s

The water plants Enydra Fluctuans and Ipomoea aquatica (water spinach) were used to treat the waste water produced at the pig farm. There were six levels with 4 replications to compare: 0, 20, 40, 60, 80, 100% pig waste with water. Each container was seeded with a fixed weight of shoots of water spinach and Enydra fluctuans. The biomass was harvested after 30 days.

The results showed that water spinach and Enydra fluctuans could survive when planted in piggery waste water at all dilutions, but biomass yield decreased with increasing concentration of the pig waste. All indices of water quality improved with time the trends being most marked at the highest concentrations of pig waste. Levels of crude protein and phosphorus in aerial parts of both plants increased as the concentration of pig waste water increased. There appeared to be no differences between the two plants in their capacity to improve water quality and accumulate nutrients.

Introduction

Piggery waste consists of faeces, urine, litter, redundant feed and water for cleaning the pens. . Unlike the excreta from cows or domestic fowls, it is more difficult to control the waste from pigs. Moreover, it seems that that there has been limited use of pig excreta as fertilizer in agriculture (Ho Kim Hoa and VTV 2002). The waste from livestock can be a serious source of pollution of soil, water and air. It can directly affect human health. Development of algae blooms stimulated by the nutrients in live stock waste can compound the degree of pollution (Khuat Mai Chi 2002). The possibility to grow water plants, especially Enydra fluctuans and water spinach (Ipomoea aquatica), to treat the piggery waste water is a newly proposed method in Vietnam.

Material and methods

Animals and housing

There were 4 sows and 20 piglets in the farm with four pens for sows and four pens for piglets. All the pigs were fed a commercial concentrate diet. Water was used to clean the pig house twice daily.

Experiment arrangements

The experiment was designed as a factorial 2*6 arrangement with 3 replications (blocks). Each replication consisted of 12 plastic vessels (6 levels; two types of water plant). The treatments were allocated at random within each block

Thirty-six 60 litre plastic vessels were buried into the soil so that the distance from the vessels’ surface to the soil was 0.2m. They were sited under a polyethylene roof to avoid the rain. Waste water from the piggery was mixed with clean water from an underground well, so that the distance from the water surface to that of the vessel was 0.1m. Cuttings of Enydra fluctuans and water spinach (about 0.5 kg in each case) were introduced into the vessels. No additional waste was added during the experimental period which lasted 32 days.

Samples of the experimental media were taken every 8 days, a total of 5 times. The media in the vessel was not stirred before collecting the sample, which was done by dipping a beaker at a distance of 20cm from the water surface. The beaker was rinsed twice with the media before taking the final sample which was then put in a sealed bottle. Measurements were made of pH, N-NH₄⁺, P-PO₄^3-, BOD and DO.

The weight of biomass in the aerial part, Height of the plant and length of roots were measured at the same time of collecting the samples of the media. At the end of the experiment, samples of the plants were dried at 100ºC to determine DM content. Other samples were dried at 60 ºC for subsequent analysis of N, ash, water extractable DM and NDF.

Analytical methods

pH, DO and BO were measured with digital meters (pH 320/Set 2, model 100739, Oxi 320/Set, model 200212, Oxitop OC 100, model TS606-G/2), respectively. NH₄⁺ and PO₄^3- were measured by colorimetry (Photo Lap S12).

DM, ash and Kjeldhl nitrogen (N) were determined according to AOAC (1990). Neutral detergent fibre (NDF) was analyzed by the method of Van Soest and Robertson (1985).

Statistical analysis.

All the data were coded for subsequent statistical analysis using the General linear model option of the ANOVA software of Minitab (release13.2). Sources of variation were: plant species, dilution level, interaction plant*dilution and error.

Results and discussion

Characteristics of the waste used in the experiment

Table 1: Characteristics of waste from the pig house
Items	mg/litre
DO	0.03
BOD₅	57.5
N-NH⁺₄	36.9
PO₄^3-	50.4

The changes of concentration of dissolved oxygen (DO)

At day 0, the dissolved oxygen (DO) concentration in the Enydra fluctuans treatment showed a significant decline with increasing concentration of pig waste in the media; however, at 30 days DO levels had recovered to those observed at 0 days, with no difference among dilution levels (Figure1). Trends at 0 days were similar for water spinach, but at 30 days levels were higher than at at 0 days, but with a declining trend according to degree of concentration of the pig waste (Figure 2). These results are similar to those reported by Le Van Hoi (2006) that there was an improving environment when water plants were grown in polluted water.


Figure 1: Changes in DO (mg/litre) of Enydra fluctuans at 0 and 30 days according to rate of addition of pig waste	Figure 2: Changes in DO (mg/litre) of water spinach at 0 and 30 days according to rate of addition of pig waste

The changes of concentration of biochemical oxygen demand (BOD)

At 0 days, the BOD₅ value increased according to rate of addition of the pig waste (Figure 3). However, by 30 days, the BOD was close to zero for all levels of pig waste with no differences between the two water plants. These results for BOD after 30 days are acceptable according to the standard of water quality in Vietnam which is < 25 mg/litre.

