A Pilot-scale Demonstration of Reverse Osmosis Unit for Treatment Of

ENERGY, RESOURCES AND ENVIRONMENTAL TECHNOLOGY Chinese Journal of Chemical Engineering, 20(2) 302311 (2012)

A Pilot-scale Demonstration of Reverse Osmosis Unit for Treatment of Coal-bed Methane Co-produced Water and Its Modeling*

QIAN Zhi ()1, LIU Xinchun ()1, YU Zhisheng ()1,**, ZHANG Hongxun ()1and J Yiwen ()21 College of Resources and Environment, Graduate University of Chinese Academy of Sciences, Beijing 100049,

China 2 Earth College, Graduate University of Chinese Academy of Sciences, Beijing 100049, China

Abstract This study presents the first demonstration project in China for treatment of coal-bed methane (CBM) co-produced water and recycling. The work aims to provide a research and innovation base for solving the pollution problem of CBM extraction water. The reverse osmosis (RO) unit is applied to the treatment of CBM co-produced water. The results indicate that system operation is stable, the removal efficiency of the total dissolved solids (TDS) is as high as 97.98%, and Fe, Mn, and F are almost completely removed. There is no suspended solids (SS) de-tected in the treated water. Furthermore, a model for the RO membrane separation process is developed to describe the quantitative relationship between key physical quantitiesmembrane length, flow velocity, salt concentration, driving pressure and water recovery rate, and the water recovery restriction equation based on mass balance is de-veloped. This model provides a theoretical support for the RO system design and optimization. The TDS in the CBM co-produced water are removed to meet the drinking water standards and groundwater quality standards of China and can be used as drinking water, irrigation water, and livestock watering. In addition, the cost for treat-ment of CBM co-produced water is assessed, and the RO technology is an efficient and cost-effective treatment method to remove pollutants. Keywords coal-bed methane co-produced water, high salt, pretreatment process, mass balance, reverse osmosis

1 INTRODUCTION

With the development of coal-bed methane (CBM) extraction, the treatment of water co-produced in the process is very important. With growing water short-ages and rapid development of CBM industry in China, optimal use of the CBM co-produced water can not only resolve the water conflicts between mine ar-eas and adjacent agricultural production zones, but also solve local water shortage problems.

There are abundant CBM resources in China. The CBM is composed mainly of methane, which is a high-quality fuel. Based on the calculation, 1 m3 CBM can substitute 1.13 L 93# gasoline [1]. The develop-ment process for CBM is generally divided into three phases: exploration, test production and mining. Water is produced from wells in each phase and it generally takes six months or longer to be drained out. It is high-salinity water, and the total dissolved solids (TDS) in CBM co-produced water are generally 1000 mgL1 or more. The primary concern with CBM co-produced water is the amount of Na+ and its influ-ence on the environment. Long-term irrigation of soil with the water may result in deterioration of physical and chemical properties of soil, such as soil infiltration and permeability and aggregate stability, which render soils unsuitable for plant growth and even threaten the safety of local drinking water [24]. Therefore, CBM co-produced water must be treated before discharge

and cost-effective technologies are needed for the wa-ter to be used for beneficial purposes, such as irriga-tion, livestock or wildlife watering and habitats, and various industrial uses [57].

Typically, technologies for treatment of high- salinity water include evaporation, ion exchange, elec-trodialysis and reverse osmosis [7]. The evaporation method, which is mainly used for seawater desalina-tion, requires massive heat; also, high salinity water will cause fouling on the heat exchanger surface [7]. The dissolved salts or minerals can be removed by ion-exchanger, but the pre- and post-treatment are re-quired for high efficiency and the operation of regen-eration of resin is complicated [7]. Dallbauman and Sirivedhin employed electrodialysis for treatment of high salinity water co-produced in oil-gas fields, ob-taining a TDS removal efficiency of 93.4%96.5% with a voltage 6.5 V and time of 60 min [8]. However, the membrane module needs frequent cleaning and fluctuations in water quality have a great impact on the effectiveness of the electrodialysis method. High pressure reverse osmosis (RO) processes have been the technology of choice for high-salinity water de-salination in the US and many other countries [9, 10]. The market share of RO desalination was 43% in 2004 and is forecasted to increase up to 61% in 2015 [11]. The advantages of RO include low energy require-ments, low operating temperature, small footprint, modular design, and low water production costs. Re-verse osmosis with high desalination efficiency, for

Received 2012-01-06, accepted 2012-02-21.

