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International Journal of Phytoremediation Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/bijp20
Phytoremediation Potential of Selected Plants for Nitrate and Phosphorus from Ground Water a
T. Sundaralingam & N. Gnanavelrajah
a
a
Department of Agricultural Chemistry, Faculty of Agriculture , University of Jaffna , Sri Lanka Accepted author version posted online: 12 Sep 2013.Published online: 27 Sep 2013.
To cite this article: T. Sundaralingam & N. Gnanavelrajah (2014) Phytoremediation Potential of Selected Plants for Nitrate and Phosphorus from Ground Water, International Journal of Phytoremediation, 16:3, 275-284, DOI: 10.1080/15226514.2013.773279 To link to this article: http://dx.doi.org/10.1080/15226514.2013.773279
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International Journal of Phytoremediation, 16:275–284, 2014 C Taylor & Francis Group, LLC Copyright ISSN: 1522-6514 print / 1549-7879 online DOI: 10.1080/15226514.2013.773279
PHYTOREMEDIATION POTENTIAL OF SELECTED PLANTS FOR NITRATE AND PHOSPHORUS FROM GROUND WATER
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T. Sundaralingam and N. Gnanavelrajah Department of Agricultural Chemistry, Faculty of Agriculture, University of Jaffna, Sri Lanka The phytoremediation potential of three aquatic plants namely, water lettuce (Pistia stratioes), water hyacinth (Eichhornia crassipes), and water spinach (Ipomoea aquatica) for nitrate N and phosphorus from nutrient treated ground water was assessed. A total of twelve treatment combinations including four levels of nitrate (expressed as nitrate N 0, 20, 40, and 60 mg/l) and three levels of phosphorus (0, 20, and 40 mg/l) were treated for the total volume of 1 and 20 liters of water respectively, for Pistia stratiotes and Eichhornia crassipes. For Ipomoea aquatica ten treatment combinations with five levels of nitrate N (0, 10, 20, 40, and 50 mg/l) and two levels of phosphorus (0 and 5 mg/l) were treated to 3 liters of water. The design used was a two factor factorial with three replicates. Water was analyzed at weekly interval for nitrate N and phosphorus. Pistia stratiotes, Eichhornia crassipes and Ipomoea aquatica had the potential to remove nitrate N between 61.5–91.8%, 40–63.5%, and 29.3–75% during the period of six, three and three and weeks, respectively. In addition, 90–99%, 75–97.2%, and 75–83.3% of phosphorus was removed from water by Pistia stratiotes, Eichhornia crassipes and Ipomoea aquatica respectively, during the same period. KEY WORDS: Pistia stratioes, Eichhornia crassipes, Ipomoea aquatica, nitrate pollution, ground water
INTRODUCTION Ground water is a precious scarce natural resource used for drinking and other domestic purposes, irrigation and industrial uses in different parts of the world. It has been reported that if the drinking water contains more than 10 ppm nitrate-nitrogen (45 ppm nitrate), it could affect the health of infants, giving rise to “blue babies” (WHO 1984; L’hirondel et al. 2006). Nitrate is relatively non toxic, but its metabolites and reaction products such as nitrite, nitric oxide, and N-Nitroso compounds, have raised concern. Excessive nitrite may cause a life-threatening hemoglobin malfunction in infants, and may be converted to carcinogenic nitrosaminos during digestion, posing a possible cancer risk for all ages (Vogtmann and Biederman 1985). On the other hand the nutrient loading such as nitrogen and phosphorus lead to the pollution problem called “Eutrophication”, a
Address correspondence to T. Sundaralingam, Department of Agricultural Chemistry, Faculty of Agriculture, University of Jaffna, Sri Lanka. E-mail: [email protected] 275
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process whereby water bodies receive excess inorganic nutrients, especially nitrogen and phosphorus, which stimulate excessive growth of plants and algae. Nitrate pollution of ground water due to heavy doses of fertilizers and manures has been reported in many countries. The population in the Jaffna peninsula, Sri Lanka has always been depended on the water stored in the underground Miocene limestone and sand aquifers for its drinking water and water for irrigation of agricultural lands. The nitrate pollution of ground water has been reported by many workers from long past (Mageswaran and Mahalingam 1983; Nagarajah et al. 1988; Jeyaruba and Mikunthan 2008). Though nitrate pollution of ground water has been reported more than two and a half decade back, scanty of research has been done to remedy such problem in this region. Nitrate removal from drinking water is a challenging problem which demands high cost technology such as ion exchange technology etc. On the other hand phosphorus removal from waste water also is another issue to be studied. As these two elements are essential plant nutrients, phytoremediation could be adopted to solve these problems. This plant-based remediation technology has the potential to be low-cost, low-impact, visually benign, and environmentally sound (Cunningham and Ow 1996). The primary motivation behind the development of phytoremediation technologies is the potential for low-cost remediation (Ensley 2000). Moreover, these treated plants could be used as nutrient source for crops, animals or as vegetables for human depending on the species. Water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes) have been studied for their phytoremediation potential for various water quality parameters such as biological and chemical demand (Zimmels, Kirzhner, and Malkovskaja 2006, 2008; Alade and Ojoawo 2009) and nutrient loads of nitrogen and phosphorus (Ho and Wai-kin Wong 1994; Jianobo, Zhihui, and Zhaozheng 2008; Akinbile and Yusoff Mohd 2012) and found to be effective in improving waste water quality. Similarly water spinach (Ipomoea aquatica) was also reported to have phytoremediation potential of nutrients from waste water (Hu et al. 2008). All the previous studies have been conducted in waste water where there is possibility of ample of both macro and micro nutrients. In the present study potential of selected aquatic plants to phytoremediate ground water is studied. The ground water studied is highly hard water (hardness - 375 mg/L) due to the calcium content derived from limestone aquifer. The potential of such plants in hard water or drinking water has not been studied. Moreover, water spinach is a popular vegetable and the plants used for phytoremediation treatment could be used as vegetables provided these plants have nitrate content below the recommended level. However, there is scanty of information regarding the nitrate content of plant tissues after remediation treatment. This information is especially important to recommend for human consumption of such plants after remediation. On this background experiments were conducted in the Department of Agriculture Chemistry, Faculty of Agriculture, University of Jaffna, Sri Lanka to assess the phytoremediation potential of three aquatic plants namely, water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes) and water spinach (Ipomoea aquatica) on removal of nitrate and phosphorus from nutrient treated ground water. The specific objectives of the study were: (1) To assess the removal of nitrate and phosphorus from treated water at different time interval by the three aquatic plants. (2) To assess the nutrient content of aquatic plants after nutrient removal from water. (3) To estimate the nitrate content of water spinach after phytoremediation to assess its suitability to use as vegetable.
