Removal of Ammonia from Hatirjheel Water through Phytoremediation

Abstract

In Bangladesh, most surface water bodies are susceptible to contamination from disposal of untreated domestic and industrial wastewater. Surface water bodies receiving wastewater are characterized by low levels of DO and high concentrations of BOD, COD, Ammonia and other nutrients. Year-long monitoring of Hatirjheel water quality showed sustained high concentrations of Ammonia, with concentrations approaching 28 mg/l in at some locations; such high concentration of Ammonia is adversely affecting the entire ecosystem of Hatirjheel. In this study, pilot-scale experiments have been carried out to assess possible removal of Ammonia from Hatirjheel water through phytoremediation utilizing three plant species: (a) Water lettuce, (b) Duckweed, and (c) Water hyacinth. Among these, water hyacinth was found to be efficient in removing Ammonia from water; Ammonia concentration was reduced from 14.5 mg/l to about 1 mg/l within a week. Nitrification and incorporation of ammonia/nitrate into algal mass, with concomitant rise in pH, have been found to be important mechanisms for transformation of ammonia in the experimental systems. The sediment of Hatirjheel has been found to contribute significant amount of ammonia to the water column; estimated ammonia flux varied from 0.60 to 13.5 mg ammonia per kg of sediment. While phytoremediation holds promise for removal of Ammonia from water, ammonia flux from the bottom sediments of Hatirjheel could make it difficult to remove Ammonia from Hatirjheel water.

Full text

175
IICSD-2015
International Conference on Recent Innovation in Civil Engineering for Sustainable Development
(IICSD-2015)
Department of Civil Engineering
DUET - Gazipur, Bangladesh
Removal of Ammonia from Hatirjheel Water through Phytoremediation
Mehnaz Shams, Iftaykhairul Alam, Md. Atauzzaman and Muhammad Ashraf Ali
1
Department of Civil Engineering, Bangladesh University of Engineering and Technology (BUET),
Dhaka 1000, Bangladesh
Abstract
In Bangladesh, most surface water bodies are susceptible to contamination from disposal of untreated
domestic and industrial wastewater. Surface water bodies receiving wastewater are characterized by low
levels of DO and high concentrations of BOD, COD, Ammonia and other nutrients. Year-long
monitoring of Hatirjheel water quality showed sustained high concentrations of Ammonia, with
concentrations approaching 28 mg/l in at some locations; such high concentration of Ammonia is
adversely affecting the entire ecosystem of Hatirjheel. In this study, pilot-scale experiments have been
carried out to assess possible removal of Ammonia from Hatirjheel water through phytoremediation
utilizing three plant species: (a) Water lettuce, (b) Duckweed, and (c) Water hyacinth. Among these,
water hyacinth was found to be efficient in removing Ammonia from water; Ammonia concentration was
reduced from 14.5 mg/l to about 1 mg/l within a week. Nitrification and incorporation of
ammonia/nitrate into algal mass, with concomitant rise in pH, have been found to be important
mechanisms for transformation of ammonia in the experimental systems. The sediment of Hatirjheel has
been found to contribute significant amount of ammonia to the water column; estimated ammonia flux
varied from 0.60 to 13.5 mg ammonia per kg of sediment. While phytoremediation holds promise for
removal of Ammonia from water, ammonia flux from the bottom sediments of Hatirjheel could make it
difficult to remove Ammonia from Hatirjheel water.
Keywords: Flux of ammonia, phytoremediation, water column
1. Introduction
Ammonia occurs naturally in water bodies arising from microbiological decomposition of nitrogenous
compounds in organic matter; ammonia is also introduced into surface water bodies through discharge
of wastewater. At particularly high concentrations it can harm aquatic lives [1]. Hatirjheel serves very
important hydrologic functions of draining and detaining storm water from a large area of Dhaka city.
Although designed to retain storm water, the storm sewers discharging into Hatirjheel carry both
storm water and sewage, causing pollution of the water body. One of the major pollutants in
Hatirjheel water is ammonia, which is adversely affecting the entire ecosystem of Hatirjheel. Organic
sludge accumulating at the bottom sediment of Hatirjheel undergoes decomposition and releases the
decomposition products, including ammonia, in the water column. This study assesses removal of
ammonia from water through phytoremediation [2, 3, 4, 5] utilizing three commonly available plant
species.
2. Material And Methods
2.1. Collection of plant samples and water
The Khude Pana (Local name) or Duckweed (Azolla pinnata) and Topa Pana (Local name) or Water
lettuce (Pistia stratiotes) plant samples were collected from ponds in Gazipur, while the Kochuripana
1
Corresponding Author, Professor of Civil Engineering, BUET, Dhaka; Email:mashrafali88@gmail.com;
Tel.: 01713-043325
Paper ID: EE-002

