News - August 3, 2022 | 07:54 pm PT

HCMC’s water supply, lifeblood of 13 million, faces serious problems

Increasing number of pollutants, an outdated water distribution network and salt intrusion combine to pose an unprecedented, grave threat to HCMC water security.

"Oil stain down the river."

The 6 a.m. announcement jolted Dinh Xuan Hoa awake and he rushed to the Hoa An pump station around 30 km away from Ho Chi Minh City.

"It was the most stressful Sunday in all my 33 years as head of the pumping station," Hoa said, recalling the first time he had to deal with oil contaminating the water supply.

Five employees who lived close to the station were soon dispatched to the scene. The director of the Thu Duc water treatment plant downtown came along as well.

About 14 km away from the scene, at another water treatment plant, employees from its water quality management department were also summoned. Water samples were frequently tested taken to see if there was any oil in them.

Since 2009, the possibility of such a scenario playing out had been envisaged and prepared for by the Saigon Water Corporation (Sawaco), but it had not actually happened until now.

Hoa said how quickly they deal with such problems would decide the likelihood of an environmental crisis akin to what happened in 2019, when water supply at a plant in Hoa Binh became contaminated with oil.

The oil stains ebbed and flowed with every wave pushing against the two layers of buoys strung across a 140 m length. They were close to the pumps where raw water would be sucked into the plant. They had already stained black the surrounding dykes. People threw buoys around 175 m long into the water to block the oil, but even this was not enough.

Tran Kim Thach, head of the water quality management department of Sawaco, asked for the raw water to be checked every 15 minutes. What worried him most unfortunately came true: two of three water treatment plants detected oil in their water supply.

Thach immediately ordered that all water be flushed out of the system, hoping that this would remove all the oil as well. After discharging around 10,000 m3 of water within two hours, the oil was gone, thankfully.

Such incidents are ticking time bombs for any water supply system, especially in HCMC, which is almost entirely dependent on outside sources for freshwater.

Oil, which can be seen with the naked eye, is far from the most troublesome threat to the water supply. There are hundreds of other colorless, odorless pollutants out there that can trigger another environmental crisis, one that might be detected way too late.

According to a report by the Ministry of Natural Resources and the Environment, the total amount of wastewater released throughout the Dong Nai River could have reached 4.7 million m3 a day in 2020. The amount of wastewater released by daily activities in this river alone has already accounted for one-third the amount of wastewater released by the entire country. Water quality in the Saigon River, one of the most polluted rivers in southern Vietnam, has been dropping year after year as well.

Over the past 10 years, the Saigon and Dong Nai rivers have been the fuel that drives economic growth in the Southern Key Economic Zone, which grows 1.5 times faster than the national average. In 2019 alone, the region has provided over 5.1 billion m3 of water to numerous plants, accounting for 68.3 percent of all the water used for industrial purposes in Vietnam.

But at the same time, more and more wastewater is being discharged into rivers every day, all the way downstream.

"The state of the economy and the environment are always inversely proportional to one another," said professor Le Huy Ba, adding that the push for GDP growth in HCMC, along with its high population growth at 2.28 percent a year, means the burden on the environment and its resources is getting ever heavier, especially when most fields of development require water as a resource.

Environment pays the price

"Using fuel comes with a price, and in this case, it’s the environment (that pays it)," Ba said.

In just seven years (2014 to 2020), the amount of industrial wastewater discharged into rivers has increased eleven-fold, from 110,000 to 1.21 million m3 a day. And it’s not simply the sheer amount of wastewater that’s the problem; the types of pollutants present are also getting more diverse and harder to detect.

Over the past decade, numerous pollutants and contaminants, both chemical and biological, have been found very often in these areas, especially the Saigon River section running through Binh Duong and HCMC. Not only do they change the color, taste and smell of the water, they also trigger gastrointestinal symptoms like diarrhoea.

In accordance with regulations issued by the environment ministry, water quality near the surface must be evaluated every six months and tap water must be evaluated every month.

A 2021 survey by the Asian Water Research Center (CARE) said new pollutants have been detected in the Saigon River and they have not been included in water quality metrics by both the environment ministry and the health ministry. Specifically, the center found 106 out of 205 known organic micropollutants in the samples.

The results of another study released last April revealed that certain micropollutants, produced through industrial, agricultural and daily activities, were found in the water supply in HCMC and its neighbors Tay Ninh and Binh Duong.

