.

[0047] The method of step (3) can utilise at least one sludge blanket sensor for determining when the floc or agglomerated component has separated from the clarified water component of the cationic flocculant and/or coagulant-treated water. The method can comprise the step of the at least one sludge blanket sensor triggering conveyance of the floc or agglomerated component to the anionic flocculant in step (4).

[0048] The clarifying tank can comprise at least one sludge blanket sensor associated with the clarifying tank. The at least one sludge blanket sensor can be operably connected to a programmable logic controller (PLC), microcontroller, human machine interface (HMI) or the like.

[0049] The method can comprise the step of conveying the cationic flocculant and/or coagulant-treated water from the cationic flocculant and/or coagulant dosage point for separation in step (3). This can be achieved in any suitable way. For example, a pump can be used to convey the cationic flocculant and/or coagulant-treated water for separation in step (3). The pump can be operably connected to a programmable logic controller (PLC), microcontroller, human machine interface (HMI) or the like.

[0050] The method can comprise the step of collecting the clarified water component of the cationic flocculant and/or coagulant-treated water.

[0051] The method can comprise the step of conveying the clarified water component to a clarified water collection tank, container or reservoir. This can be achieved in any suitable way. Any suitable type of collection tank, container or reservoir can be used. For example, a pump can be used to convey the clarified water component to the clarified water collection tank, container or reservoir. The pump can be operably connected to a programmable logic controller (PLC), microcontroller, human machine interface (HMI) or the like.

[0052] The method can comprise the step of measuring the total suspended solids (TSS) content of the clarified water. This is to ensure that the cationic flocculant and/or coagulant treated water has been flocked or agglomerated correctly and that there is no carryover or that it has not been over-flocked and has floc carry over. This step can be carried out in any suitable way. For example, a TSS meter can be used. Preferably, an inline TSS meter is used. The TSS meter can be operably connected to a programmable logic controller (PLC), microcontroller, human machine interface (HMI) or the like.

[0053] Step (4) can be carried out in any suitable way. The dosage of anionic flocculant can be calculated in any suitable way. In some embodiments, anionic flocculant dosage rate is based on volumetric flow rate which is calculated by a flow meter and/or pump that conveys the floc or agglomerated component from the clarifier. The flow meter and/or pump can be operably connected to a programmable logic controller (PLC), microcontroller, human machine interface (HMI) or the like.

[0054] In some embodiments, the dosage is calculated by reference to a predetermined stoichiometric relationship between the anionic flocculant and TSS content and flow rate. In some embodiments, the dosage of anionic flocculant is automatically calculated and adjusted based on the TSS content and flow rate.

[0055] For step (4), an anionic flocculant dosing system comprising an anionic flocculant can be used. The anionic flocculant dosing system can comprise a PLC, microcontroller, human machine interface (HMI) or the like for automatically calculating and adjusting the dosage of the anionic flocculant based on volumetric flow rate. In some embodiments, a PLC, microcontroller, human machine interface (HMI) or the like utilises a reading from a pump or flow meter to determine the correct dosage rate of the anionic flocculant and then controls at least one operably connected dosing pump (eg. peristaltic dosing pump).

[0056] The anionic flocculant dosing system can comprise an anionic flocculant reservoir, tank or container containing the anionic flocculant. Any suitable type can be used.

[0057] Step (4) can have an anionic flocculant dosing point at which point the anionic flocculant mixes with the floc or agglomerated component.

[0058] The method of step (4) can comprise thoroughly mixing the anionic flocculant with the floc or agglomerated component. This can be achieved in any suitable way. The anionic flocculant dosing system can, for example, comprise an inline static mixer, inline dynamic mixer or a pump (such as a progressive cavity pump (PCP)). The mixer or pump can be operably connected to a programmable logic controller (PLC), microcontroller, human machine interface (HMI) or the like.

[0059] The anionic flocculant dosing system can comprise at least one but preferably two pumps (eg. PCP) for pumping anionic flocculant from the anionic reservoir, tank or container to the inline static mixer, inline dynamic mixer or a PCP at the anionic flocculant dosing point. In some embodiments, the at least one pump can be operably connected to the PLC, microcontroller, human machine interface (HMI) or the like for regulating the pump and adjusting the dosage of the anionic flocculant.