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(Local name) or Water hyacinth (Echhornia erassipes) plants were collected from Dasherkandi area
(close to Aftabnagar). Water samples were collected in large drums (150 L capacity) from Hatirjheel.
2.2. Phytoremediation experiments
Two glass aquariums (thickness of glass having 1 cm) with dimensions of 3’x3’x2.5’ (91cm x 91cm x
76cm) were used for carrying out the phytoremediation experiments and placed on the rooftop of
Civil Engineering Building, BUET. In the first phase, phytoremediation experiments were carried out
using Water lettuce and Duckweed; while during the second phase, phytoremediation experiments
were carried out using Water hyacinth. For comparison, blank experimental set up with only
Hatirjheel water (and no plants) was used in both phases.
2.3. Estimation of ammonia flux from sediment
Two 70 liter plastic buckets were used in the experimental set up; 20 liter sediment sample collected
from Hatirjheel was placed in one bucket. Then 30 liters of Hatirjheel water was added to both the
buckets. Initially both buckets were placed in a shaded area (away from sunlight); subsequently, the
buckets were kept under sunlight to see the possible effect of sunlight on ammonia
removal/transformation.
3. Result And Discussion
3.1. Phytoremediation experiments with Water lettuce and Duckweed
Figure 1 shows variation of ammonia concentration in water samples from the first phase of
experiments with Water lettuce and Duckweed. While ammonia removal from the water samples was
very efficient within a week, the plants do not appear to have any effect on ammonia removal, since
ammonia removal from water samples with plants were almost identical to that of the “blank”.
Possible mechanisms of ammonia removal from water are: (1) Conversion of ammonia to nitrate
(nitrification); (2) Escape of ammonia to air; (3) Uptake of ammonia by plants; and (4) Incorporation
of ammonia into algal mass.
Figure 1. Variation of ammonia concentration in water Vs Time
If the increase in nitrate concentration comes from conversion of ammonia to nitrate, then the
estimated maximum conversion of ammonia to nitrate for the three samples is as follows (see Figure
2): Sample 1: (11.6 – 3.4) = 8.2 mg/l (67.0% of initial ammonia conc.) ; Sample 2: (8.1 – 3.5) = 4.6
mg/l (35.6% of initial ammonia conc.); Blank 2: (7.7 – 1.9) = 5.8 mg/l (45.0% of initial ammonia
conc.). Hence, at the peak level of nitrate concentration, conversion of ammonia to nitrate could
account for significant removal/ transformation of ammonia in the water samples (see Figure 2).
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
NH3-N(mg/L)
Day
Sample 1
with Topa
Pana
Sample 2
with Khude
Pana
Blank
Sample 1
Blank
Sample 2

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Figure 2. Variation of nitrate concentration in water Vs Time
This conversion (from ammonia to nitrate) should be accompanied by lowering of pH (due to release
of H+); however, pH of all water samples increased during the first week of experiment (see Figure 3).
So a process was active that increased the pH of water samples significantly. The chemical reaction
for formation of algae is often written as follows:
16 CO2 + 16 NO3 + HPO42- + 122 H2O + 18 H+ = C106H263O110N16P + 138 O2 … … … (1)
So, algal bloom, accompanied by consumption of H+, could be responsible for the observed rise in pH
of water (see Eq. 1). High algae (specifically Chlorophyll a) concentrations (see Table 1) and elevated
levels of DO in the water samples support this phenomenon. So it appears that incorporation of
ammonia/nitrate in algal mass may be responsible for removal/ transformation of ammonia in the
experimental water samples.
Figure 3. Variation of pH in water Vs Time
Table 1: Chlorophyll a concentration in water samples from the first phase of experiment
Sample
ID
Date of
testing
Days after
commencement of
experiment
Chlorophyll a
(μg/L)
1
08/02/2015
32
168.7
2
08/02/2015
32
158.6
Blank 1
08/02/2015
27
203.6
Blank 2
08/02/2015
12
554.0
0
5
10
15
20
25
NO3-N (mg/L)
Day
Sample 1
with Topa
Pana
sample 2
with Khude
Pana
Blank
Sample 1
Blank
Sample 2
0
1
2
3
4
5
6
7
8
9
10
11
pH
Day
Sample 1
with Topa
Pana
Sample 2
with Khude
Pana
Blank
Sample 1
Blank
Sample 2

