**3. Membrane process and their integration: energy and environmental impact**

In GCC countries, 42% desalinated water is produced by membrane processes. Conventional SWRO processes consume 7–17 kWhpe/m<sup>3</sup> primary energy (equivalent to 3–8 kWhelec/m<sup>3</sup> ) for seawater desalination and they emit 3.0 kg/m<sup>3</sup> CO2 to the environment [112]. Currently, major online SWRO plants in Saudi Arabia and future proposed projects is presented in **Table 3**.

Most of the SWRO plants are operated under saline water conversion cooperation (SWCC), and their overall recovery varies from 17 to 40% depending upon feedwater quality. Four major plants, namely (i) Jeddah, (ii) Rbigh, (iii) Jubail and (iv) Shuqaiq operational data were collected, and analysis results are presented.

#### **3.1. SWRO and hybrid cycle results and discussion**

**Figure 7(a–c)** shows the seawater, retentate and distillate concentration for four mentioned plants. It can be seen that Red seawater feed concentration varies from 37,000 ppm in Jeddah to 40,000 ppm in Jubail. The retentate maximum concentration was observed at Jeddah, 60000 ppm due to better recovery. The distillate concentration met the WHO standard, <500 ppm, except at Rbigh where it can reach to 800 pm and it mixed with thermaldriven processes distillate before distribution to end users.


**Table 3.** Major SWRO plants in operation and future proposed projects in Saudi Arabia. They need extensive pretreatment and still recovery is only up to 40% maximum.

At these four locations, we also analyzed the CO2 emission and chemical rejection in the brine and applied to overall capacity in GCC according to SWRO market share. **Table 4** shows the CO2 emission and chemical rejection per day in the GCC region by SWRO processes only.

biomimetic membranes, isoporous block copolymer membranes and aligned nanotube membranes for energy efficiency [128–135]. In terms of commercialization, most of the proposed materials are farthest (5–10 years) from commercial reality. On the other hand, SWRO processes [136, 137] can be integrated with proposed AD cycle to improve process performance.

**Figure 7.** Six-month results of four major SWRO plants in Saudi Arabia. (a) Seawater feed concentration, (b) SWRO

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Membrane process can be integrated with AD cycle for energy efficiency and to reduce environmental impact. AD cycle can operate at high concentration, almost near crystallization

Both technologies are readily available and can be implemented in near future.

**3.2. Membrane process integration with AD cycle**

retentate concentration and (c) distillate concentration.

The alarming situation, huge amount of CO2 emission to environment and chemical rejection to sea on daily basis can be clearly observed by conventional SWRO process operation. These processes cannot be terminated due to water requirement, but they can be improved.

Impact of SWRO processes can be minimized either by material development or process improvements. The variety of efficient materials have been proposed such as (i) catalytic nanoparticle-coated ceramic membranes, (ii) zeolitic, (iii) inorganic-organic hybrid nanocomposite membranes and (iv) bio-inspired membranes that includes protein-polymer hybrid

**Figure 7.** Six-month results of four major SWRO plants in Saudi Arabia. (a) Seawater feed concentration, (b) SWRO retentate concentration and (c) distillate concentration.

biomimetic membranes, isoporous block copolymer membranes and aligned nanotube membranes for energy efficiency [128–135]. In terms of commercialization, most of the proposed materials are farthest (5–10 years) from commercial reality. On the other hand, SWRO processes [136, 137] can be integrated with proposed AD cycle to improve process performance. Both technologies are readily available and can be implemented in near future.

#### **3.2. Membrane process integration with AD cycle**

At these four locations, we also analyzed the CO2

Rabigh phase (3) 600,000 2019 Alugair 10,000 2019 Omluj 18,000 2020 Yanbu-4 450,000 2020 Jubail phase (3) 330,000 2021

The alarming situation, huge amount of CO2

and still recovery is only up to 40% maximum.

