CA3053050A1 - Self-coagulant and zero / reduced liquid discharge process for high hardness / high alkalinity wastewater treatment - Google Patents

Abstract

The invention proposes an efficient process for the treatment of high alkalinity and high hardness wastewaters (ion exchange regeneration wastewater, IERW) using a hybrid chemical/membrane treatment process. The method uses both waste streams as a novel self-coagulant for the chemical treatment. The high hardness wastewaters are capable of removing a significant portion of contaminants from high alkaline wastewaters. The proposed method can operate with a zero liquid discharge (ZLD) configuration and a low operating cost since requires zero/minimized expense for chemical coagulant. Two-hybrid technologies were developed; the first method involved treating the high alkaline wastewater with a hybrid of self-coagulant conditioning and membrane separation treatment. In the second process, the high alkaline waste stream was purified with membrane separation and then the concentrated retentate was treated by self-coagulant conditioning and a second membrane unit.

Description

Self-coagulant and zero / reduced liquid discharge process for high hardness / high alkalinity wastewater treatment 1 Description 1.1 Background of The Invention The importance of the water as lifeline of many industrial applications is well known. Therefore, many inventions are developing to enhance water treatment systems.
Traditionally, different water treatment methods such as chemical treatment, membrane separation processes or a combination of them can be used to treat high alkalinity wastewaters streams;
however, these treatments usually require a significant dosage of coagulants to operate at high efficiency.
Moreover, these processes are usually followed by producing other waste streams to the system whether it is produced sludge from the chemical treatment or the concentrated retentate stream of the membrane filtration processes. This presents economically and ecologically undesirable results since the mentioned disadvantages can significantly increase the maintenance and capital cost of the operation.
The present invention suggested a novel coagulant using high hardness wastewater (e.g. IERW), which is a waste stream produced in different applications such as ion exchange (IX) processes.
IX units are commonly used in the purification processes for the removal of magnesium and calcium ions. In the regeneration of the IX process, a high saline brine solution is produced known as IERW. The disposal of the IERW is challenging since it contains a relatively high concentration of calcium and magnesium or other cations / anions. Thus, it is highly beneficial to reuse this waste stream for other applications.
The main objective of this invention is to propose a highly efficient hybrid treatment, which is capable of operating with a minimized/zero coagulant cost and producing high-quality water for different industrial and residential applications.

1.2 Description This invention introduces two hybrid processes for the treatment of high alkalinity wastewaters.
The chemical treatment using the IERW as the coagulant was configured in these processes to cut down the operational cost, which is spent on purchasing commercial coagulants. The IERW
conditioning was proved to be capable of removing different contaminants such as silica ions and organic matters.
The first scenario involves pre-treating the high alkalinity wastewater by IERW conditioning followed by applying membrane filtration as the final treatment. A one-stage treatment using IERW conditioning might be enough depending on the target specification of the treated water.
Moreover, another chemical pre-treatment can be applied before the membrane filtration unit based on the properties of the produced effluent from IERW conditioning unit and requirement of the membrane filtration module. The IERW conditioning is capable of removing a significant portion of organic matters and silica ions, which lowers the fouling propensity and improves the separation performance of the membrane. The type of membrane filtration unit can be selected based on the target specification of the treated water. For example, reverse osmosis membranes can be used in case of requiring a higher quality treated water.
In the second scenario, the high alkalinity water can be treated using a direct membrane filtration unit and this treatment can be followed by treating the concentrated retentate with a hybrid of IERW conditioning and a second membrane filtration unit. The filtration type and water recovery of the membrane separation can be adjusted according to the properties of the wastewater and the fouling characteristic of the filtration.
These integrated processes also are capable of operating with a zero liquid discharge (ZLD) configuration since all of the produced waste streams from these treatments can be reused for other purposes. The produced sludge from IERW conditioning can be utilized as an industrial by-product due to presence of calcium sulfate and silicate. Furthermore, the concentrated retentate of the membrane filtrations contained a high concentration of sodium chloride making it ideal to be reused as the regeneration solution for the IX module. The ZLD
system will be further clarified in the examples.
The invention can be explained in more details by presenting an example of the applicability of this process in an industrial operation.