[0060] In some embodiments, a PLC, microcontroller, human machine interface (HMI) or the like can be operably connected to the at least one sludge blanket sensor and a pump, and regulate the conveyance of the floc component to the anionic flocculant dosing point.

[0061] In one embodiment, the anionic flocculant has a charge density of from 1% to 100%, especially from 1% to 10% or from 10% to 40%. The anionic flocculant may have a charge density of from 1% to 20% or from 1% to 2 5 %; or from 20% to 40% or from 25% to 40%.

[0062] In one embodiment, the anionic flocculant has a molecular weight of from 3 million to 9 million g/mol, or from 9 million to 15 million g/mol, or greater than 15 million g/mol.

[0063] Any suitable type or types of anionic flocculant can be used (eg. a mixture of different flocculants). The anionic flocculant can be a polyelectrolyte flocculant. The anionic flocculant can be an anionic polymer. Preferably, the anionic flocculant comprises acrylamide/sodium acrylate copolymer acid (also called sodium 2-propenoate 2-propenamide polymer; acrylamide; acrylic acid copolymer, sodium salt; acrylic acid/acrylamide copolymer, sodium salt; 2-propenoic acid, polymer with 2-propenamide, sodium salt; 2-propenoic acid, polymer with 2-propenamide, sodium salt acrylamide, sodium acrylate polymer 2-propenoic acid, polymer with 2-propenamide, sodium salt 2-propenoic acid, polymer with 2-propenamide, sodium salt acrylamide, sodium acrylate polymer; CAS No. 25987-30-8; and 'CW305' as used herein). Examples of anionic flocculants include EM533, EMA8335, CE333 FAS, EM635, EM640CT and EM430 available from SNF Australia.

[0064] Any suitable dosage of anionic flocculant can be used. For example, the dosage range can be from about 0.015 ml/L of the anionic flocculant (eg. acrylamide/sodium acrylate copolymer acid) per 1 L of the floc or agglomerated component, to about 0.021 ml/L of the anionic flocculant (eg. acrylamide/sodium acrylate copolymer acid) per L of the floc or agglomerated component. This range includes all values between 0.015 and 0.021. Preferably, the dosage is a fixed dosage of about 0.018 ml/L of the anionic flocculant (eg. acrylamide/sodium acrylate copolymer acid) per L of the floc or agglomerated component.

[0065] After or during steps (2) and (4) fluid may be mixed, such as with an inline static and/or mechanical mixer. The mixing may be performed using open or closed tank mechanically agitated mixers, or static mixer tanks that may contain baffles.

[0066] Step (5) can be carried out in any suitable way. For step (5) a separator can be used. Any suitable type of separator can be used. For example, a screw press can be used. The screw press can comprise an inlet for the floc component. The floc component may be more dense than the floc or agglomerated component of the cationic flocculant and/or cationic coagulant treated water. The screw press can separate a solids component of the floc component from a clarified water component of the floc component. The separator may employ gravity separation, filtration (including vacuum and pressure filtration), a mechanical filter press, and storage, conditioning and treatment tanks. Such processes may be designed to optimise residence time distribution and/or may be designed to behave as a continuous stirred tank reactor.

[0067] The method can comprise the step of collecting the clarified water component of the anionic flocculant-treated water and this can be achieved in any suitable may.

[0068] The method can comprise the step of conveying the clarified water component of the anionic flocculant-treated water to a clarified water collection tank. This can be achieved in any suitable way. Any suitable type of collection tank, container or reservoir can be used. For example, a pump can be used to convey the clarified water component to the clarified water collection tank, container or reservoir.

[0069] The method can comprise the step of measuring the total suspended solids (TSS) content of the clarified water. This is to ensure that the cationic flocculant and/or coagulant treated water has been flocked or agglomerated correctly and that there is no carryover or that it has not been over-flocked or agglomerated and has carry over. This step can be carried out in any suitable way. For example, a TSS meter can be used. Preferably, an inline TSS meter is used. The TSS meter can be operably connected to a programmable logic controller (PLC), microcontroller, human machine interface (HMI) or the like. TSS may be measured as outlined above for step (1).

[0070] The method of can comprise the step of collecting, and optionally disposing of, the solids component. This can be achieved in any suitable way.

