VietNamNet Bridge – After persuading the managing board of Da Nang Technology College, lecturer Tran Minh Thao set up the first toxic sewage treatment project for the school’s laboratory building.

New method: Mountain roadsides in Da Nang need protection from erosion and landslides. The city has developed a vetiver grass system to replace concrete walls used for this purpose.

It is a vetiver (Vetiveria Zizanioides) grass system – the first-ever biological sewage treatment model in Da Nang that uses grass to treat sewage.

The project is a 200sq.m garden with 5,000 vetiver grass bushes, which filter 10 cubic metres of toxic sewage from the laboratory, releasing safe waste water into the environment each day.

“It’s amazing,” Thao said. “We measured that over 90 per cent of heavy metals contained in the sewage dissolved in the process. Heavy metal levels in the sewage water met safety standard of waste water for Viet Nam.”

He said continuous tests of the grass system were carried out daily over the past two years.

“Not many plants and normal grass species could grow in the poisonous, contaminated sewage and soil, but vetiver grass could exist in the toxic habitat and reduce the contamination,” he said. “We tested that the grass could clear arsenic and cyanide – the two most poisonous chemicals. It’s an easy and quick solution against polluted environment in context of a lack of pollution treatment funding in Viet Nam.”

Thao estimated that it costs VND7 million to chemically treat one cubic metre of waste water at Khanh Son Dump, while vetiver grass garden would require just VND1 million to do the same thing.

He said his research revealed the importance of the grass’s roots in cleaning toxic chemicals. It acted as a filter

He said a root can grow 10 times as long as it sprouts, from 5cm to 70cm after one month. Thao said he even watered the vetiver grass with water from the dump.

The 39-year-old lecturer said he was preparing for a treatment project at Khanh Son Dump – the biggest of its kind in Da Nang.

He said the vetiver grass treatment project could clean 500 cubic metres of water from the dump per day.

According to Phan Thi Nu from Da Nang urban environment company, the city discharged nearly 700 tonnes of waste each day.

"The city reserves an annual fund of VND7 billion (US$333,000) for waste collection and treatment, but it could not solve the problem of pollution from dumps, as the city’s garbage is still buried or burned at dumps,” Nu said.

The 48.3ha dump has polluted underground water and the environment in suburban areas.

She said a vetiver grass system could be an option for cleaning the area around the dump, along with the development of a garbage treatment plant to recycle plastic and other solid waste.

Desalinisation

Vetiver grass was also used in a desalinisation project for 250ha of farmland in Cam Thanh Commune on the Thu Bon River in Hoi An.

The farm, which was affected by high salinity due to rising sea levels, has not been used for gardening in recent years.

Nguyen To Quyen, a member of the project, said the grass would be installed as a “green dyke” to protect land from becoming saline.

“The grass fence would help recover from 30 to 60 per cent of saline land in the area, while it would prevent mouse or snakes from approaching due to its scent,” Quyen said.

Research on vetiver grass has showed that its leaves could kill 90 per cent of young mammal pests.

Quyen said another vetiver grass project had been created to recover a large area of impoverished farmland in the Central Highlands’ Kon Tum Province.

Sa Thay District in the province has nearly 34,000ha of infertile rice farmland – 75 per cent of the district’s farming area – due to erosion and overuse of chemical fertilisers and pesticides.

She said farmers in the district would restore soil fertility within six months to a year of growing vetiver grass.

Green anchor

In 2001 and 2003, the Ministry of Agriculture and Rural Development and Ministry of Transportation allowed the use of vetiver in disaster mitigation and infrastructure protection. A slope of 3,000km on the Ho Chi Minh Trail, river banks and sea dyke in An Giang, Quang Ngai and Nam Dinh provinces benefited from the grass.

Bui Thanh Binh, an engineer working on the Ho Chi Minh Trail said the grass helped stabilise the surface of sloping terraces.

“We had to cast concrete in protection of the upper part of the roadside in mountainous areas that the Ho Chi Minh Trail run through. However, concrete dyke protection sometimes could not prevent erosion and landslides in the rainy season,” Binh said.

