Affiliations: Environmental Engineering Division, Department of
Chemistry, ITER SOA University, Jagamora, Bhubaneswer – 751030, Orissa, India | P.G. Department of Environmental Sciences (Auto.),
Sambalpur University Jyoti Vihar - 768019, Orissa, India
Abstract: The physico-chemical characteristics of rice mill wastewater was
measured and the effect of rice mill wastewater on respiration and enzyme
activities (amylase, invertase, protease and dehydrogenase) of rice cropped
soil was investigated under field and pot conditions at 15 days interval for 90
days. For the pot experiment five different concentrations (0, 25, 50, 75 and
100%) of rice mill wastewater was used. The results of the field experiment
revealed significant difference in the soil respiration and enzyme activities
rates of control and experimental plots from 30 days onwards. After 90 days the
soil respiration and enzyme activities were inhibited by about 25-34% in
experimental plots, whereas the results of the pot experiment revealed a
maximum increase of about 36% in soil respiration and 24-45% in enzyme
activities (amylase, invertase, protease and dehydrogenase) in 50% wastewater
irrigated soil and a maximum decrease of about 40% in soil respiration and
24-40% in enzyme activities in 100% wastewater irrigated soil. The adverse
effects of rice mill wastewater (100%) on soil respiration and enzyme
activities were attributed to alkaline pH (8.0) of wastewater with higher
contents of phenols (35 mg^{-1}l), silica (58 mg^{-1}l)
and sodium (235 mg^{-1}l).
Significant increase in soil respiration and enzyme activities at lower
concentrations (i.e. 50%) may be due to the fact that, the above parameters
being in the diluted form could favour the microflora to boost their
activities. On the basis of above findings, we suggest that the rice mill
wastewater should be diluted up to 50% before use for agricultural purpose.
However, further works on the effect of rice mill wastewater on different crops
and soil animals are needed to corroborate the present findings.
