Vetiver and its use to control effluent from China’s pig farms.

By Xia Hanping, South China Institute of Botany, Guangzhou, China

Adapted and translated by China Vetiver Network

China ia the world’s largest pig production country. China had 450 million pigs (early 1996), accounting for 57.4% of the total in the world. In the recent years pig-raising changed from small farm holder to concentrated and large scale production. This is quite typical in Guangdong Province. In 1998 there were over 1600 pig farms which produced more than 500 commercials pigs each year, in which there were over 130 pig farms which produced over 10000 commercial pigs each year. Accordingly, how to deal with the polluted wastes and water became a big problem. As a large pig farm which produces over 10000 commercial pigs, there produced 100-150 ton wasted water each day, which includes pig manure collected from slotted floor, containing large amount of nutrients.

It was estimated that there were 10 million ton wastes produced in Guangdzhou City in 1996, with Chemical Oxygen Demand (COD) of 10060 mg/L in average, and total annual COD for 104 900 ton. During the same period in 1996 there were total wasted water for 1035 million ton and total COD for 156 200 ton in Guangzhou City. It indicated that COD amount produced by pig farms accounts for 67.14% of the total, although the wasted amount accounts for only 1.01% of the total. To protect river water, the Guangdong Provincial Government released a regulation on 1 September 1999 requesting that all wasted water from animal farms should be disposed before flowing into the river.

1. Methods to deal with wasted water: artificial wet land

There are some methods to dispose wasted water derived from pig farms, such as physical, chemical, and biological. Because the chemical method costs a lot and has second pollution problem, it is rarely used at present. The wasted water derived from pig farms, different from other industrial wasted water, is characterized by high content of N and P which are decomposable. As a result, the pig farm induced water is treated by following steps: separating solids and liquid — anerobic treatment — aerobic treatment. What this research dealt with is the last step aerobic treatment. Since 1970’s some hydrophilic plants such as water hyacinth was introduced to oxygenating pond filled with wasted water from pig farm, which was treated through ‘separating solids and liquid’ and ‘anerobic treatment’. However it remains problems such as it needs large area for establishing ponds; the treatment site is subject to deterioration; it can not work smoothly through the whole year; the second pollution happened if large amount of plants produced.

Another method is that artificial wet land was established, instead of ponds, on which some hydrophilic fascicular plants were planted. The Reed Bed System is an example in both China and abroad since 1980’s. This kind of wet land treatment can reduce solid suspended substance, BioOxygen Demand (BOD), N, P, and heavy metal elements contents in the water. In the beginning of 1980’s the wet land was composed by earth, but later by sand and stones in order to reduce land area. Because the medium material effects the consequence of the treatment. For instance, the medium consisting much carbonate can promote the eutrofication of phosphor, while soil containing much organic matter can absorb more pollutants, present study uses stone fragment in order to reduce interaction between medium and wasted water.

The paper was to select and evaluate some species of plants which were suitable for the wet land treatment.

2. Materials and method

This study was conducted at a large pig farm which produces 30000 commercial pigs each year in Guangzhou City. The farm uses slatted floor washing two times each day with water. It uses sieve plate to separate solids and liquid which passed through deposition pond, adjust pond, and anerobic pond before entering into wet land.

2.1 Materials

Altogether 12 species of plants were used (Table 1).

Table 1. Background information of tested plants

Species of plants Family Ecological site
Vetiveria zizanioides Gramineae upland
Saururus chinensis Saururaceae upland
Cyperus alternifolius Cyperaceae upland
Pennisetum purpureum Gramineae upland
Calla palustris Araceae beside ditch
Alocasia macrorrhiza Araceae beside ditch
Cyperus exaltatus Cyperaceae pond
Polygonum hydropiper Polygonaceae pond
Polygonum lapathifolium Polygonaceae pond
Juncellus serotinus Cyperaceae beside ditch
Ranuneulus cantoniensis Ranunculaceae pond
Scirpus triangulatus Cyperaceae beside ditch

2.2 Plant selection and evaluation. The selection and evaluation was implemented qualitatively, including: tolerant to wet and hydraulic circumstance, low temperature and pollution, production of large bio-mass, strong root system, perennial - easy for reproduction, less subject to diseases, with stiff stems, easy to harvest, economic value, and with high view and admire.