* Supported by the National Basic Research Program of China (2011ZX05060-005; 2009ZX05039-003), the National Natural Science Foundation of China (21106176), the President Fund of GUCAS (Y15101JY00) and the National Science Foundation for Post-doctoral Scientists of China (20110490627).

** To whom correspondence should be addressed. E-mail: [email protected]

Chin. J. Chem. Eng., Vol. 20, No. 2, April 2012 303


which water quality fluctuations have no negative ef-fect on the treatment effectiveness, is a feasible tech-nology for high-salinity water treatment [1214].

The CBM co-produced water in Liulin County of Luliang City, Shanxi Province, China, is high-salinity water. In this work, a system with sand filtration (pre-treatment) + ultrafiltration (pretreatment) + RO is em-ployed for treatment of CBM production water in Liulin. The effects of treatment process, the system perform-ance and the reuse feasibility are examined according to the output water quality and treatment cost.

Many mass transfer models have been developed for the flux of salt and water through RO membranes [1519]. Song et al. [16, 17] put forward the conception of thermodynamic equilibrium that restricts the recov-ery of membrane and provided an alternative way for optimization of membrane design and operation con-ditions. In this work, based on mass balance principle, mass transfer equations for water and salt are derived, and a model depicting the relationship between salt retention, TDS concentration and water recovery is obtained. The water recovery restriction equation is developed based on mass balance. Furthermore, dif-ferent operation ways of RO process are discussed and appropiate operating conditions are determined ac-cording to the theoretical model.

2 PILOT-SCALE EXPERIMENTAL

2.1 Process

The feed water was CBM field co-produced wa-ter from Liulin County of Luliang City, Shanxi Prov-ince. A process with sand filtration + UF + RO was utilized for treatment of the water with the capacity of 100 m3d1. First, the raw water was aerated to increase dissolved oxygen in water, and then passed through a manganese sand filter, sand filter and bag filter to re-move Fe, Mn and suspended solids (SS). The water passed the UF system and then went through a secu-rity filter into the RO system. Finally, the output water from RO entered storage tanks. The process flowsheet is shown in Fig. 1, and Fig. 2 shows an on-site picture of the pilot-scale demonstration unit built in this work.

Figure 2 On-site photograph of the pilot-scale demonstration

2.2 Treatment units

2.2.1 Pretreatment (1) Manganese sand filter Raw water entered the manganese sand filter

through the jet aeration. The manganese sand filter consists of a filter plate, with the upper plate filled with 12 mm manganese sand particles, which re-move most of the SS, colloids, Fe, Mn and other im-purities, and reduces turbidity.

(2) Sand filter The sand filter is in form of a filter plate. Quartz

sands of 0.51 mm and 12 mm in diameter are loaded from top to bottom within the sand filter, with a filter-ing accuracy of under 20 m. The sand filter mainly removes SS and colloids to further reduce turbidity and ensure that the turbidity of the output water is less than 3 NTU.

(3) UF system An X50 polypropylene hollow fiber ultra-filtration

membrane is used in the UF system, with a molecular weight cutoff (MWCO) in the range of 80000100000 (membrane pore size of 0.10.25 m), the treated wa-ter turbidity less than 0.3 NTU and silting density in-dex (SDI) less than 4. The system has six sets of membranes arranged in parallel with a single mem-brane flux of 24 m3h1 and area of 105 m2. The con-centrated water from UF is totally recirculated.

