WO2020003148A2 - Reverse osmosis process - Google Patents

Reverse osmosis process Download PDF

Info

Publication number
WO2020003148A2
WO2020003148A2 PCT/IB2019/055383 IB2019055383W WO2020003148A2 WO 2020003148 A2 WO2020003148 A2 WO 2020003148A2 IB 2019055383 W IB2019055383 W IB 2019055383W WO 2020003148 A2 WO2020003148 A2 WO 2020003148A2
Authority
WO
WIPO (PCT)
Prior art keywords
charged cations
reverse osmosis
cation exchange
osmosis unit
ppm
Prior art date
Application number
PCT/IB2019/055383
Other languages
French (fr)
Other versions
WO2020003148A3 (en
Inventor
John Arthur Bewsey
Original Assignee
J. A. J. Technologies (Pty) Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by J. A. J. Technologies (Pty) Ltd filed Critical J. A. J. Technologies (Pty) Ltd
Publication of WO2020003148A2 publication Critical patent/WO2020003148A2/en
Publication of WO2020003148A3 publication Critical patent/WO2020003148A3/en

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/04—Feed pretreatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/10—Accessories; Auxiliary operations
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/42—Treatment of water, waste water, or sewage by ion-exchange
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2311/00—Details relating to membrane separation process operations and control
    • B01D2311/04—Specific process operations in the feed stream; Feed pretreatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2311/00—Details relating to membrane separation process operations and control
    • B01D2311/25—Recirculation, recycling or bypass, e.g. recirculation of concentrate into the feed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2311/00—Details relating to membrane separation process operations and control
    • B01D2311/25—Recirculation, recycling or bypass, e.g. recirculation of concentrate into the feed
    • B01D2311/252—Recirculation of concentrate
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2311/00—Details relating to membrane separation process operations and control
    • B01D2311/26—Further operations combined with membrane separation processes
    • B01D2311/2623—Ion-Exchange
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/42—Treatment of water, waste water, or sewage by ion-exchange
    • C02F2001/425—Treatment of water, waste water, or sewage by ion-exchange using cation exchangers
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/10—Nature of the water, waste water, sewage or sludge to be treated from quarries or from mining activities
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2303/00—Specific treatment goals
    • C02F2303/16—Regeneration of sorbents, filters

