Journal of Engineering Research, Volume 20 No. 1March 2015

An Evaluation of Nutrient Uptake by Water Hyacinth (Eichornia Crassipes) In a Horizontal Surface Flow Domestic Sewage Treatment

PlantA. E. Adeniran

Department of Civil & Environmental Engineering, University of Lagos, Nigeria E-mail: eadeniran@unilag.edu.ng

Abstract

Pollution of water bodies resulting from untreated discharge of sewage is a source of concern; particularly in developing economies. Research efforts in the handling of municipal sewage in developing countries have involved the use of water hyacinth (Eichornia Crassipes) to purify sewage for possible re-use of the effluent water for domestic purposes. In this paper the effect of the growth of water hyacinth on selected sewage quality parameters is therefore examined. Weekly observations of the influent and effluent parameters were carried out for a period of 24 weeks. The water hyacinth plant covered the entire pond area of 370m

2 in 11 weeks. The observed parameters

were progressively reduced to acceptable levels over the observation period. With the water hyacinth based domestic sewage system, the removal efficiencies of colour, turbidity, Biochemical Oxygen Demands, Total Dissolved Solids, Nitrate, Phosphate and E-coli were 100%, 92.95%, 83.98%, 88.98%, 75.98%, 87.06% and 99.65% respectively. It is noted that the energy required to process the sewage through this system is only 13% of the energy required to treat the same amount of sewage through a conventional sewage system; therefore, the use of water hyacinth plant on domestic sewage pond is a viable and cheaper alternative method of domestic sewage treatment.

Keywords: Pollutant remediation, Water hyacinth, domestic sewage, influent and effluent qualities

1.0 Introduction

Water pollution is one of the most serious problems facing many third world countries today. Billions of gallons of wastewater from cities and housing settlements, industries and agriculture are being generated daily, most of which are discharged into fresh water. This has been made worse through a steady population growth without the development of social infrastructure (Ayade, 1998; Adeniran, 2011; Adeniran et al, 2013; Adeniran and Aina, 2015). While the demand for water requirements for agricultural, domestic and industrial uses continue to increase as a result of economic and industrial growth, fresh water resources are becoming more and more unfit for use due to the discharge of untreated sewage and industrial effluent into them.

In the developed countries, greater capital and technological resources have helped to cope with the waste disposal problem effectively, but the situation in developing countries is still inadequate. In view of this, low cost and appropriate options for the treatment of sewage are being investigated. Constructed wetlands (CW), are now widely used as an accepted method of treating wastewater and are cheaper than traditional wastewater treatment plants (Mthembu et al., 2013). CW is appealing to developing nations in the tropics due to the high rate of plant growth (Kivaisi, 2001; Zhang et al., 2014). Wetlands, which are being constructed worldwide, are designed and operated for wastewater treatment at the secondary and tertiary level (Campbell and Ogden, 1999; Gopal, 1999; Kadlec and Knight, 1995; Kadlec, 1995; Al-Hashimi, 2013). Several physical, chemical and biological processes are involved in the transformation and consumption of organic matter and plant nutrients within the wetland (Cooke, 1994; Gale et al., 1993, Al-Hashimi, 2013). The use of vascular aquatic plants has proved to be a cheap means of wastewater management. The suitability of using vascular aquatic plants for wastewater treatment basically emanates from their capacity for nutrient removal from aqueous solutions (Wolverton and McDonald, 1978). Water hyacinth in particular has received much attention because of its hardiness and high productivity, especially when grown in