[0071] Preferably, the method results in at least about 80% of the TSS content being removed from the untreated water. Preferably, at least about 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100% of the TSS content is removed from the untreated water by the treatment with the cationic flocculant and/or cationic coagulant and anionic flocculant steps. TSS measurements can be taken prior to step (2), after step (3) and after step (5). Again, TSS measurements may be performed as outlined above for step (1).

[0072] Preferably, the suspended solids/particles that remain in the clarified water component of the floc component have a particle size distribution essentially as shown in Table 3.

[0073] In preferred embodiments, the untreated water is groundwater, originating from a coal seam gas (CSG) well. However, water from other types of mining operations may be applicable.

[0074] The method may comprise adding one or more further agents to the untreated water, the cationic flocculant and/or coagulant treated water, the clarified component of the cationic flocculant and/or coagulant-treated water; the anionic flocculant treated water; or the clarified water component of the anionic flocculant-treated water. Such one or more further agents may improve the removal of suspended solids from the fluid stream. The dosage of such further agents may comprise, for example, stoichiometrically or proportionally. The dose of such one or more further agents may be based on a measured property of the untreated water, the cationic flocculant and/or coagulant treated water, the clarified component of the cationic flocculant and/or coagulant-treated water; the anionic flocculant treated water; or the clarified water component of the anionic flocculant-treated water.

[0075] According to a second aspect of the present invention, there is provided a system for removing suspended solids from untreated water originating from a well, said system comprising:

[0076] (1) a total suspended solids (TSS) meter for measuring the TSS content and flow rate of untreated water;

[0077] (2) a cationic flocculant and/or coagulant dosing system comprising a cationic flocculant and/or coagulant, for treating the untreated water with a calculated dosage of the cationic flocculant and/or coagulant based on the TSS content and the flow rate of the untreated water, to produce cationic flocculant and/or coagulant-treated water comprising a floc or agglomerated component;

[0078] (3) a clarifier for separating the floc or agglomerated component of the cationic flocculant and/or coagulant-treated water from a clarified water component of the cationic flocculant and/or coagulant -treated water;

[0079] (4) an anionic flocculant dosing system comprising an anionic flocculant, for treating the separated floc or agglomerated component with a calculated dosage of the anionic flocculant, to produce anionic flocculant-treated water comprising a floc component; and

[0080] (5) a screw press separator for separating the floc component of the anionic flocculant-treated water from a clarified water component of the anionic flocculant-treated water.

[0081] In an embodiment of the second aspect, there is provided a system for removing suspended solids from untreated water originating from a well, said system comprising:

[0082] (1) a total suspended solids (TSS) meter for measuring the TSS content and flow rate of untreated water;

[0083] (2) a cationic flocculant dosing system comprising a cationic flocculant, for treating the untreated water with a calculated dosage of the cationic flocculant based on the TSS content and the flow rate of the untreated water, to produce cationic flocculant-treated water comprising a floc component;

[0084] (3) a clarifier for separating the floc component of the cationic flocculant-treated water from a clarified water component of the cationic flocculant-treated water;

[0085] (4) an anionic flocculant dosing system comprising an anionic flocculant, for treating the separated floc component with a calculated dosage of the anionic flocculant, to produce anionic flocculant-treated water comprising a more dense floc component; and

[0086] (5) a separator for separating the more dense floc component of the anionic flocculant-treated water from a clarified water component of the anionic flocculant-treated water.

[0087] It is to be appreciated that features of the method (first aspect) can be features of the system (second aspect) and vice-versa.

[0088] Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying figures.

Brief Description of the Figures

[0089] Figure 1. Schematic of a system for removing suspended solids from untreated water originating from a CSG well, according to an embodiment of the present invention.

[0090] Figures 2-10. Each graph shows the time taken to settle solids from water sourced from a particular well containing a particular amount of total suspended solids, using different concentrations of cationic flocculant CW304 and anionic flocculant CW305 (jar tests).

[0091] Figures 11-14. Each graph shows total suspended solids versus chemical dosage (CW304 and CW305), for different settling times.

[0092] Figures 15-17. Each graph shows total suspended solids versus chemical dosage (CW304 and CW305).

[0093] Figure 18. Graph of chemical dosage rate (CW304) versus total suspended solids, for settling.

[0094] Figure 19. Graph of chemical dosage (CW304) versus settling time.