**Plant name Capacity (m<sup>3</sup>**

104 Desalination and Water Treatment

CO2

Future projects

and applied to overall capacity in GCC according to SWRO market share. **Table 4** shows the

**Table 3.** Major SWRO plants in operation and future proposed projects in Saudi Arabia. They need extensive pretreatment

emission and chemical rejection per day in the GCC region by SWRO processes only.

to sea on daily basis can be clearly observed by conventional SWRO process operation. These

Impact of SWRO processes can be minimized either by material development or process improvements. The variety of efficient materials have been proposed such as (i) catalytic nanoparticle-coated ceramic membranes, (ii) zeolitic, (iii) inorganic-organic hybrid nanocomposite membranes and (iv) bio-inspired membranes that includes protein-polymer hybrid

processes cannot be terminated due to water requirement, but they can be improved.

**/day) Overall recovery (%)**

Umm Lujj 4400 24 1986 SWCC Haql 4400 30 1989 SWCC Duba 4400 31 1989 SWCC Al-Barik 2275 17 1983 SWCC

Barge Raka, 24,981 SWCC [118]

Jeddah phase (4) 400,000 2019 SWCC [122]

Jeddah phase-II 48,848 35 1994 SWCC [113] Rabigh 168,000 40 2009 RAWEC [114] Shuqaiq-II 212,000 40 2010 NOMAC [115] Ras Azzour 307,000 40 2014 SWCC [116] Shuaiba I & II 76,800 40 2003 SEPCO [117] Shuaiba III Extension, 150,000 40 2009 SEPCO [118] Medina-Yanbu Phase II 127,825 35 1995 SWCC [119] North Obhor, Jeddah 12,500 35 2006 SAWACO [120] Jeddah-1 56,800 35 1989 SWCC [121]

emission and chemical rejection in the brine

**Commissioning Operator Ref**

emission to environment and chemical rejection

Membrane process can be integrated with AD cycle for energy efficiency and to reduce environmental impact. AD cycle can operate at high concentration, almost near crystallization


\* SWRO electricity consumption = 3.5 kWhelec/m<sup>3</sup> , Power plant conversion efficiency = 47%.

\*\*CO2 emission rate = 0.527 kg/kWhpe.

\*\*\*Pretreatment chemical values are taken from four plants and published literature [123–127].

**Table 4.** Energy consumption, CO2 emission and chemical rejection by all SWRO plants in GCC. The severe impact on environment and marine life can be observed clearly.

enable AD cycle to operate more than 80% recovery, over 250,000 ppm. Experiments were conducted up to 250,000 ppm concentration to investigate salt concentration effect on heat transfer. **Figure 8(a)** shows salt crystallization in evaporator at 250,000 ppm. Soft scale deposition, in the form of white powder, was observed at high concentration that can be easily washed out by spraying as shown in **Figure 8(b)**. **Figure 9** shows concentration effect on heat transfer at different evaporator temperatures. It can be seen that even at high concentration the heat transfer coefficient has reasonable value that shows successful operation of AD cycle

**Parameters SWRO Hybrid cycle % Saving by hybridization (%)**

SO4 3636.4 1348.1 170

**Table 5.** Comparison of SWRO and its hybrid with AD cycle. The superiority of hybrid cycle can be seen clearly from

or AlCl3 1272.7 471.8 170

**Figure 9.** Effect of salt concentration and evaporator temperature on heat transfer coefficient of AD evaporator. The AD

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at highest concentration without fouling and scaling chances.

Total PE consumption (GWhpe/day)\* 81.3 40.9 98.9

Disinfection, NaOCl 36.4 13.4 170

Flocculation, Polyelectrolyte 145.6 53.9 170 Antiscaling, polycarbonic acid 72.8 26.9 170 Dechlorination, NaHSO3 109.2 40.4 170

[137].

emission (ton/day) 42,855.2 21,550.1 98.9

cycle evaporator can operate as low as 7°C.

CO2

\*

Pretreatment chemicals (ton/day)

AD electricity consumption = 1.38kWhelec/m<sup>3</sup>

Acid for pH adjustment, H2

Coagulation, FeCl3

summary table.

zone, without fouling and corrosion chances due to low temperature operation. In addition to zero chemical injection, it also has minimal impact on environment as it operated with renewable energy. In this way, this hybridization will not only help to reduce CO2 emission but also chemical rejection to the sea.

