Abstract:
Integrated Development of Hatirjheel Area Including Begunbari Khal project was undertaken with
a view to connect the eastern and western part of Dhaka City. During wet season number of storm
sewers are carrying domestic sewage and industrial wastewater into the lake. Although the
implementation of the project has brought about a significant change in the overall environment of
Dhaka City, but the water quality of the lake and sludge deposition specially behind Hotel
Sonargaon still remains as a serious concern.
Constructed Floating Wetland (FCW), a low-cost green treatment technology is a viable option to
enhance the pollutant removal abilities of various water bodies. The system purifies water through
the microorganism living in the plant roots of CFW. Bacteria colony grows up within nodule or
root which helps to reduce the water pollution.
A primary research on removal ability of CFW for Hatirjheel Lake water was done with the twofold objectives: (1) To evaluate the removal of pollutants including nutrients from the polluted
surface water of Hatirjheel Lake through the application of CFW system and (2) To investigate the
influence of seasonal variation on the removal process of pollutants. To conduct the research total
eight plastic water containers of dimension 6'x3'x4' were used for the experimental set up behind
Hotel Sonargaon. Two locally available plants like Cana Indica (Kolabati) and Phragmites
Australis (Nol Ghas) were used and one-month time was given for plants to grow. Afterwards
matching with the inlet and outlet flow pattern of Hatirjheel Lake, experimental containers were fed
with 200 liters of daily dosing. Then water samples were taken from the container once in a week
and were sent to MIST Lab for getting results on several water quality parameters like BOD5,
COD, DO, Nitrate, Ammonium, Orthophosphate, Colour, TDS and TSS. A total of eleven-week
(20 October to 21 January 2018) data were collected during dry season and six-week (14 August to
20 September 2018) data during wet season. A blank/reference sample was taken to compare the
water quality variation with time. The performance of the plants was evaluated in terms of
removing nutrients, contaminants and heavy metals from the lake water. The removal ability
during dry season was found much better than wet season. Removal capability of the system were
found quite high for some parameters like (COD 82%, Color 83%, TSS 85%, Orthophosphate 78%,
Ammonium 80% and BOD5 55%) and moderate performance for other parameters like TDS 50%,
Nitrate 62%, DO 32%. The experiment showed great potentials in terms of removing heavy metals
like As, Cd, Cr, and Pb. As a whole the system was found to be effective as an environment
friendly and low-cost technology for enhancing the water quality of Hatirjheel Lake and this
approach can be applied in other lakes and waterbodies in Dhaka City.