Definitions

  • RO Reverse Osmosis
  • a process for treating an aqueous feed containing singly and multiply charged cations including the steps of:
  • a) passing the aqueous feed through a cation exchange process comprising a cation exchange resin which gathers the multiply charged cations to produce a feed stream containing singly charged cations and depleted of multiply charged cations, and a loaded cation exchange resin;
  • the loaded cation exchange resin is treated with the brine to produce a regenerated cation exchange resin and a precipitate of the multiply charged cations.
  • the aqueous feed may be an effluent stream from an acid mines water treatment plant containing more than 1000, typically more than 2000, more than 3000 and up to 15000 ppm total dissolved solids.
  • the singly charged cations may be potassium, ammonium and/or sodium, typically sodium.
  • the multiply charged cations may include doubly charged cations such barium, magnesium and/or calcium, strontium, zinc, copper and many other doubly charged cations but they are usually present in minor amounts.
  • the multiply charged cations may include triply charged cations such as aluminium, iron, manganese and other multiply charged cations but they are usually present in minor amounts.
  • the cation exchange resin may be a strong based acid resin, for example a macroporous styrene DVB resin such as IndionTM 525, typically with a particle size greater than 100 microns, preferably greater than 300 microns, and an exchange capacity greater than 2 equivalents/ltr.
  • a strong based acid resin for example a macroporous styrene DVB resin such as IndionTM 525, typically with a particle size greater than 100 microns, preferably greater than 300 microns, and an exchange capacity greater than 2 equivalents/ltr.
  • the regenerated cation exchange resin may be separated from the precipitate, typically by selective filtration with a filter having 100 micron, typically 300 micron or greater open spacing.
  • the separated regenerated cation exchange resin is preferably recycled to step a).
  • the cation exchange process step c) comprises one or a series of continuous stirred tank reactors (CSTRs) operating in series with the aqueous feed running counter-current to the flow of the cation ion exchange resin although column technology can be used for small water treatment flows.
  • CSTRs continuous stirred tank reactors
  • the feed stream containing singly charged cations and depleted of doubly and multiply charged cations from step a) typically contains less than 50, less than 25, preferably less than 10 ppm multiply charged cations, and may contain more than 500, typically more than 1000 ppm singly charged cations.
  • the reverse osmosis unit at step b) may comprise a low energy, fouling resistant membrane and is typically run at a feed pressure of 20 to 100 bar, preferably 30 to 70 bar, more preferably 40 to 60 bar, typically about 50 bar, and produces a brine containing greater 50 000, greater than 80 000, greater than 100 000, greater than 1 10 000 and up to 150 000 ppm total dissolved solids.
  • the brine may contain greater than 10 000, greater than 20 000, greater than 30 000 and up to 50000 ppm singly charged cations, typically sodium cations.
  • a water product from the reverse osmosis unit typically contains less than 200, preferably less than 150, more preferably less than 100 ppm total dissolved solids.
  • the cation regeneration step c) preferably takes place in a CSTR as this makes it easier to separate out the precipitate that is formed in the regeneration process.
  • the precipitate at step c) is typically a sulphate of a singly charged cation, typically calcium sulphate (CaS0 4 .2H 2 0). This precipipate may be converted to Plaster of Paris (CaS0 4 .1/2 H 2 0) or anhydrite (CaS0 4 ) by heating.
  • the aqueous feed may contain more than 500 ppm, typically more than 900 ppm bicarbonate anions, more than 1000 ppm, typically more than 1400 ppm sulphate anions and more than 10, more than 100, possibly more than 150 ppm chloride anions.
  • the brine at step b) may contain more than 20 000 ppm, typically more than 5 000 ppm bicarbonate anions, more than 30 000 ppm, typically more than 40 000 ppm sulphate anions and more than 4000, typically more than 5000 ppm chloride anions.
  • Figure 1 is a flow diagram of a process of the invention.
  • the process of the present invention removes heavy metals and doubly charged cations using ion exchange resins on the incoming feed water before being processed in a standard reverse osmosis (RO) plant to give high quality water and a concentrated singly charged cation brine which is used to regenerate the loaded ion exchange resins.
  • the singly charged cation will usually be sodium as this cation is predominantly found in mines and underground waters although potassium and ammonium ions can function to achieve the regeneration step.
  • a waste water feed (10) containing bicarbonate, sulphate and chloride anions, and multiply charged cations (including calcium and other doubly charged cations such as copper, barium, and magnesium, and possibly triply charged cations such as aluminium and manganese), and singly charged cations such as potassium, ammonium and sodium is passed through a cation exchange process, indicated generally by the numeral (12), to remove the multiply charged cations.
  • the cation exchange process (12) consists of continuous stirred tank reactors (CSTRs) (14a-d) operating in series with the aqueous feed (16) running counter-current to the flow of the cation ion exchange resin (18).
  • a treated feed stream (20), with multiply cations removed and singly charged cations remaining is passed to a RO unit (22).
