brackish groundwater utilization potential of beach …

E-proceedings of the 38th IAHR World CongressSeptember 1-6, 2019, Panama City, Panama

doi:10.3850/38WC092019-1918

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BRACKISH GROUNDWATER UTILIZATION POTENTIAL OF BEACH WELLS IN KUWAIT- A CASE STUDY

HARISH BHANDARY(1), ASIM AL-KHALID(2) , S. CHIDAMBARAM(3) & A. MUKHOPADHYAY(4)

(1,2,3,4) Kuwait Institute for Scientific Research (KISR), Water Research Center, Al-Jahez Street, P.O. Box 24885, Safat, 13109 Kuwait

[email protected]; [email protected]; [email protected]; [email protected]

ABSTRACT

A study was conducted at the Kuwait Petroleum Corporation (KPC) campus for the efficient utilization of groundwater supply from beach wells for KPC’s offices and greenery activities of its buildings. It is intended to utilize about 300 m3/d of freshwater for irrigation, fountains, and cooling system. This amount of freshwater may need about 600–700 m3/d of groundwater from the beach wells to be produced and treated. Three test holes were drilled, drill cuttings and representative groundwater samples were collected. Subsequently, two monitoring and two production wells were drilled, constructed and groundwater samples were collected. Groundwater samples were analyzed for water quality parameters. Pumping test and recovery tests were carried out in the newly constructed wells. The sediment study showed bottom suspension and rolling beach environment dominated by fine, medium and coarse sand. The groundwater quality at the study area is brackish and is of NaCl type reflecting the salinity from the nearby seawater. From the pumping test data analyses it is inferred that the groundwater at the vicinity can be extracted from one production well at a time at the rate of 655 m3/d with stable water table and water quality. It is recommended to design a Reverse Osmosis (RO) unit (spiral wound membrane configuration) to treat the groundwater with an average feed water flow rate of 25 m3/h to produce high quality freshwater of salinity 100 to 300 mg/L. It is expected that about 12.5 to 15 m3/h fresh water can be produced from this unit.

Keywords: Fresh water; pumping test; production well; reverse osmosis.

1 INTRODUCTION Kuwait is a country with huge water shortages because of the scarcity of the natural water resources. Freshwater in Kuwait is a very precious and scarce. The over-exploitation of freshwater in Kuwait has led to severe water shortage that forced the government of Kuwait to compensate these shortages by constructing seawater desalination plants, which is a burden on the Kuwaiti economy. Therefore, groundwater should be used wisely and in a sustainable manner. About 90% of groundwater supply in Kuwait is used for irrigation and greenery activities. Some is used for blending with distillate water, livestock feeding, and construction work. In the light of the aforementioned, a study was conducted at the Kuwait Petroleum Corporation (KPC) headquarter premises for the efficient utilization of groundwater supply from beach wells for KPC’s offices and greenery activities of its buildings. It is intended to utilize about 70,000 g/d (300 m3/d) of freshwater for irrigation, fountains, and cooling system. This amount of freshwater may need about 160,000–180,000 g/d (600–700 m3/d) of groundwater from the beach wells to be produced and treated. Therefore, one of the objectives of this study is to conduct a detailed research to assess the utilization potential of groundwater near the beach at KPC’s offices and buildings in terms of quantity (safe yield of the production zones in the vicinity of KPC) and quality, in a way that pumping the required volume of groundwater does not cause saline water to move upwards (up coning processes), which at the end of the day increases the salinity beyond the limits that the planned treatment unit need to work efficiently.

2 METHODOLOGY Based on the provided area and the available information of the aquifer characteristics, drilled 3 test boreholes (depth intervals are 15, 30 and 50 m), 2 production wells (depths are 30 to 50 m), and 2 observation wells are drilled. These wells were sampled in a distributed manner to ensure the coverage of the potential production areas. The drilling program was carried out to generate credible data on the subsurface soil. The test holes were used for collecting drill cuttings and representative groundwater samples. A step test, followed by pumping test, was carried out with the Well KPC-03 as the pumping well and the other three wells (KPC-01, KPC-02 and KPC-04) as the monitoring wells. The step test data were evaluated in the traditional way (Jacob, 1947) by plotting normalized drawdown data (observed drawdown/pumping rate) against the pumping rate. An