2 1.3 Description of The Drawings Figure A shows the schematic flow diagram of the hybrid process for the treatment of high alkaline wastewater using self-coagulant conditioning and a one-stage membrane filtration. The stream-1 and stream-2 are the produced high hardness and alkaline wastewaters, respectively.
The stream-1 and stream-2 are directed to the self-coagulant reactor for chemical treatment. The stream-3 is the MgCl2 solution that can be used as an additional coagulant if needed. After the removal of contaminants by self-coagulant conditioning, the produced effluent (stream-4) can be further treated using a softening and membrane unit. These two post-treatments are optional and can be utilized based on the application and the targeted specification of the treated water. The stream-5 is the produced effluent from the softening unit and was used as the feed of the membrane filtration. The stream-6 is the purified water using this technique and is directed to the required section for reuse. The stream-7A and stream-7B are the side streams or produced sludge of the self-coagulant reactor and softening unit, respectively. The stream-7A
and stream-7B are directed to the sludge dewatering units for maximum water recovery. The produced effluent from sludge dewatering unit 1 and 2 are the stream-8 and stream-9, respectively.
These two streams were directed to the purification process for further treatment. The stream-10 and stream-11 are the dry sludge of the sludge dewatering unit 1 and 2, respectively. These streams can be used as industrial by products through waste extraction. The stream-12 is the concentrated retentate of the membrane unit and is most likely a high salinity solution, which can be reused for other applications (e.g. the regeneration solution for IX process).
Figure B demonstrates the schematic flow diagram of the proposed integrated system for the treatment of high alkaline wastewater using a two-stage membrane filtration by integrating the self-coagulant conditioning as a chemical treatment for second membrane unit.
The stream-1 and stream-2 are the produced high hardness. The stream-2 is proposed to be used as the feed water of the first membrane filtration unit. The stream- 3 is the permeate water produced from the membrane unit 1 and can be used as purified water. The stream-4 is the concentrated retentate of the membrane unit 1 and is expected to have a higher concentration of contaminants compare to the initial high alkaline wastewater. The stream-4 is directed to the self-coagulant reactor for purification using chemical treatment. The produced effluent from the self-coagulant reactor is labeled as strean-5 and is used as the feed water of the second membrane filtration unit. The stream-8 is the permeate water of the membrane unit-2 and can be used for other industrial

3 proposes. The stream-9 is the sludge stream of the self-coagulant reactor and is directed to the sludge dewatering unit. The stream- 10 is the produced effluent of the sludge dewatering unit and is moved to the treatment process for further purification. The stream-11 is the dry sludge of the sludge dewatering unit and can be used as industrial by-product. The stream-12 is the concentrated retentate of the membrane unit and is most likely a high salinity solution, which can be reused for other applications (e.g. the regeneration solution for IX
process).
2 Detailed Description of Preferred Example Embodiments The present invention can be further explained by presenting the details of a process used for the treatment of produced water from SAGD operation called BBD water. Two general sections are provided to clarify the details of this example. First, the potential of ion exchange regeneration wastewater (IERW) containing magnesium ions to act as a coagulant for steam-assisted gravity drainage (SAGD) boiler blowdown (BBD), was demonstrated with the aim of reducing the water consumption in a SAGD plant. After identifying the applicability of IERW
conditioning, different membrane-based separation scenarios were examined to further purify the IERW-treating BBD water. In the second section, the feasibility of implementing these hybrid coagulation-membrane processes for the treatment of the boiler blow-down (BBD) from an oil sands SAGD operation was explored. The above-mentioned sections are written below:
2.1 Efficient Treatment of Oil Sands Produced Water: Process Integration Using Ion Exchange Regeneration Wastewater as a Chemical Coagulant Steam-assisted gravity drainage (SAGD) technology is considered a practical process to recover bitumen from oil sands reservoirs [1-4]. The SAGD process uses two parallel horizontal wells, which are drilled above each other deep underground into the oil sand reservoir. To increase the temperature and thus reduce the viscosity of the bitumen, steam is injected through the upper well and the low viscous drained bitumen collected into the lower well as a mixture to be pumped to the surface for bitumen extraction. This process requires a high volume of fresh