  • the cation exchange process (12) is operated so that the calcium level, in particular, is kept at all times below the point where gypsum is being produced in the membranes of the RO unit. For example, the calcium is kept at a level below 500ppm during the passage through the RO unit. It is not necessary for the singly charged cations to be removed as they are not offensive to the operation of the RO unit. Thus, as sodium is usually present in these types of water the circuit will quickly stabilize into running as a neutral sodium process i.e.
  • the RO unit (22) produces a treated water stream (24) and a brine (26) with a high sodium concentration from 5% up to 15%, typically from 8% up to 15% and from 10% up to 15%.
  • the next stage of the process is to use the high sodium concentrate brine (26) in the cation exchange process (12) to regenerate the catex resin in the return process into the sodium form before returning to the start of the extraction mode.
  • Loaded catex resin (28) from the CSTR (14a) is passed to a regeneration CSTR (30).
  • Loaded catex resin in the regeneration CSTR (30) is treated with the brine (26) to remove the multiply charged cations.
  • the regeneration CSTR (30) exchanges the cations, including calcium and magnesium, off the catex resin and returns it back to the sodium form while excreting the multiply charged ions into the water phase.
  • the calcium (which is usually the major species) will then react rapidly with the sulfate in the solution and precipitate out thus driving the equilibrium rapidly towards the complete sodium regeneration phase, to produce a slurry (32) comprising regenerated catex resin and gypsum precipitate.
  • the slurry (32) is passed through a coarse filter (34) (with approximately 300 micron apertures) and regenerated catex resin (36) is separated from the gypsum/brine slurry to give a high quality CaS0 4 .2H 2 0 (38).
  • This gypsum can be easily converted to Plaster of Paris (CaS0 4 .1/2 H 2 0) or anhydrite (CaS0 4 ) by heating.
  • the process may be carried out to achieve an equilibrium of calcium and sulphate ions to ensure maximum precipitation of gypsum.
  • the regenerated catex resin (36) is recycled to CSTR (14d) in the cation exchange process (12).
  • a residual much reduced concentrate - this can be as much as 50% of the TDS - (48) from the regeneration CSTR (30) then becomes a sodium salt solution saturated with gypsum and is processed further by a process such as that described in WO2015/159232 (the content of which is incorporated herein by reference), herein referred to as the“KNeW process” to give the fertilizers potassium nitrate, ammonium sulfate and salt.
  • An important aspect of the process is that the amount of water to be recovered through the KNeW process is only about 5% of the mainstream contaminated feed water and that the feed to the RO plant has all the calcium salt removed in the form of gypsum thus considerably reducing the maintenance and cost of operation of the RO system while substantially reducing the size and the amount of anions to be removed by the KNeW process.
  • CSTRs continuous stirred tank reactors
  • RO systems can operate without calcium pre-treatment and without anti-scaling additives.
  • the volume of water to be treated by the KNeW process will be around 4% (but less than 10%) of the original feed volume making the KNeW plant much smaller and lower capital cost.
  • the system of the present invention can be retrofitted to all RO systems removing their inherent disadvantages of expensive maintenance, gypsum pre-treatment and brine elimination.
  • the ion exchange resin used is Indion 525 with a mean particle size of 500 microns and an exchange capacity of 2.1 equivalents / Itr.
  • The“FEED” column data - shown in Table 1 - is a typical analysis of water being sent to waste after neutralization with lime, oxidation to turn ferrous iron to insoluble ferric salt, and filtering off the precipitate produced - being mostly gypsum and iron hydroxide.
  • This effluent having 3525 mg/ltr of dissolved solids, is unacceptably high for disposal to a water course and must be further treated before disposal or reuse.
  • the column -“After catex” - shows an analysis of the water after the doubly charged cations have been exchanged for the singly charged cation - in this case sodium - and can then be fed to an RO unit without the gypsum problem arising.
  • The“RO product water” is a typical analysis of an eluate from an RO unit with the“RO Brine” being the analysis of the brine stream exiting the RO unit after the pure water stream has been extracted.
  • the TDS level is at 120000 mg/ltr (12%) which is an economic concentration that can be achieved at around 50 bar feed pressure to the RO unit. This achieves a 32.2 x concentration of the feed without precipitation problems occurring from insoluble salts deposition.
  • This brine is contacted with the catex resin in the calcium/magnesium state in a CSTR where the exchange to the sodium state takes place rapidly as all the calcium and the sulfate ions react to form insoluble gypsum.
  • the resin is separated through a filter screen having a 300-micron open spacing which allows the fine gypsum slurry and the treated water to pass while the resin proceeds back to the FEED contact section.
  • the gypsum slurry is then filtered to recover a good quality gypsum for use in the ceramics and cement industries while the aqueous phase is fed to a KNeW process for conversion to fertilizer, salt and residual water for return to the FEED section.
  • the FEED flow starts at 4500m3/hr of which 4360 m3/hr is recovered as good reusable water while 140m3/hr is sent to recovery in the gypsum extraction section and the KNeW process.
  • KNeW process only 6m3/hr is lost to evaporation while the balance of 134m3’hr is returned to the FEED section.
  • the overall recovery of water as potable or high quality industrial water is above 98%

