Treating Salinity in Groundwater: DPHE now trying out nanofiltration in Bagerhat

Thousands of people in five upazilas of Bagerhat -- a coastal district where fresh drinking water is scarce due to high salinity in groundwater -- are once again getting their hopes up on a probable solution to their longstanding water crisis.

After failures in ensuring safe drinking water for the residents through the application of various methods -- including preserving surface water in conventional water ponds, incorporating sand filtration devices with the ponds and most recently, installation of rainwater harvesting equipment -- the Department of Public Health Engineering (DPHE) this time has come up with nanofiltration technology to treat saline water in the area.

In Morrelganj upazila, Balbhadrapur village resident Shekhar Das said, "The ponds and the sand filters here and in surrounding areas have been out of order for a while. We have been buying a 20-litre water jar for Tk 35 to 40."

Seeing a sign of hope in the new devices, he said excitingly, "We have an acute shortage of drinking water. Installation of these nanofilters will solve our longstanding pure water crisis here."

Under an ambitious pilot project undertaken for Rangamati, Bagerhat and Faridpur, the DPHE, in Bagerhat alone, is installing 75 nanofiltration devices in Sharankhola, Mongla, Chitalmari, Kachua and Morrelganj upazilas where installation of deep tube well is not a viable option.

With an estimated cost of Tk 20.5 lakh, each nanofiltration device is supposed to treat 960 litres of fresh groundwater per hour in four steps, pumped in from a nearby water pond with an electric water pump. 

According to DPHE, out of the total 75 nanofiltration devices currently being installed in Bagerhat, 18 are being installed in Sharankhola, 14 in Mongla, 9 in Chitalmari, 9 in Kachua and 25 in Morrelganj.

DPHE officials hope that all the devices will be open for public by August 30 this year.

Ripon Das, chairman of Banagram Union Parishad in Morrelganj upazila, said, "Work is underway to install two nanofilters in Jaipur and Balabhadrapur villages in my union."

He hoped that the new devices will solve the longstanding freshwater crisis for residents in the area.

"Finding fresh drinking water is a severe problem in my area. With the nanofilter being installed here, the water problem in this area will be solved," hoped Selim Sikder, a member of Ward-2 in Badhal Union Parishad under Kachua Upazila.

FM Ismail Hossain, executive engineer of DPHE in Bagerhat, said the pilot project is being carried out in five out of nine upazilas in Bagerhat, some areas in Faridpur and Rangamati to treat groundwater with high salinity and arsenic contamination.

No chemical is used in the filtration process of nanofiltration technology and impure water is turned into safe drinking water through the use of different types of filters, he added.