All the plants were pre-planted on sands before water cultivation so that they could be adapted to later polluted water cultivation. Several steps were used: (1) select some species of plants through reviewing literatures, visiting experts, and field investigations. (2) Collect these plants and planted them in the plot filled with sands with 10 m (long) x 6 m (wide) x 40 cm (deep) over the cement ground. The sand was submersed by diluted pig farm liquid. (3) Plant water-cultivation with different concentrations of pig farm liquid to evaluate the pollution tolerance.

The plants were evaluated with 5 items (parameters): pollution tolerance (as q1), bio-mass (q2), root system (q3), view and admire (q4), and easy to manage including easy for reproduction, less subject to diseases, with stiff stems, easy to harvest (q5). Each parameters has its own weigh based on their importance as 30 (as c1), 25(c2), 25(c3), 10(c4), 10 (c5) respectively. The total remark (M) would be:

2.3 Water cultivation

Liquid used for the cultivation came from the pig farm after deposition and (missing text to be inserted later)

Table 2. Liquid concentration (mg/L)

Treatment

COD

NH3-N

C1

1040

150

C2

1300

200

C3

1900

240

C4

2200

290

C5

2800

390

Table 3. Growth behavior under water cultivation

Concentration

C2& C1

C3

C5&C4

remark

Duration (days)

2

4

6

9

2

4

6

9

2

4

6

9

Vetiveria zizanioides

N

N

N

N

N

N

N

N

N

N

N

N

 

Saururus chinensis

N

N

N

N

L

ML

S

S

L

ML

S

S

 

Cyperus alternifolius

N

L

L

Lb

N

L

L

Lb

N

L

L

Lb

 

Pennisetum purpureum

L

L

ML

ML

L

L

ML

ML

L

L

ML

ML

 

Calla palustris

N

L

L

L

       

N

L

ML

S

 

Alocasia macrorrhiza

N

L

L

L

N

L

ML

ML

N

N

L

ML

 

Cyperus exaltatus

 

N

N

N

N

N

N

 

N

N

ML

r

 

Polygonum hydropiper

N

N

N

N

N

N

N

N

N

N

N

N

C2

Polygonum lapathifolium

N

N

L

L

N

N

L

L

N

N

L

L

C2

Juncellus serotinus

 

L

L

L

 

L

ML

ML

 

L

ML

ML

C5

Ranunculus cantoniensis

N

L

L

L

       

N

L

ML

N

 

Scirpus triangulatus

N

L

ML

MLb

N

L

ML

Nr

N

L

ML

Nr

C2

N - normal, L - withered at stem base, ML withered at middle and base, S- serious wilted, b- sprouted at rootstock, r- rotted in roots

Table 4 Comprehensive evaluation of 12 species adaptable to pig farm induced wet land waste water

Items

Pollution tolerance

Biomass

Roots

View & admire

Easy to manage

Total

Remark

Weight (%)

30

25

25

10

10

100

Vetiveria zizanioides

80(24)

80(20.0)

90(22.5)

80(8)

100(10)

84.5

2

Saururus chinensis

70(21)

50(12.5)

50(12.5)

60(6)

50(5)

57.0

7

Cyperus alternifolius

80(24)

100(25.0)

100(25.0)

100(10)

100(10)

94.0

1

Pennisetum purpureum

50(15)

85(21.0)

70(17.5)

80(8)

100(10)

71.5

4

Calla palustris

40(12)

50(12.5)

50(12.5)

50(5)

60(6)

48.0

10

Alocasia macrorrhiza

80(24)

75(18.8)

50(12.5)

50(5)

60(6)

66.3

6

Cyperus exaltatus

70(21)

80(20.0)

80(20.0)

80(8)

100(10)

79.0

3

Polygonum hydropiper

100(30)

25(6.3)

30(7.5)

50(5)

40(4)

52.8

8

Polygonum lapathifolium

90(27)

25(6.3)

30(7.5)

50(5)

40(4)

49.8

9

Juncellus serotinus

60(18)

80(20.0)

50(12.5)

80(8)

100(10)

68.5

5

Ranunculus cantoniensis

40(12)

30(7.5)

30(7.5)

60(6)

50(5)

38.0

12

Scirpus triangulatus

30(9)

40(10.0)

50(12.5)

80(8)

50(5)

44.5

11

* The figures are the evaluation marks for a plant under single parameter (pollution tolerance, for example); the figures inside brackets obtained by the mark multiply the weight (for example,

for vetiver: 80 x 30 % = 24

3. Results and analysis

3.1 Water cultivation results Vetiver Table 3 indicated that vetiver grew well and expressed no difference in first 9 days under 3 different concentrations. Observation on 14th day the grass still grew well. Observation on 30th day, there was obvious difference among the treatments, i.e. the plant grew best for C2 followed by C3, while C5 grew poorest. It indicated that vetiver can grow well under COD of 1300 mg/L and NH3-N 200 mg/L.