Abstract

This invention relates to process for treating effluent from an acid mines treatment plant 10 containing singly and multiply charged cations. The aqueous feed is passed through a cation exchange process 12 comprising a cation exchange resin which gathers the multiply charged cations to produce a feed stream 20 containing singly charged cations and depleted of multiply charged cations, and a loaded cation exchange resin 8. The feed stream 20 is passed through a reverse osmosis unit 22 to produce a brine 26 containing singly charged cations and a water product 4. The loaded cation exchange resin 28 is treated with the brine 26 to produce a regenerated cation exchange 32 resin and a precipitate of the multiply charged cations 38.

Description

REVERSE OSMOSIS PROCESS
BACKGROUND OF THE INVENTION
Reverse Osmosis (RO) is a widely used process for purifying high salinity water, such as sea-water or brackish underground water. However, these waters generally contain considerable amounts of calcium and sulfate which quickly reach saturation level in the RO membranes - 2000 mg/ltr - when the feed water is concentrated. Much effort and cost is applied to ensuring that the precipitated gypsum does not condense into the expensive membranes causing a drop in water flux and reducing the usable life of the membranes - which are very expensive to replace. The second difficulty for RO plants is to find a sink for the brines that are inevitably produced. These brines may not be disposed of underground so expensive and limited storage is the only other option at present.
It is an object of the present invention to address these problems. SUMMARY OF THE INVENTION
According to the present invention, there is provided a process for treating an aqueous feed containing singly and multiply charged cations, including the steps of:
a) passing the aqueous feed through a cation exchange process comprising a cation exchange resin which gathers the multiply charged cations to produce a feed stream containing singly charged cations and depleted of multiply charged cations, and a loaded cation exchange resin;
b) passing the feed stream through a reverse osmosis unit to produce a brine containing singly charged cations and a water product; wherein
c) the loaded cation exchange resin is treated with the brine to produce a regenerated cation exchange resin and a precipitate of the multiply charged cations.
The aqueous feed may be an effluent stream from an acid mines water treatment plant containing more than 1000, typically more than 2000, more than 3000 and up to 15000 ppm total dissolved solids.
The singly charged cations may be potassium, ammonium and/or sodium, typically sodium.
The multiply charged cations may include doubly charged cations such barium, magnesium and/or calcium, strontium, zinc, copper and many other doubly charged cations but they are usually present in minor amounts.
The multiply charged cations may include triply charged cations such as aluminium, iron, manganese and other multiply charged cations but they are usually present in minor amounts.
The cation exchange resin may be a strong based acid resin, for example a macroporous styrene DVB resin such as Indion™ 525, typically with a particle size greater than 100 microns, preferably greater than 300 microns, and an exchange capacity greater than 2 equivalents/ltr.
The regenerated cation exchange resin may be separated from the precipitate, typically by selective filtration with a filter having 100 micron, typically 300 micron or greater open spacing.
The separated regenerated cation exchange resin is preferably recycled to step a).
Preferably, the cation exchange process step c) comprises one or a series of continuous stirred tank reactors (CSTRs) operating in series with the aqueous feed running counter-current to the flow of the cation ion exchange resin although column technology can be used for small water treatment flows.
The feed stream containing singly charged cations and depleted of doubly and multiply charged cations from step a) typically contains less than 50, less than 25, preferably less than 10 ppm multiply charged cations, and may contain more than 500, typically more than 1000 ppm singly charged cations.
The reverse osmosis unit at step b) may comprise a low energy, fouling resistant membrane and is typically run at a feed pressure of 20 to 100 bar, preferably 30 to 70 bar, more preferably 40 to 60 bar, typically about 50 bar, and produces a brine containing greater 50 000, greater than 80 000, greater than 100 000, greater than 1 10 000 and up to 150 000 ppm total dissolved solids. The brine may contain greater than 10 000, greater than 20 000, greater than 30 000 and up to 50000 ppm singly charged cations, typically sodium cations. A water product from the reverse osmosis unit typically contains less than 200, preferably less than 150, more preferably less than 100 ppm total dissolved solids. The cation regeneration step c) preferably takes place in a CSTR as this makes it easier to separate out the precipitate that is formed in the regeneration process.