2.2.2 RO system The spiral wound RO membrane is a composite

polyamide membrane (BW30-400) with a desalination rate higher than 99.5% for a single membrane, which is 1.016 m long and 0.1016 m in diameter. The height of membrane channel is 1103 m and membrane re-sistance is 81010 Pasm1. The RO unit is operated at the pressure around 1.8 MPa. The RO membrane sys-tem consists of three membrane modules, with three membrane components arranged in series for each membrane module. Membrane modules are in a 21 arrangement. The first treatment stage is composed of two membrane modules and the concentrated water produced by the first stage enters a second stage with a single membrane module. Concentrated water is gen-erated in the second stage, while pure water generated in the first and second phases enters a storage tank.

2.3 Analysis of water quality

The analysis of water quality is based on the Drink-ing Water Standard Test Methods (GB/T5750-2006), Underground Water Standards (GB/T14848-1993) and Drinking Water Standards (GB 5749-2006).

3 MODEL FOR RO SYSTEM BALANCEEQUATIONS FOR CHEMICAL COMPONENTS

The RO system consists of two stages, the first stage containing 2 pressure vessels and the second stage containing 1 pressure vessel. Spiral-wound module is


the predominant RO element used in the RO process. Feed water flows along the channel parallel to the central line of the module and an unwound flat sheet membrane with same channel height is employed to represent characteristics of the corresponding spi-ral-wound RO module as shown in Fig. 3. The fol-lowing assumptions are made. Firstly, the mixing in the transverse direction of the channel is complete, u(x) is the crossflow velocity and v(x) is the permeate ve-locity of the membrane. Secondly, the salt retention rate for all membrane elements in the same stage is same, 98.8% for the first stage and 97.5% for the second stage. As shown in Fig. 3, the height of an infinitesi-mal element is H, the length is dx, and the width is dy.

Applying the mass balance principle to the in-finitesimal element of CBM co-produced water on the surface of the membrane shown in Fig. 3, the relation between u(x) and v(x) can be expressed as

2

2

2

H OH O

H O

( ) ( )d d d ( ) ( )d d d

( )d d d

u x xH x y t v x x x y t

xx

H x y tt

(1)

The mass balance equation for the water flowing in the membrane can then be obtained

2 2

2

H O H OH O

( )( )

u xH v x H

x t

(2)

The process from starting running the membrane system to reaching steady state can be described by Eq. (2). For a steady state, the density of water is not a function of time, so Eq. (2) can be simplified to

d ( ) ( ) 0du xH v x

x (3)

In addition, the TDS concentration distribution, c(x), along the membrane channel, which is affected by both water and salt transfer across the membrane, is very important for RO. Letting r be the membrane salt retention rate and applying the mass balance princi-ple on the infinitesimal element for salt concentration, the balance equation can be obtained. The balance

equation is applied to depict the concentration variation of components in CBM co-produced water along the filtration channel, such as 3HCO

, 23CO , Cl , 2Ca ,

2Mg and Na . The attention is mainly focused on the total salt (TDS) concentration in this study.

( ) ( ) d d d ( ) ( )(1 )d d d

d d d

c x u xH x y t c x v x r x y t

xc H x y tt

(4)

At steady state, Eq. (4) can be rewritten as d ( ) d ( ) ( ) ( )(1 )( ) ( ) 0

d du x c x c x v x rc x u x

x x H

(5)

Substituting Eq. (3) into Eq. (4) and integrating, we have

0

( )

0

1 ( )d ( ) d( ) ( )

c x x

c

rv xc x xc x Hu x

(6)

Substituting ( ) d ( ) / dv x H u x x into Eq. (6) and in-tegrating, a concise relationship between c(x) and u(x) is obtained

00( ) ( )

ruc x cu x

(7)

If u(x) is known, the TDS concentration at any point in the membrane channel can be calculated. Also, v(x) can be obtained accordingly.