[0095] Figure 20. Graph of chemical dosage rate (CW304) versus settling time.

[0096] Figures 21-27. Each graph shows total suspended solids versus dosage rate (different concentrations of CW304), showing upper, lower and ideal dosage rates.

[0097] Figure 28. Graph of total suspended solids versus ideal dosage rate (CW304).

Description of the Preferred Embodiments

[0098] In the figures like reference numerals refer to like features.

[0099] In a preferred embodiment, the invention is used in Coal Seam Gas (CSG) well operations where silt and solids present in water are returned to surface during well cleaning operations. This untreated water (also referred to as 'raw fluid' or 'raw water) is typically high in salinity and pH. A chemical analysis of untreated water from eight different wells is shown below in Table 1.

[00100] Table 1. Chemical analysis of raw water from eight CSG wells.

Wells

Well 1 Well 2 Well 3 Well 4 Well 5 Well 6 Well 7 Well 8 Average

Parameter Units Rig Rig Rig Rig Rig Rig Rig Rig

ED040F: Dissolved Major Anions

Sulfate as S04 2- mg/L 1 <1 1 3 3 <1 3 3 2

Sulfur as S mg/L <1 <1 <1 1 1 <1 1 <1 1

Silicon as Si02 mg/L 9.7 8.9 7.6 9 6.7 11.8 10.9 15.5 10.0125

Silicon mg/L 4.53 4.16 3.54 4.21 3.12 5.51 5.09 7.23 4.67375

ED093F: Dissolved Major Cations

Calcium mg/L 12 12 11 15 18 15 12 18 14.125

Magnesium mg/L 4 4 4 7 8 4 4 5 5

Sodium mg/L 1740 1740 1850 2380 2570 1830 2120 2320 2068.75

Potassium mg/L 9 9 13 68 67 14 10 13 25.375

ED093T: Total Major Cations

Calcium mg/L 16 12 12 26 34 25 13 12 18.75

Magnesium mg/L 5 4 4 8 9 5 4 5 5.5

Sodium mg/L 1870 1690 1820 2450 2660 1920 1990 1940 2042.5

Potassium mg/L 10 9 13 71 70 15 10 11 26.125

EP002: Dissolved Organic Carbon (DOC)

Dissolved Organic Carbon mg/L 37 3 11 24 11 11 14 14 15.625

EP005: Total Organic Carbon (TOC)

Total Organic Carbon mg/L 42 2 11 20 10 8 13 18 15.5

[00101] Outliers are shown in italics.

[00102] Water solids content is measured using a total suspended solids (TSS) meter with readings from 0 grams / litre to 500 grams / litre, but typically 5-50 grams per litre. The particle sizes vary from less than 1 micron to 100 microns, with the most by volume typically less than 10micron. The TSS meter utilises a combined infrared absorption scattered light technique that measures the lowest turbidity values in accordance with DIN EN 27027 and then converts the reading to TSS.

[00103] Referring now to Figure 1, untreated water (raw water) from a CGS well 1 is conveyed to a SCUFTM unit 3 (or a blast tank) via a blooie line. The unit 3 is described in PCT/AU2011/000899 filed 15 July 2011, the entire contents of which are incorporated herein by reference. Briefly, the flow rate of the raw water decreases and gas is separated from the raw water within an impingement separator 3A (degasser) of the unit 3. Degassed raw water 10A then collects with a settling or collection compartment 3B of the unit 3. An onboard pump 3C conveys the degassed raw water 10A from the settling compartment 3B into a storage tank 5 (tank water - 10B). A pump 6, typically a progressive cavity pump (PCP) pump, of 450-600 litres per minute in flow rate, pumps the raw water 1OB to a clarifier unit 9 (lamella separator) via a TSS meter 7, flow meter 2 and a cationic flocculant dosing point of a cationic flocculant dosing system 8.

[00104] The cationic flocculant and/or coagulant dosing system 8 includes a PLC and human machine interface (HMI) 20 which utilises the reading from the TSS meter 7 and the flow meter 2 to determine the correct dosage rate of cationic flocculant and/or coagulant, for addition to the degassed raw water at the cationic flocculant and/or coagulant dosing point.