The precipitate at step c) is typically a sulphate of a singly charged cation, typically calcium sulphate (CaS04.2H20). This precipipate may be converted to Plaster of Paris (CaS04.1/2 H20) or anhydrite (CaS04) by heating.
The aqueous feed may contain more than 500 ppm, typically more than 900 ppm bicarbonate anions, more than 1000 ppm, typically more than 1400 ppm sulphate anions and more than 10, more than 100, possibly more than 150 ppm chloride anions.
The brine at step b) may contain more than 20 000 ppm, typically more than 5 000 ppm bicarbonate anions, more than 30 000 ppm, typically more than 40 000 ppm sulphate anions and more than 4000, typically more than 5000 ppm chloride anions.
BRIEF DESCRIPTION OF THE DRAWING
Figure 1 is a flow diagram of a process of the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
The process of the present invention removes heavy metals and doubly charged cations using ion exchange resins on the incoming feed water before being processed in a standard reverse osmosis (RO) plant to give high quality water and a concentrated singly charged cation brine which is used to regenerate the loaded ion exchange resins. The singly charged cation will usually be sodium as this cation is predominantly found in mines and underground waters although potassium and ammonium ions can function to achieve the regeneration step. With reference to Figure 1 , a waste water feed (10) containing bicarbonate, sulphate and chloride anions, and multiply charged cations (including calcium and other doubly charged cations such as copper, barium, and magnesium, and possibly triply charged cations such as aluminium and manganese), and singly charged cations such as potassium, ammonium and sodium is passed through a cation exchange process, indicated generally by the numeral (12), to remove the multiply charged cations. In a preferred embodiment of the invention, the cation exchange process (12) consists of continuous stirred tank reactors (CSTRs) (14a-d) operating in series with the aqueous feed (16) running counter-current to the flow of the cation ion exchange resin (18). A treated feed stream (20), with multiply cations removed and singly charged cations remaining is passed to a RO unit (22). The cation exchange process (12) is operated so that the calcium level, in particular, is kept at all times below the point where gypsum is being produced in the membranes of the RO unit. For example, the calcium is kept at a level below 500ppm during the passage through the RO unit. It is not necessary for the singly charged cations to be removed as they are not offensive to the operation of the RO unit. Thus, as sodium is usually present in these types of water the circuit will quickly stabilize into running as a neutral sodium process i.e. if the catex resin is in the sodium form at the start of the extraction phase then the multiply charged cations will be exchanged for sodium in the water phase while these ions will be absorbed onto the resin leaving the feed (20) to the RO unit (22) calcium free - and thus gypsum free. This will leave a feed (20) to an RO unit (22) being a solution of almost entirely sodium sulfate and sodium chloride which both stay in solution up to above the 20% m/v level thus ensuring no precipitation in the membranes. It should be noted that the osmotic pressure of a sodium sulfate solution is very much lower than a sodium chloride solution, giving the result that sulfate rich waters can be concentrated to a far greater extent than sodium chloride solutions. The process has shown that sodium sulfate solutions can be concentrated to above 16% in a standard RO unit whereas high sodium chloride solutions are not able to be concentrated much above 8% economically. Thus, the process can give economic“brines” with concentrations above 10% and some approaching 15%, all having no fouling factor.
The RO unit (22) produces a treated water stream (24) and a brine (26) with a high sodium concentration from 5% up to 15%, typically from 8% up to 15% and from 10% up to 15%.
The next stage of the process is to use the high sodium concentrate brine (26) in the cation exchange process (12) to regenerate the catex resin in the return process into the sodium form before returning to the start of the extraction mode. Loaded catex resin (28) from the CSTR (14a) is passed to a regeneration CSTR (30). Loaded catex resin in the regeneration CSTR (30) is treated with the brine (26) to remove the multiply charged cations. The regeneration CSTR (30) exchanges the cations, including calcium and magnesium, off the catex resin and returns it back to the sodium form while excreting the multiply charged ions into the water phase. The calcium (which is usually the major species) will then react rapidly with the sulfate in the solution and precipitate out thus driving the equilibrium rapidly towards the complete sodium regeneration phase, to produce a slurry (32) comprising regenerated catex resin and gypsum precipitate. The slurry (32) is passed through a coarse filter (34) (with approximately 300 micron apertures) and regenerated catex resin (36) is separated from the gypsum/brine slurry to give a high quality CaS04.2H20 (38). This gypsum can be easily converted to Plaster of Paris (CaS04.1/2 H20) or anhydrite (CaS04) by heating. The process may be carried out to achieve an equilibrium of calcium and sulphate ions to ensure maximum precipitation of gypsum.