"These pollutants may affect water sources used by citizens as they were found near the sites where HCMC gets its raw water," said Professor Nguyen Phuoc Dan of CARE, adding that he had to send the samples to Sweden for analysis as Vietnam still lacked the technology and resources for such tests.

Fortunately, these micropollutants were detected at low levels and were still within international standards. But it was an indicator that the water supply was being polluted and that the issue cannot be overlooked.

Dan said factories and industrial complexes should have been placed in downstream areas, like HCMC or Ba Ria-Vung Tau, instead of upstream areas like Binh Duong and Tay Ninh as the pollutants they produce would affect the water downstream.

"HCMC cannot completely manage the water quality on its end," he said, adding that the planning for the construction of industrial complexes should be done depending on regions, not localities.

Dao Phu Khanh, deputy head of the department of environmental health and school medicine under the HCMC Center for Disease Control, said stable organic pollutants are among the most toxic of pollutants. Not only can they be carcinogenic and hard to get rid of, but also propagated over large distances and be accumulated inside organisms.

As someone whose job is to monitor the water quality in HCMC, Khanh said he has never seen these kinds of pollutants in the water supply, simply because they are not included in the water quality evaluation list. This also means that there are no specific standards to see if certain levels of these pollutants are safe or not.

"If we do discover the presence of these pollutants in raw water, we would also have to test the quality of tap water to measure their levels, as well as routinely monitor them and evaluate risks. It would be dangerous if tap water has high levels of these substances," he said.

More and more chemicals

While raw water sources for HCMC, home to 13 million people, are proving to be more unsustainable than ever, the city’s 140-year-old water treatment and distribution system is not able to keep up with economic growth. Most worryingly, when an emergency arises, it lacks a contingency plan to respond to it.

Tran Kim Thach, head of the water quality management department, said HCMC uses pre-oxidation and coagulation methods to filter its water. The water is then treated with chlorine to get rid of microorganisms before it reaches people’s homes.

"The poorer the raw water quality is, the more chemicals would need to be used," said Thach.

Furthermore, this filtration system can only satisfy basic water quality criteria. There needs to be more technological solutions in the future to deal with more novel organic pollutants in the water, such as antibiotics or organic micropollutants, he said. And even then, current technologies cannot treat water contaminated with salt, he added.

Over the last seven years, the amount of chemicals used for water treatment in HCMC has always been higher than current standards set by the Ministry of Construction, especially at the Tan Hiep water treatment plant. For example, the amount of lime used for water filtration is around 10-13 times the current threshold, the amount of chlorine around 1.8-2.6 times and the amount of polyaluminum chloride three times higher.

"The water sources of HCMC are much more polluted than usual, so the amount of chemicals required to purify them also gets higher," Thach reiterated.

Despite the fact that the current tap water quality in HCMC satisfies standards set by the health ministry, its water treatment system is considered too "ancient" and prone to many risks, Thach said. For example, if the ammonium level in the water gets too high and chlorine is still used to treat it, toxic substances like nitrites or nitrates could be produced, causing numerous symptoms if ingested, including kidney stones.

Problems are not confined to the water treatment system; they extend to how HCMC distributes its water throughout the city.

Workers at Thu Duc water supply plant in HCMC. Photo by Sawaco

Contaminated tap water

In 2014, HCMC went through a major water crisis when the health ministry discovered that the three largest water treatment plants in the city failed to meet quality standards, including those related to chlorine, manganese and iron levels. This meant that tap water in certain areas of the western part of the city was contaminated with several diarrhoea-causing bacteria species.

An investigation revealed that inconsistent water pressure inside the pipes caused the problem. Water pressure was too high in areas near the treatment plants and too low in downstream areas. For example, water pressure in Thu Duc City could be 16 times as high as the water pressure in Binh Chanh District. The difference in water pressure caused sediments like iron and manganese to latch onto the pipes, and when there was a hydraulic disturbance, these sediments would be swept along with the water flow, contaminating it.

Another issue is the fact that the speed of water running inside the pipes is also inconsistent. Water running too slowly would allow the chlorine in it to evaporate, and once the water reached where it needed to be, there was not enough chlorine in it to kill germs.

These are some of the most classic weaknesses of HCMC’s 60-year-old water distribution network, which is 8,200 km long.

