Green power for clean water 

Old and weather-beaten, 60-year-old Abdul Gofur waits for a regular but precious treat - a few gulps of sweet water. It is water that does not taste salty and bitter, something his whole village in Sarankhola, a coastal village near the Bay of Bengal, is used to drinking.

And he waits for the return of his grandson from school carrying the sweet water as he has been doing every day since his school installed a fascinating machine to turn saline water into sweet drinking water.

As the little steps of third grader Mitul are heard outside the fisherman's tin-shed house, a smile cracks across Gofur's face.

"Ah, here comes my water. Perfect water. Sweet water," Gofur says sitting in his makeshift house that had to be shifted several times in the last decade with the tides of the mighty Baleshwari River becoming more ravenous over the years.

The river, as well as the groundwater in the adjacent areas, have been turning saltier each year as salinity encroaches in the ground water here. The bitter, salty taste of the brackish water would put off anyone from the capital Dhaka, some 250km away.

"Dada, your water," Mitul says as he tosses a much used one-litre mineral water bottle on his grandfather's bed. He then darts out the door to join his raucous playmates by the Baleshwari.

A rooftop water treatment plant in Sarankhola upazila of Bagerhat with solar desalination systems that harvest solar energy to purify water through the process of evaporation and condensation, the way nature makes rain. Photo: TBS

Gofur takes a swig from the bottle. Drops of water roll down his greying scraggly beard.

"What can we do; there's no source of sweet water around, except the water plant at Mitul's school," Gofur's says as his voice drowns in the gales of laughter of the playing children dotting the blackened muddy bank of the river in the bright sun.

The same sun is turning saline water of the river into sweet potable water on the rooftop of Mitul's school about half a kilometre away at Purba Khontakata, using an innovative but simple and effective technology coming all the way from Australia.

Solar desalination systems comprise simple devices that harvest solar energy to purify water through the process of evaporation and condensation. As the salts and other contaminants do not evaporate with the water, the processed water is perfectly tasteless, odourless, and contamination-free, just like rainwater, as the device replicates the way nature makes rain.

Installed by a green pilot project undertaken by The Department of Public Health Engineering (DPHE) under the project titled "Providing Safe Drinking Water Through Installing Environment-friendly Solar Desalination Systems", 1,140 solar desalination units have been installed in 16 coastal districts.

Most of these units have been installed on the rooftops of schools across the project locations. Depending on the number of the students, there are up to two solar units, each consisting of five panels.

The solar desalination unit on the roof of Mitul's school - 105 no. Khontakata United Government Primary School - produces enough water for its 170 students.

"The five-panel unit treats around 100 litres of water every day," said Farid Ahmed, the headmaster of the school, adding, "We are very happy that our students get enough clean water for drinking."

As salinity has increased in the coastal area, women and children walk a long way to fetch drinking water everyday. 

For the students of the school, the rooftop water treatment plant is a pure source of happiness. 

As the headmaster was showing around the plant to a visitor recently, a group of students came up the stairs with a jar to fetch water. 

"The water tastes so good," said Sayma, a student of class four. "We don't have to go to the PSF for water anymore."

Villagers across the coastal zone rely heavily on Pond Sand Filters (PSF) for drinking water. As many PSFs went out of order after the cyclones Sidr and Aila, the number of fresh water sources have dwindled.

While the desalination plants have been installed primarily for the students, nearby households also sometimes collect water from the plant.

"I went to the PSF with a jar to fetch water three times this morning. I failed to collect any. There is a long queue," said Mahmuda Begum, a mother of three, who came to the school for water with a couple of other women.

Asked why she has to go to the PSF while there is a safe water source near her home, Mahmuda said, "If we take all the water, what will the children drink?"

The other women in the group nodded in agreement and stressed the need for more of such water treatment plants.

"Drinking water is scarce here. In a few weeks, even the ponds will dry up. Last summer, we had to buy drinking water," another woman, Shamsunnahar said.

A 20-litre jar of water is Tk20 or more here. That's a lot for the villagers.

