Tap water in Ben Tre is contaminated with salt.

Many water treatment plants draw water from rivers and canals during the saltwater intrusion season, forcing tens of thousands of households in Ben Tre province to use saline water.

Around noon in mid-February, Ms. Dang Thi Hong Lac, 59 years old, residing in Hamlet 2 (Luong Phu Commune, Giong Trom District), released tap water into the reservoir and then measured the salinity. The reading on the meter was 2.2 parts per thousand, exceeding the permissible limit of 0.5 parts per thousand.

"This water isn't suitable for cooking, but it's still good for bathing and washing clothes. When the salinity reaches 3-4 parts per thousand, I'll pump up the water I've stored in the ditch to use because I'm worried the salt will damage my washing machine and water heater," said Mrs. Lac, adding that after the historic drought and saltwater intrusion five years ago, she built seven reservoirs holding nearly 10 cubic meters of fresh water, enough for her whole family to cook during the dry season.

Ms. Lac discharges tap water contaminated with salt into a reservoir for bathing and washing. Photo: Hoang Nam

A little over a kilometer away, due to the saline contamination of their tap water, Nguyen Thanh Mong's family relies solely on three cubic meters of fresh water stored in a tank on their porch for cooking. Mr. and Mrs. Mong have three children and belong to a near-poverty household, with only a 1.5 cubic meter cement tank. Last year, thanks to donations from benefactors, they acquired two additional plastic tanks, each capable of storing 1.5 cubic meters of water.

"The stored freshwater can last for about 3 months; if the salinity lasts longer, we'll probably have to ask for water from the commune's supply points," said Mr. Mong, 42, adding that in Hamlet 2, there is a service that pumps freshwater to homes for 100,000 VND per cubic meter. Meanwhile, each cubic meter of saline tap water costs just over 8,000 VND.

Mr. Nguyen Huu Hieu, Chairman of the People's Committee of Luong Phu commune, said that more than 1,400 households in the area use tap water, accounting for nearly 80% of the households in the area. Of these, about 500 households live near the large river area and are more affected by salinity than other areas.

The commune has a water treatment plant with a capacity of 90 cubic meters per hour, but because it draws water from rivers and canals, it is still contaminated with salt, fluctuating between 1.1 and 2.2 parts per thousand. To meet the freshwater needs of the people, the plant has invested in a desalination system with a capacity of 2.5 cubic meters per hour.

When the water salinity exceeds 0.5 parts per thousand, the plant will operate the water purification system to supply fresh water to residents three times a week, at a rate of 60 liters per household, at the same price as tap water. The commune has also arranged six centralized rainwater harvesting points, each with a 15 m3 storage tank, prioritizing access for disadvantaged households during the dry season.

Ben Tre currently has 60 water treatment plants managed by the Department of Construction and the Department of Agriculture and Rural Development. In addition to plants drawing water from the closed irrigation system, there are also privately invested plants. Currently, these plants draw water directly from rivers and canals, resulting in salinity levels of 0.1-3.1 parts per thousand.

Operating a desalination machine in Thanh Phu town. Photo: Hoang Nam

Mr. Nguyen Xuan Hoa, Deputy Director of the Ben Tre Rural Water Supply and Sanitation Center, said that the unit currently manages 32 water treatment plants, serving approximately 98,000 households. After Tet (Lunar New Year), salinity levels at water treatment plants in Giong Trom and Mo Cay Nam districts tend to increase, especially during high tides.

"Currently, in addition to 15,000 households using water that meets standards, there are about 13,000 households using water with a salinity level above one part per thousand, while the remaining households all use tap water with a salinity level below one part per thousand," Mr. Hoa said.

This center has equipped 29 desalination systems at the plants, transferring water from plants with low salinity to higher salinity areas to address the problem of saltwater intrusion. In addition, the unit plans to use barges to transport raw water from major river systems that are not yet affected by salinity to the plants to supply the local population.

According to the Ben Tre Meteorological and Hydrological Station, the deepest saltwater intrusion since the beginning of the dry season occurred in mid-February, lasting about a week with a salinity of 4 parts per thousand, 44 to 53 km from the main river mouths. The forecast predicts that the deepest saltwater intrusion will occur in March, with a salinity of 4 parts per thousand 50-69 km from the Cua Dai, Ham Luong, and Co Chien rivers, deeper and lasting longer than the multi-year average.

Hoang Nam

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