THE VETIVER SYSTEM

FOR

PREVENTION AND TREATMENT OF CONTAMINATED WATER AND LAND

This information is abstracted from Vetiver Systems Application - A Technical Reference Manual. Authors - Paul Truong, Tran Tan Van, and Elise Pinners. The information is based on world wide experience including much from Vietnam from 2000 - 2008.

 

CONTENTS

1. INTRODUCTION

2. HOW THE VETIVER SYSTEM WORKS

3. SPECIAL FEATURES SUITABLE FOR ENVIRONMENTAL PROTECTION PURPOSES

3.1 Morphological attributes

3.2 Physiological attributes

4 PREVENTION AND TREATMENT OF CONTAMINATED WATER

4.1 Reducing or eliminating the volume of wastewater

4.2 Improving wastewater quality

5. TREATMENT OF CONTAMINATED LANDS

5.1 Tolerance to adverse conditions

5.2 Mine rehabilitation and phytoremediation

6. REFERENCES

7. LINKS

1. INTRODUCTION

In the course of researching the application of its extraordinary attributes to soil and water conservation, vetiver was also found to possess unique physiological and morphological characteristics particularly well suited to environmental protection, particularly in the prevention and treatment of contaminated water and land. These remarkable characteristics include a high level of tolerance to elevated and even toxic levels of salinity, acidity, alkalinity, sodicity, and a whole range of heavy metals and agrochemicals, as well as exceptional ability to absorb and tolerate elevated levels of nutrients to consume large quantities of water in the process of producing a massive growth under wet conditions.

Applying the Vetiver System (VS) to wastewater treatment is an innovative phytoremediation technology that has tremendous potential. VS is a natural, green, simple, practicable and cost-effective solution. Most importantly, vetiver’s leaf by-product offers a range of uses from handicrafts, animal feeds, thatches, mulch and fuel, to name just a few.

Its effectiveness, simplicity and low cost makes the Vetiver System a welcome partner in the many tropical and subtropical countries that provide domestic, municipal and industrial wastewater treatment and require mine phytoremediation and rehabilitation.

2. HOW THE VETIVER SYSTEM WORKS

VS prevents and treats contaminated water and soil in the following ways:

Preventing and treating contaminated water:

  • Eliminating or reducing the volume of wastewater.
  • Improving the quality of wastewater and polluted water.

Preventing and treating contaminated land:

  • Controlling off site pollution.
  • Phytoremediation contaminated land.
  • Trapping eroded materials and trash in runoff water.
  • Absorbing heavy metals and other pollutants.
  • Treating nutrients and other pollutants in wastewater and leachate.

3. SPECIAL FEATURES SUITABLE FOR ENVIRONMENTAL PROTECTION PURPOSES

As addressed in another folio, several of vetiver’s special characteristics are directly applicable to wastewater treatment, among them the following morphological and physiological attributes:

3.1 Morphological attributes

  • Vetiver grass has a massive, deep, fast-growing root system capable of reaching 3.6m deep in 12 months in good soil.
  • Its deep roots ensure great tolerance to drought, allow excellent infiltration of soil moisture, penetrate compacted soil layers (hard pans), thus enhancing deep drainage.
  • Most of the roots in vetiver’s massive root system are very fine, with average diameter 0.5-1.0mm (Cheng et al, 2003). This provides an enormous volume of rhizosphere for bacterial and fungal growth and multiplication, thus enabling absorption of contaminants and the process of breakdown such as nitrification.
  • Vetiver’s erect, stiff shoots can grow to three meters (nine feet). When planted close together they form a living porous barrier that retards water flow and acts as an effective bio-filter, trapping both fine and coarse sediment, and even rocks in runoff water - Photo 1.

Photo 1: Morphological characteristics of vetiver

3.2 Physiological attributes

  • Highly tolerant to soil high in acidity, alkalinity, salinity, sodicity and magnesium.
  • Highly tolerant to Al, Mn, and heavy metals such as As, Cd, Cr, Ni, Pb, Hg, Se and Zn in the soil and water (Truong and Baker, 1998).
  • Highly efficient in absorbing dissolved N and P in polluted water - Figure 1.
  • Highly tolerant to high levels of N and P nutrients in the soil - Figure 2.
  • Highly tolerant to herbicides and pesticides.
  • Breaks down organic compounds associated with herbicides and pesticides.
  • Regenerates rapidly following drought, frost, fire, saline and other adverse conditions, once those adverse conditions are mitigated.

