water hyacinth (eichhornia crassipes) - TJournal

Transnational Journal of Science and Technology

August 2012 edition vol. 2, No.7

WATER HYACINTH (EICHHORNIA CRASSIPES) CULTURE IN SEWAGE: NUTRIENT REMOVAL AND POTENTIAL APPLICATIONS OF BYE-PRODUCTS

A. S. Aremu Department of Civil Engineering, University of Ilorin, Ilorin, Kwara State, Nigeria

S. O. Ojoawo Department of Civil Engineering, Ladoke Akintola University of Technology, Ogbomoso, Nigeria

G. A. Alade Department of Civil Engineering, University of Ibadan, Ibadan, Nigeria

Abstract: The nutrient removal by water hyacinth culture in sewage and potential applications of the generated bye-products was investigated. After a 28-day experimental period, the water hyacinth cultured sewage had reduced 8.9% of BOD5, 9.2% of COD, 45.5% of nitrate, 37.8% of phosphorous and 7.5% of faecal coliform. The pH value also dropped from 8.6 to 7.8 while the initial pungent odour of the raw sewage was no more noticeable. However colour grade and turbidity increased by 34.6% and 27.4% respectively. The final effluent was found to be suitable for non-drinking purposes like crop irrigation and keeping aquatic animals. In the course of nutrient removal, harvested water hyacinth plants and sludge which settled at the bottom of the plastic pool were generated as byeproducts. Based on the properties of these bye-products, they can find useful applications in agriculture, construction, and energy generation.

Key Words: Sewage, water hyacinth, nutrient removal, bye-products, sludge

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Introduction Raw wastewater may contain pollutants such as oxygen-depleting substances, suspended solids, nutrients, toxic chemicals and pathogens (Mihelcic and Zimmerman, 2010), that must be given suitable treatment before it is released to the environment. Over the years, several wastewater treatment technologies have been designed and operated at full scale while some more recent ones are on experimental scale. These technologies are classified as physical, aquatic, or terrestrial systems (UNEP-IETC, 1998). Recent studies have confirmed that in aquatic wastewater treatment systems, aquatic weeds are low-cost powerful bioagents which purify wastewater lying under them by physical, chemical and biological actions (Abbasi and Abbasi, 2010). Among these aquatic weeds, water hyacinth (Eichhornia Crassipes) has received great attention because of its obstinacy and high productivity especially when grown in domestic sewage lagoons (McDonald and Wolverton, 1980). Water hyacinth is also known to have a promising potential for the removal of toxic metals and other pollutants from aquatic environments (Mahamadi and Nharingo, 2010), though the purification of sewage by water hyacinth has not yet been generally embraced in some parts of the world (Alade and Ojoawo, 2009). Meanwhile in other parts, majorly developed countries, water hyacinth has been used to remove nutrients or pollutants from wastewaters (Boyd, 1970; Scarbrook and Davies, 1971; Wolverton and McDonald, 1978; Rai et al., 1994; Yedla et al., 2002; Xia, 2008; Abbasi and Abbasi, 2010). A simple progression diagram of the treatment process by water hyacinth culture in wastewater and bye-products derivation is shown in Figure 1. The process involves growing water hyacinth in wastewater in order to provide an avenue which enhances wastewater treatment. As shown in the figure, the main objective of growing water hyacinth in wastewater is to optimize contaminant recovery from wastewater and produce an effluent which is suitable for further treatment, reuse or discharge to a receiving water body. Once in wastewater, water hyacinth proliferates rapidly gaining up to 0.38 shoot/day in 28 days (Kutty et al., 2009). This high growth rate necessitates frequent harvesting of the plant tissues so as to enhance nutrient removal mechanisms and prevent the return of pollutants to the wastewater by desorption from live plants and decomposition of dead plant tissues (Abbasi and Abbasi, 2010). As a design criterion, water hyacinth biomass must be harvested periodically to keep the population between 80 and 120 tons /hectare/day so as to efficiently reduce nutrient concentrations at retention times less than 10 days (Hermosillo and Sarquis, 1990). Also, in the course of wastewater treatment, sludge is a bye-product which was produced as a result of digestion and assimilation of contaminants. It consists of inorganic substances and micro104