The recovery, R, of a RO process is often used to indicate the performance of the process. R is defined as

0

( )1 u xRu

(8)

With Eqs. (7) and (8), the relation between water re-covery rate and TDS concentration is expressed as

1

01rcR

c

(9)

This simple equation based on the mass balance principle is applicable for various membranes. This

Figure 3 Schematic description of filtration channel


expression combines c, r and R in a concise form. The salt retention rate, r, is a characteristic of the membrane. In other words, once the feed TDS concentration c0 is fixed, the variation of water recovery rate is inde-pendent of other parameters and can be determined only by the value of c for a certain membrane system.

In order to acquire the velocity of water along the filtration channel, the permeate velocity model [19], based on the membrane transport theory, is introduced

m

1( ) ( )v x pR

(10)

where p is the transmembrane pressure, is the osmotic pressure and Rm is membrane resistance. Owing to the friction between the water flow and the channel wall and spacers in the membrane channel, the transmembrane pressure decreases along the mem-brane channel. p along the channel can be calculated as follows [20]

0 2 0

12( ) ( )dxkp x p u x x

H

(11) where p0 is the initial transmembrane pressure, k is a friction coefficient, and is the viscosity of the solution.

Empirical relationships are usually employed to determine the osmotic pressure based on a collective measurement of the total amount of salts in the water. The empirical equation of osmotic pressure usually takes the following form

( )f c x (12) The osmotic coefficient f converts salt concentra-

tion to osmotic pressure. According to the calculation, the simulated crossflow velocity and permeate veloc-ity in both stages agree well with the operation data when the value of f is set to 61 PaLmg1.

With Eqs. (3), (10), (11) and (12), the crossflow velocity distribution along the membrane channel can be described as

00 02 0

m

d ( ) 1 12 ( )dd ( )

rx uu x k u x x f c p

x HR u xH !

(13) Dividing the membrane channel into n segments

of equal intervals x, if the interval is small enough, Eq. (13) for every interval can be transformed to

00 0 02

m

d ( ) 1 12d ( )

ri i

i ii

u x uk u x f c px HR u xH

!

(14) where subscript i indicates segment i. Integration of Eq. (14) gives u(x). The Runge-Kutta-Fehlberg method (denoted RKF45) is employed to solve the differential equation with three initial values, ui0, ci0 and p0.

4 RESULTS AND DISCUSSION

4.1 Chemical analysis of CBM co-produced water

The chemical components of CBM co-produced water are mainly 3HCO

, 23CO , Cl , 2Ca , 2Mg

and Na , etc., accompanied by a small amount of K+, F, etc. Hg, Cd, 6Cr , As and Zn were not de-tected. Table 1 shows the water quality of the CBM production water in Liulin. The water from wells No. 1, 2 and 3 is produced in the early stage, while that from No. 4 and 5 is produced during the intermediate stage. A single well has water production of 410 m3d1 in the early stage and reaches 20 m3d1 for normal extraction. These wells are all located in the same mining area, so the water quality is similar for the same stages. It can be seen from Table 1 that the CODMn of CBM co-produced water is low, in the range 0.53.6 mgL1, which means a low level of organic pollution. However, the water has a higher content of K , Na and Cl in the range of 16134782 mgL1, which is high salt water.The percentage content of Na K is more than 90%. The water quality data of wells No. 4 and 5 indicate that the concentrations of K , Na and Cl decrease as mining time increases, but the water still needs further treatment before discharge.