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At pH above 9.26, ammonia escapes to air from water. But as discussed earlier, the rise in pH was
mainly due to formation of algal mass. So escape to air was probably not the dominant mechanism for
ammonia removal. Also due to the identical removal rate of ammonia from all samples including
blanks, uptake of ammonia by plants do not appear to be the dominant ammonia removal mechanism.
3.2. Phytoremediation experiments with Water hyacinth
Figure 4 shows variation of ammonia concentration in water samples from the second phase of
experiments with Water hyacinth. Concentration of ammonia decreased with time in both samples in
identical rate and it comes close to a stable level after about 6 to 7 days.
Figure 4. Variation of ammonia concentration in water Vs Time
For these experiments, conversion of ammonia to nitrate does not appear to be significant, as peak of
nitrate concentration was only about 6 mg/l, and eventually nitrate concentration goes down,
indicating other mechanisms for removal of nitrate (see Figure 5).
Figure 5: Variation of nitrate concentration in water Vs Time
The pH value of the water sample with Water hyacinth decreased during the course of the experiment,
as shown in Figure 6. Thus, for the sample with Water hyacinth, formation of algal mass does not
appear to be an important mechanism for removal/transformation of ammonia/nitrate. Also, the pH
value of the water sample with Water hyacinth did not reach 9.26; hence, escape of ammonia into air is
not an important mechanism for ammonia removal/transformation from the water sample with Water
hyacinth. On the other hand, the pH of the “blank” increased significantly (see Figure 6). So reduction
of ammonia for the blank sample appears to be due to incorporation of ammonia/nitrate in algal mass.
As the three possible mechanisms (i.e., incorporation into algal mass, nitrification, escape to air) do
not appear to be important mechanisms for ammonia removal for the water sample with Water hyacinth,
the only logical way for removal of ammonia from the water sample with Water hyacinth is uptake of
ammonia by the Water hyacinth plants.
0
5
10
15
20
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
NH3-N (mg/L)
Day
Sample 1 with
Kochuripana
Blank sample
0
2
4
6
8
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
NO3-N (mg/L)
Day
Sample 1 With
Kochuripana
Blank sample

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Figure 6: Variation of pH in water Vs Time
3.3. Estimation of ammonia flux from sediment to water column
Figure 7 shows Ammonia concentration of water samples in contact and without contact with
Hatirjheel sediment. Ammonia concentration in in contact with Hatirjheel sediment is always higher
than that without the sediment. It shows that ammonia is contributed to the water column from the
sediment. Figure 7 also shows that Ammonia removal from both the water samples was relatively
slow in the absence of direct sunlight and became very fast in direct sunlight, signifying the role of
sunlight in formation of algal mass and removal of ammonia from water. The estimated ammonia flux
from sediment to water column (in mg Ammonia per kg of sediment) varies from 0.6 to 13.6 (Table 2).
Thus, contribution of ammonia from sediment to the water column could be significant.
Figure 7: Variation of ammonia concentration in water Vs Time
Table 2: Estimation of ammonia flux from sediment
Date
Estimated Ammonia Flux from Sediment
(mg Ammonia/kg of Sediment)
13/06/2015
8.5
14/06/2015
11.0
15/06/2015
11.8
16/06/2015
11.9
17/06/2015
13.6
18/06/2015*
12.8
19/06/2015*
--
20/06/2015*
0.7
21/06/2015*
0.6
*Samples were kept without direct exposure to direct sunlight up to 17th June 2015; from 18th June, 2015 the
samples were kept in sunlight.
0
2
4
6
8
10
12
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
pH
Day
Sample 1 With
Kochuripana
Blank sample
0
2
4
6
8
10
12
14
16
NH3-N (mg/L)
Day
Sample with sludge
(without sunlight)
Sample without sludge
(without sunlight)
Sample with sludge
(with sunlight)
Sample without sludge
(with sunlight)

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4. Conclusions
Uptake of ammonia by Water lettuce and Duckweed has not been found to be significant. But, Water
hyacinth appears to be efficient in removing ammonia from water. Sediment of Hatirjheel contributes
significant amount of ammonia to the water column. More detailed study should be carried out to
better understand the removal of ammonia from water by Water hyacinth, including factors affecting
removal and removal rates along with the feasibility of this process. Also a study should be carried out
for detailed assessment of contribution of sludge in ammonia concentration in Hatirjheel.
5. References
[1] Francis-Floyd, R., Watson, C., Petty, D., and Pouder, D. B. (2012), Ammonia in Aquatic
Systems, University of Florida Fisheries and Aquatic Sciences Department, Document TA16.
[2] Anandha V. R., Kalpana S. (2015), Performance Analysis of Nutrient Removal in Pond Water
Using Water Hyacinth and Azolla with Papaya Stem, International Research Journal of
Engineering and Technology (IRJET), Vol. 2(1).
[3] Headley, T.R., Tanner, C. C. (2011), Innovations in constructed wetland treatment of storm
waters utilizing floating emergent macrophytes. Critical Reviews in Environmental Science and
Technology.
[4] Hettiarachchi, G. M., Nelson N. O., Agudelo-Arbelaez S. C., Mulisa Y. A., and Lemunyon J. L.
(2012), Phytoremediation: protecting the environment with plants. Kansas State University.
[5] Williams, J. B. (2002), Phytoremediation in wetlands ecosystems: Progress, Problems and
Potential. Critical Rev. Plant Sci. 21(6): 607-635