[00105] The cationic flocculant and/or coagulant dosing system 8 includes a cationic flocculant and/or coagulant 8F, since suspended solids of the raw water are typically negatively charged. The cationic polymer/flocculant/coagulant is polydiallyldimethylammonium chloride (also known as polyDADMAC, polyDDA; polyquaternium-6; CAS No. 26062-79-3; 'CW304' as used herein). PolyDADMAC is a cationic coagulant.

[00106] The cationic flocculant and/or coagulant dosing system 8 includes a cationic flocculant and/or coagulant reservoir/tank 8A containing the cationic flocculant and/or coagulant 8F.

[00107] The cationic flocculant and/or coagulant dosing system 8 includes an inline static mixer 8C, inline dynamic mixer 8C or a progressing cavity pump (PCP) 8C. The mixer and pump 8C are operably connected to the PLC and HMI 20. The cationic flocculant and/or coagulant-dosed degassed raw water needs to be agitated either through an inline static mixer 8C, inline dynamic mixer 8C or injected into the suction side of a PCP 8C if installed in series to ensure sufficient mixing of the flocculant and/or coagulant 8F with the degassed raw water 1OB prior to entry into the clarifier unit 9.

[00108] The cationic flocculant and/or coagulant dosing system 8 includes two peristaltic dosing pumps 8B for pumping flocculant and/or coagulant from the flocculant and/or coagulant reservoir/tank 8A to the inline static mixer 8C, inline dynamic mixer 8C or a PCP 8C at the cationic flocculant and/or coagulant dosing point. The pumps 8B are operably connected to the PLC and HMI 20.

[00109] Since the flocculant and/or coagulant is sourced in the form of a concentration, it is first diluted with clean water to be of a volume that can be pumped successfully to the cationic flocculant and/or coagulant dosing point. This is typically 0.1% to 0.25% w/v (if originally in powder form) or 0.2% to 0.5% w/v if supplied as a hydrocarbon emulsion form, or can be dosed neat if supplied as a dispersion polymer to suit the lower (1g/L TSS) and upper (250g/L TSS) limit of the peristaltic dosing pump (two pumps 8B are used to get to 500g/L).

[00110] A suitable dosage rate for the cationic coagulant (polyDADMAC, CW304) was determined empirically. The results of jar tests and other studies are summarised in Figures 2-

28. Figures 26-28 show upper and lower dosage limits as well as an ideal dosage rate. The dosage range can be from about 0.0003 ml/L of the cationic coagulant per 1 g/L TSS, to about 0.0006 ml/L of the cationic coagulant per 1 g/L TSS. Ideally, the dosage is about 0.0004 ml/L of the cationic coagulant per 1 g/L TSS.

[00111] At the cationic flocculant and/or coagulant dosing point the cationic flocculant and/or coagulant is thoroughly mixed with the degassed raw water within the inline static mixer 8C, inline dynamic mixer 8C or PCP 8C prior to entry into the clarifier unit 9, to form cationic flocculant and/or coagulant-treated water 1OC. In this way, a floc component/flocked solids or agglomerated component is formed.

[00112] The clarifier unit 9 includes a water inlet 9A, clarifying tank 9B, settling plates 9C extending within the clarifying tank 9B, collection hoppers 9D, a respective outlet 9E at a bottom of each hopper 9D, a clarified water outlet 9F, and a respective sludge blanket sensor 9G associated with each hopper 9D.

[00113] The clarifying tank 9B of the clarifier unit 9 is either large in volume (16,000 litres) or smaller in volume, (10,000 litres) with inclined settling plates 9C in a 50x5Omm grid at 60 degrees. Solids of the flocculant and/or coagulant-treated water 1OC passing through the clarifying tank 9B settle on the plates 9C, combine with one another, and fall via gravity to the hoppers 9D of the clarifying tank 9B, leaving behind a clarified water component 1OE at a top of the clarifying tank 9B.

[00114] The clarified water component 1E flows out of the clarifying tank 9B via the overflow outlet 9F into a clean water pump out tank 11. The clarified water component 1OE is either pumped to an onsite storage tank 12 (water - lOG), back to the rig mud tank 13 or is pumped into the gathering network 14. The pump may be operably connected to the PLC and HMI 20. A gathering network pump is controlled via a PLC 20 to ensure that upper pressure limits and upper flow limits are not exceeded. This is to avoid triggering a gathering network fault which may cause an entire field to be shut down.