JER 20(1) 51-60 A. E. Adeniran 52

sewage (Rogers et al., 1972; Aremu et al., 2012). The plant grows luxuriantly in sewage and has an extensive root system that allows it to absorb nutrients directly from the water (Matsui et al., 2013). In Nigeria, the application of water hyacinth for wastewater treatment is gradually gaining ground. Ogunlade (1992) reported its potentials as a mopping agent and scavenger of heavy and toxic elements in industrial and domestic effluents. Akobundu (1987) reported the use of water hyacinth for wastewater treatment by some agencies. The capacity of this plant to purify water rests on its ability to vigorously extract nutrients from its medium. Laboratory analysis has shown that water hyacinth is of a high absorptive capacity (Soerjani, 1984; Ayade, 1998; Adeniran, 2011). The plant’s ability to extract chemical substances such as nitrates, phosphates, and ammonia, silicate, chlorine and sulphur deposited in the aquatic habitat from industrial and domestic effluent is remarkable (Ogunlade, 1992; Aremu et al., 2012). Its vigorous growth and repeated cultivation coupled with its capacity to extract nutrients efficiently from its medium makes it a good macrophyte for the remediation of turbid and polluted waters. The most important functions of the macrophytes in the treatment of wastewater relate to physical effects which they induce therein (Brix, 1997). For example, wetlands involve settling of suspended particulate matter, which is the prime cause for reduction of BOD levels in the treated wastewaters. . The macrophytes provide good conditions for physical filtration and a large surface area for attached microbial growth and activity (Brix, 1997). Over the years, the use of artificially constructed wetlands for wastewater treatment has been increasing considerably (Bhamidimarri et al., 1991; Chescheir et al., 1991; Hammer, 1990; Moshiri, 1993; Reuter et al., 1992; Schwartz and Boyd, 1995; Tripathi and Shukla, 1991). The general practice provides evidence that wetlands remove contaminating nutrients and solids from the wastewater. The major characteristics of water hyacinth, that make them an attractive biological support media for bacteria, are their extensive root system and rapid growth rate (Adeniran, 2011). In the University of Lagos (Unilag) sewage treatment plant, on which this paper is based, water hyacinth plant has been selected in view of its high growth rates. This plant grows rapidly under favourable conditions in a nutrient-rich environment such as domestic sewage. This aim of this paper is to report the research conducted on the Unilag biological sewage plant to evaluate the dynamics of the efficiency of the water hyacinth treatment plant in improving the effluent quality parameters as the spatial growth of the plant increases. The results provide estimates of the area to be covered, and the time to be reached before wastewater can reach the FEPA (1991) acceptable quality levels for discharge into the receiving waters. 2.0 Materials and Method In order to investigate the performance and the efficiency of water hyacinth plant as alternative method of domestic sewage, a water hyacinth based biological treatment plant was designed and constructed at the Service Area of University of Lagos. The pond consists of six beds connected in series. The entire pond covers an area of 367 sq. m. with average depth of 0.675m. The arrangement and number of ponds as well as flow configuration were selected to increase the hydraulic retention time and consequently enhance the performance of the system (Figure 1). Domestic sewage, from the University of Lagos sewer system, at a flow rate of 7.87m3/s (380m3/day) and pre-treated under anaerobic condition in a septic tank was introduced into

JER 20(1) 51-60 A. E. Adeniran 53

the ponds. One week old water hyacinth plants (Eichhornia crassipes) obtained from natural specimens grown in polluted canal at Iwaya, near the University of Lagos, Nigeria were planted on the ponds (Figure 2.0). Initially, a total of 15.6m3 of water hyacinth was planted on the pond i.e. an average of 2.6m2 per bed. The area covered by the water hyacinth on each bed was measured weekly for 24 weeks. The water hyacinth covered the entire area of 367m2 after eleven (11) weeks (Figure 3). Withering plants were regularly removed to ensure the integrity of the results obtained.

Figure 1: Layout Plan of Water Hyacinth Sewage Treatment Pond

Fig. 2: Water hyacinth initially planted on Sewage Beds Fig. 3: Sewage Beds covered by Water hyacinth

The sewage samples were collected and analyzed, at the influent and effluent points, for pH, colour and turbidity, Total Dissolved Solids (TDS), Five-day Biological Oxygen Demand (BOD5), Nitrate, Phosphate, and e-coli. Sample collections and laboratory analyses were carried out in accordance with American Water Works Association (AWWA), Standard Methods for the

JER 20(1) 51-60 A. E. Adeniran 54

Examination of Water and Wastewater (2012) and well as the Nigerian Institute of Standards (NIS), Nigerian Standards for Drinking Water Quality, NIS 554: 2007. 3.0 Results and Discussion 3.1 Results: In this work, samples of the sewage at influent and effluent points (Figure 1) were collected in respectively on a weekly basis for 24 weeks. The average of the three samples was recorded for each point. The samples were analysed in the laboratory and the average of the results obtained are as tabulated in Table 1.0. Also, the growth patterns of the water hyacinth plants on each bed were monitored and measured. The results obtained for the growth pattern of the water hyacinth plants are tabulated in Table 2.

