Analysis of Raw Water Quality of Water Supply Intakes of Maha Oya

Maha Oya is one of the main rivers in Sri Lanka, very much used for drinking waterextraction. It flows through five important districts of Sri Lanka offering water throughfourteen water supply intakes, eight of which are located along the main river while othersare scattered along the tributaries. Only three of the associated plants offer conventionaltreatment for water. This river receives much organic waste from the upstream. Industrialdischarges and harmful anthropogenic activities are common in the final stretch of the river.This study aims to investigate the contamination of Maha Oya water around each intakepoints along the main river and to find causes. Samples were collected from water supplyintakes during both high and low flow rate conditions. Analysis was done on pH, turbidity,DO, COD, BOD, phosphate, Nitrate, Sulfate, Chloride, Fluoride, Coliform and heavy metalswhich were selected based on the drinking water quality requirements of the country.According to the results, Mawanella Intake records high BOD and Coliform counts due to themunicipal and house hold discharges from the townships, overflow of Soakage pit and septictanks of Mawanella town during rainy seasons. Waste load coming from three tributariesconfluences was attributed to high values of BOD, COD and coliform count while cultivationin the vicinity has increased the nutrient at the Hirwadunna intake. COD value of thesampling location at the Allawwa intake is very high. As it is located in the Allawwa town,waste from the town is disposed to the river directly and concentration is very high duringlow flow conditions. Girulla intake is polluted mainly from bank erosion due to theanthropogenic activities like cay mining. COD and BOD values are comparatively high dueto direct discharges. Pollution associated with Bamukuliya intake is due to the discharge ofMakandura IP. The effect is reduced when it comes to the Bambukuliya intake even though itexceeds the COD for drinking water with simple treatment. Sea intrusion has not affected theBambukuliya intake due to the salinity barrier at Bambukuliya. Heavy metal concentration ofall intakes are below the respective standards.

Performance of tropical vertical subsurface flow constructed wetlands for leachate treatment at different hydraulic loading rates

This study is focused on the investigation of three different types of plant species namely; Narrow leaf Cattail (Typha angustifolia), Green Bulrush (Scirpus atrovirens) and Umbrella Palm (Cyperus alternifolius) for treatment of leachate. Twelve laboratory scale subsurface flow constructed wetland models were operated in batch mode. Four models, each containing similar plant species were fed with synthetic leachate having four different concentrations (25%, 50%, 75% and 100%) and 7 days HRT was given. The duration of a batch run was 12 weeks. Removal efficiencies of BOD5, COD, PO43-, TC, and TN were measured. Evapotranspiration (ET) loss of each test run was also assessed. According to the results, the constructed wetland planted with Umbrella palm and fed with 25% leachate showed the best pollutant removal efficiencies of 99.26% for BOD5, 99.61% for COD, 98.78% for TN and 97.34%for TC. Highest ET potential of 93.57% was also observed from the constructed wetland with umbrella palm fed with 25% leachate. Two way ANOVA analysis was carried out for each plant species and leachate concentration and the Umbrella Palm species was identified as the best for leachate treatment.Key words: Constructed wetlands, landfill leachate, plant species and pollutant remova

Modeling the Water Quality of Attanagalu Oya

Attanagalu Oya is an economically important river in Sri Lanka which is a major source of supplying potable water, water for industries, irrigational activities and for the maintenance of aquatic ecosystems. Rapid urbanisation and anthropogenic activities in the catchment area increase the level of pollution of the river basin and it is one of the river basins that is constantly affected byfloods. The current study focused on the statistical analysis of data that had been acquired through assessment of the water quality of Attanagalu Oya and the impact of rainfall on the river basin using 16 water quality parameters collected from 10 water quality monitoring stations and 5 rainfall gauging stations. The trends in rainfall in the river basin and water level were investigated using Mann-Kendall’s test and Sen’s slope estimator test. The results of trend analysis of rainfall showed a negative trend in January and a positive trend in June for the Katunayake rain gauge station. The results of monthly trend analysis for the water level confirmed the potential for flood occurrence in May. Generalised linear and ARIMA models were developed to predict daily precipitation and water level of the river basin and flood alerts in Attanagalu Oya were forecasted with sufficient leadtime. Multivariate analysis revealed that cluster analysis is an efficient technique to identify homogeneous clusters among sampling sites and water quality parameters. Moreover, the principal component analysis and factor analysis determined the major sources of pollutants contributing towards water pollution in each identified homogeneous cluster. The ordinal logistic model fitted predicts the flood alerts with an accuracy of 93.7%. Therefore, the results and techniques used for this study could be applied in further research work to explore the pollution extent of the river. Thus, this model can be used by the respective authorities for decision making purposes in effective water quality management.Keywords: Attanagalu oya, Water quality, Multivariate analysis, Trend analysi