Saururus chinensis It can grow well under COD of 1300 mg/L and NH3-N of 200 mg/L (treatment C2), but it can not grow under COD 1900 mg/L and NH3-N 240 mg/L (treatment C3).

Cyperus alternifolius It grew well on 9th day with new tiller appeared under treatment C1, but the leaves of all of the plant turned into yellow on 9th day under treatments C2, C3, and C5, except for that the main stem remained green. The roots of all of the treatments became red with many new buds most of them were under water level. On 30th day the plants of all of the treatments had new tillers with 4-5 cm high.

Pennisetum purpureum The elephant grass could not grow under COD 1300 mg/L and NH3-N 200 mg/L.

Calla palustris, Alocasia macrorrhiza, and Ranuneulus cantoniensis All the 3 grasses wilted seriously with increasing days under C4 but they were effected slightly under C1. It indicated that the 3 grasses could not grow under COD 2200 mg/L and NH3-N 290 mg/L, but could grow under COD 1040 mg/L and NH3-N 150 mg/L.

3.2 Evaluation to water cultivation

Table 4 shows the results of comprehensive evaluation on 12 species adaptable to pig farm induced wet land. It indicated that the best species are vetiver, Cyperus alternifolius, and Cyperus exaltatus. However, further test showed that Cyperus exaltatus became wilted and dry during autumn and it did not grow until next spring. It means that the grass can not grow the whole year to improve the polluted water system. Therefore only vetiver and Cyperus alternifolius were the two plants for this purpose and were selected for further studies.

4. Discussion

4.1 Effect of pig farm water on the plants All the 12 species of plants were pre-planted on sands for a period so that they could be more suitable to the polluted pig farm water. The experiment showed that there was great variance between different plants because of the great difference of the components, organic matter and NH3-N in particular. Different concentration of organic matter causes anerobic condition to a certain degree, while less oxygen lead to disorder of root respiration and the increase of ethene and the aging of plants. Besides, the extra dissociated ammonia may limit electron transition system during respiration.

4.2 Tolerance of plants to polluted water Pang Jinhua (1997) reported that Eichhornia crassipes and Alternanthera philoxeroides can tolerate maximum COD of around 1000 mg/L, but Ipomoea aquatica can tolerate COD 1300 mg/L or higher. Li Fangbai (1996) reported that what effected the root system was neither COD nor electronic Conductivity (EC). It was dissolve oxygen (DO).

4.3 Selection of plants Plants and micro-organs as well can be used to deal with polluted water. In the past only hydraulic plants were considered. Ding Shurong (1992) applied land plant Lolium multiflorum to purify organic wasted water. Present research confirmed that land plants can be useful, especially those their ancestors were hydraulic or lived in swamp. In the past the low concentration of COD 100-300 mg/L had been used, while in present test high COD of 2800 mg/L was used. It means that high concentration would be possible for future study.

It took 9 days (30 day the longest) for the present study. The initiation concentration of the water effected later plant growth. For example, on 30th day there was great difference on vetiver growth between treatments: C2 the beast, followed by C3, C5 was the worst, caused by the initiation concentration. The observation period can be longer for similar experiments.

5. Summary

Vetiver, Polygonum hydropiper, Polygonum lapathifolium, Cyperus alternifolius could grow under COD 2800 mg/L and NH3-N 390 mg/L.; Alocasia macrorrhiza, Cyperus exaltatus, Saururus chinensis, Juncellus serotinus, elephant grass, Calla palustris, Ranuneulus cantoniensis could grow under COD 1300 mg/L and NH3-N 200 mg/L; Scirpus triangulatus could grow under COD 1040 mg/L and NH3-N 150.

Evaluation on pollution tolerance, bio-mass, root system, view and admire, management feasibility, vetiver and Cyperus alternifolius can be used to treat pig farm induced polluted water and was selected for further study.