4 water, and currently about 80% - 90% of the boiler feed water (BFW) is coming from the recycled oil sands affected water.
Recently, significant attention has been given to water treatment methods of SAGD plants since a poor quality feed water for the steam generator will lower the efficiency of the boiler, as such BFW purity should be at an acceptable level. In SAGD industry, once through steam generators (OTSG) are widely used to generate steam. To provide feed water for OTSG, water treatment processes should reduce silica and hardness concentration to <50 mg/L and <1 mg/L, respectively. Also, the BFW should have total dissolved solid (TDS) and oil content, lower than 7000 mg/L and 0.5 mg/L [1,5,6]. Ion exchange regeneration treatment is a commonly used method to remove hardness from the BFW by replacing the calcium and magnesium ions with sodium ions [7]. In this process, a concentrated sodium chloride solution regenerates the ion exchanger. The purpose of the regeneration is to replace the calcium and magnesium ions, which were removed from the wastewater and retained in the ion exchanger, with sodium ions and return the resin to its original state. Therefore, this process results in wastewater with a high concentration of calcium, and magnesium, which is called the ion exchange regeneration waste (IERW) [8,9]. After removing hardness, the treated water is directed to the boiler, and the IERW
is discharged to the disposal system. The OTSG steam generation process typically produces 80% steam quality resulting in a concentrated solution, which is known as boiler blowdown (BBD). The BBD's impurity concentration is much higher than the BFW. In a typical SAGD
plant, an amount of the BBD is recycled back to the water treatment section, and the rest is discharged to the disposal system. In conventional approaches, BBD can be treated for reuse with the help of membrane filtrations, evaporation, chemical and biological treatment techniques.
However, these methods increase the capital cost and energy consumption of the SAGD plant and can result in significant waste [1]. What's more, the use of water treatment applications for the reuse of BBD demands specialized and expensive equipment. Therefore, it is highly beneficial to use inexpensive but efficient technology to treat the BBD.
In conventional water treatment plants, flocculation is an essential technique to separate impurities from contaminated water solutions [10,12,13]. At present, various types of coagulants (such as lime, soda ash, caustic) are used in wastewater treatment plants to improve the efficiency of the chemical process [14].

Although extensive research has been carried out using chemical coagulants to treat the BBD, the majority of those coagulants are not environmentally friendly and require a high dosage.
Furthermore, usage of chemical additives may overload the water treatment system and increase the operating resources and costs. As such, if a waste stream in the SAGD
plant can be used as a coagulant, this will lead to a more cost and energy effective process for BBD
treatment.
Therefore, the major objective of this study is to investigate the feasibility of using the currently unusable IERW as the coagulant to treat the BBD under different treatment conditions. This wastewater contains a high concentration of magnesium and calcium that can potentially act as an effective coagulant in reducing the silica and organic content of BBD
water.
This is the first report to our knowledge discussing the possibility of using ion exchange regeneration wastewater and boiler blowdown as a coagulant for the treatment of SAGD process water and exploring the resource recovery from coagulated sludge waste.
Another important aspect of using IERW as the coagulant is that by applying this method of treatment, the extra cost and energy for the disposal of both IERW and BBD can be reduced. Finally, the chemical composition of the resulting sludge from this water treatment process was analyzed to explore the feasibility of resource recovery.
During experimental trails, two BBD water samples (BBD-1 and 13BD-2) with varying dissolved organic content were used. The IERW and BBD were used as a self-coagulant to treat the combined stream. The characteristics of BBD samples and IERW are presented in Table I.
Additionally, another BBD wastewater sample was prepared by increasing the pH
and silica concentration of the boiler feed water. The properties of the synthesized BBD
(BBD-2) are written in Table 1.
Table 1: The properties of BBD-1, IERW and BBD-2 water at room temperature.
BBD reported Parameter Unit IERW BBD-1 BBD-2 in literature [1,2]
TDS ppm 66625 375 6525 25 2212 35 4026-17200 pH 6.20 0.11 11.66 0.01 11.60 0.10 10.50-12.33 Turbidity NTU 0.25 0.05 0.86 0.06 0.20-53 UV absorbance at 254 -- 0.07+0.01 0.72+0.04 0.55-0.87 nm SUVA254 - 1.04+0.15 0.77+0.08 - 2.75-5.21 TOC ppm 6.71+0.07 92.12+0.11 274+2.40 695-2482 Silica ppm as SiO2 5.22+0.48 77.60+1.50 165+0.13 65-Magnesium ppm 2201+351 0.24+0.03 57.3+1.10 0.68-0.08 _ Calcium ppm 9455+1059 2.97+2.59 310+2.20 4.25-4.80 Sodium ppm 22165+3244 1806+130 1830+59 819-5199 Chloride ppm 80650+4203 40 6 - 494-6715 Sulfate ppm 320+57 1230+310 - -In order to analyze the coagulation process, a few measurable variables were selected for the chemical process. The control factors and the selected levels for this design are provided in Table 2. These control factors were chosen based on the common industrial practices to treat the wastewaters using chemical coagulant. For all of the experiments, the mixing (coagulation) and precipitation time were 30 minutes. According to these variables, a total number of sixteen runs were conducted for this work. For all of the experiment, the response variables considered were turbidity, silica concentration and total organic carbon (TOC).
Table 2: Full factorial design factors and levels Levels Factors Unit IERW to BBD ratio Volumetric ratio (IERW:BBD) 1:12 2:12 Temperature C 40 80 The speed of the stirring rpm 0 60 2.1.1 Removal efficiency analysis of treated water Figure 1 presents the removal percentage of TOC and silica for different experimental trials after the chemical treatment. Based on this figure, the removal percentage for silica varied from 97.77% to 99.44% and the removal percentage for TOC was from 78.64% to 83.22%.
The removal percentages were obtained by comparing the initial value of the parameters in the BBD-1 to the treated supernatant samples. The mean removal percentage of all eight runs for TOC and silica concentration was 81.06% + 0.82% and 98.63% 0.61%, respectively.
Therefore, using the IERW for the BBD-1 treatment resulted in a high removal percentage of organic matter and silica concentration for all of the experimental runs.
100 , ____________________________________ 86 . 0 Slime Removal (%) - 85 TOG Removal (%) -ci 0¨...
i 0 .-.9et. .