Even that pricey water is not available to all. A local NGO distributes it only to its microcredit scheme members. Others have to drink unsafe water.

A growing risk

Apart from drinkability, salinity intrusion in groundwater over the years has raised a host of issues.

According to the DPHE, the standard limit of salinity for drinking water is 0%. But different studies measured the salinity value of drinking water across the coast at 4% and above.

Additionally, while the WHO-recommended dietary intake of sodium is 2 g/day, studies have found that many people living in the coastal areas of Bangladesh are consuming 5–16 g/day sodium in drinking water alone during the dry season, depending on their water source.

For them, sodium consumption via drinking water far exceeds that taken through daily food intake, putting them in serious health risks, altered blood pressure, hypertension, diarrhoea etc.

An icddr,b study in the coastal districts found that high blood pressure or hypertension was about 12% more prevalent than the national average.

Another icddr,b study showed that the likelihood of miscarriage among women living near the coast was 1.3 times higher than women who live inland.

Between 2012 and 2017, the icddr,b scientists registered 12,867 pregnancies in Chakaria, near Cox's Bazar. They monitored the women through their pregnancy term and found that women in the coastal plains, living within 20km of the coastline and 7m above sea level, were 1.3 times more likely to miscarry than women who lived inland.

Though the 1.3 times may not seem high enough to ring alarm bells, the duration of the study and the number of participants is what made the findings more concerning.

Apart from health risks, rising salinity may also become a reason for more displacement in the future, with Chattogram and Khulna districts likely to see the highest within-district additional migration, estimated between 15,000 and 30,000 migrants per year, said another 2018 study conducted jointly by the International Food Policy Research Institute (IFPRI) and the Ohio State University.

Concern over maintenance

Meanwhile, back in Sarankhola, while the users of water treatment plants are happy with the outcome of the project, they worry those would go the same way as the PSFs.

Concern has risen regarding the fate of the solar Carocell desalination units after the end of the two-year project cycle.

The supplier of the units, F Cubed Water Limited, has been maintaining the devices so far, but for the majority of the lifespan of the devices, which are supposed to last for 10 years, maintenance will depend on the local users.

"The communities, somehow, are not willing to take over the maintenance of the units despite their sufferings," said Farid Ahmed, headmaster of Khontakata United Government Primary School.

Some locals say that more solar desalination plants can be set up in places where they will be taken care of.

Some project officials seeking anonymity mentioned that these solar units are vulnerable to cyclonic wind. The units, however, can be disassembled for safe storage prior to cyclone landfall, the supplier told The Business Standard.

Is there a business opportunity?

The water treatment business has found its way to the coast since cyclone Sidr. So do these solar desalination plants have a chance to tap into the market?

"Given the cost of the system, which I have heard is north of Tk4 lakh, I don't think anybody will be interested in starting a business using these," Farid Ahmed opined.

A project official, too, raised concern over the cost of solar Carocell technology, which requires Tk2 per litre of water treatment over its lifespan.

Responding to this, Prottoy Khan, managing director of F Cubed Water Limited, said, "We currently import the product from our parent company in Australia. Previously, being an environmentally-friendly solar powered technology for clean drinking water, there was an exemption for VAT on import and all parts of the plant were under one import code. This is no longer the case. High import duties have now been imposed.  

"We have asked the NBR[National Board of Revenue] to review and reinstate the previous exemption to make it more affordable so we can do more installations. We also intend to manufacture the Carocell in Bangladesh to create employment, but we will need to have more favourable import conditions to establish a factory here," Khan added.

If the government scales up the project, F Cubed will be able to manufacture desalination systems in Bangladesh instead of Australia, and the price of the units will come down, Khan hoped. He also mentioned that the solar desalination project can earn Bangladesh carbon credits.

"When we calculate the cost of a project, we almost always forget to calculate the environmental cost of it," Khan said, adding, "The environmental cost of unsustainably drawing groundwater is huge."

Using surface water as much as possible is good for the health of the planet and the people, Khan concluded.