[00115] The TSS content of the clarified water is measured by an inline TSS meter 21. This is to ensure that the cationic flocculant and/or coagulant-treated water has been flocked or agglomerated correctly and that there is no carryover or that it has not been over-flocked or agglomerated and has carry over (such as floc carry over). The TSS meter 21 operably connected to the PLC and HMI 20.

[00116] When the floc/flocked solids or agglomerated component has reached a predetermined level within the hoppers 9D, monitored by the sludge blanket sensors 9G connected to a PLC 20, a pump 15 pumps a floc/flocked solids or agglomerated component 1OD to a screw press unit 16 via an anionic flocculant dosing point of an anionic flocculant dosing system 17. The pump 15 is operably connected to the PLC and HMI 20.

[00117] The anionic flocculant dosing system 17 includes an anionic flocculant 17F, since the floc/flocked solids or agglomerated component 1OD is overall positively charged. The anionic flocculant/coagulant comprises acrylamide/sodium acrylate copolymer acid (also called sodium 2-propenoate 2-propenamide polymer; acrylamide-acrylic acid copolymer, sodium salt; acrylic acid/acrylamide copolymer, sodium salt; 2-propenoic acid, polymer with 2 propenamide, sodium salt; 2-propenoic acid, polymer with 2-propenamide, sodium salt acrylamide, sodium acrylate polymer 2-propenoic acid, polymer with 2-propenamide, sodium salt 2-propenoic acid, polymer with 2-propenamide, sodium salt acrylamide, sodium acrylate polymer; CAS No. 25987-30-8; CW305).

[00118] A suitable dosage rate for the anionic flocculant (acrylamide/sodium acrylate copolymer acid, CW305) was determined empirically. The results of jar tests and other studies are summarised in some of the Figures. The dosage range can be from about 0.015 ml/L of the anionic flocculant per 1 L of the floc component/flocked solids or agglomerated component 1OD, to about 0.021 ml/L of the cationic flocculant and/or coagulant (eg. acrylamide/sodium acrylate copolymer acid) per 1 L of the floc component/flocked solids or agglomerated component 1OD. Preferably, the dosage is a fixed dosage of about 0.018 ml/L of the cationic flocculant and/or coagulant per 1 L of the floc component/flocked solids or agglomerated component 1OD. The anionic flocculant dosage rate is based on volumetric flow rate which is calculated by the pump 15 that conveys the floc or agglomerated component from the clarifier 9.

[00119] The anionic flocculant dosing system 17 includes an anionic flocculant reservoir/tank 17A containing the anionic flocculant 17F. The flocculant 17F is diluted to increase mixing performance and is typically diluted to 0.1% with clean water.

[00120] The flocculant dosing system 17 includes a PCP 17C. The flocculant 17F is injected directly into the suction side of the PCP 17C at a rate of 0.018ml/litre of neat chemical per litre of floc component/flocked solids component 1D, being controlled by a PLC 20. In this way there is sufficient mixing of the flocculant 17F with the floc component/flocked solids component 1OD prior to entry into the screw press unit 16. The anionic flocculant 17F tends to further clump the positively charged floc/flocked solids of the floc/flocked solids component 1OD together to form more dense (tightly-knit) floc/flocked solids1OE.

[00121] A floc/flocked solids component 1OE (which may be a more dense floc/flocked solids component) then enters the screw press unit 16 where it is further reduced in volume, and a clarified water component extracted from the floc/flocked solids component 1OE is conveyed to the clean water pump out tank 11. Solids 1OF extracted using the screw press unit 16 fall via gravity into a skip bin 18 where they are then transported to a disposal facility.

[00122] The TSS content of the clarified water is measured by the inline TSS meter 21. This is to ensure that the cationic flocculant and/or coagulant-treated water has been flocked correctly and that there is no carryover or that it has not been over-flocked or agglomerated and has carry over (such as floc carry over).

[00123] A biocide dosing system 19 having a pump 19C and storage tank 19A containing biocide 19F can be used to treat the clarified water component 10E.

[00124] Table 2 below shows the amount of suspended solids before ('Raw') and after ('Treated') treatment with the cationic flocculant/coagulant and anionic flocculant. The data show that the TSS content reduction for eight different wells ranged from about 98% to about 100%.