¨ 41µ 1 41 -83 ;52;

tX Ce cz 98.6 - + -80 (.) 98 - ' _________________ ' 76 Experimental Run Figure 1: Removal percentage of silica and TOC for all of the experimental trials The characterization of the supernatant samples from the chemical treatment process indicated that the treated water had a low concentration of magnesium, organic matter and silica ions.
However, in the supernatant samples, the concentration of calcium and sodium increased significantly after the treatment. Since the calcium concentration varied based on the IERW
dosage, the average concentration of calcium was presented based on the two different dosages of the IERW, 598 and 1102 ppm for the lower and higher dosages of IERW, respectively.

The turbidity varied from 1.1 to 17.3 NTU for different runs. This result indicates a noticeable change in the results for different conditions indicating a significant effect of the controllable parameters on the turbidity of the treated water. The significance of the different factors is more evident when comparing run 1 and 8 since all of their factor levels are different. This is because after adding the coagulant, the silica and organic matters were removed from dissolved phase, but the formed flocs were not precipitated in the given time and remained suspended in the supernatant phase; the turbidity measurements confirm this explanation.
Based on the variation of the turbidity and the design factors, the optimized level for each parameter can be estimated. For temperature, removal efficiency was highest at 80 C, and the removal was higher when the IERW and BBD-1 were mixed for 30 minutes at 60 rpm.
Furthermore, increasing the dose improved the flocculation and precipitation so 2:12 volume ratio is recommended coagulant dose to achieve better water quality.
2.1.2 Industrial by-products The treatment of BBD-1 with IERW lead to coagulation followed by sludge formation and water recovery. The physicochemical characterization of the precipitated flocs was further performed to explore resources recovery from the sludge waste. The produced sludge after IERW treatment was analyzed using SEM, EDX, FTIR, XPS and XRD techniques. SEM and EDX
analyses show the morphology and composition of the sludge residue (Figure 2 (a), (b) and (c)). The SEM
micrographs show continuous amorphous phase with the semi-crystalline domain, and an average size of the particles, which was about 5 gm. The elemental composition of the sludge was obtained from the EDX analysis include Ca, Mg, Cl, Si, Na, 0 and C. It was demonstrated that the concentration of Mg and Ca was high in the precipitated solids. This result shows that particles were entrapped by magnesium due to flocculation mechanism, which confirms the silica and organic matter removal by using the IERW as the coagulant [46-49].
In order to identify the major chemical species and functional groups present in the sludge, FTIR
analysis of the solid precipitates were performed which is demonstrated in Figure 2 (d). The peak at 1007 cm-1 can be attributed to the Si-0 band and the peaks from 1156-1200 cm-1 can be assigned to silica bonding. The 1631 cm-1, 650 cm-1 and 3398 cm-1 bands can be the characteristics of bending vibration of 0-H. The 874 cm-1 peak observed at the low-frequency region can represent Mg-0 vibration. According to literature, peak at 1447 cm-1 with high intensity can be due to the presence of C032- [18,50,51]. Therefore, FTIR data are in agreement with EDX results suggesting the existence of Mg, Ca and Si in the precipitated sludge.
x103 re ' , = 1r 4 , it µ. 4 - Mg 11=111C21 C 24,10 I
t 0 37,81 13.09 C CI 16.63 .., 21 ' 1 2 - Ca 6.31 0 i * , 17 a IIIL SI 2.03 0.4 , ' =µ,,,,,\ s C r ':11t:1'1.,7:111, Si it) Ca _ 0 10 pm ¨ 0 1 2 3 4 5 6 7 8 x10-2 Energy (keV) 8.
40.,.,.........-si 1447 Itii, 7 = 6 .
M i' 1631 .10- iit allip '`. ch 650 4. 874 11156 .1'.
.41001/4 w . 1 43 i 1086 A = , 1007 i 'A*
i 0- .
ci 500 1000 1500 2000 2500 b 2 pm ¨
Wavenumbers (crril) Figure 2: SEM, EDX and FTIR analysis of the precipitated sludge obtained after the treatment of BBD
water with IERW. Representative SEM images with a magnification of a) 100x, b) 330x, and c) EDX
results. (d) Representative FTIR spectra of precipitated sludge obtained after the treatment of BBD water with IERW.
To further investigate the elemental composition of the precipitated sludge and their ionic state, XPS analysis was performed. Figure 3 shows the XPS survey spectrum of the precipitated sludge and the high-resolution spectra of Ca 2p and Mg 2p. The peaks in the survey spectrum were assigned to Ca, Mg, Si, Na, Cl, 0, S, and C in the solid sample. The peak at 167.3 eV in the survey indicate oxygenated sulfur species, possibly ¨SO4. These results are in agreement with EDX, FTIR and removal percentages. Furthermore, different atomic percent of these elements, given in Figure 3 (a), confirms the precipitation of corresponding compounds after the chemical treatment. Figure 3 (b) shows the high-resolution spectra for Mg 2p with a peak binding energy around 50.0 eV, which is close to those reported for magnesium hydroxides in the literature.
These results shows that magnesium was mostly precipitated as magnesium hydroxide [52]. The Ca 2p high-resolution spectra clearly shows well-defined peaks at 351.0 eV and 347.5 eV
corresponding to 2p 1/2 and 2p 3/2 respectively with a peak area ratio of 1:2.
The Ca2+ chemical shifts between various compounds (e.g., sulfates and carbonates) fall within a small range (<
1 eV), so it is not possible to identify the nature of Ca2+ compounds from XPS
data alone.
Therefore, XRD analysis was performed on the sludge samples as the diffraction data can be used as fingerprints for sample identification.
The XRD pattern of the precipitated sludge collected after the treatment of BBD water with IERW is given in Figure 4. The presence of CaSO4, Mg(OH)2, CaCO3 and NaCI were identified after fingerprinting the standard spectra of these compounds with the XRD
pattern of the sludge.
The XRD results further confirm the EDX, FTIR and XPS results and show successful sedimentation of BBD-1 water in the presence of IERW coagulant. Moreover, based on the presence of calcium sulfate, which is considered as an industrial product, it can be concluded that this sludge has the potential to be used as a by-product through the extraction of calcium sulfate.