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Figure 1: Higher capacity for the uptake of N and P than other plants

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Figure 2: High level of tolerance to and capacity to absorb P and N

4. PREVENTION AND TREATMENT OF CONTAMINATED WATER

Extensive R&D and Applications in Australia, China, Thailand and other countries have established that vetiver is highly effective in treating polluted wastewater from domestic and industrial discharges.

4.1 Reducing or eliminating the volume of wastewater

Vegetative methods currently are the only feasible and practicable way to totally eliminate or reduce wastewater on a large scale. In Australia, vetiver has largely displaced trees and pasture species as the most effective way to treat and dispose of landfill leachate, and domestic and industrial effluent.

To quantify the water use rate of vetiver, it is estimated that for 1kg of dry shoot biomass under ideal glasshouse conditions, vetiver will use 6.86L/day. Since the biomass of 12-week-old vetiver, at the peak of its growth cycle, is about 30.7 t/ha, a hectare of vetiver potentially would use 279KL/ha/day (Truong and Smeal, 2003).

4.1.1 Disposal of septic effluent

In 1996, VS was first applied in Australia to treat sewage effluent. Later trials demonstrated that planting about 100 vetiver plants in a park area less than 50m2 completely dried up the effluent discharge from a toilet block. Other plants, including fast-growing tropical grasses and trees, and crops such as sugar cane and banana, failed (Truong and Hart, 2001).

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Photo 2: Vetiver cleaned up blue green algae in four days (left) Sewage effluent containing high Nitrate (100 mg/L) and Phosphate (10 mg/L). (right) Sewage effluent after four days: VS reduced N level to 6 mg/L (94%) and P to 1 mg/L (90%).

4.1.2 Disposal of landfill leachate

Disposal of landfill leachate is a large problem in major cities, since it is usually highly contaminated with heavy metals, as well as organic and inorganic pollutants. Australia and China have addressed this problem by using leachate collected at the bottom of the dumps to irrigate vetiver planted on the top of the landfill mound and retaining dam walls. Results to date have been excellent. In fact, vetiver’s growth was so vigorous that, during the dry period, the landfills did not generate enough leachate to irrigate the plants. Planting 3.5ha of vetiver effectively disposed of 4 ML of leachate a month in summer and 2 ML a month in winter (Percy and Truong, 2005).

4.1.3 Disposal of industrial wastewater

In Queensland, Australia, a large volume of industrial wastewater generated by a food processing facility (1.4 million litres/day) and a beef abattoir (1.4 million litres/day) was successfully dispersed by land irrigation using vetiver (Smeal et al, 2003).

4.2 Improving wastewater quality

Off-site pollution is the greatest threat to the world environment. Although widespread in industrialized nations, it is particularly serious in developing countries, which often lack sufficient resources to mitigate the problem. Vegetative methods are generally the most accessible and efficient ways to improve water quality.

4.2.1 Trapping debris, sediment and agro-chemicals in agricultural lands

In Australia research studies conducted on sugar cane and cotton farms show that vetiver hedges effectively trap particulate-bound nutrients such as P and Ca; herbicides such as diuron, trifluralin, prometryn, and fluometuron; and pesticides such as α, β and sulfate endosulfan and chlorpyrifos, parathion, and profenofos. If vetiver hedges were established across drainage lines, these nutrients and agrochemicals could be retained on-site (Truong et al. 2000) - Figure 3.

An experiment conducted in Thailand at the Huai Sai Royal Development Study Centre, Phetchaburi Province, shows that vetiver contour hedgerows planted across the slope form a living dam while, at the same time, its root system forms an underground barrier that prevents water-borne pesticide residues and other toxic substances from flowing into the water body below. Thick culms just above the soil surface also collect debris and soil particles carried along the waterway (Chomchalow, 2006).

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Figure 3: Herbicide concentration in soil deposited on up- and down-stream vetiver filter strips.

4.2.2 Absorbing and tolerating pollutants and heavy metal

Vetiver’s usefulness in treating polluted water lies in its capacity to quickly absorb nutrients and heavy metals, and its tolerance to elevated levels of these elements. Although the concentrations of these elements in vetiver plants are often not as high as those of hyper-accumulators, its very fast growth and high yield (dry matter production up to 100t/ha/year) allows vetiver to remove a much higher volume of nutrients and heavy metals from contaminated lands than most hyper-accumulators.