Table 1.0: Water Hyacinth-Based Sewage Influent and Effluent Quality Parameters

Time

(Week)

BOD

Colour

Turbidity

TDS

Nitrate

Phosphate

e-coli

Influent (mg/l)

Effluent (mg/l)

Influent (pcu)

Effluent (pcu)

Influent (mg/l)

Effluent (mg/l)

Influent (mg/l)

Effluent (mg/l)

Influent (mg/l)

Effluent (mg/l)

Influent (mg/l)

Effluent (mg/l)

Influent cfc/100ml

Effluent cfc/100ml

0 509.00 508.00 218.00 195.00 110.00 100.00 610.00 520.00 9.60 9.50 22.30 19.60 1,987.60 1,980.00

1 508.00 208.00 220.00 80.00 90.00 64.20 600.00 250.00 9.60 15.60 22.40 13.80 1,986.60

1,750.00

2 510.00 200.00 215.00 65.00 89.00 52.60 610.00 200.00 9.50 12.80 20.20 10.00 1,989.00

580.00

3 515.00 152.00 210.00 55.00 95.00 40.80 620.00 210.00 9.25 6.80 22.50 9.60 2,419.60

345.00

4 508.00 145.00 210.00 60.00 90.00 35.00 630.00 180.00 10.20 3.40 24.60 9.50 2,419.60

205.00

5 520.00 120.00 200.00 50.00 85.00 35.00 620.00 150.00 9.70 3.20 22.00 8.60 1,986.30

114.00

6 525.00 110.00 210.00 48.00 95.00 35.00 630.00 135.00 9.80 3.00 23.80 8.00 1,920.80

80.00

7 510.00 114.00 215.00 35.00 90.00 32.00 610.00 135.00 9.60 3.84 22.50 8.80 1,985.80

62.00

8 510.00 115.00 220.00 25.00 95.00 30.00 600.00 125.00 9.80 4.60 20.50 6.88 1,915.90

49.00

9 500.00 114.00 200.00 20.00 90.00 26.00 600.00 120.00 9.80 4.80 20.20 6.50 1,987.30

40.00

10 518.00 112.00 210.00 20.00 100.00 25.00 620.00 110.00 13.60 4.20 20.10 6.35 2,118.60

32.00

11 515.00 110.00 220.00 18.00 110.00 24.00 680.00 95.00 13.80 4.30 20.40 5.85 2,119.80

30.00

12 520.00 108.00 200.00 20.00 110.00 25.00 590.00 90.00 12.90 6.00 20.60 5.73 2,120.00

25.00

13 515.00 107.00 200.00 20.00 115.00 23.00 620.00 81.00 13.90 5.80 22.80 5.62 2,123.00

15.00

14 500.00 110.00 180.00 15.00 95.00 21.00 610.00 79.00 13.60 5.60 22.40 6.90 2,419.60

22.00

15 520.00 105.00 200.00 13.00 90.00 18.00 620.00 76.00 13.80 4.80 20.20 7.80 2,419.60

20.00

16 525.00 102.00 210.00 10.00 85.00 15.00 630.00 75.00 12.90 3.90 22.50 10.80 1,986.30

14.00

17 510.00 100.00 215.00 5.00 95.00 14.20 620.00 76.00 12.80 3.60 24.60 7.50 1,920.80

12.00

18 510.00 97.00 220.00 5.00 90.00 12.60 630.00 75.00 10.20 3.70 22.00 6.30 1,985.80

13.00

19 500.00 96.00 200.00 0.00 95.00 12.50 610.00 73.00 9.70 3.40 23.80 5.70 1,915.90

10.00

20 518.00 94.00 210.00 0.00 90.00 12.20 600.00 72.00 9.80 3.20 22.50 3.60 1,987.30

9.60

21 520.00 92.00 220.00 0.00 95.00 10.10 600.00 72.00 9.60 2.30 20.50 2.40 2,118.60

9.60

22 518.00 85.00 200.00 0.00 90.00 7.50 620.00 74.00 9.80 2.35 20.20 2.60 1,987.60

8.00

23 515.00 85.00 210.00 0.00 95.00 7.50 610.00 73.00 9.80 2.35 20.10 2.50 2,118.70 7.00

24 518.00 83.00 215.00 0.00 95.00 6.70 621.00 74.00 9.70 2.33 20.10 2.60 ,989.90 7.00

Table 2.0: Growth of Water Hyacinth in Each Bed of Unilag Domestic Sewage Pond Week Bed1

(m2)

Bed2

(m2)

Bed3

(m2)

Bed4

(m2)

Bed5

(m2)

Bed6

(m2)

Total Area

(m2)