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MATERIALS AND METHODS In this study three different aquatic plants were tested for their phytoremediation potential. They were water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes), and water spinach (Ipomoea aquatica). Water lettuce and water hyacinth were collected from small tanks in the Northern Province, Sri Lanka. Water spinach was collected from farmer’s field. The sampled plants were placed in cement tank with ground water under natural sun light for two weeks to let them adapt to the new environment. Then the plants of the same size were selected for further experiments. As water spinach is a vegetable it was tested for its potential to phytoremediate drinking water which is the well water in this region. To test whether addition of phosphorus in small quantity will benefit the rate of phytoremediation, two rates of phosphorus and four rates of nitrate were studied as a two factor factorial experiment. Other two plants were tested to find their potential to remove nitrate and phosphorus from waste water or water used for livestock feeding. For all the experiments ground water was used. For the experiment with water spinach the well water used had 8 mg/L nitrate N and 0.4 mg/l phosphorus. Total hardness of water was 375 mg/L. For this water five levels of nitrate nitrogen (0, 10, 20, 40, and 50 mg/L) and two levels of phosphorus (0, 5 mg/L) were treated. For the experiment with other two plants, four levels of nitrogen (0, 20, 40, and 60 mg/L) and three levels of phosphorus (0, 20, and 40 mg/L) were treated. The design used was a two factor factorial with three replicates. Plants were removed from water when they turn brown which indicates their tendency to decompose if allowed further. Opened 1.5 litters volume plastic bottles containing 1 liter water were used to grow water lettuce. Water lettuces having approximately 5cm diameter were selected and placed one each in the treated bottles. 25 litters volume plastic buckets filled with 20 liters of water were used to grow the water hyacinth. The plants having same height and same number of leaves were selected for experiment and placed one plant per bucket. Water spinach was grown in five liter capacity plastic container filled with three liters of water. Cuttings of same length and weight were used for the experiment. The length and weight of the cuttings were measured before and after the experiment. Different volumes of water and containers were selected based on the root volume of each plant. Water samples were collected once a week to measure the nitrate nitrogen (Vendrell and Zupanii 1990) and phosphorus (Olsen and Sommers 1982) concentration colourimetrically. After harvesting, plants were subjected to nutrient analysis to find out the total nitrogen and total phosphorus content. The study was conducted up to six, three, and three weeks respectively, for Pistia stratiotes, Eichhornia crassipes and Ipomoea aquatica based on the time taken for the leaves to turn brown. RESULTS AND DISCUSSION Nitrate N Removal Potential of Tested Plants The weekly collected data were statistically analyzed with ANOVA using SAS package. The results showed that there was no interaction between phosphorus level and nitrate N removal. Hence, each nutrient removal is discussed separately. As the volume of water used for treatment of each plant varied, results of experiments with each plant is also analyzed and discussed separately. Pistia stratiotes. Statistically significant increase in N removal was observed with increasing N concentrations in Pistia stratiotes treated water. Among the concentrations, 68.5 mg/L recorded maximum mean nitrate N removal of 7.7mg/L followed by 48.5 mg/L,
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T. SUNDARALINGAM AND N. GNANAVELRAJAH Table 1 Nitrate N removal by Pistia stratiotes and total N in tissues
N level
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1(8.5 mg/L) 2(28.5 mg/L) 3(48.5 mg/L) 4(68.5 mg/L)
N removal N removal (mg/L) Week (mg/L) 1.3d 3.3c 5.0b 7.7a
1 2 3 4 5 6
11.3a 3.0b 3.7b 2.9bc 2.0c 3.2b
N removed end of 6th week (mg/L)
% removal at the end of 6th week
Total nitrogen (mg/100g) in tissues
7.8 19.8 30 46.2
91.8 69.5 61.5 67.4
2260d 2846.7c 3223.3b 4161.7a
28.5 mg/L, and 8.5 mg/L, where the amount removed were 5.0 mg/L, 3.3 mg/L, and 1.3 mg/L respectively. Highest (11.3 mg/L) mean N removal was recorded in the first week interval. But removal from 2nd, 3rd, 4th, and 6th week interval did not show significant difference from each other (Table 1). The percentage reduction of nitrate N by Pistia stratiotes at different levels of nitrate N in water at the end of third week also shows an increasing trend with increasing concentration of nitrate N in water. The highest percentage (91.8%) reduction was recorded from the concentration of 8.5 mg/L and the removal amount was 7.8 mg/L. However, 69%, 61%, and 67% of N was removed from water having initial nitrate N concentrations of 28.5 mg/L, 48.5 mg/L, and 68.5 mg/L respectively. A comparison of total nitrogen content of Pistia stratiotes obtained from different N concentration in water shows that plants growing in the higher concentration had a higher N content in their tissues (Table 1). The total N content of Pistia stratiotes was recorded as 2260 mg/100 g, 2846.7 mg/100 g, 3223.3 mg/100 g, and 4161.7 mg/100 g grown in water having nitrate N concentrations of 8.5 mg/L, 28.5 mg/L, 48.5 mg/L, and 68.5 mg/L respectively. Eichhornia crassipes. Table 2 shows nitrate N removal under different concentration at different week intervals and total N of Eichhornia crassipes at the end of 3rd week. There was a significant increase in nitrate N removal with increasing nitrate concentration in water. On average, 1.8 mg/L, 3.8 mg/L, 8.6 mg/L, and 14.4 mg/L were removed from water having nitrate N concentrations of 8.5 mg/L, 28.5 mg/L, 48.5 mg/L, and 68.5 mg/L respectively. The results show a decreasing trend in N removal with time. Highest (10.1 mg/L) mean nitrate N removal was observed in first week interval and the amount removed was 6.8 mg/L and 4.7 mg/L at the end of 2nd and 3rd week intervals respectively. Table 2 Nitrate N removal by Eichhornia crassipes and Total N in tissues
N level 1(8.5 mg/L) 2(28.5 mg/L) 3(48.5 mg/L) 4(68.5 mg/L)
N removal N removal (mg/L) Week (mg/L) 1.8d 3.8c 8.6b 14.4a
1 2 3
10.1a 6.8b 4.7c
N removed end of 3rd week (mg/L)
% Removal at the end of 4th week
5.39 11.4 25.80 42.13
63.5 40 53.2 61.5
N refers NO3 − - N. Means with similar letters within a column are not statistically different at p = 0.05.
Total nitrogen(mg/100) In tissues 1304.0b 1295.7b 1375.2b 1735.2a
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Table 3 Nitrate N removal by Ipomoea aquatica and Nitrate N and Total N in tissues N level 1(4 mg/L) 2(14 mg/L) 3(24 mg/L) 4(44 mg/L) 5(54 mg/L)
N removal N removal Nitrate N removed end of % Removal end NO3 −-N in tissues (mg/L) Week (mg/L) 6th week (mg/L) of 3rd week (mg/Kg) 0.9c 3.5b 4.6b 5.3b 7.8a
1 2 3
3.6b 4.9a 4.3ab
2.7 10.5 13.8 12.9 23.4
67.5 75 57.5 36.1 43.3
Total N in tissues (mg/100g)
8.0b 6.9b 17.8ab 22.7a 26.3a
1208b 1841a 2037a 2132a 2170a
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N refers NO3 − - N Means with similar letters within a column are not statistically at p = 0.05.
The percentage nitrate N removal of Eichhornia crassipes was also studied in different concentrations of N in water. A significant increase in N removal was observed with increasing N concentration in water. At the end of third week 5.4 mg/L, 11.4 mg/L, 25.8 mg/L, and 43.2 mg/L N were removed from the water having initial N concentration of 8.5 mg/L, 28.5 mg/L, 48.5 mg/L, and 68.5 mg/L respectively (Table 2). Total N content of Eichhornia crassipes were observed as1304 mg/100 g, 1295.7 mg/100 g, and 1375.2 mg/100 g in tissues grown in water having N concentration of 8.5 mg/l, 28.5 mg/l and 48.5 mg/l respectively. Highest (1735 mg/100 g) total N content was recorded in plants grown in water having nitrate N concentration of 68.5 mg/L and the difference was statistically significant. Ipomoea aquatic. Table 3 shows means of nitrate N removal for different levels of nitrate N at different week intervals. Generally the N removal showed an increasing trend with increasing nitrate concentration in water. The average mean N removals of 0.9 mg/L, 3.5 mg/L, 4.6 mg/L, 4.3 mg/L, and 7.8 mg/L were recorded from water having the initial concentration of 4 mg/L,14 mg/L,24 mg/L, 44 mg/L, and 54 mg/L respectively. In the case of Ipomoea aquatica, highest (4.9 mg/L) nitrate N was removed in 2nd week interval followed by 3rd week (4.3 mg/L) and 1st week (3.6 mg/L). This is in contrast to the removal pattern of other two plants where highest nitrate removal was recorded during first week. This could have been attributed due to the late root development in Ipomoea aquatica which was treated as cuttings where as other two plants were treated as plants with developed root system. The percentage reduction of nitrate N by water spinach at different levels at third week shows a general increasing trend of nitrate N removal from water with increasing nitrate N concentration of water. Nitrate N removal of 2.7 mg/L, 10.5 mg/L, 13.8 mg/L, 12.9 mg/L, and 23.4 mg/L was recorded at the initial concentration of 4 mg/L, 14 mg/L, 24 mg/L, 44 mg/L, and 54 mg/L respectively. The highest percentage (75%) reduction was occurred in the concentration of 14 mg/l, while the lowest percentage (29.3%) reduction was recorded in the concentration of 44 mg/l. It could be concluded that within the range of 4 to 54 mg/L of nitrate N concentration water spinach has at least a 29% phytoremediation potential. Nitrate N content of Ipomoea aquatica. The study of nitrate N content of Ipomoea aquatica is important if the plants used as phyto- remedeators are to be used as vegetables, as higher nitrate N ingestion is harmful for health. Table 3 shows the nitrate N content in Ipomoea aquatica with different treatments at the end of third week. An increasing trend of nitrate N accumulation in plants, with increasing nitrate N in water is observed. Similar results of higher nitrate N availability in soils enhancing nitrate N accumulation in plant tissues were recorded by other workers as well (Kallio et al. 1980; Ignasio et al. 2006) possibly due to the excess nitrate N that do not involve in metabolic
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T. SUNDARALINGAM AND N. GNANAVELRAJAH Table 4 Mean values of P removal Pistia stratiotes
P level 1(0.4 mg/L) 2(20.4 mg/L) 3(40.4 mg/L)
P removal (mg/l) 0.06c 3.35b 6.67a
Week
P removal (mg/l)
P removed At the end of 6th week (mg/L)
% removal end of 6th week
Total phosphorus (mg/100g) in tissues
1 2 3 4 5 6
17.3a 1.7b 0.4c 0.3c 0.3c 0.2c
0.36 20.09 20.24
90 98.5 99.6
398c 852b 1368a
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Means with similar letters within a column are not statistically different at p = 0.05.