In Southern Vietnam, a demonstration trial was set up at a seafood processing factory to determine the length of time that effluent should remain in the vetiver field before its nitrate and phosphate concentrations were reduced to acceptable levels. Test results showed that total N content in wastewater was reduced by 88% and 91% after 48 and 72 hours of treatment, respectively, while the total P was reduced by 80% and 82% after 48 and 72 hours of treatment. The total amount of N and P removed in 48- and 72-hour treatments were not significantly different (Luu et al, 2006). Following these tests, a number of fish farms in the Mekong Delta adopted the VS to stabilize fishpond dikes, to purify fishpond water, and to treat other farm wastewater - Photo 3.

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Photo 3: Erosion control and wastewater treatment at a freshwater fish farm in the Mekong Delta

In northern Vietnam, wastewater discharged from a small paper factory at Bac Ninh and a small nitrogen fertilizer factory at Bac Giang is as highly polluted with nutrients and chemicals as landfill leachate. The factories release their wastewater directly into a small river in the Red River Delta. Installed at both sites, vetiver became well established after two months. At this writing, the grass at the paper factory at Bac Ninh is generally in good shape, except for a few sections next to the polluted water, where it shows symptoms of toxicity. On the other hand, despite the highly polluted conditions, vetiver is established and growing well at the nitrogen fertilizer factory at Bac Giang. Excellent growth has been recorded for this site under semi-wetland conditions, where vetiver is expected to reduce pollutant levels significantly - Photo 4.

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Photo 4: Left: Vetiver at Bac Ninh; right: at Bac Giang.

In Australia, five rows of vetiver were sub-surface irrigated with effluent discharge from a septic tank. After five months, total N levels in the seepage collected after two rows were reduced by 83%, and after five rows by 99%. Similarly, total P levels were reduced by 82% and 85%, respectively (Truong and Hart, 2001). Figure 4.

In China, nutrients and heavy metals from pig farms are key sources of water pollution. Wastewater from pig farms contains very high levels of N and P and also Cu and Zn, which are added to feed as growth promoters. Results show that vetiver has a very strong purifying action. Its ratio of uptake and purification of Cu and Zn is >90%; As and N>75%; Pb is between 30% -71% and P is between 15-58%. Vetiver’s ability to purify heavy metals and N and P from pig farms is ranked as: Zn>Cu>As>N>Pb>Hg>P (Liao et al, 2003).

4.2.3 Wetlands

Natural and constructed wetlands effectively reduce the amount of contaminants in runoff from both agricultural and industrial lands. Using wetlands to remove pollutants requires the use of a complex variety of biological processes, including microbiological transformations and physio-chemical processes such as adsorption, precipitation or sedimentation, plants such as Iris pseudacorus, Typha spp, Schoenoplectus validus, and Phragmites australis. At an average consumption rate of 600 ml/day/pot over 60 days, vetiver used 7.5 times more water than Typha (Cull et al. 2000). A wetland was constructed to treat sewage effluent generated by a small rural town. The project’s goal was to reduce or eliminate the 500ML/day effluent produced by this small town before discharge into the waterways (Photo 5). Astonishingly, the vetiver wetland has absorbed all the effluent produced by this small town (Ash and Truong, 2003). Table 1. Under wetland conditions in Australia, vetiver had the highest water use rate, when compared with wetland.

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Figure 4: Effectiveness of N reduction in domestic sewage

 

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Photo 5: Left: Vetiver wetland; right: leachate disposal in Australia

Table 1: Effluent quality levels before and after vetiver treatment.