organisms which settle out at the bottom of the pond. The properties of sludge vary with the type of wastewater and type of treatment given to that wastewater (Metcalf and Eddy, 2003). However, because of the generalized inherent properties of sludge, immediate processing for economic use or safe disposal is required. From previous studies, the bye-products of a water hyacinth culture in sewage are not usually investigated with nutrient uptake. This study aims to investigate nutrient uptake with analyses of the bye-products associated with water hyacinth culture in sewage. When the potentials of these bye-products are investigated, they could be exploited for economic use, thereby prompting means of resource and cost recovery from aquacultural wastewater treatment facilities. Materials and Methods The culture medium which is raw sewage was obtained from a cesspool serving residential buildings for students at the University of Ibadan, Nigeria. Specimens were filled by funnel into 25 litre kegs and corked immediately to prevent them from turning septic before the commencement of the experiment. Water hyacinth plants of the same age group were collected from a water hyacinth stand at the same University. The plants were about 3-4 weeks old and below the flowering stage. Plastic bowls of 1.5 m diameter and 70 litre capacity were graduated as container for the water hyacinth plants and raw sewage. The pilot plant of the water hyacinth treatment facility was set up in a greenhouse. One of the calibrated plastic bowls was filled with raw sewage up to 65 litre capacity and carefully stocked with water hyacinth plants, covering the total surface area of the bowl. The plants were kept in active growing phase by clipping dead plant tissues and removing them from the culture every week. Another calibrated plastic bowl which served as the control, was also filled with raw sewage up to 65 litre capacity and was not stocked with water hyacinth plants. Grab samples were taken from the culture medium in 2-litre transparent plastic containers at the initial experimental set up time, and at 7, 14, 21 and 28 days after the initial grab sample was taken. The change in the volume of the culture medium was measured at each instant prior to taking of grab samples. The parameters monitored for each grab sample were colour, turbidity, odour, pH value, nitrate, phosphorous (measured as phosphate), heavy metals, Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), and faecal coliforms. Each grab sample was tested in triplicate using the standard methods described by APHA (1998). After the final grab sample was taken from the culture medium, all the water hyacinth plants were harvested and the water column between the plastic surface and the accumulated sediments was 105



removed. The water hyacinth plants were taken to the laboratory for analyses immediately after harvesting while the organic particles and detritus plant material that settled at the bottom of the plastic pools (sludge) were partially de-watered and sun-dried for two weeks for complete removal of moisture. The de-watered sludge was ashed at 700oC for six hours in a furnace to remove organic matter. The resulting sludge ash was analyzed according to the prescribed official methods for analysis described by the Association of Official Agricultural Chemists (A.O.A.C, 1984). Results and Discussion Heavy metals which could affect the performance of water hyacinth plants during the treatment process were not detected from the raw sewage. The treatment performance of water hyacinth culture and control experiment at 0, 7, 14, 21 and 28 days retention periods are shown in Table 1 and 2 respectively. As the retention time increased, there was generally a continuous decrease in values of BOD5, COD, coliform count, colour, turbidity and odour, and an increase in values of nitrate (NO3-) and phosphate (PO43-) in both systems. Nevertheless, the water hyacinth culture recorded lower amounts of these parameters. A comparison of the results in Table 1 and 2 showed that the water hyacinth culture after 28 days had reduced the amount of BOD5 by 8.9%; COD, 9.2%; nitrate 45.5%; phosphate 37.8% and faecal coliform, 7.5%. The pH value also dropped from 8.6 to 7.8 while the initial pungent odour of the raw sewage was no more noticeable. On the other hand, colour grade and turbidity increased by 34.6% and 27.4% respectively. The quality of the effluent from the water hyacinth culture after 28 days showed that it is suitable for non-drinking purposes like crop irrigation and fishing when compared with WHO stream standard (WHO, 2004a and 2004b). Also, because aquatic animals require a substantial level of phosphorous in their ratio, the phosphate content of the final effluent (63.3%) is an indication of its suitability for rearing aquatic animals. A high evapo-transpiration rate was observed in the water hyacinth cultured sewage (decrease of 1.5% liquid content). It is believed that the transpired water vapor could be condensed, collected, and reused. An analysis of the harvested water hyacinth plants showed that the samples had average moisture and dry matter content of 93% and 7% respectively. The chemical composition of water hyacinth expressed on dry matter basis is presented in Table 3. It indicated that the plant had a low mineral content and contained a high amount of nitrogen (1.6%) and sulphur (0.8%). The minerals present in dry matter as presented in Table 4 are crude protein (10.1%), crude fibre (18.1%) and ash content (19.3%). In terms of general utility, the harvested water hyacinth plants could be used directly or after processing, as soil additives, mulch, fertilizer, green manure, pulp and fiber for 106