process tend to accumulate in tissues (Corre and Breimer 1979). The nitrate N content of 8.0 mg/Kg, 6.9 mg/Kg, 17.8 mg/Kg, 22.7 mg/Kg, and 26.3 mg/Kg were observed in plants grown in water containing nitrate N 4 mg/l, 14 mg/l, 24 mg/l, 44 mg/l and 54 mg/l respectively. Joint FAO/WHO Expert Committee on Food Additives (JECFA 2002) has established an Acceptable Daily Intake of nitrate N as 3.7 mg/Kg body weight/day. According to ADI limit a 6 month baby (7–8 kg), 1 year child (9–11 kg) and an adult (50–60 kg) may ingest 26–30 mg nitrate N/day, 33–40 mg nitrate N/day, 180–225 mg nitrate N/day without harmful effects. Accordingly the Ipomoea aquatica used to phytoremediate water with highest nitrate N of 54 mg/l, which recorded highest nitrate N content of 26.3 mg/kg, could be used as vegetable even for infants without any harmful effects. This is a win-win situation where the remediation technique not only reduces nitrate N pollution but also yields a nutritional vegetable. There was no significant variation in total nitrogen content of Ipomoea aquatica within the range of 14–54 mg/l nitrate N concentration in water. The total nitrogen content of 1207.5 mg/100 g was recorded in the nitrate N concentration of 4 mg/l in water (Table 3). Phosphorus Removal by tested Plants. Table 4 shows means of phosphorus removal with different concentration of phosphorus in water at different week intervals. The results show phosphorus reduction was significantly increased with increasing concentration of phosphorus in water. Average mean phosphorus removal was recorded as 0.06 mg/L, 3.35 mg/L, and 6.67 mg/L from the water having initial concentrations of 0.4 mg/L, 20.4 mg/L and 40.4 mg/L respectively. At the end of first week an average of 17.3 mg/L of phosphorus was removed from the water. It was significantly higher compared to removal in other week intervals. The mean amount of phosphorus removed in 2nd, 3rd, 4th, 5th, and 6th week intervals were recorded as 1.7 mg/L, 0.4 mg/l, 0.3 mg/L, 0.3 mg/L, and 0.2 mg/L respectively. Phosphorus removal was increased with increasing initial concentration and recorded as 0.36 mg/L, 20.1mg/L, and 40.02 mg/L from the initial concentration of 0.4 mg/L, 20.4 mg/L, and 40.4 mg/L respectively, recording a percentage removal greater than 90 in all treatments. The highest percentage (99.6) removal was recorded in water having 40.4 mg/L of phosphorus. At the end of the study period (6 weeks) the highest (1368 mg/100 g) total P content was measured in plants grown in the concentration of 40.4 mg/L followed by 20.4mg/L (852 mg/100 g) and 0.4 mg/L (398 mg/100 g) respectively (Table 4). The similar trend of increasing removal of phosphorus from water and increasing total phosphorus content of
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Table 5 Mean values of P removal by Eichhornia crassipes
P level 1(0.4 mg/l) 2(20.4 mg/l) 3(40.4 mg/l)
P removal (mg/l) 0.1c 6.5b 13.1a
Week
P removal (mg/l)
P removed end of 6th week (mg/L)
% removal end of 3rd week
Total phosphorus (mg/100g) in tissues
1 2 3
16.0a 2.8b 0.9c
0.3 19.48 39.27
75 95.5 97.2
837c 1838b 2046a
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Means with similar letters within a column are not statistically different at p = 0.05.
plants grown in water with increasing concentration of phosphorus confirm the removal mechanism is phytoextraction, also called phytoaccumulation. Eichhornia crassipes. Table 5 shows means of phosphorus removal under different concentration of phosphorus at different week intervals. The results show phosphorus removal was significantly increased with increasing concentration. The average mean concentrations of 0.1 mg/L, 6.5 mg/L, and 13.1 mg/L were removed from the initial concentration of 0.4 mg/L, 20.4 mg/L, and 40.4 mg/L respectively. Means of weekly phosphorus removal show decreasing trend with duration, Therefore highest reduction (16 mg/L) was observed in first week followed by 2.8 mg/L in 2nd week and 0.9 mg/L in 3rd week. The amount of phosphorus removed from water in three weeks increase with increasing phosphorus concentration. Concentration of 0.3 mg/L, 19.5 mg/L, and 39.3 mg/L were removed from the initial concentration of 0.4, 20.4, and 40.4 mg/L respectively. Highest (97.2%) and lowest (75%) percentage of removal was recorded in the concentrations of 40.4 mg/L and 0.4 mg/L respectively. Means of total phosphorus content in Eichhornia crassipes at different concentrations were measured. The results revealed that the total phosphorus content of Eichhornia crassipes was increased with increasing concentration in water and it was recorded as 837 mg/100 g, 1838 mg/100 g and 2046 mg/100 g in the concentration of 0.4 mg/L, 20.4 mg/L, and 40.4 mg/L respectively (Table 5). Ipomoea aquatic. Average phosphorus removal was recorded as 0.1 mg/L and 1.5 mg/L in the nitrate concentration of 0.4 mg/L and 5.4 mg/l respectively. While the weekly mean phosphorus removal was high in 1st week and recorded as 1.2 mg/L and the removal of 0.8 mg/L and 0.4 mg/L were recorded in 2nd and 3rd week intervals. The amount of 0.3mg/L and 4.5mg/L were removed from the initial concentration of 0.4 mg/L and 5.4 mg/L respectively at the end of three weeks. Therefore the phosphorus reduction efficiency of Ipomoea aquatica was 75% and 83.3% at the concentration of 0.4 mg/L and 5.4 mg/L respectively. The phosphorus content of 192 mg/100 g and 229 mg/100 g were recorded in Ipomoea aquatica under the phosphorus concentration of 0.4 mg/L and 5.4 mg/L respectively. So this indicates that the total phosphorus content of and Ipomoea aquatica significantly differed between two different concentrations (0.4 mg/L, 5.4 mg/L) at probability level of 0.05 (Table 6). The average mean dry matter increase of 1.4 g, 2.6 g, 2.4 g, 2.5 g, and 2.4 g were recorded in Ipomoea aquatica under the nitrate N concentration of 4 mg/L, 14 mg/L, 24 mg/L, 44 mg/L, and 54 mg/L respectively. Similar to dry matter, length increase of Ipomoea aquatica cuttings was measured in weekly intervals. Statistical analysis of the data revealed that there was general increase in length with increasing concentration of
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T. SUNDARALINGAM AND N. GNANAVELRAJAH Table 6 Mean values of P removal by Ipomoea aquatic
P level
P removal (mg/l) 0.1b 1.5a
1(0.4 mg/L) 2(5.4 mg/L)
Week
P removal (mg/l)
1 2 3
1.2a 0.8b 0.4c
P in Ipomoea aquatica (mg/100g)
P removed end of 3rd week (mg/L)
% Removal end of 3rd week
192b 229a
0.3 4.5
75% 83.3%
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Means with similar letters within a column are not statistically different at p = 0.05.
nitrate in water. But significantly lower increase in length was observed from plants grown in the nitrate concentration of 4 mg/L (Table 7).