Figure 3: Changes in BOD value according to rate of addition of pig waste for the two water plants

The changes of concentration of ammonia nitrogen (N-NH₄⁺)

At 0 days, there were expected increases in ammonia concentration according to added amounts of pig waste (Figure 4). By 30 days, the ammonia levels were close to zero for both water plants. This indicates that the water spinach and Enydra fluctuans can use nitrate and ammonia nitrogen for their metabolism. Phytoplankton can also absorb large amounts of ammonia N, and they are considered to be the dominant factor controlling the concentration of ammonia nitrogen in waste water.

Figure 4: Changes in ammonia concentration according to rate of addition of pig waste for the two water plants

The changes of total phosphorus

Phosphorus is introduced in pond water in order to stimulate phytoplankton blooms, enhance the abundance of natural food organisms, and promote greater aquaculture and livestock production (Boyd 1990). The data in Figure 5 show that dissolved phosphorus was being taken up by the water plants (and phytoplankton?) (Claude 1990).

Figure 5: Changes in total phosphorus according to rate of addition of pig waste for the two water plants

Table 2. Ph values

The changes in pH value

At 0 day, the pH of the media showed a linear decrease with increasing concentration of pig waste (Figure 6). By 30 days, the pH had increased at all concentrations of waste for Enydra fluctuans. However, this trend was observed only after 40% addition of waste in the case of water spinach. This result is similar to that observed by Phong (2005) who cultivated Vetiver grass in pig waste. .

Figure 6: Changes in pH value of two water plants

Growth of water plants

There were linear increases in plant height for both water plants at all concentrations of pig waste in the media (Table 3) with higher values for water spinach, compared with Enydra fluctuans , and when the waste concentration was 40% compared with 100% (Figures 7 and 8).

Table 3: Changes in height of the two water plants during the experiment according to concentration of pig waste in the media
Treatment	Days				SE	P
Treatment	0	10	20	30	SE	P
Water spinach
0	50.04^a	75.67^b	68.94^c	121.04^d	1.36	0.001
20	50.20^a	74.53^b	106.78^c	129.34^d	1.63	0.001
40	50.38^a	75.49^b	118.97^c	150.74^d	2.17	0.001
60	50.35^a	84.12^b	136.17^c	160.43^d	1.34	0.001
80	48.44^a	55.63^b	95.81^c	126.10^d	1.18	0.001
100	52.55^a	60.38^b	106.33^c	117.38^d	1.60	0.001
*Enydra fluctuans*
0	50.00^a	36.25^b	79.67^c	81.86^c	2.98	0.001
20	50.00^a	24.95^b	98.95^c	103.45^d	0.41	0.001
40	50.00^a	58.80^b	80.10^c	87.28^d	0.70	0.001
60	50.00^a	50.38^a	78.25^b	83.30^b	2.01	0.001
80	50.00^a	30.30^b	70.94^c	76.39^d	0.56	0.001
100	50.00^a	46.00^a	77.40^b	78.75^b	1.65	0.001
^{a, b, c, d, e, f:}Means within rows with different superscript are different at P<0.05 0, 20, 40, 60, 80, 100= 0, 20, 40, 60, 80, 100% concentration of piggery waste water


Figure 7. Changes in height water plants after 30 days with 40% pig waste mixed with water	Figure 8. Changes in height of water plants after 30 days with 100% concentration of pig waste mixed with water

Trends in root length were similar to those for green biomass (Table 4; Figures 9 and 10

Table 4: Changes in root length of the two water plants during the experiment according to concentration of pig waste in the media
Treatment	Days				SE	P
Treatment	0	10	20	30	SE	P
Water spinach
0	4.22^a	12.57^b	14.03^b	21.53^c	0.58	0.001
20	3.99^a	12.49^b	15.69^c	21.66^d	0.23	0.001
40	4.38^a	10.63^b	14.54^c	18.20^d	0.25	0.001
60	3.82^a	8.87^b	14.24^c	19.48^d	0.36	0.001
80	4.13^a	7.94^b	12.31^c	16.45^d	0.24	0.001
100	4.20^a	8.62^b	11.58^c	18.13^d	0.53	0.001
*Enydra fluctuans*
0	5.55^a	2.50^b	7.88^c	15.19^d	0.27	0.001
20	1.03^a	0.42^a	12.60^b	18.10^b	2.00	0.001
40	4.53^a	1.50^a	10.51^b	13.60^b	0.77	0.001
60	3.23^a	2.73^a	7.68^b	13.75^c	0.53	0.001
80	3.62^ab	2.07^a	6.47^bc	9.18^c	0.87	0.001
100	4.65^a	3.20^b	6.40^c	12.58^d	0.33	0.001
^{a, b, c, d, e, f:} Means within rows with different superscript are different at P<0.05 0, 20, 40, 60, 80, 100= 0, 20, 40, 60, 80, 100% concentration of piggery waste