[00125] Table 2. TSS reduction.

RSS Well1 ell 2 Well 3 Well 4 Well 5 Well 6 Well 7 Well 8 REDUCTION

Parameter Units Raw Treated Raw Treated Raw Treated Raw Treated Raw Treated Raw Treated Raw Treated Raw Treated

SolidS g/L 16.10.283 7.55 0.066 5.47 0.032 8.83 0.226 11.9 0.082 19.6 0.099 14.2 0.045 9.98 0.074

Reductionfrom0% 98% 99% 99% 97% 99% 99% 100% 99% Raw to Treated

[00126] Table 3 below shows the particle size distribution for eight different wells before and after treatment with the cationic flocculant/coagulant and anionic flocculant.

[00127] Table 3. Particle size distribution.

Well 1 Well 2 Well 3 Well 4 Well 5 Well 6 Well 7 Well 8

Param. Units Raw Treated Raw Treated Raw Treated Raw Treated Raw Treated Raw Treated Raw Treated Raw Treated Av.

Dv(10) um 1.85 1.37 1.63 1.2 1.85 1.19 1.75 1.45 2.34 1.37 1.84 1.27 2.29 2.21 1.9 1.05 28%

Dv(50) um 8.9 5.06 6.68 4.24 7.83 4.9 6.48 5.1 14.2 4.7 9.2 5.42 13.2 10.6 7.6 3.36 38%

Dv(90) um 26.4 17.5 22.8 17.5 29.3 110 25.2 15.2 78.7 15.2 35.3 20.7 42 38 27.3 10.2 40%

[00128] Dv(10), Dv(50), Dv(90) - 10%, 50% & 90% of particles are under those respective sizes.

[00129] Outliers are shown in italics.

[00130] Table 4 below shows the percentage of reduction of TSS content for nine different wells.

[00131] Table 4. Average field analyses.

Well Raw Water Treated Water Units % Reduction Comments

30 1 %SS 97% Field Measured Averages

1000 355 NTU 65% Field Measured Averages

1 24.6 g/L No field TSS reading post treatment

22 0.50 %SS 98% Field Measured Averages

1000 139 NTU 86% Field Measured Averages

2 18 g/L No field TSS reading post treatment

11 0.50 %SS 95% Field Measured Averages

1000 400 NTU 60% Field Measured Averages

3 20 g/L No field TSS reading post treatment

27% 0.00 %SS Field Measured Averages

1000 142 NTU 86% Field Measured Averages

4 27.5 g/L No field TSS reading post treatment

30 0.50 %SS 98% Field Measured Averages

1000 215 NTU 79% Field Measured Averages

478 g/L Field Measured Averages @ first 200bbls from GL

95 %SS Field Measured Averages @ first 200bbls from GL

27.2 g/L No field TSS reading post treatment

16 0.50 %SS 97% Field Measured Averages

1000 254 NTU 75% Field Measured Averages

6 27.6 g/L No field TSS reading post treatment

7 0.5 %SS 93% Field Measured Averages

1000 36.8 NTU 96% Field Measured Averages

7 32.3 g/L No field TSS reading post treatment

16 0.18 %SS 99% Field Measured Averages

1000 482 NTU 52% Field Measured Averages

8 9 g/L No field TSS reading post treatment

7.3 0.5 %SS 93% Field Measured Averages

1000 260 NTU 74% Field Measured Averages

[00132] Hence, the two-stage flocculation/coagulation system as exemplified provides a satisfactory method of, or system for, removing suspended solids from untreated water originating from a well, particularly water from a CSG well.

[00133] Whilst the above has been given by way of illustrative example of the invention, many modifications and variations may be made thereto by persons skilled in the art without departing from the broad scope and ambit of the invention as herein set forth.

[00134] The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.

[00135] The term "comprise" and variants of the term such as "comprises" or "comprising" are used herein to denote the inclusion of a stated integer or stated integers but not to exclude any other integer or any other integers, unless in the context or usage an exclusive interpretation of the term is required.