4.2 Process performance

The treatment effect for CBM co-produced water in each processing unit is shown in Table 2. For the pretreatment process, the contaminants in raw water can be removed to some extent by filtration, adsorp-tion and chemical reaction of the manganese sand fil-ter, sand filter and UF process. The CODMn removal rate is 45.7%, TDS removal is 4.94%, Cl removal is

Table 1 Water quality of CBM co-produced water

Well pH CODMn /mgL1 TDS

/mgL1 K+

/mgL1 Na+

/mgL1Ca2+

/mgL1Mg2+

/mgL13NO

/mgL1F

/mgL1Cl

/mgL1

24SO

/mgL1

23CO

/mgL13HCO

/mgL1

1# 7.78 2.1 5466 7.4 1852.2 20.1 26.7 1.4 2.5 1973.2 143.3 N.D. 1797.52# 7.62 2.9 4782 7.7 1698.4 20.4 24.2 1.2 1.3 1984.8 149.5 N.D. 1454.43# 7.49 2.6 4650 6.9 1681.2 19.8 31.1 1.4 1.5 1917.8 141.9 N.D. 1454.44# 8.40 0.5 1613 5.8 583.5 8.7 4.2 0.2 10.3 326.1 28.4 23.86 1058.25# 7.91 3.6 1620 13.4 602.0 12.6 4.6 0.4 8.8 330.0 27.0 N.D. 1121.4

Note: N.D. stands for not detected.


42.4% and NH3-N removal is 46.2%. The turbidity of output water from the UF is below 0.5 NTU, guaran-teeing good water quality into the RO unit. The tur-bidity removal efficiency of the UF is high, but the salt removal rate is low, because the UF membrane is a porous one and the salt ion, which has a diameter smaller than the MWCO of the UF membranes, can not be retained. The RO membrane is a selective membrane that allows water to pass through only. RO unit can remove various contaminants effectively, es-pecially TDS.

The RO was the core processing unit and the treatment system could remove most contaminants. The total removal rates for CODMn, NH3-N, Cl and TDS were 81.0%, 85.4%, 97.7%, and 99.7%, respec-tively. The water quality meets the Drinking Water Standards (GB 5749-2006).

4.3 RO model simulations

4.3.1 Effects of TDS concentration of CBM co-produced water

Equation (7) gives a relationship between salt concentration c and flow velocity of feed water u in the membrane channel. The salt concentration in the concentrated water c increases with the decline of the crossflow velocity. The distribution of salt concentra-tion c along the membrane channel can be obtained if u(x) is known, while the distribution of u along the filtration channel can be obtained if other parameters are given. Eq. (14) uses the segment x of membrane channel, the value of ci0 for every interval x can be obtained from Eq. (7).

Converting the crossflow velocity into the water recovery rate using Eq. (8), Eq. (9) can be used to simulate the variation of recovery rate with salt con-centration of concentrated water. The results are shown in Fig. 4. The recovery does not always increase sharply in the process and the value of R tails off and

approaches a plateau when the salt concentration reaches a certain level. This result dictates that there is a limit to the recovery of the brine with a certain feed salt concentration when treated in RO membrane sys-tem, and the higher the feed salt concentration, the lower the recovery rate restriction. The critical point where the limit of recovery rate is approached, which is important for RO system design and operating con-dition optimization, can be found from Eq. (9) as does in Fig. 4. For example, for CBM co-produced water with a salt concentration of 5196 mgL1, R begins to increase extremely slowly when the salt concentration reaches 26000 mgL1, which means that a value of R of 79% is the threshold value for feed water with a concentration of 5196 mgL1; any attempt to enhance R further will result in a sharp increase in driving pressure or membrane length and is therefore neither cost-effective nor feasible. Thus R of 79% and con-centrated water of 26000 mgL1 can be regarded as the theoretical limits under the condition (with operat-ing parameters normally below these values) when the

Table 2 Treatment effects of units in term of water quality index

Pretreatment

Manganese sand Multi-medium UF RO

Water quality Raw water

Output Removal/% Output Removal/% Output Removal/% Output Removal/%

Removal/%

turbidity/NTU 409 12.4 96.97 1.4 88.71 64.29


RO system and operating conditions are being de-signed.