Tests

Fresh influent (mg/l)

Results 2002/03 (mg/l)

Results 2004

(mg/l)

PH (6.5 to 8.5)*

pH 7.3-8.0

pH 9.0-10.0

pH 7.6-9.2

Dissolved Oxygen (2.0 mg/l min.)*

0-2

12.5-20

8.1-9.2

5 Day BOD (20 -40 mg/l max)*

130-300

29 to 70

7-1

Suspended solids (30-60 mg/l max)*

200-500

45 to 140

11-16

Total Nitrogen (6.0 mg/l max) *

30-80

13 to 20

4.1-5.7

Total Phosphorous (3.0 mg/l max) *

10-20

4.6 to 8.8

1.4-3.3

*License requirements

China raises the most pigs in the world. In 1998, Guangdong Province alone supported more than 1600 pig farms; 130+ farms produced more than 10,000 commercial pigs annually. Large piggeries produce 100-150 tons of wastewater per day, including pig manure collected from slatted floors, which contain high nutrient loads. Consequently, the disposal of wastewater from pig farms is a huge problem. Wetlands are considered to be the most efficient way to reduce both the volume and high nutrient loads of piggery effluent. To determine the plants best suited for the wetland system, vetiver was included in test of the most promising dozen species, which initially ranked the top three as vetiver, Cyperus alternifolius, and Cyperus exaltatus. However, further testing revealed that Cyperus exaltatus wilted and became dormant during autumn, rejuvenating in the next spring. Since effective wastewater treatment requires year-round growth, only vetiver and Cyperus alternifolius were determined to be suitable for wetland treatment of piggery effluent (Liao, 2000) - Photo 6.

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Photo 6: Left: Vetiver pontoon in pig farm ponds in Bien Hoa; right: in Guangzhou, China

In Thailand very solid research has been conducted in the last few years on the application of VS to treat wastewater in constructed wetlands. One study used three ecotypes of vetiver (Monto, Surat Thani, and Songkhla 3) to treat wastewater from a tapioca flour mill, employing two treatment systems: (a) holding wastewater in a vetiver wetland for two weeks and then draining it, and (b) holding wastewater in a vetiver wetland for one week and then draining it off continuously for a total of three weeks. In both systems Monto displayed the most rapid growth of shoot, root, and biomass, and absorbed the highest levels of P, K, Mn and Cu in the shoot and root (Mg, Ca and Fe in the root, and Zn and N in the shoot). Surat Thani absorbed the highest levels of Mg in the shoot and Zn in the root, and Songkhla 3 absorbed the highest levels of Ca, Fe in the shoot, and N in the root maximally (Chomchalow, 2006, cit. Techapinyawat 2005).

4.2.4 Computer modelling for industrial wastewater

Computer models have become increasingly indispensable tools to manage environmental systems, including complex wastewater management plans such as industrial wastewater disposal. In Queensland, Australia, the Environmental Protection Authority has adopted MEDLI (Model for Effluent Disposal using Land Irrigation) as a basic model for industrial wastewater management. The most significant recent development in the use of VS for wastewater disposal is vetiver’s MEDLI calibration for nutrient uptake and effluent irrigation (Vieritz, et al., 2003), (Truong, et al., 2003a), (Wagner, et al., 2003), (Smeal, et al., 2003).

4.2.5 Computer modelling for domestic wastewater

A computer model was developed recently in sub-tropical Australia to estimate the vetiver planting area needed to dispose of the total black and grey water output from each house. For example, a vetiver planting area of 77m2, at density of 5 plants/m2, is required to serve a household with six people, based on an output of 120L/person/day.

4.2.6 Future trend

As water shortages loom worldwide, wastewater should be considered as a renewable resource rather than as a problem that requires disposal. The current trend is to recycle wastewater for industrial and domestic use instead of disposing of it. Therefore, VS’ potential as a simple, hygienic and low cost way to treat and recycle wastewater resulting from human activities is enormous. Figure 5.

A most exciting development in wastewater treatment is vetiver’s use in soil-based reed beds. In this new application, output water quality and quantity can be adjusted to satisfy a set standard. GELITA APA, Australia is developing and testing this system. Full details of this system are found in (Smeal et al. 2006). Figure 6.

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Figure 5: Layout of a domestic disposal system

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Figure 6: Workings of a typical reed bed

5. TREATMENT OF CONTAMINATED LANDS

Among the most significant developments in environmental protection within the last 15 years are vetiver’s documented tolerances to adverse soil conditions and to heavy metal toxicities. These benchmarks have opened up a new field for VS application: the rehabilitation of toxic and contaminated lands.