La Van Hieu of the Da Nang-based Construction Advanced Technology Limited Company (SBTV) explained that the grass root can grow 3m deep within the first year. Then it acts as an anchor to prevent soil on the slope from being washed out during the rainy season.

“Many sloping mountain roadsides along the Ho Chi Minh Trail and mountain resorts in Hue, Da Nang, Quang Nam and Dak Lak were protected by green cover of vetiver grass,” Hieu said. "A square metre of vetiver in protection of upper roadsides costs only VND100,000 (US$4.70). Meanwhile, one square metre of concrete wall costs VND700,000 ($33).

"From 2011 onwards, we had grown vetiver on 4,000sq.m of sloping land on Son Tra Mountain and a section of roadside along Ba Na Mountain to prevent landslides during the rainy season. When the powerful Nari Storm hit in 2013, the green vetiver layer kept the road wall stable.”

Hieu said his company, which is a member of the Viet Nam Vetiver Network recognised by Vetiver Network International, developed a 5ha vetiver nursery in Hoa Nhon Commune in Da Nang to provide saplings for protecting roadside slopes and mountainsides in Viet Nam.

According to Thao, vetiver grass could feed cattle or compost in farming.

Thao said vetiver grass could help clean and recycle water at aquaculture farms, or treat waste at livestock farms.   

Many functions

Tran Tan Van, director of the Viet Nam Institute of Geo-sciences and Mineral Resources and Director of the Viet Nam Vetiver Network, said vetiver has been planted in more than 40 provinces and cities to mitigate a spate of environmental problems.

He said many scientific reports presented at the sixth International Vetiver Conference in Viet Nam last year focused on the importance of vetiver in different ranges with water and soil pollution, desertification, climate change and disaster mitigation, as well as prevention of erosion and stabilising river banks and sea dykes.

“The grass has been used to protect highway dykes, cover waste dumps near coal mines, and on dioxin-contaminated soil in some provinces in Viet Nam,” Van said. "It’s a mass solution for the worst environment pollution and for protecting infrastructure projects and beaches from erosion.”

A survey on vetiver use for dioxin contamination has been implemented at Bien Hoa Airport, but the research hasn’t been completed yet.

Van added that the grass can be used to reduce greenhouse gas emissions to fight climate change.

The geologist said Viet Nam has yet to process the grass as a material for crafts, textiles and oil production, or as vetiver-made textile products and souvenirs from Thailand and India.

Tran Van Man of Da Nang’s Planning and Investment Department said the grass has been planted on the Co Co River’s banks.

Man, who is the Viet Nam Vetiver Network Co-ordinator, said developing the use of vetiver grass was necessary.

Vetiver grass has been developed by the World Bank (WB) for the purpose of soil protection and water resources for agriculture since the 1980s. In the past 20 years, vetiver grass has been grown in more than 100 tropical and subtropical countries in Ocenia, Asia, Africa and Latin America to treat waste water (both household and industrial) and waste matter in mining areas or contaminated areas.

Thao said the grass would help Da Nang deal with waste treatment and pollution at industrial zones to fulfill the city’s target of becoming a ‘green city’ by 2025.

Coming clean: A vetiver grass system is set up to treat waste water at Da Nang Technology College. The grass has been an effective solution to deal with poisonous sewage.         Fields of green: Vetiver grass grows at a nursery centre in Hoa Nhon Commune in Da Nang City.         Fortified: Vetiver grass is planted on a sloppy mountain road side along Ho Chi Minh Trails.           Grass guy: Dr.Tran Minh Thao takes care of a pot of vetiver (Vetiveria Zizanioides) grass at a garden of Da Nang City’s Technology College. He built up the first toxic sewage treatment project for his college’s laboratory. VNS Photos Cong Thanh             Laying waste to waste: Vetiver grass is grown to protect a river bank section in Thua Thien-Hue Province.

By Cong Thanh

VNS