paper making, animal feed, human food, organic malts for biogas production, and for composting (Polprasert, 1989). Low cost input in the culture technology for raising substantial amounts of fish is another way to make use of the harvested water hyacinth (Mishra et al., 1988). However, the excessive moisture content, low mineral content, mineral imbalance and possibility of contamination (due to contact with human or animal waste and other contaminants), limits its suitability for edible purposes. Also, water hyacinth could provide double functions in a paper factory as an absorbent of pollutants and a supplement for paper pulp material (Widyanto et al., 1983). The prospect of using water hyacinth as substrate for biogas production is auspicious. The analyzed water hyacinth contained appreciable amounts of crude protein (10.1%) as presented in Table 4, which is source of nitrogen for biogas production. One kilogram of fresh plant produces 370 litres of gas, 69% of which is methane (Parsons and Cuthbertson, 2001). This gas could be used for meeting energy demands such as heating, cooking, lighting and electricity production (Gunnarsson and Petersen, 2007). The raw sludge which settled at the bottom of the plastic pool was essentially composed of organic particles and detritus plant materials. It was brownish in colour and had inoffensive odor. Sewage sludge when applied to soils provides a source of plant nutrients and is an effective soil amendment, though its effectiveness depends on its composition, characteristics of the soil and plant species to be grown (Polprasert, 1989). The chemical properties of the sludge ash collected after the burning process are presented in Table 5. Sludge ash contained small amounts of inorganic substances per kilogram, the highest being calcium with 10.0g/kg. Considering the nature of sludge ash, it could partly replace the constituents of concrete (Tay and Show, 1991; Aremu and Ige, 2004), because it does not contain substances which are known to adversely affect the strength and properties of cement. It was found that replacement of cement with 5.0% - 20.0% of sludge ash would have a marginal effect on the short-term compressive strength of hardened concrete (Aremu and Ige, 2004). Furthermore, the properties of sludge ash can also be improved with additives, or processing to produce bricks (Tay, 1987), or cement clinker (Lam et al., 2010). In view of the chemical composition of decayed tissues of harvested water hyacinths and wastewater sludge, both could provide major plant nutrients such as nitrogen, potassium, phosphorus and micro-plant nutrients such as copper, iron, and zinc, and organic matter for improving the soil structure. Sludge ash is exceptionally rich in calcium while water hyacinth ash which is 19.3% of dry matter has commercial value as base for fertilizers. Some soil properties could be improved by mulching the soil with hyacinth and sludge. A blend of water hyacinth and sludge could also achieve 107



higher biogasification and methane yield as much as 0.5m3 kg-1 of added volatile solids (Biljetina et al., 1987). Conclusion This study confirmed the ability of water hyacinth to remove pollutants from wastewater. The final effluent after the 28-day experiment complied with standards for non-drinking purposes like crop irrigation and fishing but did not meet WHO’s standard for potable water supply. The byeproducts of wastewater treatment; harvested water hyacinth plants and sludge, could find applications in agriculture, as raw materials, replacement for construction materials and as energy sources. However, fluctuations in the chemical composition of water hyacinth and sludge under different conditions make it difficult to predict a general usefulness as animal feed, energy generator, compost or bio-fertilizer. To eliminate the risks of mineral imbalance and contamination (due to contact with human fecal matter and other impurities), it is suggested that the bye-products should be used for non-edible purposes, or processed before use. Optimum benefit could be achieved from these bye-products if used in situ on a small scale with minimum processing.