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alternative method of the evaluation of total well loss, following Kawecki (1995), was also carried out by plotting total well loss and normalized well loss against pumping rate. The pumping test was conducted at a rate of 100 Igpm (655 m3/d) and continued for 72 hours. The water level recovered to the original level within the six hours of stoppage of pumping. Various methods of analysis of pumping test data acquired from an unconfined aquifer were used to estimate the aquifer properties (Kruseman and De Ridder, 1970). For some of the interpretation methods, the software AQTESOLV Pro 4.0 (Duffield, 2007) was used. The pumping test data was used to determine the hydraulic conductivity and the storage coefficient of the Kuwait Group sediments that underlie the study area and host the groundwater. Also, the pumping tests was conducted to determine the aquifer and well losses coefficients in order to determine the best efficiency and an optimal pumping rate that meets treatment unit requirements. Three samples were collected from test holes (TH-01, TH-02, TH-03) with different depths. Two samples from production wells (KP-03, KP-04) with a depth of 50m and two samples from monitoring well (KPC-01, KPC-02) with depth of 30m. The collected samples were analyzed for major cations and anions (Na, K, Ca, Mg, Cl, PO4and SO4) using ion chromatograph (ASTM D6919-09 and SMEWW Method No.4110). Nutrients (NO3, NO2, NH4) was analyzed using discrete analyzer (SMEWW Method No. 4500 G, E, F and C), trace metals (Fe, Li, B and Br) using ICP-OES (USEPA 1996) and H2S using the Iodometric method (SMEWW 4500-S2--F) in the Water Research Center (WRC) laboratory at the Kuwait Institute for Scientific Research (KISR).The standard methods have been adopted to analyze the water quality parameters in the laboratory as explained in the standard methods for the examination of water and wastewater (APHA, 2015).

3 RESULTS AND DISCUSSION 3.1 Grain size analysis The well cuttings were studied for grain size analysis was carried out for the locations TH 1, TH 2 and TH 3, using the following intervals (Gravel, Coarse sand, Medium sand, Fine Sand, Silt and Clay). Table 1 shows the descriptive analysis of Grain size parameters.

Table 1. Descriptive analysis of grain size parameters

3.2 Pumping test and determination of aquifer characteristics Barring the extreme values obtained from Cooper and Jacob Distance – Drawdown method (Procedure II)

(Cooper and Jacob, 1946) method, the average transmissivity is in the range of 400 – 1000 m2/d in the study area (Table 2). An overall average value of 700 m2/d for the KPC headquarter premises is in line with the unconsolidated sandy nature of the aquifer. Limited values of specific yield (SY) indicate a range of 0.25 – 0.5 with an average value of 0.38, which is also in line with the unconfined nature of the aquifer. In general, the estimated transmissivity value in the neighborhood of the Well KPC-03, however, ranges between 120 – 400 m2/d with an average of 280 m2/d. The extent of the loss in the potentiometric head during pumping due to the inherent characteristics of the aquifer around the pumping well KPC-03, and the loss in the immediate neighborhood of the well and in the wellbore due to turbulent flow has been estimated from the step test data.

Table 2. Aquifer parameters estimated from the pumping test data

Method Well Type T (m2/d)

S Sy Kz/kr Average T (m2/d)

Average S

Average Sy

Theis Recovery Method (Theis, 1935)

KPC-01 Monitoring 600 - - -

445 - - KPC-02 Monitoring 532 - - - KPC-03 Pumping 162 - - - KPC-04 Monitoring 484 - - -

Cooper & Jacob Method (Cooper and Jacob, 1946)

KPC-01 Monitoring 998 6.93E-3 - -

650 0.0023 - KPC-02 Monitoring 666 1.82E-3 - - KPC-03 Pumping 120 1.16E-10 - - KPC-04 Monitoring 285 3.12E-4 - -

Cooper & Jacob Distance – Drawdown Method (Procedure II) (Cooper and Jacob, 1946)

All wells except KPC-01

Pumping & Monitoring

53 0.025 - - 53 0.025 -

KPC-01 Monitoring 856 0.008 - - 565 0.0022 -

Core Sample Depth in m

Gravel Coarse Sand Medium Sand Fine Sand Silt and Clay

(2 mm) (0.600 mm) (0.212 mm) (0.063 mm) (<0.063 mm)

Core 1 TH-01 15 4.24 21.81 36.94 32.69 4.33

Core 2 TH-02 30 4.62 31.94 49.58 12.04 1.82

Core 3 TH-03 50 11.08 34.58 42.18 10.64 1.53


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Cooper & Jacob Method (Procedure III) (Cooper and Jacob, 1946)

KPC-02 Monitoring 958 0.00075 - - KPC-03 Pumping 160 25E-16 - - KPC-04 Monitoring 285 0.000134 - -