DISCUSSION Nitrate (from 252 mg/L to 25 mg/L) and phosphorus (from 47.5 mg/L to 12.4 mg/L) removal from a pilot lagoon sewage system by Pistia stratiotes has already been reported (Fonkou et al. 2002). They also reported higher total nitrogen content of plants (4.09–5.10%) compared to the lower total nitrogen (2.3–4.2%) in the present study. This is because the plants were grown in water containing less nitrate (maximum 68.5 mg/L) compared to the previous experiment (252 mg/L). Another study by Qin et al. (2010) using Pistia stratiotes in treatment plots of two storm water detention ponds revealed that the inorganic N (NH4 + and NO3 −) concentrations in Pistia stratiotes treated water were more than 50% lower than those in non-treated water and Pistia stratiotes in treated water contained average N and phosphorus concentrations of 1.7 and 0.37% DM respectively. Potential of Eichhornia crassipes to remove nitrogen and phosphorus from in wastewater of a textile mill (Gamage and Yapa 2001), from upgraded facultative lagoon (Wolverton and McDonald 1979), and a lake (Sangeeta 2007) also has been reported. Similarly nitrogen and phosphorus removal from eutrophic water of deep flow technique (Hu et al. 2008) using Ipomoea aquatica also has been reported. However, according to Alade and Ojoawo (2009), nitrogen and phosphorus content of waste water treated with Eichhornia crassipes was increased by 77.5% and 66.3% respectively. The increased nitrate and phosphate ion concentration would have been due to the mineralization of the organic matter found in waste water. As the ground water has negligible organic matter content there was no possibility of nutrient mineralization in the present study. Table 7 Means of dry matter increase in Ipomea aquatic
N level 1(4 mg/L) 2(14 mg/L) 3(24 mg/L) 4(44 mg/L) 5(54 mg/L)
Dry matter increase (g)
Length increase (cm)
1.4a 2.6a 2.4a 2.5a 2.4a
12.8b 21.0a 23.5a 24.5a 27.3a
P level
Dry matter increase (g)
Length increase (cm)
1(0.4 mg/L) 2(5.4 mg/L)
2.0a 2.4a
19.8a 23.8a
N refers NO3 − - N Means with similar letters within a column are not statistically different at p = 0.05.
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RECOMMENDATION All the past studies were carried out in waste water. The present study was carried out using ground water which is used as drinking water for human and animals. This study therefore indicates that nitrate pollution of ground water for human consumption can be overcome by phytoremediation technique using Ipomoea aquatica. As Ipomoea aquatica is used as a vegetable it will be accepted by people. Moreover, for livestock consumption ground water can be phytoremediated using either Eichhornia crassipes or Pistia stratiotes as these plants are also used as animal feed. On the other hand as reported by other workers quality of waste water could be improved by either Pistia stratiotes or Eichhornia crassipes (Zimmels et al. 2006, 2008; Alade and Ojoawo 2009) or Ipomoea aquatica (Hu et al. 2008). As present study indicate that these three plants could be grown in ground water having hardness, any waste water generated from industries using ground water, loaded with either nitrate or phosphorus can also be remediated using any of these plants. CONCLUSIONS The three tested plants have the potential to remove nitrate and phosphorus from ground water having hardness of 375 mg/L. Pistia stratiotes was able to remove 61.5–91.8% of nitrate N from treated water for the period of six weeks. Highest removal was observed during first week interval. Phosphorus was efficiently removed than nitrate N by Pistia stratiotes and it was recorded as 90–99%. The nitrate N removal by Eichhornia crassipes was significantly increased with increasing nitrate concentration in water. The removal rate of nitrogen was recorded from 40–63.5% and highest (10.1 mg/L) nitrate N was removed during first week interval. Eichhornia crassipes had better removal effect on phosphorus than nitrogen and it was 75–97.2%. The study using and Ipomoea aquatica showed that there was a significant reduction in nitrate N in water and it was observed in the range of 29.3–75%. Highest nitrate N removal was observed in 2nd week interval (4.9 mg/L). The highest nitrate N in tissues of Ipomoea aquatica was recorded as 26.3 mg/kg in the concentration of 54 mg/L of nitrate in water. Therefore Ipomoea aquatica used for phytoremediation treatment could be used as vegetable without any harmful effects even by infants according to the ADI (Acceptable Daily Intake) by JECFA (FAO/WHO 2002). REFERENCES Akinbile CO, Yusoff Mohd S. 2012. Assessing water hyacinth (Eichhornia crassopes) and lettuce (pistia stratiotes) effectiveness in aquaculture waste water treatment. Int J Phytorem 14(3):201–21. Alade GA, Ojoawo SO. 2009. Purification of Domestic Sewage by Water-Hyacinth (Eichhornia Crassipes). Int J of Environ Tech Manage 10 (3/4):286–294. Corre WJ, Breimer T. 1979. Nitrate and Nitrite in Vegetables. Center for Agricultural Publishing and Documentation (Wageningen, Netherlands); 2009 February. Available from: http://www. cababstractsplus.org/Abstract.aspx?AcNo=19810717971. Cunningham SD, Ow DW. 1996. Promises and prospects of Phytoremediation. J of Plant Physio 110:715–719. Ensley BD. 2000. Rationale for the Use of Phytoremediation. In: Raskin I, Ensely BD, editors. Phytoremediation of toxic metals: Using plants to clean-up the environment. New York (NY): John Wiley Publishers. p. 231–246. FAO/WHO. 2002. Summary and Conclusions. Joint FAO/WHO Expert Committee on Food Additives, Fifty-ninth meeting, 2002. Available from: www.fao.org/es/ESN/Jecfa/59corr.pdf.
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Fonkou T, Agendia P, Kengne I, Akoa A, Nya J. 2002. Potentials of water lettuce (Pistia stratiotes) in domestic sewage treatment with macrophytic lagoon systems in Cameroon. Proceedings of International Symposium on Environmental Pollution Control and Waste Management, 7–10 January 2002, Tunis (EPCOWM’2002), p.709–714. Gamage NS, Yapa PA. 2001. Use of water hyacinth (Eichhornia crassipes (Mart) solms) in treatment systems for textile mill effluents. A case study. J Natn Sci Foundation Sri Lanka 29(1&2):15–28. Ho YB, Wai-kin Wong. 1994. Growth and macronutrient removal of water hyacinth in a small secondary sewage treatment plant. Resour Conserv Recycl 11(1–4):161–178. Hu MH, Ao YS, Yang XE, Li TQ. 2008. Treating eutrophic water for nutrient reduction using an aquatic macrophyte (Ipomoea aquatica Forsskal) in a deep flow technique system. Agri Water Manage 95:607–615. Ignasio I, Carmen L, Aparicio-tejo Pedro AP, Julio M. 2006. The influence of 3,4-dimethhylpyrazole phosphate and dicyandiamide on reducing nitrate accumulation in spinach under Mediterranean conditions. J Agri Sci 144(6):555–562. Jeyaruba T, Mikunthan T. 2008. Health hazards by nitrate pollution of ground water in intensified agricultural areas. Proceedings of the 33rd International geological congress. Oslo. 2008 Aug 6–14. Jianobo LU, Zhihui FU, Zhaozheng YIN. 2008. Performance of a water hyacinth (Eichhornia crassipes) system in the treatment of wastewater from a duck farm and the effects of using water hyacinth as duck feed. J Environ Sci 20(5):513–519. Kallio H, Linko RR, Tikanmaki E, Puntari I. 1980. Effect of nitrapyrin on nitrapyrin residues and nitrate content in red beetroots fertilized with urea. J Sci Food Agri 31(7):701–708. L’hirondel JL, Avery AA, Addiscott T. 2006. Dietary Nitrate: Where is the Risk? Environ Health Perspect 114(8): A458–A459. Mageswaran R, Mahalingam S. 1983. Nitrate nitrogen content of well water and soil from selected areas in Jaffna peninsula. J Natn Sci Foundation Sri Lanka 11(1):269–275. Nagarajah S, Emerson BN, Abeykoon V, Yogalingam S. 1988. Water quality of wells in Jaffna and Kilinochchi Districts. Tropical Agric 144:15–20. Olsen SR, Sommers LE. 1982. Phosphorous. In: Page AL, Miller RH, Keeney DR, editors. Methods of soil analysis part 2 Chemical and microbiological properties. 2nd ed. Agronomy monograph no.9. Madison (WI): ASA-SSSA. p. 404–407. Qin L, Zhenli LH, Donald AG, Peter JS, Xiaoe Y. 2010. Phytoremediation to remove nutrients and improve eutrophic storm waters using water lettuce (Pistia stratiotes L.). Environ Sci Pollut Res 17(1):84–96. Sangeeta D. 2007. Role of Macrophytes in improving water quality of an aquatic eco-system. J Appl Sci Environ Manage 11(4):133–135. Vendrell PF, Zupanii J. 1990. Determination of soil nitrate by transnitration of salicylic acid. Comm Soil Sci Plant Anal 21:1703–1705. Vogtmann H, Biederman R. 1985. The nitrate story: no end in sight. Nutrit Healt 3:217–239. WHO 1984. International Standards for Drinking-Water. Geneva: World Health Organization. Wolverton BC, McDonald RC. 1979. Water hyacinth (Eichhornia crassipes) productivity and harvesting studies. Econ Bot 33:1–10. Zimmels Y, Kirzhner, F Malkovskaja A. 2006. Application of Eichhornia crassipes and Pistia stratiotes for treatment of urban sewage in Israel. J Environ Manage 81(4):420–428. Zimmels Y, Kirzhner, F Malkovskaja A. 2008. Application and features of cascade aquatic plants system for sewage treatment. Ecol Eng 38(2):147–161.