References:

Abbasi, S. A. and T. Abbasi, 2010. Factors which facilitate wastewater treatment by aquatic weedsthe mechanism of the weeds’ purifying action. Inter. J. Environ. Studies, 67: 349-371. Alade, G. A. and S. O. Ojoawo, 2009. Purification of domestic sewage by water-hyacinth (Eichhornia crassipes). Int. J. Environ. Technol. and Manage., 10: 286-294. American Public Health Association (APHA), 1998. Standard Methods for the Examination of Water and Wastewater, 14th Ed. American Public Health Association, New York, U.S.A. A.O.A.C, 1984. Official Methods of Analysis. Association of Official Agricultural Chemists. Washington, U.S.A. Aremu, A. S. and O. A. Ige, 2004. Effects of sludge ash on short-term compressive strength of hardened concrete. J. Research Inform. Civil Eng., 1: 11-20. Biljetina, R., V. J. Srivastava, D. P. Chynoweth and T.D. Hayes, 1987. Anaerobic digestion of water hyacinth and sludge. In Aquatic plants for Water Treatment and Resource Recovery, Ed K.R. Reddy and W. H. Smith, Magnolia Publishing, Orlando, Florida, U.S.A. Boyd, C., 1970. Vascular aquatic plants for mineral nutrient removal from polluted waters. Fran. 108



Rat., 74: 95-103. Gunnarsson, C. C. and C. M. Petersen, 2007. Water hyacinths as a resource in agriculture and energy production: A literature review. Waste Manage., 27: 117-129. Hermosillo, O. M. and S. Sarquis, 1990. Design considerations for waste water treatment with water hyacinth E. Crassipes. Environ. Technol., 11: 669-674. Kutty, S. R. M., S. N. I. Ngatenah, M. H. Isa and A. Malakahmad, 2009. Nutrients removal from municipal wastewater treatment plant effluent using Eichhornia Crassipes. World Aca. of Sci., Eng. and Technol., 60:1115-1123. Lam, H. K., J. P. Barford and G. McKay, 2010. Utilization of incineration waste ash residues as portland cement clinker. Chemical Eng. Trans., 21: 757-762. Mahamadi, C. and T. Nharingo, 2010. Utilization of water hyacinth weed (Eichhornia Crassipes) for the removal of Pb (II), Cd(II) and Zn (II) from aquatic environments: an adsorption isotherm study. Environ. Technol., 31: 1221-1228. McDonald, R. C. and B. C. Wolverton, 1980. Comparative study of wastewater lagoon with and without water hyacinth. Econ. Botany, 34:101-110. Metcalf and Eddy, 2003.Wastewater Engineering Treatment and Reuse, 4th Edition. McGraw- Hill, New York, U.S.A. Mihelcic, J. R. and J. B. Zimmerman, 2010. Environmental Engineering: Fundamentals, Sustainability, Design. John Wiley and Sons, Inc., New York, U.S.A. Mishra, B. K., A. K. Sahu, and Pani, K. C., 1988. Recycling of the aquatic weed, water hyacinth, and animal wastes in the rearing of Indian major carps. Aquaculture, 68: 59-64. Parsons, W. T. and E. G. Cuthbertson, 2001.Noxious Weeds of Australia, 2nd Edition. CSIRO Publishing, Australia. Polprasert, C., 1989. Organic Waste Recycling. John Wiley and Sons Ltd, Chichester, England. Rai, S., M. S. Narayanswami, S. H. Hasan, D. C. Rupainwr and Y. C. Sharma, 1994. Removal of cadmium from wastewater by water hyacinth. Int. J. Environ. Studies, 46: 251-262. Scarsbrook, E. and D. E. Davies, 1971. Effect of sewage effluent on growth of five vascular aquatic species. Hyacinth Control J., 9: 26-30. Tay, J.H. and K.Y Show, 1991.Clay-blended sludge as light weight aggregate concrete materials. J.Env. Eng. Div., ASCE, 117: 834-844. Tay, J.H., 1987. Bricks manufactured from sludge. J. Env. Eng. Div., ASCE, 113: 278-283. UNEP-IETC, 1998. Sourcebook of Alternative Technologies for Freshwater Augmentation in Latin 109