Neuman (1974) Method All Wells Pumping & Monitoring

394 0.0047 0.5 0.07 394 0.0047 0.5

Theis (1935) Method

KPC-01 Monitoring 1000 0.03 - 0.1

800 0.0099 - KPC-02 Monitoring 1285 0.0052 - 0.1KPC-03 Pumping 413 0.0025 - 0.1KPC-04 Monitoring 500 0.002 - 0.1

Tartakovsky-Neuman (2007) Method

KPC-01 Monitoring 909 0.03 0.5 0.1

703 0.0456 0.25 KPC-02 Monitoring 500 0.15 0.15 0.1 KPC-03 Pumping 407 2.46E-7 0.25 0.1 KPC-04 Monitoring 997 0.0025 0.1 0.01

Moench (1997) Method

KPC-01 Monitoring 1711 0.0239 0.1 0.01

986 0.0084 0.40 KPC-02 Monitoring 1007 0.0053 0.5 0.01 KPC-03 Pumping 400 0.0020 0.5 0.01 KPC-04 Monitoring 825 0.0025 0.5 0.01

3.3 Losses estimated from step test data Following Kawecki (1995), the total well loss (Lw) was calculated as:

Lw = sw(t) – s(rw, t) [1]

Where, sw(t) is the observed drawdown in time t and s(rw, t) is the theoretical drawdown at well face, given by the relation:

𝑠(𝑟𝑤 , 𝑡) = 1

4𝜋𝑇∑ (𝑖=𝑛

𝑖=1 𝑄𝑖 − 𝑄𝑖−1) ln2.25𝑇(𝑡−𝑡𝑖)

𝑟𝑤2 𝑆

[2]

as long as un< 0.01, ui being given by rw2S/4T(t-ti) where:

S = storage coefficient T = transmissivity t = time such as tn≤t ≤tn+13

Qi = discharge at time ti rw = true well radius

Using an average T value of 280 m2/d and S value of 0.025 (derived from Cooper Jacob distance drawdown method, Procedure II) for Well KPC-03, the total loss values at the end of each pumping stage was calculated as indicated above. The fitted lines and the equations can be used for the estimation of total well loss in the Well KPC-03 for any specified discharge rate.

3.4 Estimate of safe discharge rate The theoretical drawdown (s) due to pumping in a well is given by the relation:

𝑠 = 2.30𝑄

4𝜋𝑇log

2.25𝑇𝑡

𝑟2𝑆 [3]

Where, u = r2S/4Tt is < 0.01. In the present case, with an average transmissivity (T) value of 280 m2/d, storage coefficient (S) value of

0.025 and for time (t) = 1 min, u value is 5.18E-4; therefore, Eq. 3 should be applicable for computing the theoretical drawdown in the well for any time greater than 1 minute. The computed theoretical drawdown due to turbulent flow (well loss = C.Q2) and the well drawdowns for various discharge rates, computed using the concept of total well loss of Kawecki (1995), are presented in Table 3.

Table 3. Theoretical drawdown, total loss as per Kawecki (1995) and total drawdown in Well KPC-03

Discharge Rate (m3/d)

Theoretical Drawdown

(m)

Total Loss (Kawecki, 1995)

(m)

Total Drawdown (m)

Remarks

655 3.75 11.24 14.99 Drawdown too low

1310 7.50 20.56 28.06 Drawdown in the acceptable range

1965 11.25 35.13 46.38 Drawdown too high

The figures presented in the tables suggest that the discharge rate of 1965 m3/d (300 Igpm) is too high for the well. The well discharge may, however, be fixed at 1310 m3/d (200 Igpm) or lower that should allow the


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water level to remain at a reasonable height above the pump during pumping. For Well KPC-04, that is located in an area with better transmissivity, above withdrawal rate should also be very safe.

A large drawdown has the additional risk of causing upconing of more saline water from depth that will have the potential for jeopardizing the specified feed water quality required by the desalination system. The discharge need to be controlled and pumping well may need to be developed further to reduce the drawdown due to the formation damage around the well from the invasion by the drilling mud and the drilling activity. The lateral seawater encroachment due to the drop in the potentiometric head should not be a big problem in this particular case as seawater is the normal feed water for desalination plants in Kuwait. For its corrosive nature and the associated health hazards, the lateral movement of hydrogen sulfide (H2S) rich water may, however, be a problem.

In comparing the pumping test with six days EC varies with time. In first day EC starts with 12,630 µs/cm and rises upto 17,540 µs/cm. In second day EC starts with 10,890 µs/cm and rises upto 18,010 µs/cm whereas in third day it starts with 12,100 µs/cm and rises with 18,060 µs/cm. In first three days EC starts with lesser concentration and rises upto the concentration of 18,000 µs/cm. EC steadily increases from 4th day and it varies with 18,000 µs/cm in rest of the days, the continuous pumping of three days increases the concentration and its almost stable around 18,000µs/cm as shown in Figure 1.

