ASSESSMENT OF RICE MILL WASTEWATER AND ITS IMPACT ON GERMINATION AND SEEDLING GROWTH OF RICE

Abstract

An investigation was carried out to assess the suitability for agricultural purpose of 21 rice mill wastewater samples collected from different locations of Dinajpur sadar upazila, Birol upazila, Bochagonj upazila of Dinajpur district. Analyses included pH, EC, TDS (Total dissolved solids), cations (Ca2+, Mg2+, Na+, K+, Cu2+, Mn2+, Fe3+) and anions (HCO3-, SO4 2-, PO4 3- and Cl-). Several computed variables such as SAR (Sodium adsorption ratio), hardness (HT), permeability index (PI), Kelly‟s ratio, Gibbs ratio and potential salinity to evaluate the suitability of wastewater for specific uses. The wastewater were found basic (pH varied from 6.38 to 6.90) and suitable for rice. Wastewater samples contained Ca2+, K+ and Na+ as the dominant cations and HCO3- and Cl- were the dominant anions. According to EC value, the samples were excellent and good for germination purposes. The SAR value of all water samples under test were excellent classes. Maximum samples were within hard class regarding hardness. Based on, Cl- and PO4 3- all rice mill wastewater samples were within the 'safe' limit for germination. The positive coefficient of correlation among pH, EC, TDS, Mg, K, HT, Ca, Mg, K, Na and HCO3 reproduced that the quality of the free soil solution may indicate the distribution of sodium ion in the absorbed phase. On the other hand the negative coefficient of correlation pH-TDS, pH-EC, pH S,pH-P, Ca-Mg,Na-Na, Na-Cl indicated that the increase of one parameter will result in the decrease of the aforementioned parameters. Germination index (GI), Final germination parcentage (FGP),Vigour index (VI), shoot and root length of rice seedlings and using different rice mill wastewater samples were also performed. The highest germination index was recorded in the treatment of T11 (10.70) rice seedlings. The highest final germination percentage(FGP) was recorded in the treatment of T15 (93.33) rice seedlings. The highest vigour index (VI) was recorded in the treatment of T10(51), T11(51), T16(51) and T21(51) rice seedlings. The highest shoot and root weight of seedlings were found in wastewater treatment. It was observed that some wastewater effluents could also delay germination and growth of rice seedlings. However, overall view the rice mill wastewater was suitable for germination and also effluent from rice mill wastewater could be utilized for irrigation purposes after proper treatment.