The regenerated catex resin (36) is recycled to CSTR (14d) in the cation exchange process (12).
A residual much reduced concentrate - this can be as much as 50% of the TDS - (48) from the regeneration CSTR (30) then becomes a sodium salt solution saturated with gypsum and is processed further by a process such as that described in WO2015/159232 (the content of which is incorporated herein by reference), herein referred to as the“KNeW process” to give the fertilizers potassium nitrate, ammonium sulfate and salt.
An important aspect of the process is that the amount of water to be recovered through the KNeW process is only about 5% of the mainstream contaminated feed water and that the feed to the RO plant has all the calcium salt removed in the form of gypsum thus considerably reducing the maintenance and cost of operation of the RO system while substantially reducing the size and the amount of anions to be removed by the KNeW process.
The continuous stirred tank reactors (CSTRs) used in the process of the invention are described in detail in WO2015/159232 (the content of which is incorporated herein by reference).
Advantages of the process of the present invention
1 . RO systems can operate without calcium pre-treatment and without anti-scaling additives.
2. RO systems will operate for much longer between replacements of the expensive membranes.
3. The gypsum produced will be clean and high quality so will be readily sold to this market
4. The KNeW process will address the RO brine problem
5. The volume of water to be treated by the KNeW process will be around 4% (but less than 10%) of the original feed volume making the KNeW plant much smaller and lower capital cost.
6. As all the calcium will be removed before the“brine” stream reaches the KNeW plant the amount of ions to be removed will be greatly reduced - of the order of 50%
7. But as sodium is not removed, the amount of Potassium Nitrate produced in the KNeW process will still be the same as before keeping the incoming value the same as a standard KNeW plant. (Only the amount of ammonium sulfate will be reduced or eliminated - in some cases - where the chlorides are low - the anex side of the plant may be not necessary at all)
8. The system of the present invention can be retrofitted to all RO systems removing their inherent disadvantages of expensive maintenance, gypsum pre-treatment and brine elimination.
Example
An example of the process is described for an effluent stream coming from an acid mines water treatment plant on the eastern basin of the Johannesburg area of South Africa. Table 1 below provides the results of the process.
The ion exchange resin used is Indion 525 with a mean particle size of 500 microns and an exchange capacity of 2.1 equivalents / Itr.
The“FEED” column data - shown in Table 1 - is a typical analysis of water being sent to waste after neutralization with lime, oxidation to turn ferrous iron to insoluble ferric salt, and filtering off the precipitate produced - being mostly gypsum and iron hydroxide. This effluent, having 3525 mg/ltr of dissolved solids, is unacceptably high for disposal to a water course and must be further treated before disposal or reuse.
The column -“After catex” - shows an analysis of the water after the doubly charged cations have been exchanged for the singly charged cation - in this case sodium - and can then be fed to an RO unit without the gypsum problem arising.
The“RO product water” is a typical analysis of an eluate from an RO unit with the“RO Brine” being the analysis of the brine stream exiting the RO unit after the pure water stream has been extracted. The TDS level is at 120000 mg/ltr (12%) which is an economic concentration that can be achieved at around 50 bar feed pressure to the RO unit. This achieves a 32.2 x concentration of the feed without precipitation problems occurring from insoluble salts deposition.
This brine is contacted with the catex resin in the calcium/magnesium state in a CSTR where the exchange to the sodium state takes place rapidly as all the calcium and the sulfate ions react to form insoluble gypsum.
The resin is separated through a filter screen having a 300-micron open spacing which allows the fine gypsum slurry and the treated water to pass while the resin proceeds back to the FEED contact section. The gypsum slurry is then filtered to recover a good quality gypsum for use in the ceramics and cement industries while the aqueous phase is fed to a KNeW process for conversion to fertilizer, salt and residual water for return to the FEED section.
The FEED flow starts at 4500m3/hr of which 4360 m3/hr is recovered as good reusable water while 140m3/hr is sent to recovery in the gypsum extraction section and the KNeW process. In the KNeW process only 6m3/hr is lost to evaporation while the balance of 134m3’hr is returned to the FEED section. Thus, the overall recovery of water as potable or high quality industrial water is above 98%
Figure imgf000012_0001

