Preliminary Study on Purification of Eutrophic

Water with Vetiver

Zheng Chunrong, Tu Cong and Chen Huairnan*

(Institute of Soil Science Academia Sinica, Nanjing 210008)

(Paper presented at the International Vetiver Grass Technology Workshop in Fuxhou, China, October 1997)

INTRODUCTION

Water eutrophication is the phenomena of the degradation of water function and the deterioration of water quality. As population increases and industrial and agricultural production develop, water eutrophication is increasingly serious[1]. How to restore eutrophic water has aroused concern. There are two ways for restoration of eutrophic water. One is to control the input of nutrients(N and P) and organic pollutants to water body, and another is to remove these substances from water.

Vetiver (Vetiveria -zizanioides) is a perennial rooty herb with fast growth, wide adaptability, and strong resistance[21]. It has been widely applied to the conservation of soil and water [2,3,4,5]. However., its application in controlling environmental pollution is very limited[5] Purifying eutrophic water with vetiver is not only to improve water

quality. but also to obtain botanical products. The objective of the present paper is to determine the possibility of purifying eutrophic water with vetiver.

MATERIALS AND METHODS

River water polluted by domestic sewage, pond water and tap water were collected for use in this experiment. Their main properties were given in Table 1. Vetiver was grown in water with "floating island- technique and allowed to grow for 4 or 5 weeks. During growth, water samples were weekly collected to determine total N and P. Total N in water was determined with Zn-FeSO, reduction and alkali distillation. Total P was measured by potassium persulfate digestion and molybdenum-blue colorimetry. At the end of the experiment, height and tillering number of vetiver were recorded.

RESULTS AND DISCUSSION

Vetiver Growth

Vetiver could normally grow In four water bodies, whereas best in river water. Net increases in plant height were 68.5-80cm. 60cm and 50cm, and tillering numbers 2-4 1 and 0 for river waters, pond water and tap water, respectively. These suggested that vetiver could be planted in water environment.

Table 1 Main Properties of Experimented Water

Items

River water (I)

River water (II)

Pond water

Tap water

Locality

Pollution

pH

Odor grade

Total N

(mg/L)

Total P

(mg/L)

Jimingsi river demestic sewage

6-7

2-3

13.8

0.94

Qinghuai river domestic sewage

7.1

4-5

10.5

1.03

Jiuhua mountain

none

7

0

0.70

0.014

Nanjing

none

7-7.5

0

0.10

ND

 

ND-Not detectable.

 

Table 2 Heiglit and Tiller Number of Vetiver Grown in Experimented Water

Items

River water (I)

River water (II)

Pond water

Tap water

Plant height(cm)

Net increase in plant height(cm)

Tiller number

90

60

4

80.5

68.5

2

70

40

1

70

40

0

 

Removal Efficiency of P and N in Water

Vetiver not only could grow normally in water, but also remove nitrogen and phosphorous from water, and thus purify eutrophic water. Table 3) showed that the removal percentage of total P was 76-91% after 2 week growth, and was high up to over 98% after ') or 4 week. The removal rate was higher in river water(l) than in river water (II). This might be because vetiver planted in river water(l) had more roots and thus stronger absorbability. The removal percentage of total N was a little less than that of total P. It was 34-45% after 1 or 2 week, and only 71-74% after 4 or 5 week. These indicate that the removal efficiency of P by vetiver is higher than that of N. Phosphorous is usually considered to be a key element for water eutrophication. In addition, the sense characteristics of river and pond water were apparently improved and the transparency increased after planting vetiver. Therefore vetiver could be used as purl . 1 - cutrophic water body.

CONCLUSION

Growth time (week)

1

2

3

4

5

River water(I):

Total P (mg/L)

Removable (%)

Total N (mg/L)

Removable (%)

River water(II):

Total P (mg/L)

Removable (%)

Total N (mg/L)

Removable (%)

0.30

68.1

9.1

34.1

 

0.083

91.2

 

 

 

0.25

75.8

5.76

45.1

0.007

99.3

 

 

 

0.065

93.7

4.40

58.1

0.009

4.0

71.0

 

0.027

97.4

 

 

 

 

 

 

0.023

97.8

2.71

74.2

 

Vetiver could normally grow in water. It is powerful to remove nitrogen and phosphorous from water, but more for phosphorous, and therefore a good plant for purifying eutrophic water and has applied prospects. These findings suggested that vetiver is worth further studying for purifying eutrophic water. The next study should be focused on the changes in COD, BOD and dissolved oxygen and the optimum growth period and treating capacity of vetiver.

ACKNOWLEDGEMENT

This study was financially supported by the China Vetiver Network.

REFERENCES

I.Bao Qing, 1993. The Policy and Target for Prevention and Control of Water Pollution and the Technology Options in China. Advances in Environmental Science(in Chinese), 1(l): 1-24

2.Tao Zhan, 1992. Vetiver-a Good Plant for Conservation of Soil and Water. World Agriculture(in Chinese), No-149-50

3. Xu Liyu and Zhou Fujian, 1997. Prospects for Application of Vetiver in Area of

Southern China. Agroforestry Today(in Chinese), 5(l): 13)- 15

4. Hu Jianye Xue Huishan and Zhou Caiwen 1997. Application of Vetiver in Development of Red Soil. Agroforestry Today(in Chinese), 5(3):55-59.

5.Vietmever N.(Zhuang Shtinvao translated). 1997. Promoting the Extension of Vetiver on a Global Scale. Vetiver Newsletter(in Chinese). 1 (2): 1-5