_______________________________________________________________________________ _ x103 20 __________________________________________________________ Mg 2p a ca as 50-I Element Wt.% if li . ! i i i i Ma ls (6 45 .
Z i i 1 C 34.16 z ! i 16 ..! 0 1 (,) 40 = 1 1 , 0 27.06 1.
35,: MAL n he 1, i ,i Na Nu CI V
12 16.68 Mg KLL p KLL Ca 7.24 c 0 ' Ca 2p I
CI S2p i Mg 5'9 0 L) ,0010111 Binding energy (eV) 8 Ca 2s 9 is i Na 5.24 Ca 2p 3,2 , 'r 4 SI 1.71 450- Ca 2p A
Mg 2p 400 -4 = O. pi.
-.
:
. .
Si 21, 350 - !
=

1000 800 600 400 200 0 -200 ,..4 250 ===', Binding energy (ev) = 354 352 350 348 346 0 ID Binding energy (eV) Figure 3: XPS analysis of the precipitated sludge. (a) XPS- survey spectrum of the precipitated sludge showing component elemental peaks identified and their relative abundance. The high-resolution XPS
spectra for Mg 2p and Ca 2p are shown in (b) and (c), respectively.

Evaporated sludge 129000 = Halite - NaCI
Brucite - Mg(OH)2 Anhydrite - CaSO4 C
886000 Calcite - CaCO3 I
I Ii i . .
. I . I . .1 .1 Al I . I L. E. I I .