Claims

1 . A process for treating an aqueous feed containing singly and multiply charged cations, including the steps of:
a) passing the aqueous feed through a cation exchange process comprising a cation exchange resin which gathers the multiply charged cations to produce a feed stream containing singly charged cations and depleted of multiply charged cations, and a loaded cation exchange resin;
b) passing the feed stream through a reverse osmosis unit to produce a brine containing singly charged cations, and a water product; wherein
c) the loaded cation exchange resin is treated with the brine from step b) to produce a regenerated cation exchange resin and a precipitate of the multiply charged cations.
2. The process claimed in claim 1 , wherein aqueous feed is an effluent stream from an acid mines water treatment plant containing more than 1000 total dissolved solids.
3. The process claimed in claim 2, wherein aqueous feed is an effluent stream from an acid mines water treatment plant containing more than 2000 ppm total dissolved solids.
4. The process claimed in claim 3, wherein aqueous feed is an effluent stream from an acid mines water treatment plant containing more than 3000 ppm total dissolved solids.
5. The process claimed in claim 4, wherein aqueous feed is an effluent stream from an acid mines water treatment plant contains up to 15000 ppm total dissolved solids.
6. The proces claimed in claim 1 , wherein the singly charged cations are potassium, ammonium and/or sodium.
7. The process claimed in claim 1 , wherein the singly chared cations are sodium.
8. The process claimed in claim 1 , wherein the multiply charged cations include doubly charged cations.
9. The process claimed in claim 8, wherein the doubly charged cations include barium, magnesium and/or calcium, strontium, zinc, and copper.
10. The process claimed in claim 1 , wherein the multiply charged cations include triply charged cations.
1 1. The process claimed in claim 10, wherein the triply charged cations include aluminium, iron, and manganese.
12. The process claimed in claim 1 , wherein the cation exchange resin may is a strong based acid resin.
13. The process claimed in claim 12, wherein the cation exchange resin is a macroporous styrene DVB resin.
14. The process claimed in claim 13, wherein the cation exchange resin is Indion™ 525.
15. The process claimed in claim 1 , wherein the cation exchange resin has a particle size greater than 100 microns.
16. The process claimed in claim 15, wherein the cation exchange resin has a particle size greater than 300 microns.
17. The process claimed in claim 1 , wherein the cation exchange resin has an exchange capacity greater than 2 equivalents/ltr.
18. The process claimed in claim 1 , wherein regenerated cation exchange resin is separated from the precipitate.
19. The process claimed in claim 15, wherein regenerated cation exchange resin is separated from the precipitate by selective filtration with a filter having 100 micron or greater open spacing.
20. The process claimed in claim 16, wherein regenerated cation exchange resin is separated from the precipitate by selective filtration with a filter having greater than 300 micron or greater open spacing.
21. The process claimed in claim 18, wherein the separated regenerated cation exchange resin is recycled to step a).
22. The process claimed in claim 1 , wherein the cation exchange process step c) comprises one or a series of continuous stirred tank reactors (CSTRs) operating in series, with the aqueous feed running counter-current to the flow of the cation ion exchange resin.
23. The process claimed in claim 1 , wherein the feed stream containing singly charged cations and depleted of multiply charged cations from step a) contains less than 50 ppm multiply charged cations.
24. The process claimed in claim 23, wherein the feed stream containing singly charged cations and depleted of multiply charged cations from step a) contains less than 25 ppm multiply charged cations.
25. The process claimed in claim 24, wherein the feed stream containing singly charged cations and depleted of multiply charged cations from step a) contains less than 10 ppm multiply charged cations.
26. The process claimed in claim 1 , wherein the feed stream containing singly charged cations and depleted of multiply charged cations from step a) contains more than 500 ppm singly charged cations.
27. The process claimed in claim 26, wherein the feed stream containing singly charged cations and depleted of multiply charged cations from step a) contains more than more than 1000 ppm singly charged cations.
28. The process claimed in claim 1 , wherein the reverse osmosis unit at step b) is run at a feed pressure of 20 to 100 bar.
29. The process claimed in claim 28, wherein the reverse osmosis unit at step b) is run at a feed pressure of 30 to 70 bar.
30. The process claimed in claim 29, wherein the reverse osmosis unit at step b) is run at a feed pressure of 40 to 60 bar.
31. The process claimed in claim 30, wherein the reverse osmosis unit at step b) is run at a feed pressure of about 50 bar.
32. The process claimed in claim 1 , wherein the reverse osmosis unit at step b) produces a brine containing greater 50 OOOppm total dissolved solids.
33. The process claimed in claim 3, wherein the reverse osmosis unit at step b) produces a brine containing greater 80 OOOppm total dissolved solids.
34. The process claimed in claim 33 wherein the reverse osmosis unit at step b) produces a brine containing greater 100 000 ppm total dissolved solids.
35. The process claimed in claim 34, wherein the reverse osmosis unit at step b) produces a brine containing greater 1 10 000 ppm total dissolved solids.
36. The process claimed in claim 35, wherein the reverse osmosis unit at step b) produces a brine containing up to 150 000 ppm total dissolved solids.
37. The process claimed in claim 1 , wherein the reverse osmosis unit at step b) produces a brine containing greater than 10 000 ppm singly charged cations.
38. The process claimed in claim 37, wherein the reverse osmosis unit at step b) produces a brine containing greater 20 000 ppm singly charged cations.
39. The process claimed in claim 38, wherein the reverse osmosis unit at step b) produces a brine containing greater than 30 000 singly charged cations.
40. The process claimed in claim 39, wherein the reverse osmosis unit at step b) produces a brine containing greater 30 000 ppm singly charged cations.
41. The process claimed in claim 40, wherein the reverse osmosis unit at step b) produces a brine containing up to 50000 ppm singly charged cations.
42. The process claimed in claim 41 , wherein the singly charged ions are sodium cations.
43. The process claimed in claim 1 , wherein the water product from the reverse osmosis unit contains less than 200 ppm total dissolved solids.
44. The process claimed in claim 43, wherein the water product from the reverse osmosis unit contains less than 150 ppm total dissolved solids.
45. The process claimed in claim 44, wherein the water product from the reverse osmosis unit contains less than 100 ppm total dissolved solids.
46. The process claimed in claim 1 , wherein cation regeneration step c) takes place in a CSTR.
47. The process claimed in claim 1 , wherein the precipitate at step c) is a sulphate of a multiply charged cation.
48. The process claimed in claim 47, wherein the precipitate is calcium sulphate (CaS04.2H20).
49. The process claimed in claim 48, wherein the calcium sulphate (CaS04.2H20) is converted to Plaster of Paris (CaS04.1/2 H20) or anhydrite (CaS04) by heating.
PCT/IB2019/055383 2018-06-26 2019-06-26 Reverse osmosis process WO2020003148A2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ZA2018/04265 2018-06-26
ZA201804265 2018-06-26