0 2.60 2.60 2.60 2.60 2.60 2.60 15.60

1 3.42 3.47 4.58 5.07 5.42 6.17 28.13

2 5.23 5.61 7.05 7.48 7.77 8.06 41.20

3 6.62 7.51 8.32 9.51 9.76 10.09 51.81

4 11.21 11.84 12.70 13.01 14.69 16.25 79.70

5 14.54 16.33 19.35 20.55 21.47 23.98 116.22

JER 20(1) 51-60 A. E. Adeniran 55

6 17.66 19.03 24.41 29.50 31.90 32.94 155.44

7 28.70 28.80 34.56 39.60 43.20 53.50 228.36

8 31.54 32.83 43.78 52.34 55.94 57.60 274.03

9 47.02 52.28 56.88 61.20 61.20 61.20 339.78

10 57.66 58.92 59.00 61.20 61.20 61.20 359.18

11 61.20 61.20 61.20 61.20 61.20 61.20 367.20

12 61.20 61.20 61.20 61.20 61.20 61.20 367.20

13 61.20 61.20 61.20 61.20 61.20 61.20 367.20

14 61.20 61.20 61.20 61.20 61.20 61.20 367.20

15 61.20 61.20 61.20 61.20 61.20 61.20 367.20

16 61.20 61.20 61.20 61.20 61.20 61.20 367.20

17 61.20 61.20 61.20 61.20 61.20 61.20 367.20

18 61.20 61.20 61.20 61.20 61.20 61.20 367.20

19 61.20 61.20 61.20 61.20 61.20 61.20 367.20

20 61.20 61.20 61.20 61.20 61.20 61.20 367.20

21 61.20 61.20 61.20 61.20 61.20 61.20 367.20

22 61.20 61.20 61.20 61.20 61.20 61.20 367.20

23 61.20 61.20 61.20 61.20 61.20 61.20 367.20

24 61.20 61.20 61.20 61.20 61.20 61.20 367.20

. 3.2 Discussion 3.2.1 Water Hyacinth Growth Profile: The growth profile of the water hyacinth on the sewage ponds is plotted against time. It is observed that the growth profile follows an exponential profile. The plant grew slowly in the first few weeks and then grew exponentially until the 11th week when the whole pond was covered with the plant. It was observed that the growth pattern increased from Bed 1 to Bed 6 just as the quality of the sewage improved as shown in Figure 4. To prevent nitrification that may result from overcrowding, the water hyacinth plants were weeded regularly with particular attention to the withering ones. Figure 4: Growth Profile for each of Six Beds Figure 5: Influent and Effluent Colour Level

3.2.2 Colour: Figure 5 compares the weekly levels of influent and effluent colour from week 0 to week 24. It was observed that the colour of the effluent improved progressively and significantly during the observation period. The effluent colour improved from initial level of 195pcu to 80pcu in week 1 and finally to 0pcu from week 19 to week 24. Also, the analysis of

Influent Colour

Effluent Colour

JER 20(1) 51-60 A. E. Adeniran 56

the percentage removal of colour is presented in Figure 12. It was observed that the water hyacinth-based sewage treatment plant was able to achieve 100% removal level for colour. 3.2.3 Turbidity: Figure 6 compares the weekly levels of influent and effluent Turbidity from week 0 to week 24. It was observed that turbidity of the effluent improved progressively and significantly during the observation period. The effluent turbidity improved from initial level of 100HTU to 64.2HTU in week 1 and finally to 6.7 HTU at week 24. Also, analysis of the percentage removal of turbidity is presented in Figure 12. It was observed that the water hyacinth-based sewage treatment plant was able to achieve 92.93% removal level for turbidity at the end of the 24 weeks observation. Figure 6: Influent and Effluent Turbidity Figure 7: Influent and Effluent TDS

3.2.4 Total Dissolved Solids (TDS): Influent and effluent samples collected were analyzed for the TDS on a weekly basis. The influent TDS levels ranged from 590mg/l to 630mg/l, whereas the effluent levels ranged from 520 mg/l to 74mg/l. Figure 7 compares the influent TDS with the effluent TDS. It is observed that the TDS of the effluent improved progressively to 74mg/l at the end of the 24th week. It is observed from Figure 12 that the removal efficiency of the water hyacinth based domestic sewage treatment plant increased from 14.75% in the 1st week to 88.08% in the 24th week. 3.2.5 5-day Biochemical Oxygen Demands (BOD5): The sewage influent and effluent samples were collected and analyzed under laboratory condition for 5-day BOD at 20oC. The influent-effluent comparison chart for BOD5 is presented in Figure 8. Also the percentage removal of BOD5 over the observation period is presented in Figure 12. The influent values of BOD ranged from 500mg/l to 525mg/l and the effluent levels ranged from 508mg/l to 83.0mg/l, giving the percent removal in the range of 0.2% to 83.98%.

