Abstract:
The tropic state of a water body is important to maintain its sustainablity. Nitrogen and phosphorus
are the main nutrients which determines the tropic levels. The eutrophic water bodies host large
quantities of organisms, including algal blooms (Cyanobacteria). Cyanobacteria is observed in nature
similar to the other algae species in all eutrophic aquatic ecosystems. Cyanobacteria is well
recognized for its effective toxins such as Microcystins and Cylindrospermopsins. In July, 2020, the
Microcystins levels of Allewella and Lenabatuwa lakes in Kamburupitiya area were 2 µgL-1
and 1.7
µgL-1
, respectively, which exceeds the WHO recommendation of 1 µgL-1
. Therefore, efficient and
cost effective method for controlling eutrophication is timely essential. An artificial floating wetland
is an innovative method which has been successfully practiced all over the world. The present
study focused on the purification of a tank in the Faculty of Agriculture, University of Ruhuna,
Kamburupitiya with artificial floating wetland consisted with three plant species; Ipomoea aquatia
(Kangkung), Acorus calamus (Wada kaha) and Bacopa monnieri (Lunuwila).The main objective
is to find the most suitable plant species for water purification based on absorption and biomass
accumulation of N and P in each species. The experiment was conducted for three and half months
as a randomized complete block design with three replicates and 36 plants per each replicate from
each species. One week old plants were established in the 2m x 2m styro foam structure. Water
quality parameters (pH, Temperature, DO, NH4
+
-N, NO3
-
-N, PO4
3-
, Zooplankton and
Phytoplankton) were tested twice during the study period to identify the water quality in the particular
tank. Plant parameters (Total N and P, plant height and root shoot ratio) were measured and were
analyzed by one-way ANOVA using SAS software. According to the results Wada kaha has the
significantly (P < 0.05) highest nitrogen absorption capacity (0.098 ppm) and Kang kung (0.042
ppm) and Lunuvila (0.019 ppm) are followed by more to less absorption capacity. As phosphorus
absorption, Wada kaha has significantly higher (P < 0.05) capacity (0.21 ppm) and Lunuvila (0.09
ppm) is with second highest absorbance treatment and Kang kung (0.06 ppm) is with the least.
The findings of the present study reveal that the artificial floating wetlands are suitable for removing
nitrogen and phosphorus from eutrophic water bodies