Acqua di mare alla spina: come funziona la desalinizzazione

Global freshwater resources account for only 0.325% of the earth’s total water, and desalination technology is becoming a key solution for coastal cities to solve the “water crisis”. This article reveals the comprehensive advantages of reverse osmosis in terms of efficiency, cost and sustainability through technology comparison, environmental assessment and economic analysis.

1. Water Intake System

Il impianto di desalinizzazione adopts a cage-type water intake design  that is 300 meters offshore and 25 meters deep. This technology controls the flow rate below 0.1m/s, which is much lower than the average flow rate in the Tasman Sea (1.5m/s), and successfully realizes zero involvement of marine organisms. Compared with the traditional shallow water intake, the microbial content in the deep water area is reduced by 67% , which guarantees the safety of water quality from the source.

2. Pre-treatment systems

Filtration Levels	Technical Means	Removal Rates
Primary	Tumbler Screen	99.8% suspended solids (>5mm)
Secondary Anthracite	Quartz Sand	94% Algae and Colloids
Tertiary	Ultra Filtration Membrane	Turbidity < 1NTU

The sludge produced by pretreatment is centrifuged and dewatered with a solid content of 25% (original data), which improves the processing efficiency by 3 times compared with the traditional sedimentation method.

3. Reverse Osmosis Technology

The desalination plant is equipped with 36,000 pieces of 8-inch composite membranes, achieving an average daily water production of 6,900 liters from a single membrane at 60 bar pressure. Compared with earlier cellulose acetate membranes, the desalination rate of polyamide membranes has increased from 98.5% to 99.7% . Conversion of concentrated water pressure for utilization through an energy recovery device (ERD) reduces power consumption to 3.8kWh per ton of water, saving 70% energy compared to traditional distillation.

4. Post-treatment

1. Calcium and magnesium adjustment: food grade calcium carbonate is added to raise the hardness to 80-120mg/L
2. pH balance: carbon dioxide injection to control the pH at 7.0-8.5
3. Disinfection treatment: 0.5ppm chloramine continuous bacterial inhibition.
   This process makes the boron content of effluent water <0.5mg/L, which is better than WHO standard (2.4mg/L).

5. Ecological optimization of concentrated brine discharge

Through the diffusion nozzle system , 58% of the concentrated brine (salinity ~6.5%) was completely mixed with seawater within 2 minutes, and monitoring showed that salinity returned to its natural level 500 meters away from the discharge . This design reduces the impact on benthic organisms by 82% compared to a direct discharge pipe .

6. Engineering Innovations in Pipeline Transmission and Distribution

The 18-kilometer dual pipeline system uses FRP lining technology, compared to traditional cast iron pipes:

• Corrosion resistance increased by 15 times
• Water loss reduced from 7% to 0.3%.
• Maintenance cycle extended to 50 years

7. Comparative technical and economic analysis

Indicators Reverse Osmosis	Multi-stage Flash	Basso	Temperature Multi-effect
Cost per ton of water (US$)	0.48	1.2	0.9
Construction period (months)	18	36	28
Carbon Emissions (kg/m³)	1.8	4.2	3.5

8. Global Application Prospects and Challenges

Reverse osmosis has captured 67% of the seawater market, but faces:

1. membrane contamination prevention and control: Sydney plant extends membrane life to 7 years with 0.1μm security filter
2. energy innovation: Saudi Arabia Rabigh 3 project combined with photovoltaic power generation to reduce energy consumption to 2.6kWh per ton of water.
3. Policy support: Australia’s Water Security Plan 2030 provides a 30% tax credit for desalination projects.

Sintesi

Modern desalination has broken through the shackles of “high energy consumption” to create a sustainable water solution through intelligent pre-treatment, high-efficiency membrane modules, and eco-discharge design. With advances in materials science  and the integration of renewable energy sources, reverse osmosis has the potential to reduce the global cost of desalination by a further 40% by 2030 , and to provide a source of life for 2 billion coastal dwellers.

Casi di studio recenti

• Sistema di osmosi inversa dell'acqua di mare per bere 51m³
• Impianto di desalinizzazione per isola domestico usato 40m³
• Desalinizzazione commerciale dell'acqua salmastra 240 m3

• SWRO in container per il Polo Artico 
• BWRO in contenitore per bere in caso di siccità
• Impianto di desalinizzazione dell'acqua salmastra per l'irrigazione