Effluent Turbidity

Influent Turbidity

Effluent TDS

Influent TDS

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Figure 8: Influent and Effluent BOD Figure 9: Influent and Effluent Nitrate Figure 10: Influent and Effluent Phosphate Figure 11: Influent and Effluent E-coli

3.2.6 Removal of Nitrate-nitrogen ions: The nitrates levels of the influent and effluent to and from the domestic sewage water hyacinth treatment plant were obtained and analyzed throughout the study period. The influent concentrations of nitrate into the treatment plant ranged from 9.6mg/l to 13.8 mg/l, whereas the effluent ranged from 15.6mg/l to 2.33 mg/l (Figure 9). The removal of nitrate improved from 1.04 % in the 1st week to 75.98% in the 24th week as shown in Figure 12. It was observed that the effluent nitrate levels for the 1st and 2nd weeks were higher than the influent nitrate levels. As the water hyacinth plants continued to increase in area of coverage, the effluent nitrate levels continued to drop. Nitrate is one of the nutrients required for the growth of the water hyacinth plant. 3.2.7 Removal of Phosphate: The influent concentrations of phosphate into the treatment plant ranged from 24.6mg/l to 20.1mg/l, whereas the effluent phosphate progressively reduced from 20.6mg/l to 2.4mg/l (Figure 10). The percentage removal of nitrate improved from 7.62% after the 1st week to 87.06% after the 24th week (Figure 12). 3.2.8 E-coli: Samples for E-coli were collected from the influent and the effluent points. The influent E-coli levels ranged from 1915 to 2420 cfu/100ml, whereas the effluent levels ranged

Influent BOD

Effluent BOD

Influent Nitrate

Effluent Nitrate

Influent E-coil

Effluent E-coil

Effluent Phosphate

Influent Phosphate

Time (Week)

Ph

osp

hat

e (m

g/l)

JER 20(1) 51-60 A. E. Adeniran 58

from 7 to 1980 cfu/100 ml. The comparison of Influent-Effluent E-coli levels as determined for each week is shown in Figure 11. The percent removal is shown in Figure 12. It should be noted that the ability of the water hyacinth based domestic sewage plant to drastically reduce the e-coli from sewage makes its effluent adaptable for other low cost water reuse options. 3.2.9 Overall Efficiency of the Water Hyacinth Sewage Treatment Plant: The efficiency of the water hyacinth based domestic sewage water treatment plant system is determined, in this study, in terms of the improvement to the sewage quality parameters of the effluent compared with the influent. The percentage of removal for each of the parameters monitored weekly during the 24-week period of this study is shown in Figure 12.

Figure 7: Influent and Effluent TDS

Figure 12: Removal Efficiency of Water Hyacinth Sewage Treatment Plant

At the end of the study period, the removal efficiency of colour, turbidity, BOD, TDS, Nitrate, Phosphate and E-coli were 100%, 92.95%, 83.98%, 88.98%, 75.98%, 87.06% and 99.65% respectively. This showed that the water hyacinth based domestic sewage water treatment plant is efficient in improving the sewage quality parameters. The levels of all the observed parameters meet with FEPA (1991) standards for the discharge of sewage effluents into water streams.

Table 3: Effluent Results compared with the Nigerian Effluent limitation Guidelines (FEPA, 1991)

Parameter Units Effluent Observed

Limit for discharge to surface water

Remarks

TDS mg/l 74.0 2000 Below Limit

Turbidity HTU 6.7 Not stated Ok

Colour PCU 0.0 7(Lovibond unit) Below Limit

Iron(Fe) Mg/l 0.28 10 Below Limit

Phosphate Mg/l 2.6 500 Below Limit

Nitrate Mg/l 2.0 10 Below Limit

e-coli MPN/100ml 7 400MPN/100ml Below Limit

BOD Mg/l 83.0 30 Below Limit

4.0 Conclusion The following specific conclusion may be drawn from the study:

JER 20(1) 51-60 A. E. Adeniran 59

It was found that the percent removal of different parameters investigated in the study increased over time and sewage effluent improved progressively.

The percent removal for parameters observed ranged from 76% to 100% confirming the efficacy of the water hyacinth based sewage treatment plant as a reliable sewage treatment option.

The effluent water from the sewage plant is of quality that may be processed further for drinking or for agricultural use.

Acknowledgement The author is grateful to the Management of the University of Lagos, Nigeria for making available the funds and facilities used for this study as part of the innovations in the services of the Department of Works & Physical Planning of the University. The contributions of Mr. P. S. Ayodeji, Mrs. Tinuke Aina and Mr. Afolabi Apara in performing laboratory and field tests are hereby acknowledged. References Adeniran A. E. (2011). Alternative Sewage Treatment Option: The Effect of use of Water Hyacinth (Eichornia

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