5.1 Tolerance to adverse conditions

5.1.1 Tolerance to high acidity, aluminium and manganese toxicity

Research shows that vetiver growth was not affected, when adequately supplied with N and P fertilizers, even under extremely acidic conditions (pH = 3.8) and at a very high level of soil Aluminium Saturation Percentage (68%). Field tests confirm that vetiver grows satisfactorily at soil pH=3.0 and Aluminium level between 83-87%. However, since vetiver cannot survive an Aluminium saturation level of 90% at soil pH = 2.0, its threshold tolerance is between 68% and 90%. This tolerance is exceptional, since most plants are adversely affected at levels less than 30%.

Photo 7: Under field conditions, vetiver thrives at soil pH=3.8 and Al saturation of 68% and 87%.

Photo 8: Vetiver growth was unaffected at pH=3.3 and at extremely high Mn level of 578 mg/kg. between

Further, vetiver growth remained unaffected when the extractable manganese in the soil reached 578 mg/Kg, the soil pH was as low as 3.3, and plant manganese content was as high as 890 mg/Kg. Given its high tolerance to Al and Mn toxicity, vetiver has been used successfully to control erosion in acid sulfate soils with actual soil pH around 3.5 and oxidized pH as low as 2.8 (Truong and Baker, 1998) - Photos 7 and 8.

Photo 9: Vetiver tolerates high soil salinity. Note 3rd pot from left represents half the salinity of sea water.

5.1.2 Tolerance to high soil salinity and sodicity

Given its salinity threshold level of ECse = 8 dS/m, vetiver compares favourably with some of the most salt-tolerant crop and pasture species grown in Australia, including Bermuda Grass (Cynodon dactylon) with a salinity threshold of 6.9 dS/m; Rhodes Grass (Chloris gayana) (7.0 dS/m); Wheat Grass (Thynopyron elongatum) (7.5 dS/m) and barley (Hordeum vulgare) (7.7 dS/m). With an adequate supply of N and P, vetiver grew satisfactorily on Na bentonite tailings with Exchangeable Sodium Percentage of 48% and a coalmine overburden with an exchangeable sodium level of 33%. The sodicity of this overburden was further exacerbated by the very high level of magnesium (2400 mg/Kg) compared to calcium (1200 mg/Kg) (Truong, 2004).

5.1.3 Distribution of heavy metals in vetiver plant

The distribution of heavy metals in vetiver can be divided into three groups:

  • Zn was almost evenly distributed between shoot and root (40%).
  • Small amounts of As, Cd, Cr and Hg absorbed were translocated to shoots (1%-5%).
  • Moderate amounts of Cu, Pb, Ni and Se were translocated to the top (16%-33%) (Truong, 2004).

Table 2: Threshold levels of heavy metals: Vetiver and other plants

Threshold levels in soil

Threshold levels in plant (mg/Kg)

Heavy Metals

(mg/Kg) (available)

Vetiver

Other plants

Vetiver

Other plants

Arsenic

100-250

2

21-72

1--10

Cadmium

20-60

1.5

45-48

5-20

Copper

50-100

Not available

13-15

15

Chromium

200-600

Not available

5-18

0.02-0.20

Lead

>1 500

Not available

>78

Not available

Mercury

>6

Not available

>0.12

Not available

Nickel

100

7-10

347

10-30

Selenium

>74

2-14

>11

Not available

Zinc

>750

Not available

880

Not available

5.1.4 Tolerance to heavy metals

Vetiver is highly tolerant to As, Cd, Cr, Cu, Hg, Ni, Pb, Se and Zn. Table 2 above..

5.2 Mine rehabilitation and phytoremediation

Given its extraordinary morphological and physiological characteristics, vetiver has been used successfully to rehabilitate mine waste rock and phyto-remediate mine tailings in:

  • Australia: coal, gold, betonite and bauxite.
  • Chile: copper.
  • China: lead, zinc and bauxite (Wensheng Shu, 2003).
  • South Africa: gold, diamond and platinum.
  • Thailand: lead.
  • Venezuela: bauxite (Lisena et al. 2006 and Luque et al.2006).

Photo 10: Upper: Bauxite mine at Los Pijiguaos, Venezuela protected with vetiver (note the planting of the steep slope by using ropes). Lower: Nickel mine in the Philippines - Vetiver and coir matting used to protect this slope covering 2 ha. (Noah Manarang)

6. REFERENCES

Ash R. and Truong, P. (2003). The use of vetiver grass wetland for sewerage treatment in Australia. Proc. Third International Vetiver Conf. China, October 2003.