Claims (17)

Claims

1. A method of removing suspended solids from untreated water originating from a well, comprising the steps of:

(1) measuring the total suspended solids (TSS) content and flow rate of the untreated water;

(2) treating the untreated water with a calculated dosage of a cationic flocculant and/or cationic coagulant based on the TSS content and flow rate of the untreated water, to produce cationic flocculant and/or coagulant-treated water comprising a floc or agglomerated component;

(3) separating the floc or agglomerated component of the cationic flocculant and/or coagulant-treated water from a clarified water component of the cationic flocculant and/or coagulant-treated water;

(4) treating the separated floc or agglomerated component with a calculated dosage of an anionic flocculant, to produce anionic flocculant-treated water comprising a floc component; and

(5) separating the floc component of the anionic flocculant-treated water from a clarified water component of the anionic flocculant-treated water using a screw press separator.

2. The method of claim 1, wherein: - the cationic flocculant and/or cationic coagulant is a cationic flocculant, and the cationic flocculant-treated water comprises a floc component; and - the anionic flocculant-treated water comprising a floc component is an anionic flocculant treated water comprising a more dense floc component.

3. The method of claim 1, wherein the cationic flocculant and/or cationic coagulant is a cationic coagulant.

4. The method of claim 4, wherein the cationic coagulant has a molecular weight of from 20,000 to 1 million.

5. The method of any one of claims 1 to 4, wherein the cationic flocculant and/or coagulant is a polymer.

6. The method of any one of claims 1 to 5, wherein the cationic coagulant and/or cationic flocculant is or comprises a polyacrylamide, a polyacrylate, an acrylamide dimethylaminoethyl acrylate copolymer, a polyamine, a polyethyleneimine, polyamidoamine or a polyethylene oxide.

7. The method of any one of claims 1 to 6, wherein the cationic flocculant and/or coagulant is polydiallyldimethylammonium chloride.

8. The method of any one of claims I to 7, wherein about 0.0003 ml/L of undiluted cationic flocculant and/or coagulant per 1 g/L TSS, to about 0.0006 ml/L of undiluted cationic flocculant and/or coagulant per 1 g/L TSS is used.

9. The method of any one of claims 1 to 8, wherein the TSS is measured indirectly from measured turbidity.

10. The method of any one of claims 1 to 9, wherein the untreated water is degassed prior to step (1).

11. The method of any one of claims 1 to 10, wherein the dosage of a cationic flocculant and/or cationic coagulant is calculated by reference to a predetermined stoichiometric relationship between the cationic flocculant and/or cationic coagulant and the TSS content; and wherein the dosage is automatically calculated, and the amount of cationic flocculant and/or coagulant is automatically dosed.

12. The method of any one of claims 1 to 11, wherein the dosage of anionic flocculant is calculated by reference to a predetermined stoichiometric relationship between the anionic flocculant and TSS content and flow rate.

13. The method of any one of claims 1 to 12, wherein the anionic flocculant comprises acrylamide/sodium acrylate copolymer acid.

14. The method of any one of claims I to 13, wherein from about 0.015 ml/L of the anionic flocculant per 1 L of the floc or agglomerated component, to about 0.021 ml/L of the anionic flocculant per 1 L of the floc or agglomerated component is used.

15. The method of any one of claims 1 to 14, wherein the method further comprises the step of measuring the TSS content of the clarified water component of the cationic flocculant and/or coagulant-treated water.

16. The method of any one of claims 1 to 15, the method further comprising the step of measuring the TSS content of the clarified water component of step (5).

17. A system for removing suspended solids from untreated water originating from a well, said system comprising:

(1) a total suspended solids (TSS) meter for measuring the TSS content and flow rate of untreated water;

(2) a cationic flocculant and/or coagulant dosing system comprising a cationic flocculant and/or cationic coagulant, for treating the untreated water with a calculated dosage of the cationic flocculant and/or cationic coagulant based on the TSS content and the flow rate of the untreated water, to produce cationic flocculant and/or coagulant-treated water comprising a floc or agglomerated component;

(3) a clarifier for separating the floc or agglomerated component of the cationic flocculant and/or coagulant-treated water from a clarified water component of the cationic flocculant and/or coagulant-treated water;

(4) an anionic flocculant dosing system comprising an anionic flocculant, for treating the separated floc or agglomerated component with a calculated dosage of the anionic flocculant, to produce anionic flocculant-treated water comprising a floc component; and

(5) a screw press separator for separating the floc component of the anionic flocculant treated water from a clarified water component of the anionic flocculant-treated water.