Water pollution study in Nalanada Lake to improve the Water quality of Naula Water Treatment Plant
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Date
2015
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Uva Wellassa University of Sri Lanka
Abstract
Water is the largest natural resources of Sri Lanka although only a relatively low percentage of
total population is getting safe and clean water for daily use. Water is using for Drinking, bathing,
washing, and cleaning. Beside it is used for agriculture, industrial, hydropower generation.
The Nalanda reservoir located in Naula, Matale district is the main water source of Naula Water
Treatment Plant of National Water supply and Drainage Board (NWSDB). On the other hand
NWSDB faces a big problem in the dry season because pumping water had a less amount of
Dissolved Oxygen (DO) and occurring black color in pumping water. The dissolved oxygen (DO)
concentration is a primary measurement of a stream’s healthiness. The dissolved oxygen
concentration responds to the biochemical oxygen demand (BOD) load. Investigators have
continuously studied the dissolved oxygen uptake characteristics in stream water in relation to
different sinks and sources in order to develop mathematical models describing the DO
consumption.
In this reservoir percent high amount of Algae due to high nutrients content such as nitrate and
phosphorous and change that algae type seasonally. One of the objectives of this research study is
that Nitrate and Phosphorus variation in reservoir. And Main Objective was identification of the
Dissolved Oxygen (DO) Variation in Nalanda reservoir.
Methodology
In this study six sampling location points were selected and studied the variation of nitrate,
phosphorous and DO of these sampling points for four weeks of time. These data were collected
in rainy and dry season. Samples were collected from the different distances from the intake of
Naula Water Supply System. Totally 24 samples were collected from the upstream of the
reservoir. Basically, the selected pollution points are surrounding point of the reservoir. Samples
were taken from different morphological units of the reservoir. DO was analyzed at the sample
collected points and COD and BOD also analyzed using the Standard laboratory procedures.
Finally DO concentration variation was analyzed by using mathematical model called Streeter-
phelps.
Results and discussion
Eutrophication of water body is occurred under high nutrients. The nutrients such as nitrate and
phosphate distribution within selected pollution points in Nalanda reservoir is shown in figure 1.
The recommended phosphate level for maintaining healthy water to minimize algae growth is 0.1
mg/L and nitrate level is 10 mg/L (USEPA). The results shown below indicated that the nitrate
level was within required limit and phosphate level was exceeded limit. Therefore, phosphate
consuming algae species can occur in Nalanda reservoir during this period.
Description
Keywords
Mineral Sciences, Materials Sciences, Science and Technology, Waste Water Treatment, Water Pollution, Water quality