Chomchalow, N, (2006). Review and Update of the Vetiver System R&D in Thailand. Proc. Regional Vetiver Conference, Cantho, Vietnam.

Cull, R.H, Hunter, H, Hunter, M and Truong, P.N. (2000). Application of Vetiver Grass Technology in off-site pollution control. II. Tolerance of vetiver grass towards high levels of herbicides under wetland conditions. Proc. Second International Vetiver Conf. Thailand, January 2000.

Hart, B, Cody, R and Truong, P. (2003). Efficacy of vetiver grass in the hydroponic treatment of post septic tank effluent. Proc. Third International Vetiver Conf. China, October 2003.

Liao Xindi, Shiming Luo, Yinbao Wu and Zhisan Wang (2003). Studies on the Abilities of Vetiveria zizanioides and Cyperus alternifolius for Pig Farm Wastewater Treatment. Proc. Third International Vetiver Conf. China, October 2003.

Lisena, M.,Tovar,C. and Ruiz, L.(2006) “Estudio Exploratorio de la Siembra del Vetiver en un Área Degradada por el Lodo Rojo”. Proc. Fourth International Vetiver Conf. Venezuela, October 2006.

Luque, R, Lisena ,M and Luque, O. (2006). Vetiver System for environmental protection of open cut bauxite mine at Los Pijiguaos-Venezuella. Proc. Fourth International Vetiver Conf. Venezuela, October 2006

Luu Thai Danh, Le Van Phong. Le Viet Dung and Truong, P. (2006). Wastewater treatment at a seafood processing factory in the Mekong delta, Vietnam. Proc. Fourth International Vetiver Conf. Venezuela, October 2006.

Percy, I. and Truong, P. (2005). Landfill Leachate Disposal with Irrigated Vetiver Grass. Proc, Landfill 2005. National Conf on Landfill, Brisbane, Australia, September 2005

Smeal, C., Hackett, M. and Truong, P. (2003). Vetiver System for Industrial Wastewater Treatment in Queensland, Australia; Proc. Third International Vetiver Conf. China, October 2003.

Truong, P.N.V. (2004). Vetiver Grass Technology for mine tailings rehabilitation. Ground and Water Bioengineering for Erosion Control and Slope Stabilization. Editors: D. Barker, A. Watson, S. Sompatpanit, B. Northcut and A. Maglinao. Science Publishers Inc. NH, USA.

Truong, P.N. and Baker, D. (1998). Vetiver grass system for environmental protection. Technical Bulletin N0. 1998/1. Pacific Rim Vetiver Network. Royal Development Projects Board, Bangkok, Thailand.

Truong, P.N. and Hart, B. (2001). Vetiver System for wastewater treatment. Technical Bulletin No. 2001/2. Pacific Rim vetiver Network. Royal Development Projects Board, Bangkok, Thailand.

Truong, P.N., Mason, F., Waters, D. and Moody, P. (2000). Application of vetiver Grass Technology in off-site pollution control. I. Trapping agrochemicals and nutrients in agricultural lands. Proc. Second International Vetiver Conf. Thailand, January 2000.

Truong, P. and Smeal (2003). Research, Development and Implementation of Vetiver System for Wastewater Treatment: GELITA Australia. Technical Bulletin No. 2003/3. Pacific Rim vetiver Network. Royal Development Projects Board, Bangkok, Thailand.

Truong, P., Truong, S. and Smeal, C. (2003a). Application of the vetiver system in computer modelling for industrial wastewater disposal. Proc. Third International vetiver Conf. China, October 2003.

Vieritz, A., Truong, P., Gardner, T. and Smeal, C. (2003). Modelling Monto vetiver growth and nutrient uptake for effluent irrigation schemes. Proc. Third International vetiver Conf. China, October 2003.

Wagner, S., Truong, P, Vieritz, A. and Smeal, C. (2003). Response of vetiver grass to extreme nitrogen and phosphorus supply. Proc. Third International Vetiver Conf. China, October 2003.

Wensheng Shu (2003) Exploring the Potential Utilization of Vetiver in Treating Acid Mine Drainage (AMD). Proc. Third International Vetiver Conf. China, October 2003.

LINKS

POLLUTION - EFFLUENT CONTROL (WATER QUALITY IMPROVEMENT)