Two-Theta (deg) Figure 4: XRD Powder pattern of the dried sludge indicating the presence of different crystal patterns in the slurry phase 2.1.3 Softening of BBD after IERW coagulant treatment Table 3 shows that the concentration of calcium after the coagulation process by the IERW and BBD-I mixing is high. If the supernatant would be recycled, this hardness can reduce the efficacy of the SAGD plant by causing scaling on the pipes, exchangers and the boilers. Thus, soda softening was applied to remove the abundant calcium ions from the produced supernatant.
For this purpose, the supernatant of the most efficient run (run 8) was extracted from the mixture solution. Based on the IC analysis, the concentration of the chloride and sulfate in this solution was 10990 ppm and 1030 ppm, so presumably, most of the remaining calcium in the solution is in the form of non-carbonate hardness (permanent hardness) such as CaSO4 and CaCl2. This observation also demonstrates that the coagulation process significantly increased the chloride concentration of the BBD-1 however, the concentration of sulfate decreased presumably due to the formation of calcium sulfate. Soda ash (sodium bicarbonate) was chosen to remove calcium ions from the solution because this coagulant has high efficiency in the removal of permanent hardness from water. For this purpose, 5 g of soda ash was added to 1 liter of supernatant with the same experimental method as the run 8. This dosage was selected based on some primary experiments, which analyzed the hardness removal at a different dosage of soda ash.
After the sedimentation, the solution was analyzed for calcium removal. The properties of this solution are provided in Table 3. From this table, it can be observed that the concentration of calcium decreased from 1084 ppm to zero ppm, but the sodium concentration increased from 4397 ppm to 6973 ppm. This result shows that after the two treatments, almost all of the hardness was removed. It is worth noting that in a SAGD plant, the volume of BBD is only a portion of the BFW; the volumetric ratio of BBD used in this study was about 10% of the BFW.
It can be said that in the industrial practices, the treated BBD will be mixed with the BFW before entering the boilers. Therefore, the treated BBD-1 in this study can be diluted almost ten times and then be reused as the BFW. Thus, after dilution, the treated water will have an acceptable concentration range of TDS and sodium too. This provide an opportunity to use a lower volume of fresh water for the boilers.
Table 3: Comparison of the properties of the supernatant after soda softening.
Supernatant before soda Supernatant after soda Parameter Unit softening softening Calcium ppm 1084 0 Magnesium ppm 1.29 0.01 Sodium ppm 4311 6973 pH 10.75 10.96 TDS ppm 11350 16665 2.1.4 Applicability of IERW as a coagulant in the treatment of wastewaters In order to assess the treatment efficiency of IERW with other types of wastewater, a BBD-2 sample with a higher concentration of organic matter was treated with the IERW
coagulant (see Table 1). IERW water was added to the BBD-2 sample with the same experimental conditions as run 8. In this experiment, three different dosages of IERW was used for the treatment of BBD-2, and the precipitation of the mixture solution was observed for 1 hour. Figure

5 shows the effect of using different dosages of IERW for the treatment of the Athabasca BBD-2.
It can be seen that high silica and organic matter removal were achieved and the color of BBD-2 became lighter after the treatment with IERW due to the removal of organic matter. An increase in the IERW
dosage shows higher removal of TOC and silica, possibly due to the presence of more magnesium ions. These results confirm that the precipitation of the magnesium hydroxide was effective in removing the silica particles and organic matters in the BBD-2 by the coagulation-flocculation process.
100 __________________________ Silica removal IP
90 __ TOC removal IP 1111, , P442, r 7 , -o>
E 50 =
cc = , 2 12 4 12 6.12 (a) (b) (c) (d) IERW/BBD water volume ratio Figure 5: Demonstrate the treatment of BBD-2 water using IERW as coagulant.
The silica and TOC
removal percentages using IERW for the treatment of BBD-2 are depicted in the graph. The solution labelled (a) is BBD-2 and the (b), (c) and (d) represent the mixture solution after sedimentation with 2:12, 4:12, 6:12 IERW/BBD volumetric ratio, respectively.

2.1.5 Highlights of IERW conditioning In the present work, a systematic study has been conducted to investigate the feasibility of using IERW as a coagulant for the treatment of BBD and vice versa. It was observed that the IERW is capable of reducing some major impurities. These contaminants can be responsible for reducing the plant water recycling and efficiency of the OSTG, from the BBD and this takes into account not only the silica removal but also the organic matter presented in the BBD.
The efficiency of silica and TOC removal is 98.72% and 81.34%, respectively, which can be considered effective in a chemical treatment process. The turbidity measurements indicate that when the temperature decreased from 80 C to 40 C, the number of settled particles was reduced.
Moreover, it was observed that using mixing and increasing the temperature and dosage of the IERW improved the flocculation process significantly and larger flocs were formed and precipitated. However, the concentration of calcium increased after this treatment; this problem was solved by using soda ash softening process to remove the calcium from the solution. The sludge characterization supported the hypothesis of silica and organic matter removal by coagulation-flocculation of magnesium hydroxide. The usage of IERW was found to be effective for the treatment of Athabasca BBD. Therefore, even by considering the usage of a softening treatment, this process can be practiced reducing the extensive use of fresh water for BFW and eliminate the operation cost of disposal well plugging.
2.2 Integrated Coagulation-Membrane Processes with Zero Liquid Discharge (ZLD) Configuration for the Treatment of Oil Sands Produced Water In this section, different membrane-based separation scenarios were examined to reduce the TDS
concentration of the IERW-treated BBD water. The primary goal was to convert SAGD BBD
water, composing high concentration of TOC, TDS, and silica into high-quality feed water for reuse in boilers. The efficiency of the proposed separation scenarios was assessed based on permeation performance and fouling properties. Accordingly, different membrane processes were compared to nominate an economically feasible module for the treatment of the BBD
water.