America and the Caribbean. IETC Technical Publication Series 8d. http://www.unep.or.jp/ietc/Publications/techpublications/TechPub-8c/index.asp. Widyanto, L. S., A. Sopannata, and U. S. Friend, 1983. Water hyacinth as a potential plant in a paper factory. J. Aquatic Plant Manage., 21: 32–35. Wolverton, B. C. and R. C. Mcdonald, 1978. Water Hyacinth Sorption Rates of Lead, Mercury and Cadmium. ERL Report No 170, 73-88. World Health Organization (WHO), 2004a. Health Guidelines for the Use of Wastewater in Agriculture and Aquaculture, WHO Technical Report Series No. 778. World Health Organization, Geneva, Switzerland. World Health Organization (WHO), 2004b. International Standards for Drinking Water. World Health Organization, Geneva, Switzerland. Xia, H., 2008. Enhanced disappearance of Dicofol by water hyacinth in water. Environ.Technol., 29: 297-302. Yedla, S., A. Mitra and M. Bandyopadhyay, 2002. Purification of pulp and paper mill effluent using Eichornia Crassipes. Environ. Technol., 23: 453-465.

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Harvested plant biomass

Water hyacinth

Wastewater

Treated effluent

culture

Sludge Fig. 1: Progression diagram showing the treatment process by water hyacinth culture and bye-products.

Table 1: Laboratory results of grab samples taken from water hyacinth cultured sewage Treatmen t duration

3-

3-

Sampl e

BOD5 (mg/l )

COD (mg/l)

Colifor m count (CFU/m 3 l x10 )

NO (ppm )

PO4 (ppm )

pH valu e

Colour (PHCoAPH A)

Turbidit y (NTU)

Odour

Volum e of sewag e (Litres)

0

A

900.0

1424. 0

40.0

1.1

40.0

8.6

130.0

48.5

High faecal odour

65.0

7

B

716.0

1153. 0

27.0

1.5

49.4

8.3

111.0

43.4

Light

62.2

(days)

faecal odour

14

C

593.0

985.0

19.0

1.7

55.7

8.1

100.0

40.2

Odourles s

59.7

21

D

480.0

785.0

9.0

1.9

63.2

7.9

87.0

36.2

Odourles s

57.5

28

E

460.0

766.0

8.0

2.0

65.4

7.8

85.0

35.9

Odourles s

55.5

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Table 2: Laboratory results of grab samples taken from control experiment Treatmen t duration

3-

3-

Sampl e

BOD5 (mg/l )

COD (mg/l)

Colifor m count (CFU/m 3 l x10 )

NO (ppm )

PO4 (ppm )

pH valu e

Colour (PHCoAPH A)

Turbidit y (NTU)

Odour

Volum e of sewag e (Litres)

0

A

900.0

1424. 0

40.0

1.1

40.0

8.6

130.0

48.5

High faecal odour

65.0

7

B

810.0

1292. 0

32.6

1.5

50.1

8.4

108.0

42.1

Light faecal odour

62.9

14

C

720.0

1160. 0

26.0

1.8

60.3

8.2

85.0

35.6

Light faecal odour

60.8

21

D

630.0

1029. 0

18.2

2.1

70.4

8.0

63.0

29.1

Odourles s

58.7

28

E

540.0

897.0

11.0

2.5

80.5

7.8

40.0

22.6

Odourles s

56.5

(days)

112



Table 3: Chemical properties of harvested water hyacinth plants Macronutrient content Element

Composition (% dry matter)

Calcium

0.2

Nitrogen

1.6

Sulphur

0.8

Magnesium

0.2

Phosphorous

0.1

Sodium

0.03

Potassium

0.04 Micronutrient content

Element

Composition (parts per million of dry matter)

Iron

20.0

Copper

24.0

Managanese Zinc

18.0 20.0

Table 4: Mineral contents of harvested water hyacinth plants Mineral Composition (% dry matter) Crude protein 10.1 Crude fibre 18.1 Ash content 19.3

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Table 5: Chemical properties of sludge ash Element Composition (g/kg) Lead 0.1 Nickel 0.3 Manganese 0.4 Zinc 0.4 Iron 0.4 Copper 0.4 Potassium 0.6 Silicon 0.6 Sodium 0.7 Aluminium 0.8 Magnesium 0.8 Sulphur 1.3 Calcium 10.0

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