Powering freshwater access with solar desalination

Access to safe water is a fundamental natural right for all life, including humans. Yet millions still struggle to secure this necessity, particularly in vulnerable regions where climate change exacerbates existing challenges.

Freshwater scarcity is an immense global challenge, particularly in least developed countries (LDC). According to the United Nations, around 2.4 billion people live in water-stressed countries.

Bangladesh, including its coastal regions, faces the same challenges. Saline water poses a significant threat to the coastal population.

Approximately 30 million people in coastal Bangladesh rely on local water sources such as rivers, ponds, and tube wells. These sources have become increasingly contaminated with saltwater due to rising sea levels and climate-induced salinity intrusion. In some regions, the salinity levels in drinking water have reached up to 2.5 grams per litre.

World Health Organisation (WHO) recommendation for salt consumption is less than 5 gram/day. If coastal people drink 2-3 litres of water from these sources per day, they already consume far more than the recommended amount, without taking into consideration the salt intake through cooked food. 

Women are highly vulnerable to the harmful effects of saline water, which increases maternal health risks, including pre-eclampsia and gestational hypertension. Women consuming water with high sodium levels (600–900 mg/L) are in 4.4 times higher risk of these complications compared to those with lower sodium intake. Additionally, communities relying on pond water or rainwater for drinking face increased susceptibility to waterborne diseases like cholera, typhoid, and diarrhoea, with such diseases being 14% more prevalent in saline areas. Seasonal fluctuations in water sources further exacerbate these risks, particularly during the dry months when saline intrusion becomes more severe.

The situation is dire in these regions for a multitude of reasons:

• Rising sea levels: The intrusion of salinity into freshwater systems diminishes access to drinking water. 
• Climate change: Changed weather conditions, along with extended dry seasons contributes to increased water scarcity. 
• Inadequate infrastructure: Inadequate investments in water supply infrastructure means that rural communities are dependent on potentially polluted sources of water. 
• Anthropogenic factors: Bangladesh, formed at the confluence of the Ganges, Brahmaputra, and Meghna (GBM), relies on a river basin spanning 1.6 million km² across five countries. Removing water from upstream and horrible water management causes low flows during dry seasons. As a result, saline water finds its way inland. 

A key example is the Padma River, its dry-season discharge at Hardinge Bridge has declined significantly, from approximately 2,080 m³/s (1963–1975) to 910 m³/s (1976–2015), primarily due to upstream diversions and reduced monsoon flows. This reduction has weakened the freshwater flushing capacity of downstream rivers, contributing to increased salinity in coastal zones.

A recent study indicates that the freshwater-brackish water boundary migrates 20–40 km northward during dry seasons, particularly in the Moribund Delta, north of the Sundarbans, driven directly by diminished upstream discharge.

The difficult situation of water scarcity and climate change mostly affects poorer households, increasing their health risks, economic uncertainty, and social inequity. Women and children often bear the brunt of these impacts.

The National Adaptation Plan (2023–2050) of Bangladesh includes Community-Based Rainwater Harvesting and Safe Storage Program for salinity-prone coastal areas. This intervention aims to improve access to safe drinking water, especially for women and children by installing rainwater harvesting systems and training communities in water safety and maintenance.

About 30 million people in Bangladesh's coastal zones rely on increasingly contaminated water sources, putting them at higher risk of waterborne diseases and salt-related health problems, especially among women and children

Among the technologies available today, reverse osmosis (RO) is widely used to treat saline water. As the RO's fragile membranes alone cannot withstand the other impurities that the source water contains, RO always combines with multi-stage water treatment plants.

Where the source water gets treated in three or more stages to remove suspended solids, odour, and other harmful contaminants before reaching the RO membrane. Often other stages add up after the RO.

Despite technology availability to combat the crisis, there is a drawback. RO water desalination plants require a lot of uninterrupted power to function appropriately. During the dry seasons, when the demand skyrockets, saline-prone rural areas see unprecedented loadshedding.

Four to eight hour, or in the worst case up to twelve hour loadshedding was reported on The Business Standard in September 2024. Despite spending millions, the plants are no more than sitting ducks during crisis.

Load shedding worsens, exceeding 1700MW shortfall

As long as the sun keeps shining, humanity will also keep benefiting from it in one way or another. Photovoltaic (PV) solar technology shows high hopes for the regions closer to the equator.

Bangladesh, being one of them, has great potential in PV power generation due to its abundant sunlight, receiving an average of 4-6 kWh/m²/day. The country has been actively promoting renewable energy as part of its strategy to reduce reliance on fossil fuels and improve energy security.

There are many independent power producers (IPP) successfully doing business relying on sunshine. Solar on-grid systems through net energy metering (NEM) have brought down the power trade to the consumer and SME level. This allows consumers to also become power producers and enables them to sell the surplus directly to the grid, significantly reducing their energy costs.

Adding PV solar technology to the RO water desalination plants can turn the worst into the best. The technologies combined can ensure access to safe, potable water while addressing energy and environmental sustainability. The integration guarantees a consistent and reliable source of clean water for communities in need.

Solar-powered RO desalination plants deliver profound and far-reaching impacts across various dimensions. It provides a transformative solution by:

• Transforming health outcomes: Provides clean, potable water, drastically reducing the prevalence of waterborne diseases such as diarrhoea, cholera, and dysentery. Enhances overall public health, leading to improved quality of life and reduced healthcare costs.
• Saving time, reducing hardships: Saves precious time and reduces hardships specially for women and children, traditionally responsible for travelling distance to collect water. Creating opportunities for other economic activities and study.

• Strengthening climate resilience: Equips communities to adapt to climate-induced water scarcity, such as salinity intrusion and prolonged droughts. Builds long-term resilience through sustainable water management practices.

• Reducing dependence on polluting alternatives: Eliminating the need for fossil fuel alternatives, which are costly and environmentally harmful. Thus, contributing to reducing greenhouse gas (GHG) emissions.

Solar-powered RO desalination plants not only address immediate water needs but also contribute to achieving the UN Sustainable Development Goals (SDG) in areas of clean water, sanitation, climate action, and clean energy.

It empowers the communities by improving health outcomes, thus creating economic opportunities, and building resilience to climate change challenges. By introducing Solar-powered RO water desalination plant, a water justice driven community-led business model will be applied for reliable and affordable access to clean water. 

Scaling this solution will require an enabling policy, environment, and partnerships. Policies that create incentives in renewables, government-supported and/or donor-supported grants, CSR funding, even individual donations e.g., Zakat can make solar desalination affordable for the poorest people.

Local communities could effectively co-manage and operate the plants through public-private partnerships, ensuring long-term success. If done right, the initiatives can serve millions in coastal, and water stressed regions.

Muhammad Zakir Hossain Khan is the Chief Executive at Change Initiative, Dhaka

Disclaimer: The views and opinions expressed in this article are those of the author and do not necessarily reflect the opinions and views of The Business Standard.