4.3.2 Effects of membrane length According to Eq. (13), the flow velocity u(x)

along the filtration channel can be simulated. The RO system consists of two stages with the 1st stage con-taining 2 pressure vessels and 1 vessel for the 2nd stage as shown in Fig. 5. Each pressure vessel consists of 3 composite polyamide membrane elements. With the velocity distribution, the recovery rate can be cal-culated. It is interesting to note that it is impossible to enhance water recovery endlessly by increasing the length of membrane. In order to clearly describe the relationship between treatment effects and membrane length, the variations of recovery rate with the channel length in the two stages are combined in Fig. 6. Due to the difference in salt concentration, the slope of re-covery rate in the 1st stage is higher than that in the 2nd stage. The variations in recovery become mar-ginal when the membrane length exceeds 6 m. The membrane length used in the pilot-scale RO system for this study is 6 m, so a recovery rate of 71.2% can be predicted from the simulation.

Figure 5 The sketch of arrangement of membrane com-ponents with two stages

Figure 6 The variation of recovery rate with the length of membrane for two stage operation (u0 0.18 ms1, c0 5196 mgL1, p 1.8 MPa, Rm 81010 Pasm1)

The pilot-scale RO test system, with L1 3 m in the first stage, L2 3 m in the second stage, u0 0.18 ms1, c0 5196 mgL1, and p 1.8 MPa, gave a water recovery rate of 70%, which is in good agree-ment with the predicted value, indicating that the model developed in this study describes the perform-ance of spiral wound RO membrane system.

A RO system consisting of one stage with 3 pressure vessels, as shown in Fig. 7, is also simulated, to compare with the two stage operation. With the flow

velocity distribution simulated, the water recovery rate can be calculated. The variation of recovery with channel length is shown in Fig. 8, suggesting that the membrane length should not exceed 4 m for the one stage membrane arrangement. According to the calcu-lation, the recovery rate for the one stage operation is 71.2% for L 3 m, u0 0.18 ms1, c0 5196 mgL1 and p 1.8 MPa, which is the same as that with the two stage operation. It can be concluded that both one stage and two stage arrangements are equivalent if there is no the interstage booster pump between 1st stage and 2nd stage in the two stage operation.

4.3.3 Effects of driving pressure The variation of recovery with driving pressure

for the two stage operation is plotted in Fig. 9. The re-covery increases with pressure but increase little when the pressure is higher than 1.8 MPa. A recovery rate of 78% can be observed as the restriction to the treatment process under the condition, as shown in Fig. 4. Also, the required working pressure to attain a specified recovery can be determined. Pilot-scale tests were performed under different driving pressures and the results are plotted as symbols in Fig. 9. The theoretical recoveries agree very well with the experimental data. Thus the model of RO system developed in this work is validated and can be used for the design of RO unit.

4.3.4 Effects of membrane resistance Equation (13) can be used to simulate the varia-

tion of water recovery with the membrane resistance. The resistance will increase because of membrane

Figure 7 Arrangement of membrane components in one stage operation

Figure 8 The variation of recovery rate with the length of membrane for one stage operation (u0 0.18 ms1, c0 5196 mgL1, p 1.8 MPa, Rm 81010 Pasm1)


fouling, and the water recovery rate will decrease ac-cordingly. However, as shown in Fig. 10, the recovery is unchanged with the increase of resistance until a certain value is reached, which indicates that the re-covery is independent of resistance during the initial period of membrane fouling. The reason for this result is the high driving pressure. Fig. 9 shows that the re-covery increases little when the pressure exceeds 1.8 MPa. For the driving pressure of 2.0 MPa, these ex-cessive pressures can compensate for the increase of membrane resistance caused by membrane fouling, so the recovery can maintain a certain level until the membrane fouling is severe. The simulation results suggest that a high system driving pressure will result in bad membrane fouling that can not be detected ear-lier. For avoiding severe membrane fouling, the pres-sure of 1.8 MPa is appropriate from Fig. 9. Based on the discussion, the RO process will be high efficient and durable at 1.8 MPa pressure and 6 m membrane length, with 70% water recovery under the condition.