Figure 1. Variation of EC with respect to pumping time during the well development

3.5 Groundwater quality The piper facies analyses revealed the heterogeneity of the groundwater chemical composition in this area,

but a general trend from Na–Ca- Cl-SO4 waters to Na–Cl waters. Test holes samples such as TH-01 and monitoring well (KPC-01) possess Na-Ca-Cl-SO4 type and rest of the samples indicates the Na-Cl type of groundwater. These patterns indicate that the groundwater chemistries are changed by cation exchange reaction, as well as simple mixing (Richter et al., 1993; Appelo and Postma, 1999). The region of the Ca–Cl type water in few samples may be a leading edge of the seawater plume (Vengosh et al., 1991; Appelo and Postma, 1999; Jeen et al., 2001). Large proportions of the groundwaters showed Na–Cl- type that generally indicates a strong seawater influence (Pulido-Leboeuf, 2004).

3.6 Statistical analysis The statistical analysis shows correlation between Na+ and Cl- ions indicating decrease in Na+ concentration

compared to Cl- indicating the influence of other sources like leaching of salt from the surface or recharge due to evaporated/saline waters (Chidambaram et al., 2010). Poor positive correlation of SO4

2-, PO4-, NO3

-with other ions, might be because of the effect of dilution. The major ion exhibiting good to moderate correlation Cl and SO4 with Ca, Mg, Na, K mainly possible due to the impact of Seawater intrusion (Singaraja et al., 2012), Saltpan (Smith et al., 2004) in coastal region and leaching of the secondary salts precipitated along the fissures or the permeable zones of the formations (Chidambaram et al., 2009). The major ion show good, moderate to high degree of correlation with other ions and NO3, which has higher representation of the anthropogenic effluents. The negative relation of pH with Mg2+ may be due to the dominance of ion exchange process (Chapelle and Knobel, 1985).

4 CONCLUSIONS


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Three test holes were drilled initially as TH1, TH2 and TH3 with depths 15m, 30m and 50m respectively. The sediemts collected from the different boreholes were analysed and found that they were deposited in Bottom suspension and rolling in beach environment. Further it was inferred that there was poor sorting in specific depths indicating the variation in the dynamics and sediment load in the deposition environment. The wells were then developed and completed as monitoring and production wells TH3 was developed as a monitoring well (KPC-01) and that of TH1 was developed as a production well (KP-03). Similarly new monitoring (KPC-02) and Production wells (KPC-04) were also developed in the eastern part of the site. The pumping test was conducted and the inference from the data reveals that initial discharge rate from the wells should not exceed 655 m3/d. the water chemistry of the boreholes were collected and analyzed for physicochemical parameters, including microbes. The study shows that the groundwater is salty in nature and the EC stabilized around 18000µs/cm after the pumping test. The water is mostly of NaCl type reflecting the salinity form the Sea water. The Scholler Chlor alkaline indices show reverse ion exchange is predominant. The major process responsible for water chemistry was attempted with the present data and it infers that sea water, dissolution of salts and the ion exchange process play a major role. It is expected that about 50 to 60% of this water can be recovered using spiral wound membrane configuration to produce high quality permeate with concentration ranges between 100 to 300 mg/l. It is also inferred that the pretreatment and post-treatment may be applied depending on the future application.

The most technically viable and economically feasible technology to treat this water for reuse for different applications (i.e. irrigation purposes) is desalination by reverse osmosis (RO). Based on the laboratory analyses obtained, the quality of groundwater represents excellent feed water to RO. It is expected that about 50 to 60% of this water can be recovered using spiral wound membrane configuration to produce high quality permeate with concentration ranges between 100 to 300 mg/l. Pretreatment and post-treatment may be applied depending on the future application. However, attention must be paid to SO4 concentration. The system may be designed with an average feed water flow rate at 25 m3/h at maximum feed pressure of 30 bar, while the average permeate flow ranges between (12.5 to 15 m3/h). The expected number of membrane elements is 20 elements. The total energy consumption for the desalination process in the range of 2 to 3 kwh/m3.

ACKNOWLEDGEMENTS The authors would like to express their gratitude to the Kuwait Petroleum Corporation (KPC) for funding the project. The constant support and encouragement of the Kuwait Institute for Scientific Research’s (KISR’s) management is gratefully acknowledged.

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