Figure 9. Changes in length of roots of water plants after 30 days with zero pig waste in the media	Figure 10. Changes in length of roots of water plants after 30 days with 100% pig waste in the media

Accumulation of nutrients

The crude protein and phosphorus in the plants after 30 days increased with concentration of pig waste (Table 5), with a tendency for Enydra fluctuans to reach higher concentrations than water spinach at the higher levels of pig waste (Figures 11 and 12). These findings are similar to those reported by Le Van Hoi (2006), and Phong (2005).

Table 5: Accumulation of crude protein and phosphorus in the green biomass of the two water plants in media with different concentrations of pig waste
	Concentration of pig waste, %
	0	20	40	60	80	100	SE	P
Water spinach (% of DM)
Crude protein	16.86^a	18.57^ab	19.79^b	19.90^b	19.22^b	23.92^c	0.41	0.001
P-PO₄^3-	0.15^a	0.26^ab	0.30^b	0.25^ab	0.33^b	0.34^b	0.02	0.001
*Enydra fluctuans* (% of DM)
Crude protein	19.23^a	19.94^a	20.62^b	25.34^c	24.52^c	25.78^c	0.58	0.001
P-PO₄^3-	0.34^a	0.35^a	0.40^ab	0.38^ab	0.42^b	0.44^b	0.01	0.001
^{a, b, c, d, e, f:}Means within rows with different superscript are different at P<0.05 0, 20, 40, 60, 80, 100= 0, 20, 40, 60, 80, 100% concentration of piggery waste water


Figure 11. Changes in concentration of crude protein of water plants after 30 days with different concentrations of pig waste mixed with water	Figure 12. Changes in concentration of phosphate in water plants after 30 days with different concentrations of pig waste mixed with water

Conclusions

Water spinach and Enydra fluctuans survived well in water enriched with pig waste and increased in nutritive value.
Pollution, measured by BOD and dissolved ammonia and phosphorus, was reduced by growing the two plants in the pig waste.

Acknowledgements

The authors are grateful to the Swedish International Development Agency-Swedish Agency for research Cooperation with Developing countries for supporting this study through the MEKARN regional project.

References

APHA 1985 Standard methods for the Examination of Water and Waste, 16^th edition. American Public Health Association, American Water works Association and Water Pollution Control Federation, Washington, DC

AOAC 1990 Official Methods of Analysis. Association of Official Analytical Chemists. 15^thedition (K Helrick, editor). Arlington. pp 1230.

Boyd C E 1990 Water Quality for Ponds Aquaculture. Birmingham Publising Company, Birmingham, Alabama, 269pp.

Claude, 1999.

Le Van Hoi 2006 A study the change in nitrogen, Phosphorus, BOD, Fe in piggeries waste water which cultivated the vetiver grass (Vetiver Zizanoides L.), Enydrafluctuans.

Nguyen Tuan Phong 2005 Study the change in BOD, nitrogen, Phosphorus of piggeries waste water which cultivated the vetiver grass (Vetiver Zizanoides L.) and the water hyacinth (Eichhornia crassipes).

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Enydra fluctuans and water spinach (Ipomoea aquatica) as agents to reduce pollution in pig waste water

Nguyen Thiet, Nguyen Thi Hong Nhan and T R Preston*

Cantho University, Cantho, Vietnam

* University of Tropical Agriculture Foundation

nthiet@ctu.edu.vn

Abstract

Introduction

Material and methods

Animals and housing

Experiment arrangements

Analytical methods

Statistical analysis.

Results and discussion

Characteristics of the waste used in the experiment

The changes of concentration of ammonia nitrogen (N-NH4+)

The changes of total phosphorus

The changes in pH value

16.86a

18.57ab

19.79b

19.90b

19.22b

23.92c

0.41

0.001

0.15a

0.26ab

0.30b

0.25ab

0.33b

0.34b

0.02

0.001

19.23a

19.94a

20.62b

25.34c

24.52c

25.78c

0.58

0.001

0.34a

0.35a

0.40ab

0.38ab

0.42b

0.44b

0.01

0.001

Conclusions

Acknowledgements

References

The changes of concentration of ammonia nitrogen (N-NH₄⁺)

16.86^a

18.57^ab

19.79^b

19.90^b

19.22^b

23.92^c

0.15^a

0.26^ab

0.30^b

0.25^ab

0.33^b

0.34^b

19.23^a

19.94^a

20.62^b

25.34^c

24.52^c

25.78^c

0.34^a

0.35^a

0.40^ab

0.38^ab

0.42^b

0.44^b