Figure 10 The variations of water recovery rate with the membrane resistance in the two stage process (u0 0.18 ms1, c0 5196 mgL1, p 2.0 MPa)

4.4 Feasibility study for treated water reuse

Under the operating condition of 1.8 MPa pres-sure and 6 m membrane length the quality of the RO

system output water meets the Drinking Water Stan-dards (GB 5749-2006), so it can be used as domestic water as well as those for local road cleaning, water-ing plants, etc., in order to be fully utilized.

Table 3 compares the experimental results with water quality standards. Most of the indicators for the treated water meet the national first class standard for underground water, except for chloride and ammonia- nitrogen. The concentration of chlorine compounds is slightly higher than the national first class standard, and the level of ammonia-nitrogen is slightly higher than the national third class standard, but still meets the drinking water standards. Thus CBM co-produced water can meet domestic drinking water standards after the water treatment process.

Table 3 Quality of output water and comparison with standards

Items Drinking

water standard

Undergroundwater standard

( class I)

Outputwater

chroma 15 5


costs, pharmacy, labor costs and replacement and de-preciation charges. The water treatment capacity is 100 m3d1 and the output water is 70 m3d1. The treatment cost for one ton of output water is assessed to be 2.58 CNY. A promising future for civilian use of CBM co-produced water can be expected from the Table 4.

5 CONCLUSIONS

CBM fields produce large amount of high salin-ity water, which can feasibly be treated on a large- scale using an RO system. The pilot-scale test results indicate that the RO system runs smoothly and has a good treatment effect for CBM co-produced water.

With a model for the RO membrane separation process developed, the predicted values are in good agreement with experimental values. This model pro-vides a theoretical support for the RO system design and operation condition optimization.

Through the pretreatment and RO system, turbidity, Mn, Fe and F almost were almost completely removed. CODMn removal efficiency was 81.6%, while 85.4% for NH3-N, 97.0% for Cl and 97.6% for TDS. After the treatment, the output water meets the Drinking Water Standards (GB 5749-2006) in China, so it can be used for domestic water and thus be fully utilized.

NOMENCLATURE

c concentration of TDS in solution, mgL1 H height of membrane channel, m k friction coefficient L membrane length, m p transmembrane pressure, Pa R water recovery rate, % Rm membrane resistance, Pasm1 r salt retention rate, % t time, s u crossflow velocity along the membrane channel, ms1 v permeate flux along the membrane channel, ms1 viscosity, Pas osmotic pressure across the membrane, Pa

2H O density of CBM co-produced water

REFERENCES

1 Zhao, W., Guo, Z,G., Niu, W.P., The exploitation and utilization of coal-bed methane in Jincheng, Energy Technol. Manage., 5, 125127 (2011).

2 King, L.A., Wheaton, J., Vance, G.F., Ganjegunte, G.K., Water is-sues associated with coal-bed methane (natural gas) in the Powder River Basin of Wyoming and Montana, Reclamation Matters, 2, 712 (2004).

3 Vance, G.F., King, L.A., Ganjegunte, G.K., Coal-bed methane

Table 4 Estimated operating costs

Electricity bills

total installed power 30.00 kW used power 14.00 kW electricity price per kilowatt 0.51 CNYkW1h1 daily operating time 8.00 h daily electricity bills 57.12 CNYd1

Chemical costs (Counted in accordance with the maximum)

fungicides 0.60 CNYd1 (consumption: 0.20 kgd1; unit price: 3 CNYkg1)

reducing agent 1.20 CNYd1 (consumption: 0.30 kgd1; unit price: 4 CNYkg1)

flocculating agents 6.00 CNYd1 (consumption: 0.20 kgd1; unit price: 30 CNYkg1)

inhibitor 12.00 CNYd1 (consumption: 0.30 kgd1; unit price: 40 CNYkg1) chemical costs 19.80 CNYd1

Labor costs

operator 900.00 CNYm1 (based on one person) labor costs 30.00 CNYd1

Replacement and depreciation charges

filter core updating costs 6.50 CNYd1

depreciation costs 45.00 CNYd1

maintenance costs 40.00 CNYd1

total 73.50 CNYd1

Daily output water 70.00 m3d1

Total treatment costs 180.42 CNYd1

Total treatment costs 2.58 CNYm3


co-produced water: management options, Reflections, June, 3134 (2004).