Thach said there were two types of water distribution networks: ring-like networks and fishbone-like networks. A fishbone-like network would have one main pipe and several reservoirs to supply water to smaller branches. They can deal with sediments thanks to consistent water pressure, but would find it difficult to deal with situations where water supply needs to be cut in certain regions.

A ring-like network would have interconnected pipes as part of a common network, making it easier to deal with water supply cuts. But due to inconsistent water pressure, there would be more sediment to deal with.

HCMC’s water distribution network is a ring type.

"The city’s water supply network was built in the French colonial times (1880s)," Thach said.

Salt faults

Regarding the problem of salt intrusion, Tran Duy Khang, director of the Tan Hiep water treatment plant, said it’s been a specter that haunts his dreams after a salt intrusion crisis he had to deal with in 2016, the most severe one in the history of the plant.

The salinity level in the water at the Hoa Phu pump station was over 300 mg/l at the time and this lasted around four hours. In the past, the highest salinity level ever seen was just 200 mg/l over an hour, allowing the pump station to hold its ground until more freshwater came in from the Dau Tieng Lake to dilute it. But during the 2016 crisis, Dau Tieng Lake was only at 76 percent of its maximum capacity, meaning 300 million m3 of water was not available for use.

"We’ve never had to face such a dangerous situation. The pump station was forced to stop taking in raw water," Khang said, adding that it meant districts in the west of HCMC would have to face long periods of water shortage.

Khang’s phone rang constantly for those four hours. Out of all the treatment plants, only Kenh Dong could directly provide water for residential networks in the western parts of the city, but its maximum capacity was just 150,000 m3, about half of that of the Tan Hiep plant. If valves were opened to let the Thu Duc plant supply it with water, the water pressure would be very weak and sediments would occur.

After weighing options, Khang had to compromise and decided to only receive water from the Kenh Dong plant while waiting for salinity levels to fall.

"Luckily we were able to hold on. If we had to stop receiving raw water for 12-16 hours, we probably would have to resort to water trucks like in the subsidy era," he said.

In the months that followed, the feeling of tension never left the Tan Hiep plant. From January to March, the Hoa Phu pump station had to stop taking in raw water 15 different times due to high salinity.

Two predicaments

HCMC has two major areas for water supply: the Thu Duc plant in the west, which takes water from the Dong Nai River; and the Tan Hiep plant in the east, which takes water from the Saigon River. While the east side of the city has had a stable water supply regimen, the west side suffers from two predicaments at the same time: river pollution and salt intrusion.

When the dry season comes, around 800,000 families in 11 districts in the west, which account for around 36 percent of all families in the city, hold their collective breath often, waiting for an announcement from the Tan Hiep plant saying it would need to be temporarily shut down.

The 2016 water crisis has forced the Tan Hiep plant to revamp its salt intrusion prevention processes. It has extended a contract worth VND4 billion ($171,210) a year to make sure that the Dau Tieng Lake would be ready to discharge water whenever needed. Three water reservoirs were also built to be able to store water for 6-7 hours if raw water could not be taken from the rivers for some reason.

"We must be ready for another 2016 crisis in the future," Khang said.

Nagging worries

According to a 2021 climate change report by the Intergovernmental Panel on Climate Change, the amount of rainfall on the Dong Nai River is expected to rise towards the end of the century, resulting in an increase in water levels. This would mean a rise in sea levels, exacerbating the risks of salt intrusion, several experts have warned.

Freshwater pump stations downstream suffer the most from salt intrusion. Salt cannot be removed once it contaminates a freshwater source, so there would be no choice but to stop taking in water until the salinity is gone.

Even though there might be more water supply in the future, its uneven distribution throughout the year means HCMC will continue to worry about water shortages.

"HCMC’s worries for the future aren't exactly a lack of water, but the fact that there would be too much water without a way to deal with it," said Dao Nguyen Khoi, head of the environment department of the HCMC University of Science.

In a worst-case scenario, the Saigon-Dong Nai river area would be impacted by both droughts and salt intrusion during dry seasons, said Khoi. Like what happened in 2016, salinity levels in the three pump stations would be too high to use, especially for the Hoa Phu and Binh An stations.

"The water supply may increase, but if the quality can't keep up, it will be of no use," he said.

Water pollution, treatment systems that lag behind and salt intrusion exacerbated by climate change are the most dangerous threats to HCMC’s water security. As the economy grows and the population keeps rising, there will inevitably be more wastewater to deal with.

A worried Khoi warned: "We need to act soon."

Thu Hang, Thanh Ha

 
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