According to table I, the sample BBD water (BBD-1) had a high concentration of silica and organic matter. The IERW contained a high concentration of calcium, magnesium, chloride, and sodium.
2.2.1 Coagulation-Membrane Hybrid Processes Five coagulation-membrane hybrid processes were evaluated to treat BBD water.
The chemical coagulants were either IERW or soda ash solutions or a combination of both.
Figure 6 illustrates the treatment processes in a schematic flow diagram. The details of each process are as follows:
Process-1: In the first process, the BBD water (Feed-1) was treated by NF in order to evaluate the capability of a single filtration step with a 50% water recovery. The permeate solution was named BFW-1.
Process-2: In the second process, the concentrate solution (Retentate-1) of process-1 was treated by IERW (IERW conditioning). The details about this pre-treatment are provided in the previous work [38]. In summary, the chemical pre-treatment was conducted by adding IERW
as a coagulant to BBD water at a 2:12 (IERW:BBD) ratio. The mixture solution was stirred for 30 min at 60 rpm followed by 30 min of sedimentation. Afterward, the supernatant was decanted and sent to NF unit as Feed-2. The permeate solution after NE was labeled as BFW-2.
Process-3: In the third process, the BBD water was first pre-treated by IERW.
The supernatant (Feed-3) was sent to the NF unit. The resulting permeate solution was called BFW-3.
Process-4: After IERW-conditioning, most of the organic matter and silica particles were removed from the BBD water, but the concentration of the dissolved calcium ions increased significantly. In order to remove the calcium ions, the IERW-treated 13I3D
water was further pre-treated using soda ash in the fourth process [39,40]. 5000 ppm of soda ash was added to IERW-treated BBD water. After 30 min mixing at stirring speed of 60 rpm, the supernatant was sent to the NF unit as Feed-4. The permeate solution after NF was labeled as BFW-4.
Process-5: In the final process, IERW was used as a draw solution to recover water from BBD
solution in an FO process. The IERW contained a high concentration of sodium chloride (see Table 4) that can potentially provide high osmotic pressure for the FO
application [15].
Afterward, the diluted IERW was sent to NF unit as Feed-5. The resulting permeate solution was called BFW-5.

Table 4 presents the properties of the Retentate-1 and Feed-1 to Feed-5 solutions, which were labeled based on the schematic flow diagram in Figure 6.
- ' - BBD Water =
41 ' Retentate-1 , I Feed N t pk,..
_________________ OP 1ERW
conditioning !UM
con ,... ditioning riw, _....._õ,,,,,... - , I

Permeate V I Draw 1 = 1t , Feed-1 ' Feed-2 Feed , ,.., Feed Soda Ash i Softening "
, -Permeate Permeate f li Feed-ii% ,- - - --- - -- ------, t Feed-4 Feed . Feed'I
.._ =
bill'N I NF
, -Permeate Permeate BFW-1 BF W-2 , BFW-3 BFW-4 BFW-5 i , , . ,,,, ., $ . ,., .. ..
., , , Process-1 Process-2 Process-3 Process-4 Process-Figure 6: Schematic flow diagram of coagulation-membrane processes for the treatment of steam assisted gravity drainage (SAGD) BBD water.
Table 4: Properties of different feed solutions in coagulation-membrane hybrid processes.
Parameter Unit Retentate-1 Feed-1 Feed-2 Feed-3 Feed-4 Feed-5 TDS ppm 8500 6525 16,750 11,350 16,665 34,535 pH - 10.90 11.66 11.60 10.75 10.96