Publications (2)

Publication Number Publication Date
WO2020003148A2 true WO2020003148A2 (en) 2020-01-02
WO2020003148A3 WO2020003148A3 (en) 2020-04-16

Family

ID=68985931

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2019/055383 WO2020003148A2 (en) 2018-06-26 2019-06-26 Reverse osmosis process

Country Status (1)

Country Link
WO (1) WO2020003148A2 (en)

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3378336A (en) * 1966-06-17 1968-04-16 Interior Usa Sulfate removal from brines
CA2186963C (en) * 1996-10-01 1999-03-30 Riad A. Al-Samadi High water recovery membrane purification process
IL137102A0 (en) * 2000-06-29 2001-06-14 Israel Garden A process and apparatus for brine reformation
US6372143B1 (en) * 2000-09-26 2002-04-16 Hydrometrics, Inc. Purification of produced water from coal seam natural gas wells using ion exchange and reverse osmosis
US8815096B2 (en) * 2008-04-14 2014-08-26 Siemens Aktiengesellschaft Sulfate removal from water sources
US20100282675A1 (en) * 2009-05-08 2010-11-11 Lehigh University System and method for reversible cation-exchange desalination
US20110278225A1 (en) * 2010-05-03 2011-11-17 Brotech Corp., D/B/A The Purolite Company Method for purifying water by cyclic ionic exchange
US20120080376A1 (en) * 2010-10-04 2012-04-05 Pacific Advanced Civil Engineering, Inc. Use of desalination brine for ion exchange regeneration
CN106457238B (en) * 2014-04-15 2020-06-23 先驱技术有限公司 Ion exchange process

Also Published As

Publication number Publication date
WO2020003148A3 (en) 2020-04-16

Similar Documents

Publication Publication Date Title
US10392283B2 (en) Method and apparatus for treating accompanied water from a well
CN105939970B (en) System and method for removing minerals from brine using electrodialysis
AU2009238632B2 (en) Sulfate removal from water sources
US10954150B2 (en) System for removing minerals from a brine
Pérez-González et al. State of the art and review on the treatment technologies of water reverse osmosis concentrates
US20110155665A1 (en) Method and System for High Recovery Water Desalting
CN102438957B (en) Method for treatment and purification of seawater to recover high purity sodium chloride for industrial usage
CN107720782A (en) A kind of technique and system for use in carrying for dividing salt preparing potassium sulfate from high-salt wastewater
WO2014089796A1 (en) Method for treating high concentration wastewater such as ro brine
CN104071808A (en) Method for preparing industrial salt through separation, evaporation and crystallization of coal chemical strong brine
AU2010201962A1 (en) Salt purification process
CA2960697C (en) Method for treating an effluent supersaturated with calcium carbonate in the presence of phosphonate precipitation-inhibiting products
CN206901952U (en) Dense salt wastewater zero discharge and resources apparatus
US6036867A (en) Method for desalinating and demineralizing solutions containing acids and/or metal salts
GB2394678A (en) A solution rich in magnesium chloride (MgCl2) produced from seawater.
JP2004330148A (en) Method for treating dust extracted from cement kiln combustion gas
CN213771708U (en) Novel membrane treatment system for wastewater hardness removal
WO2020003148A2 (en) Reverse osmosis process
WO2007132465A2 (en) An improved membrane water desalination process
CN209368011U (en) Deposition vanadium mother liquid and wash water processing equipment for recycling
WO2014193955A1 (en) Brackish water desalination using tunable anion exchange bed
CN113955893B (en) Desulfurization wastewater treatment method and treatment system
CN109956578B (en) Pretreatment method and system for high-salinity desulfurization wastewater of coal-fired power plant
Cheng et al. Application of nanofiltration membrane in the recovery of aluminum from alkaline sludge solutions
Trus et al. Technical and economic assessment of innovative membrane technologies

Legal Events

Date Code Title Description
NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 19825560

Country of ref document: EP

Kind code of ref document: A2