Abstract:
Sugarcane molasses-based ethanol industries in Sri Lanka generate large volumes of
high strength spent wash, causing severe environmental issues. The potential toxicity
of spent wash on biological systems and the possibility of using it as a nutrition
source in agriculture has been given less attention in Sri Lanka. The present study
was conducted to assess the physicochemical characteristics of the raw spent wash
and possible cytogenotoxic effects of diluted spent wash using a plant-based bioassay
with Allium cepa (common onion). Further, to evaluate the potential of raw spent
wash as a liquid nutrition source to improve the growth of commonly grown
vegetable variety, tomato (Solanum Lycopersicum).
Selected physicochemical parameters of raw spent wash collected from the distillery
industry of Lanka Sugar Company (Pvt) Ltd, Pelwatta, were evaluated using APHA
(2017) standard procedures. Toxicity assessment was carried out after exposure
of Allium cepa bulbs to diluted spent wash (1:8) along with aged tap water (negative
control) following standard protocols. The tomato crop experiment was conducted as
an open field experiment using agricultural guidelines provided by the Department of
Agriculture with certified organic fertilizer as positive control and tap water as a
negative control. Growth morphometric attributes of the plants and fruits were
monitored for 60 days. The data were statistically analyzed using univariate
statistical methods.
The physicochemical analysis revealed that the spent wash is highly acidic with high
EC (21.93 ± 0.09 mS/cm), COD (92,101 ± 0.33 mg/L), BOD (26,116 ± 2.33
mg/L)TSS (4,076 ± 0.55 mg/L), TDS (68,656 ± 0.13 mg/L), Nitrate (255 ± 0.04
mg/L) and phosphate (38 ± 0.07 mg/L), and contained heavy metals viz. Cd, Cu, Ni,
Zn, As and Mn and K in trace amounts. Significantly decreased root growth was
found in Allium roots exposed to diluted raw spent wash with the highest root growth
delay (92%) after two days of exposure compared to the negative control (p < 0.05).
The mitotic index did not show any difference in all exposure conditions.
Significantly increased nuclear abnormalities, including micronuclei, nuclear buds,
binuclei and condensed nuclei, were observed in root tip meristematic cells of diluted
spent wash compared to the negative control (p < 0.05). Among growth-related
morphometric attributes of tomato plants treated with different spent wash doses
(0.5, 1.5, 2.5, 5.0, 7.5 and 10 mL), shoot lengths, the number of leaves and number of
buds and flowers were found to have less significant variations. In contrast, other
treatment categories recorded significantly reduced fresh fruit weight compared with
the positive control (p < 0.05). Measured fresh fruit weight was more favourable
toward high-end doses. However, this should be confirmed by repeated scientific
studies. Results of the experiments reflect that the raw spent wash may have a
cytogenotoxic effect, and the spent wash may use as a nutrition supplement by
mixing with other organic ingredients. Further experiments for different crops, soil
testing, and frequent biological effects monitoring are recommended to verify the
spent wash's nutritional use and toxic effects
Citation:
Kuruppuarachchi, H.D. (2022). Physicochemical analysis, toxicity assessment and nutrition source potential of sugarcane distillery spent wash [Master's theses, University of Moratuwa]. Institutional Repository University of Moratuwa. http://dl.lib.uom.lk/handle/123/20988