International Journal of Phytoremediation Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/bijp20
Phytoremediation Potential of Selected Plants for Nitrate and Phosphorus from Ground Water a
T. Sundaralingam & N. Gnanavelrajah
a
a
Department of Agricultural Chemistry, Faculty of Agriculture , University of Jaffna , Sri Lanka Accepted author version posted online: 12 Sep 2013.Published online: 27 Sep 2013.
To cite this article: T. Sundaralingam & N. Gnanavelrajah (2014) Phytoremediation Potential of Selected Plants for Nitrate and Phosphorus from Ground Water, International Journal of Phytoremediation, 16:3, 275-284, DOI: 10.1080/15226514.2013.773279 To link to this article: http://dx.doi.org/10.1080/15226514.2013.773279
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International Journal of Phytoremediation, 16:275–284, 2014 C Taylor & Francis Group, LLC Copyright ISSN: 1522-6514 print / 1549-7879 online DOI: 10.1080/15226514.2013.773279
PHYTOREMEDIATION POTENTIAL OF SELECTED PLANTS FOR NITRATE AND PHOSPHORUS FROM GROUND WATER
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T. Sundaralingam and N. Gnanavelrajah Department of Agricultural Chemistry, Faculty of Agriculture, University of Jaffna, Sri Lanka The phytoremediation potential of three aquatic plants namely, water lettuce (Pistia stratioes), water hyacinth (Eichhornia crassipes), and water spinach (Ipomoea aquatica) for nitrate N and phosphorus from nutrient treated ground water was assessed. A total of twelve treatment combinations including four levels of nitrate (expressed as nitrate N 0, 20, 40, and 60 mg/l) and three levels of phosphorus (0, 20, and 40 mg/l) were treated for the total volume of 1 and 20 liters of water respectively, for Pistia stratiotes and Eichhornia crassipes. For Ipomoea aquatica ten treatment combinations with five levels of nitrate N (0, 10, 20, 40, and 50 mg/l) and two levels of phosphorus (0 and 5 mg/l) were treated to 3 liters of water. The design used was a two factor factorial with three replicates. Water was analyzed at weekly interval for nitrate N and phosphorus. Pistia stratiotes, Eichhornia crassipes and Ipomoea aquatica had the potential to remove nitrate N between 61.5–91.8%, 40–63.5%, and 29.3–75% during the period of six, three and three and weeks, respectively. In addition, 90–99%, 75–97.2%, and 75–83.3% of phosphorus was removed from water by Pistia stratiotes, Eichhornia crassipes and Ipomoea aquatica respectively, during the same period. KEY WORDS: Pistia stratioes, Eichhornia crassipes, Ipomoea aquatica, nitrate pollution, ground water
INTRODUCTION Ground water is a precious scarce natural resource used for drinking and other domestic purposes, irrigation and industrial uses in different parts of the world. It has been reported that if the drinking water contains more than 10 ppm nitrate-nitrogen (45 ppm nitrate), it could affect the health of infants, giving rise to “blue babies” (WHO 1984; L’hirondel et al. 2006). Nitrate is relatively non toxic, but its metabolites and reaction products such as nitrite, nitric oxide, and N-Nitroso compounds, have raised concern. Excessive nitrite may cause a life-threatening hemoglobin malfunction in infants, and may be converted to carcinogenic nitrosaminos during digestion, posing a possible cancer risk for all ages (Vogtmann and Biederman 1985). On the other hand the nutrient loading such as nitrogen and phosphorus lead to the pollution problem called “Eutrophication”, a
Address correspondence to T. Sundaralingam, Department of Agricultural Chemistry, Faculty of Agriculture, University of Jaffna, Sri Lanka. E-mail: [email protected] 275
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process whereby water bodies receive excess inorganic nutrients, especially nitrogen and phosphorus, which stimulate excessive growth of plants and algae. Nitrate pollution of ground water due to heavy doses of fertilizers and manures has been reported in many countries. The population in the Jaffna peninsula, Sri Lanka has always been depended on the water stored in the underground Miocene limestone and sand aquifers for its drinking water and water for irrigation of agricultural lands. The nitrate pollution of ground water has been reported by many workers from long past (Mageswaran and Mahalingam 1983; Nagarajah et al. 1988; Jeyaruba and Mikunthan 2008). Though nitrate pollution of ground water has been reported more than two and a half decade back, scanty of research has been done to remedy such problem in this region. Nitrate removal from drinking water is a challenging problem which demands high cost technology such as ion exchange technology etc. On the other hand phosphorus removal from waste water also is another issue to be studied. As these two elements are essential plant nutrients, phytoremediation could be adopted to solve these problems. This plant-based remediation technology has the potential to be low-cost, low-impact, visually benign, and environmentally sound (Cunningham and Ow 1996). The primary motivation behind the development of phytoremediation technologies is the potential for low-cost remediation (Ensley 2000). Moreover, these treated plants could be used as nutrient source for crops, animals or as vegetables for human depending on the species. Water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes) have been studied for their phytoremediation potential for various water quality parameters such as biological and chemical demand (Zimmels, Kirzhner, and Malkovskaja 2006, 2008; Alade and Ojoawo 2009) and nutrient loads of nitrogen and phosphorus (Ho and Wai-kin Wong 1994; Jianobo, Zhihui, and Zhaozheng 2008; Akinbile and Yusoff Mohd 2012) and found to be effective in improving waste water quality. Similarly water spinach (Ipomoea aquatica) was also reported to have phytoremediation potential of nutrients from waste water (Hu et al. 2008). All the previous studies have been conducted in waste water where there is possibility of ample of both macro and micro nutrients. In the present study potential of selected aquatic plants to phytoremediate ground water is studied. The ground water studied is highly hard water (hardness - 375 mg/L) due to the calcium content derived from limestone aquifer. The potential of such plants in hard water or drinking water has not been studied. Moreover, water spinach is a popular vegetable and the plants used for phytoremediation treatment could be used as vegetables provided these plants have nitrate content below the recommended level. However, there is scanty of information regarding the nitrate content of plant tissues after remediation treatment. This information is especially important to recommend for human consumption of such plants after remediation. On this background experiments were conducted in the Department of Agriculture Chemistry, Faculty of Agriculture, University of Jaffna, Sri Lanka to assess the phytoremediation potential of three aquatic plants namely, water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes) and water spinach (Ipomoea aquatica) on removal of nitrate and phosphorus from nutrient treated ground water. The specific objectives of the study were: (1) To assess the removal of nitrate and phosphorus from treated water at different time interval by the three aquatic plants. (2) To assess the nutrient content of aquatic plants after nutrient removal from water. (3) To estimate the nitrate content of water spinach after phytoremediation to assess its suitability to use as vegetable.