4 Ganjegunte, G.K., Vance, G.F., King, L.A., Soil chemical changes resulting from irrigation with water co-produced with coal-bed natural gas, J. Envi. Quali., 34 (6), 22172227 (2005).

5 Vance, G.F., Zhao, H., Ganjegunte, G., Urynowicz, M.A., Gregory, R.W., Reduction in coal-bed methane (CBM) water sodicity using zeolites, In: 30 Years of SMCRA and Beyond, American Society of Mining and Reclamation Proceedings, Lexington, KY, 837844 (2007).

6 Veil, J., Puder, M.G., Elcock, D., Redweik, R.J.J., A white paper describing produced water from production of crude oil, natural gas and coal bed methane, Argonne National Laboratory, 4954 (2004).

7 Ahmadun, F.R., Pendashteha, A., Review of technologies for oil and gas produced water treatment, J. Haz. Materi., 170, 530551 (2009).

8 Dallbauman, L., Sirivedhin, T., Reclaiming produced water for beneficial use: salt removal by electrodialysis, J. Membr. Sci., 243, 335343 (2004).

9 Hyung, H., Kim, J.H., A mechanistic study on boron rejection by sea water reverse osmosis membranes, J. Membr. Sci., 286, 269278 (2006).

10 Atkinson, S., Japans largest sea-water desalination plant uses Nitto Denko membranes, Membr. Technol., 2005 (4), 1011 (2005).

11 Allison, P., Gasson, C., Intelligence, G.W., Desalination markets 20052015: A global assessment and forecast, Oxford, UK, Media Analytics (2004).

12 Tao, F.T., Curtice, S., Hobbs, R.D., Sides, J.L., Wieser, J.D., Dyke, C.A., Tuohey, D., Pilger, P.F., Reverse osmosis process successfully converts oil field brine into freshwater, Oil Gas J., 91, 8891 (1993).

13 Murray-Gulde, C., Heatley, J.E., Karanfil, T., Rodgers Jr., J.H., Myers, J.E., Performance of a hybrid reverse osmosis-constructed wetland treatment system for brackish oil field produced water, Water Res., 37 (3), 705713 (2003).

14 Bradley, R., Pilot testing high efficiency reverse osmosis on gas well produced water, In: Proceedings of the International Water Conference (61st Annual Meeting), Pittsburg, PA (2000).

15 Oh, H.J., Hwang, T.M., Lee, S., A simplified simulation model of RO systems for seawater desalination, Desalination, 238, 128139 (2009).

16 Tay, K.G., Song, L., A more effective method for fouling charac-terization in a full-scale reverse osmosis process, Desalination, 177, 95107 (2005).

17 Song, L., Hu, J.Y., Ong, S.L., Ng, W.J., Elimelech, M., Wilf, M., Performance limitation of the full-scale reverse osmosis process, J. Membr. Sci., 214, 239244 (2003).

18 A1-Bastaki, N.M., Abbas, A., Predicting the performance of RO membranes, Desalination, 132, 181187 (2000).

19 AI-Bastaki, N.M., Abbas, A., Modeling an industrial reverse osmo-sis unit, Desalination, 126, 3339 (1999).

20 Bouchard, C.R., Carreau, P.J., Matsuura, T., Sourirajan, S., Model-ing of ultrafiltration: predictions of concentration polarization ef-fects, J. Membr. Sci., 97, 215229 (1994).

Documents

A Pilot-scale Demonstration of Reverse Osmosis Unit for Treatment Of