Abstract:
Kurunegala Sewage Treatment Plant (STP) is treating both grey and black water from the
houses, hospitals and the commercial buildings around the city. The treated effluent is releasing
to the nearby Boo Ela, after meeting the quality standards of the Central Environmental
Authority (CEA). Objectives of this study were (a) to determine the irrigation water quality of
treated municipal wastewater and Boo Ela water and (b) the effect of water quality of these
water sources on the growth and yield of paddy. Selected irrigation water quality parameters
such as pH, Electrical Conductivity (EC), Total Dissolved Solids (TDS), Chloride, Sodium
Adsorption Ratio (SAR) and Nitrate-nitrogen in treated wastewater, Boo Ela (before adding
treated wastewater), and mixed water (Boo Ela water + treated wastewater) were determined.
Three sources of water namely Boo Ela (BW), treated wastewater (TW) and mixed water (MW)
were used for determine of effect on growth and yield of paddy (BG 305) as treatments. The rice
experiment was laid out according to the Complete Randomized Block Design (CRBD). Seed
germination percentage (%), plant survival percentage (%) (first week), paddy plant height (cm)
(5 day intervals), number of leaves in a one plant (5 day intervals), number of tillers per plant (5
day intervals), tiller panicle length (cm) (last week), number of seeds given by each plant (per
pot) (at the end of three months), weight of the seeds (g) (at the end of the three months) were
measured. Irrigation water quality parameters of pH (5.5-9.0), EC (2250 µS/cm), TDS (2100
mg/L), chloride ion (600 mg/L) and SAR were within the recommended limits and Nitrate nitrogen was in suitable range according to the standards provided by the Food and Agricultural
Organization (FAO). The highest and lowest seed germination percentages were obtained in BW
water and TW, respectively. The seed germination percentages are significantly affected by
sources of water (p<0.05). The survival percentage, the plant height, number of leaves, number
of tillers, panicle length, number of seeds and seeds weight were not significantly different under
three different types of irrigation water. Based on this study, the irrigation water quality of three
sources of irrigation water were suitable for irrigation of paddy and it can be concluded that the
growth and development of paddy were not affected by the prevailing water quality of three
sources of water.