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MATERIALS AND METHODS In this study three different aquatic plants were tested for their phytoremediation potential. They were water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes), and water spinach (Ipomoea aquatica). Water lettuce and water hyacinth were collected from small tanks in the Northern Province, Sri Lanka. Water spinach was collected from farmer’s field. The sampled plants were placed in cement tank with ground water under natural sun light for two weeks to let them adapt to the new environment. Then the plants of the same size were selected for further experiments. As water spinach is a vegetable it was tested for its potential to phytoremediate drinking water which is the well water in this region. To test whether addition of phosphorus in small quantity will benefit the rate of phytoremediation, two rates of phosphorus and four rates of nitrate were studied as a two factor factorial experiment. Other two plants were tested to find their potential to remove nitrate and phosphorus from waste water or water used for livestock feeding. For all the experiments ground water was used. For the experiment with water spinach the well water used had 8 mg/L nitrate N and 0.4 mg/l phosphorus. Total hardness of water was 375 mg/L. For this water five levels of nitrate nitrogen (0, 10, 20, 40, and 50 mg/L) and two levels of phosphorus (0, 5 mg/L) were treated. For the experiment with other two plants, four levels of nitrogen (0, 20, 40, and 60 mg/L) and three levels of phosphorus (0, 20, and 40 mg/L) were treated. The design used was a two factor factorial with three replicates. Plants were removed from water when they turn brown which indicates their tendency to decompose if allowed further. Opened 1.5 litters volume plastic bottles containing 1 liter water were used to grow water lettuce. Water lettuces having approximately 5cm diameter were selected and placed one each in the treated bottles. 25 litters volume plastic buckets filled with 20 liters of water were used to grow the water hyacinth. The plants having same height and same number of leaves were selected for experiment and placed one plant per bucket. Water spinach was grown in five liter capacity plastic container filled with three liters of water. Cuttings of same length and weight were used for the experiment. The length and weight of the cuttings were measured before and after the experiment. Different volumes of water and containers were selected based on the root volume of each plant. Water samples were collected once a week to measure the nitrate nitrogen (Vendrell and Zupanii 1990) and phosphorus (Olsen and Sommers 1982) concentration colourimetrically. After harvesting, plants were subjected to nutrient analysis to find out the total nitrogen and total phosphorus content. The study was conducted up to six, three, and three weeks respectively, for Pistia stratiotes, Eichhornia crassipes and Ipomoea aquatica based on the time taken for the leaves to turn brown. RESULTS AND DISCUSSION Nitrate N Removal Potential of Tested Plants The weekly collected data were statistically analyzed with ANOVA using SAS package. The results showed that there was no interaction between phosphorus level and nitrate N removal. Hence, each nutrient removal is discussed separately. As the volume of water used for treatment of each plant varied, results of experiments with each plant is also analyzed and discussed separately. Pistia stratiotes. Statistically significant increase in N removal was observed with increasing N concentrations in Pistia stratiotes treated water. Among the concentrations, 68.5 mg/L recorded maximum mean nitrate N removal of 7.7mg/L followed by 48.5 mg/L,
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T. SUNDARALINGAM AND N. GNANAVELRAJAH Table 1 Nitrate N removal by Pistia stratiotes and total N in tissues
N level
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1(8.5 mg/L) 2(28.5 mg/L) 3(48.5 mg/L) 4(68.5 mg/L)
N removal N removal (mg/L) Week (mg/L) 1.3d 3.3c 5.0b 7.7a
1 2 3 4 5 6
11.3a 3.0b 3.7b 2.9bc 2.0c 3.2b
N removed end of 6th week (mg/L)
% removal at the end of 6th week
Total nitrogen (mg/100g) in tissues
7.8 19.8 30 46.2
91.8 69.5 61.5 67.4
2260d 2846.7c 3223.3b 4161.7a
28.5 mg/L, and 8.5 mg/L, where the amount removed were 5.0 mg/L, 3.3 mg/L, and 1.3 mg/L respectively. Highest (11.3 mg/L) mean N removal was recorded in the first week interval. But removal from 2nd, 3rd, 4th, and 6th week interval did not show significant difference from each other (Table 1). The percentage reduction of nitrate N by Pistia stratiotes at different levels of nitrate N in water at the end of third week also shows an increasing trend with increasing concentration of nitrate N in water. The highest percentage (91.8%) reduction was recorded from the concentration of 8.5 mg/L and the removal amount was 7.8 mg/L. However, 69%, 61%, and 67% of N was removed from water having initial nitrate N concentrations of 28.5 mg/L, 48.5 mg/L, and 68.5 mg/L respectively. A comparison of total nitrogen content of Pistia stratiotes obtained from different N concentration in water shows that plants growing in the higher concentration had a higher N content in their tissues (Table 1). The total N content of Pistia stratiotes was recorded as 2260 mg/100 g, 2846.7 mg/100 g, 3223.3 mg/100 g, and 4161.7 mg/100 g grown in water having nitrate N concentrations of 8.5 mg/L, 28.5 mg/L, 48.5 mg/L, and 68.5 mg/L respectively. Eichhornia crassipes. Table 2 shows nitrate N removal under different concentration at different week intervals and total N of Eichhornia crassipes at the end of 3rd week. There was a significant increase in nitrate N removal with increasing nitrate concentration in water. On average, 1.8 mg/L, 3.8 mg/L, 8.6 mg/L, and 14.4 mg/L were removed from water having nitrate N concentrations of 8.5 mg/L, 28.5 mg/L, 48.5 mg/L, and 68.5 mg/L respectively. The results show a decreasing trend in N removal with time. Highest (10.1 mg/L) mean nitrate N removal was observed in first week interval and the amount removed was 6.8 mg/L and 4.7 mg/L at the end of 2nd and 3rd week intervals respectively. Table 2 Nitrate N removal by Eichhornia crassipes and Total N in tissues
N level 1(8.5 mg/L) 2(28.5 mg/L) 3(48.5 mg/L) 4(68.5 mg/L)
N removal N removal (mg/L) Week (mg/L) 1.8d 3.8c 8.6b 14.4a
1 2 3
10.1a 6.8b 4.7c
N removed end of 3rd week (mg/L)
% Removal at the end of 4th week
5.39 11.4 25.80 42.13
63.5 40 53.2 61.5
N refers NO3 − - N. Means with similar letters within a column are not statistically different at p = 0.05.
Total nitrogen(mg/100) In tissues 1304.0b 1295.7b 1375.2b 1735.2a
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Table 3 Nitrate N removal by Ipomoea aquatica and Nitrate N and Total N in tissues N level 1(4 mg/L) 2(14 mg/L) 3(24 mg/L) 4(44 mg/L) 5(54 mg/L)
N removal N removal Nitrate N removed end of % Removal end NO3 −-N in tissues (mg/L) Week (mg/L) 6th week (mg/L) of 3rd week (mg/Kg) 0.9c 3.5b 4.6b 5.3b 7.8a
1 2 3
3.6b 4.9a 4.3ab
2.7 10.5 13.8 12.9 23.4
67.5 75 57.5 36.1 43.3
Total N in tissues (mg/100g)
8.0b 6.9b 17.8ab 22.7a 26.3a
1208b 1841a 2037a 2132a 2170a
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N refers NO3 − - N Means with similar letters within a column are not statistically at p = 0.05.
