Synthetic Floating Plant Clusters for Urban Storm Water Depolluting System

Abstract

Urban storm water runoff during its flow picks up pollutants from pervious and
impervious surfaces of various urban infrastructures. Wide range of pollutants can
occur in an urban runoff which can degrade the nearby water sources. Therefore, the
urban storm water runoff needs to be treated to remove pollutants in order to
reduce its effect on ponds, lakes, rivers, etc. Various filtering materials have been
experimented for treatment of the same, but found not practicable due to high
frequency of clogging. Studies have been carried out using floating wetlands to
remove nutrients from waste streams. Researchers have evidently proved that these
systems can provide reasonable extent of treatment for the runoff waters as well.
The root zone of the plants plays a very important role in removal of organic and
inorganic, metal and nonmetal pollutant loads, which are picked up during the flow.
In the present study, the polyurethane sheet (2 nos.) having surface area of 0.2×0.2
m2 and thickness of 0.025 m and Eichhornia crassipes, are used for construction of
floating plant clusters. A channel of volume of 0.25 m3 is used as reactor for
depolluting system in which a constant flow of synthetic storm water 0.00025,
0.0005 and 0.001 m/min is maintained. A synthetic urban runoff is prepared in the
laboratory which constitutes nutrients and heavy metals. The treated water is taken
for analyzing turbidity, nitrate, phosphorus, lead, zinc and cadmium. The system
showed a promising result of >80% nutrient removal. Similarly, heavy metal removal
by floating plant clusters is found to be >85%. Hence, urban storm water collection
and conveyance system, if planned and managed properly, can be provided with
synthetic floating plant clusters as mesocosm to remove nutrients and heavy metals
from the stream.