6.20 Turbidity_ NTU 0.90 0.86 1.20 1.40 1.80 0.80 TOC ppm __ 443.30 229.80 107.70 17.00 16.60 3.00 Silica as dissolved ppm 111 77.60 3.17 1.43 0.93 3.00 mg2-, ppm 0.16 0.24 0.07 1.29 __ 0.01 1131 Ca2+ ppm 2.78 2.97 3.82 1084 0.00 Na + ppm 3975 1806 8069 4311 6973 11,436 The nanofiltration (NF) was performed using NF90 (DuPont Water Solutions (FILMTECTm)) membrane. The forward osmosis (FO) experiments were conducted by a commercial thin film composite (TFC) polyamide membrane, which was purchased from Hydration Technology Innovation (HTI, Albany, NY, USA).
2.2.2 Comparison of Different Hybrid Processes Figure 7 presents the total flux decline, flux recovery ratio, and TDS
rejection of different processes after the nanofiltration unit. These parameters were considered to select the most efficient process for the treatment of the BBD water. The total flux decline ratio demonstrates the efficiency for achieving a higher volume of the treated water under similar transmembrane pressure, and the flux recovery ratio is a measure of the fouling resistance of the membrane. The process-1 and process-2 showed a TOC removal rate of 90% and 92%, respectively. Among all the processes, process-3 showed the lowest performance with high DRt (93.4%) and low FRR
(69.7%). Process-5 can also be eliminated from the candidate pool as the transmembrane pressure for this process was elevated to 350 psi, and the permeate flux declined about 96.2%.
The three remaining processes (1, 2, and 4) showed an almost identical flux recovery ratio above 97%. Among these three processes, process-2 showed lower performance with higher flux decline and lower TDS rejection. Process-4 showed a lower flux decline (about 3.5%) than process-1, suggesting that this process can be chosen if a higher permeation rate is the selection criterion. However, if higher TDS removal is required, process-1 was more efficient than process-4 with 10% higher TDS rejection percentage.

100 - [7 / DRt N\,.. ERR Li TDS Removal . 7 7 ,f 90 - __ ...---, \ \:\
...,0 .......-C13 , .4¨.
= . ;
(1) ',.;,;';;0 77 C.) õ
1 . .,,,i,'4; 0 \s\s: 1.' " 70 -a) ,.
, t ,:,.'''''';
\':, ,

7 ,' a. :,..i \ ,, , I
> ',i:, .
,,,, , \ N
60 - \ l';',, .1..:-. :;.., :: :
,, i ,v< .
/) \, '..,.\\ I
50 /iv Process-1 Process-2 Process-3 Process-4 Process-5 Figure 7: Comparison of total flux decline (DRt), flux recovery ration (FRR), and total dissolved solids (TDS) removal of different processes.
2.2.3 Optimized hybrid process The present study evaluated different chemical-membrane hybrid processes for the treatment of BBD water in order to be reused as BFW. It was found that a direct treatment of BBD water using single-stage nanofiltration could result in the highest TDS removal from the feed solution.
Although a flux recovery of 97% was obtained after simple hydraulic washing, the high flux decline (-90%) was the notable adverse side of the direct NF treatment of BBD
water. This observation emphasizes the necessity of chemical treatment prior to the membrane filtration unit for such industrial waters. Application of dual chemical pre-treatment using IERW and soda ash solutions resulted in the highest permeation rate with lowest flux decline and highest flux recovery, demonstrating a potential solution to the fouling issue, which was also observed in other works that treated SAGD produced water with one-stage membrane separation processes [6,7,15]. Additionally, the IERW conditioning only uses a waste stream as the coagulant minimizing the operating expanse of chemical coagulant. However, lower TDS
rejection compared to direct NF treatment (70% compared to 80%) can be mentioned as the main drawback of this process. In overall, a combination of these two processes could be used as a zero-liquid discharge (ZLD) scheme by reusing the waste products in different applications. For instance, the produced sludge from the IERW conditioning unit can be used for extraction of calcium sulfate, which is used as a direct additive in many applications such as cement, water treatment, and food industries. Moreover, the concentrate solution from the NF
of soda ash treated water can be potentially used as a regeneration solution for the ion exchanger as it contains a high concentration of sodium ions. For future work, different types of membrane filtration such as RO or UF can be studied to achieve a higher efficiency or to provide a higher quality BFW for the boilers. Moreover, different levels for the operating conditions and other types of solutions for hydraulic backwashing can be selected in order to recommend an optimized condition for the hybrid process.
3 References [1] G. Hurwitz, D.J. Pemitsky, S. Bhattacharjee, E.M.V. Hoek, Targeted removal of dissolved organic matter in boiler-blowdown wastewater: Integrated membrane filtration for produced water reuse, Ind. Eng. Chem. Res. 54 (2015) 9431-9439.
doi:10.1021/acs.iecr.5b02035.
[2] R.G. Pillai, N. Yang, S. Thi, J. Fatema, M. Sadrzadeh, D. Pemitsky, Characterization and comparison of dissolved organic matter signatures in steam-assisted gravity drainage process water samples from athabasca oil sands, Energy and Fuels. 31(2017) 8363-8373.
doi:10.1021/acs.energyfuels.7b00483.

Claims

Self-coagulant and zero / reduced liquid discharge process for high hardness / high alkalinity wastewater treatment Claims The present patent application claims a method and process for treating high alkalinity wastewaters with a hybrid system. More particularly, the chemical treatment of the hybrid process will be conducted with another waste stream as the coagulant to minimize the capital and operating cost of the treatment.