The percentage nitrate N removal of Eichhornia crassipes was also studied in different concentrations of N in water. A significant increase in N removal was observed with increasing N concentration in water. At the end of third week 5.4 mg/L, 11.4 mg/L, 25.8 mg/L, and 43.2 mg/L N were removed from the water having initial N concentration of 8.5 mg/L, 28.5 mg/L, 48.5 mg/L, and 68.5 mg/L respectively (Table 2). Total N content of Eichhornia crassipes were observed as1304 mg/100 g, 1295.7 mg/100 g, and 1375.2 mg/100 g in tissues grown in water having N concentration of 8.5 mg/l, 28.5 mg/l and 48.5 mg/l respectively. Highest (1735 mg/100 g) total N content was recorded in plants grown in water having nitrate N concentration of 68.5 mg/L and the difference was statistically significant. Ipomoea aquatic. Table 3 shows means of nitrate N removal for different levels of nitrate N at different week intervals. Generally the N removal showed an increasing trend with increasing nitrate concentration in water. The average mean N removals of 0.9 mg/L, 3.5 mg/L, 4.6 mg/L, 4.3 mg/L, and 7.8 mg/L were recorded from water having the initial concentration of 4 mg/L,14 mg/L,24 mg/L, 44 mg/L, and 54 mg/L respectively. In the case of Ipomoea aquatica, highest (4.9 mg/L) nitrate N was removed in 2nd week interval followed by 3rd week (4.3 mg/L) and 1st week (3.6 mg/L). This is in contrast to the removal pattern of other two plants where highest nitrate removal was recorded during first week. This could have been attributed due to the late root development in Ipomoea aquatica which was treated as cuttings where as other two plants were treated as plants with developed root system. The percentage reduction of nitrate N by water spinach at different levels at third week shows a general increasing trend of nitrate N removal from water with increasing nitrate N concentration of water. Nitrate N removal of 2.7 mg/L, 10.5 mg/L, 13.8 mg/L, 12.9 mg/L, and 23.4 mg/L was recorded at the initial concentration of 4 mg/L, 14 mg/L, 24 mg/L, 44 mg/L, and 54 mg/L respectively. The highest percentage (75%) reduction was occurred in the concentration of 14 mg/l, while the lowest percentage (29.3%) reduction was recorded in the concentration of 44 mg/l. It could be concluded that within the range of 4 to 54 mg/L of nitrate N concentration water spinach has at least a 29% phytoremediation potential. Nitrate N content of Ipomoea aquatica. The study of nitrate N content of Ipomoea aquatica is important if the plants used as phyto- remedeators are to be used as vegetables, as higher nitrate N ingestion is harmful for health. Table 3 shows the nitrate N content in Ipomoea aquatica with different treatments at the end of third week. An increasing trend of nitrate N accumulation in plants, with increasing nitrate N in water is observed. Similar results of higher nitrate N availability in soils enhancing nitrate N accumulation in plant tissues were recorded by other workers as well (Kallio et al. 1980; Ignasio et al. 2006) possibly due to the excess nitrate N that do not involve in metabolic
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T. SUNDARALINGAM AND N. GNANAVELRAJAH Table 4 Mean values of P removal Pistia stratiotes
P level 1(0.4 mg/L) 2(20.4 mg/L) 3(40.4 mg/L)
P removal (mg/l) 0.06c 3.35b 6.67a
Week
P removal (mg/l)
P removed At the end of 6th week (mg/L)
% removal end of 6th week
Total phosphorus (mg/100g) in tissues
1 2 3 4 5 6
17.3a 1.7b 0.4c 0.3c 0.3c 0.2c
0.36 20.09 20.24
90 98.5 99.6
398c 852b 1368a
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Means with similar letters within a column are not statistically different at p = 0.05.
process tend to accumulate in tissues (Corre and Breimer 1979). The nitrate N content of 8.0 mg/Kg, 6.9 mg/Kg, 17.8 mg/Kg, 22.7 mg/Kg, and 26.3 mg/Kg were observed in plants grown in water containing nitrate N 4 mg/l, 14 mg/l, 24 mg/l, 44 mg/l and 54 mg/l respectively. Joint FAO/WHO Expert Committee on Food Additives (JECFA 2002) has established an Acceptable Daily Intake of nitrate N as 3.7 mg/Kg body weight/day. According to ADI limit a 6 month baby (7–8 kg), 1 year child (9–11 kg) and an adult (50–60 kg) may ingest 26–30 mg nitrate N/day, 33–40 mg nitrate N/day, 180–225 mg nitrate N/day without harmful effects. Accordingly the Ipomoea aquatica used to phytoremediate water with highest nitrate N of 54 mg/l, which recorded highest nitrate N content of 26.3 mg/kg, could be used as vegetable even for infants without any harmful effects. This is a win-win situation where the remediation technique not only reduces nitrate N pollution but also yields a nutritional vegetable. There was no significant variation in total nitrogen content of Ipomoea aquatica within the range of 14–54 mg/l nitrate N concentration in water. The total nitrogen content of 1207.5 mg/100 g was recorded in the nitrate N concentration of 4 mg/l in water (Table 3). Phosphorus Removal by tested Plants. Table 4 shows means of phosphorus removal with different concentration of phosphorus in water at different week intervals. The results show phosphorus reduction was significantly increased with increasing concentration of phosphorus in water. Average mean phosphorus removal was recorded as 0.06 mg/L, 3.35 mg/L, and 6.67 mg/L from the water having initial concentrations of 0.4 mg/L, 20.4 mg/L and 40.4 mg/L respectively. At the end of first week an average of 17.3 mg/L of phosphorus was removed from the water. It was significantly higher compared to removal in other week intervals. The mean amount of phosphorus removed in 2nd, 3rd, 4th, 5th, and 6th week intervals were recorded as 1.7 mg/L, 0.4 mg/l, 0.3 mg/L, 0.3 mg/L, and 0.2 mg/L respectively. Phosphorus removal was increased with increasing initial concentration and recorded as 0.36 mg/L, 20.1mg/L, and 40.02 mg/L from the initial concentration of 0.4 mg/L, 20.4 mg/L, and 40.4 mg/L respectively, recording a percentage removal greater than 90 in all treatments. The highest percentage (99.6) removal was recorded in water having 40.4 mg/L of phosphorus. At the end of the study period (6 weeks) the highest (1368 mg/100 g) total P content was measured in plants grown in the concentration of 40.4 mg/L followed by 20.4mg/L (852 mg/100 g) and 0.4 mg/L (398 mg/100 g) respectively (Table 4). The similar trend of increasing removal of phosphorus from water and increasing total phosphorus content of
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Table 5 Mean values of P removal by Eichhornia crassipes
P level 1(0.4 mg/l) 2(20.4 mg/l) 3(40.4 mg/l)
P removal (mg/l) 0.1c 6.5b 13.1a
Week
P removal (mg/l)
P removed end of 6th week (mg/L)
% removal end of 3rd week
Total phosphorus (mg/100g) in tissues
1 2 3
16.0a 2.8b 0.9c
0.3 19.48 39.27
75 95.5 97.2
837c 1838b 2046a
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Means with similar letters within a column are not statistically different at p = 0.05.