In proposed integration, the SWRO retentate, at 50,000 to 60,000 ppm, is supplied to AD cycle operating at evaporator temperature of 5–30°C. Both heat inputs, silica gel regeneration and evaporator, are supplied from renewable solar energy. This low evaporator temperature

**Figure 8.** AD cycle evaporator inside view during operation. (a) Salt crystallization at 250,000 ppm at 10°C evaporator temperature and (b) white salt deposition cleared by feed spray jet impingement. It shows AD cycle successful operation at near crystallization zone, over 80% recovery: One of the highest recovery reported up till now.

**Figure 9.** Effect of salt concentration and evaporator temperature on heat transfer coefficient of AD evaporator. The AD cycle evaporator can operate as low as 7°C.

enable AD cycle to operate more than 80% recovery, over 250,000 ppm. Experiments were conducted up to 250,000 ppm concentration to investigate salt concentration effect on heat transfer. **Figure 8(a)** shows salt crystallization in evaporator at 250,000 ppm. Soft scale deposition, in the form of white powder, was observed at high concentration that can be easily washed out by spraying as shown in **Figure 8(b)**. **Figure 9** shows concentration effect on heat transfer at different evaporator temperatures. It can be seen that even at high concentration the heat transfer coefficient has reasonable value that shows successful operation of AD cycle at highest concentration without fouling and scaling chances.


**Table 5.** Comparison of SWRO and its hybrid with AD cycle. The superiority of hybrid cycle can be seen clearly from summary table.

**Figure 8.** AD cycle evaporator inside view during operation. (a) Salt crystallization at 250,000 ppm at 10°C evaporator temperature and (b) white salt deposition cleared by feed spray jet impingement. It shows AD cycle successful operation

zone, without fouling and corrosion chances due to low temperature operation. In addition to zero chemical injection, it also has minimal impact on environment as it operated with renew-

(30–100 ppm) 3636.4 ton/day

(1–35 ppm) 1272.7 ton/day

(3 ppm) 109.2 ton/day

, Power plant conversion efficiency = 47%.

emission and chemical rejection by all SWRO plants in GCC. The severe impact on

In proposed integration, the SWRO retentate, at 50,000 to 60,000 ppm, is supplied to AD cycle operating at evaporator temperature of 5–30°C. Both heat inputs, silica gel regeneration and evaporator, are supplied from renewable solar energy. This low evaporator temperature

emission but also

/day

/day

/day

able energy. In this way, this hybridization will not only help to reduce CO2

**Parameters Quantity Units** Total GCC capacity 26 Mm3

SWRO share (42%) 10.92 Mm3

Total feed (30% recovery) 36.4 mm3

Disinfection, NaOCl or free chlorine (1 ppm) 36.4 ton/day

Flocculation, polyelectrolyte (0.2–4 ppm) 145.6 ton/day Antiscaling, polycarbonic acid (2 ppm) 72.8 ton/day

\*\*\*Pretreatment chemical values are taken from four plants and published literature [123–127].

Total primary energy (PE) consumption\* 81.3 GWh/day

emission\*\* 42,855.2 ton/day

chemical rejection to the sea.

**Table 4.** Energy consumption, CO2

CO2

\*

\*\*CO2

Pre-treatment\*\*\*

Acid for pH adjustment, H2

106 Desalination and Water Treatment

Dechlorination, NaHSO3

Coagulation, FeCl3

SO4

or AlCl3

SWRO electricity consumption = 3.5 kWhelec/m<sup>3</sup>

environment and marine life can be observed clearly.

emission rate = 0.527 kg/kWhpe.

at near crystallization zone, over 80% recovery: One of the highest recovery reported up till now.


**Table 6.** The comparison of impact of conventional SWRO and proposed hybrid cycle. The hybrid cycle reduced all parameters impact to medium and low.

The proposed AD cycle recovering 51% more from SWRO retentate booting overall recover to 81%. The final reject concentration was observed as 185,000 ppm from AD cycle. This integration will not only help to save overall energy but also environmental pollution. The summary of savings is presented in **Table 5**. It can be noticed that proposed integration can save up to 100% energy and CO2 emission. In addition, it will also help to reduce chemical rejection to sea.

The impact matrix as presented in **Table 1** for conventional SWRO processes can be modified for hybrid cycle as presented in **Table 6**. It can be observed clearly that most of the parameters impact is reduced to medium and low from initial high value. This shows that hybridization will not help to produce more water but also with minimum impact on environment and marine life along with energy efficiency.