plants grown in water with increasing concentration of phosphorus confirm the removal mechanism is phytoextraction, also called phytoaccumulation. Eichhornia crassipes. Table 5 shows means of phosphorus removal under different concentration of phosphorus at different week intervals. The results show phosphorus removal was significantly increased with increasing concentration. The average mean concentrations of 0.1 mg/L, 6.5 mg/L, and 13.1 mg/L were removed from the initial concentration of 0.4 mg/L, 20.4 mg/L, and 40.4 mg/L respectively. Means of weekly phosphorus removal show decreasing trend with duration, Therefore highest reduction (16 mg/L) was observed in first week followed by 2.8 mg/L in 2nd week and 0.9 mg/L in 3rd week. The amount of phosphorus removed from water in three weeks increase with increasing phosphorus concentration. Concentration of 0.3 mg/L, 19.5 mg/L, and 39.3 mg/L were removed from the initial concentration of 0.4, 20.4, and 40.4 mg/L respectively. Highest (97.2%) and lowest (75%) percentage of removal was recorded in the concentrations of 40.4 mg/L and 0.4 mg/L respectively. Means of total phosphorus content in Eichhornia crassipes at different concentrations were measured. The results revealed that the total phosphorus content of Eichhornia crassipes was increased with increasing concentration in water and it was recorded as 837 mg/100 g, 1838 mg/100 g and 2046 mg/100 g in the concentration of 0.4 mg/L, 20.4 mg/L, and 40.4 mg/L respectively (Table 5). Ipomoea aquatic. Average phosphorus removal was recorded as 0.1 mg/L and 1.5 mg/L in the nitrate concentration of 0.4 mg/L and 5.4 mg/l respectively. While the weekly mean phosphorus removal was high in 1st week and recorded as 1.2 mg/L and the removal of 0.8 mg/L and 0.4 mg/L were recorded in 2nd and 3rd week intervals. The amount of 0.3mg/L and 4.5mg/L were removed from the initial concentration of 0.4 mg/L and 5.4 mg/L respectively at the end of three weeks. Therefore the phosphorus reduction efficiency of Ipomoea aquatica was 75% and 83.3% at the concentration of 0.4 mg/L and 5.4 mg/L respectively. The phosphorus content of 192 mg/100 g and 229 mg/100 g were recorded in Ipomoea aquatica under the phosphorus concentration of 0.4 mg/L and 5.4 mg/L respectively. So this indicates that the total phosphorus content of and Ipomoea aquatica significantly differed between two different concentrations (0.4 mg/L, 5.4 mg/L) at probability level of 0.05 (Table 6). The average mean dry matter increase of 1.4 g, 2.6 g, 2.4 g, 2.5 g, and 2.4 g were recorded in Ipomoea aquatica under the nitrate N concentration of 4 mg/L, 14 mg/L, 24 mg/L, 44 mg/L, and 54 mg/L respectively. Similar to dry matter, length increase of Ipomoea aquatica cuttings was measured in weekly intervals. Statistical analysis of the data revealed that there was general increase in length with increasing concentration of
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T. SUNDARALINGAM AND N. GNANAVELRAJAH Table 6 Mean values of P removal by Ipomoea aquatic
P level
P removal (mg/l) 0.1b 1.5a
1(0.4 mg/L) 2(5.4 mg/L)
Week
P removal (mg/l)
1 2 3
1.2a 0.8b 0.4c
P in Ipomoea aquatica (mg/100g)
P removed end of 3rd week (mg/L)
% Removal end of 3rd week
192b 229a
0.3 4.5
75% 83.3%
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Means with similar letters within a column are not statistically different at p = 0.05.
nitrate in water. But significantly lower increase in length was observed from plants grown in the nitrate concentration of 4 mg/L (Table 7).
DISCUSSION Nitrate (from 252 mg/L to 25 mg/L) and phosphorus (from 47.5 mg/L to 12.4 mg/L) removal from a pilot lagoon sewage system by Pistia stratiotes has already been reported (Fonkou et al. 2002). They also reported higher total nitrogen content of plants (4.09–5.10%) compared to the lower total nitrogen (2.3–4.2%) in the present study. This is because the plants were grown in water containing less nitrate (maximum 68.5 mg/L) compared to the previous experiment (252 mg/L). Another study by Qin et al. (2010) using Pistia stratiotes in treatment plots of two storm water detention ponds revealed that the inorganic N (NH4 + and NO3 −) concentrations in Pistia stratiotes treated water were more than 50% lower than those in non-treated water and Pistia stratiotes in treated water contained average N and phosphorus concentrations of 1.7 and 0.37% DM respectively. Potential of Eichhornia crassipes to remove nitrogen and phosphorus from in wastewater of a textile mill (Gamage and Yapa 2001), from upgraded facultative lagoon (Wolverton and McDonald 1979), and a lake (Sangeeta 2007) also has been reported. Similarly nitrogen and phosphorus removal from eutrophic water of deep flow technique (Hu et al. 2008) using Ipomoea aquatica also has been reported. However, according to Alade and Ojoawo (2009), nitrogen and phosphorus content of waste water treated with Eichhornia crassipes was increased by 77.5% and 66.3% respectively. The increased nitrate and phosphate ion concentration would have been due to the mineralization of the organic matter found in waste water. As the ground water has negligible organic matter content there was no possibility of nutrient mineralization in the present study. Table 7 Means of dry matter increase in Ipomea aquatic
N level 1(4 mg/L) 2(14 mg/L) 3(24 mg/L) 4(44 mg/L) 5(54 mg/L)
Dry matter increase (g)
Length increase (cm)
1.4a 2.6a 2.4a 2.5a 2.4a
12.8b 21.0a 23.5a 24.5a 27.3a
P level
Dry matter increase (g)
Length increase (cm)
1(0.4 mg/L) 2(5.4 mg/L)
2.0a 2.4a
19.8a 23.8a
N refers NO3 − - N Means with similar letters within a column are not statistically different at p = 0.05.
PHYTOREMEDIATION POTENTIAL OF SELECTED PLANTS
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RECOMMENDATION All the past studies were carried out in waste water. The present study was carried out using ground water which is used as drinking water for human and animals. This study therefore indicates that nitrate pollution of ground water for human consumption can be overcome by phytoremediation technique using Ipomoea aquatica. As Ipomoea aquatica is used as a vegetable it will be accepted by people. Moreover, for livestock consumption ground water can be phytoremediated using either Eichhornia crassipes or Pistia stratiotes as these plants are also used as animal feed. On the other hand as reported by other workers quality of waste water could be improved by either Pistia stratiotes or Eichhornia crassipes (Zimmels et al. 2006, 2008; Alade and Ojoawo 2009) or Ipomoea aquatica (Hu et al. 2008). As present study indicate that these three plants could be grown in ground water having hardness, any waste water generated from industries using ground water, loaded with either nitrate or phosphorus can also be remediated using any of these plants. CONCLUSIONS The three tested plants have the potential to remove nitrate and phosphorus from ground water having hardness of 375 mg/L. Pistia stratiotes was able to remove 61.5–91.8% of nitrate N from treated water for the period of six weeks. Highest removal was observed during first week interval. Phosphorus was efficiently removed than nitrate N by Pistia stratiotes and it was recorded as 90–99%. The nitrate N removal by Eichhornia crassipes was significantly increased with increasing nitrate concentration in water. The removal rate of nitrogen was recorded from 40–63.5% and highest (10.1 mg/L) nitrate N was removed during first week interval. Eichhornia crassipes had better removal effect on phosphorus than nitrogen and it was 75–97.2%. The study using and Ipomoea aquatica showed that there was a significant reduction in nitrate N in water and it was observed in the range of 29.3–75%. Highest nitrate N removal was observed in 2nd week interval (4.9 mg/L). The highest nitrate N in tissues of Ipomoea aquatica was recorded as 26.3 mg/kg in the concentration of 54 mg/L of nitrate in water. Therefore Ipomoea aquatica used for phytoremediation treatment could be used as vegetable without any harmful effects even by infants according to the ADI (Acceptable Daily Intake) by JECFA (FAO/WHO 2002). REFERENCES Akinbile CO, Yusoff Mohd S. 2012. Assessing water hyacinth (Eichhornia crassopes) and lettuce (pistia stratiotes) effectiveness in aquaculture waste water treatment. Int J Phytorem 14(3):201–21. Alade GA, Ojoawo SO. 2009. Purification of Domestic Sewage by Water-Hyacinth (Eichhornia Crassipes). Int J of Environ Tech Manage 10 (3/4):286–294. Corre WJ, Breimer T. 1979. Nitrate and Nitrite in Vegetables. Center for Agricultural Publishing and Documentation (Wageningen, Netherlands); 2009 February. Available from: http://www. cababstractsplus.org/Abstract.aspx?AcNo=19810717971. Cunningham SD, Ow DW. 1996. Promises and prospects of Phytoremediation. J of Plant Physio 110:715–719. Ensley BD. 2000. Rationale for the Use of Phytoremediation. In: Raskin I, Ensely BD, editors. Phytoremediation of toxic metals: Using plants to clean-up the environment. New York (NY): John Wiley Publishers. p. 231–246. FAO/WHO. 2002. Summary and Conclusions. Joint FAO/WHO Expert Committee on Food Additives, Fifty-ninth meeting, 2002. Available from: www.fao.org/es/ESN/Jecfa/59corr.pdf.
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