Impact of Diluted Municipal and Sugar Mill Wastewaters on the Vegetative Growth of Oryza sativa L.

Abstract

This study evaluated the physiological and biochemical responses of two rice varieties, Basmati-385 and Shaheen Basmati, to varying concentrations of municipal sewage water (MSW) and sugar mill effluent (SME) to assess the potential use of diluted wastewater for irrigation. A controlled experiment was conducted using five treatments: distilled water (control), raw undiluted effluent, and 25%, 50%, and 75% diluted effluents. Germination kinetics, seedling biomass, photosynthetic pigments (chlorophyll a, chlorophyll b, and carotenoids), proline accumulation, and ionic composition (Na⁺, K⁺, and Ca²⁺) were analyzed to determine plant responses. Results demonstrated a concentration-dependent biphasic effect of wastewater treatments. The 25% dilution significantly enhanced germination percentage, root and shoot biomass, and photosynthetic pigment content in both rice varieties compared with the control, indicating that moderate dilution provided beneficial nutrients that promoted plant growth. In contrast, raw and highly concentrated effluents caused severe phytotoxicity, including reduced growth, impaired pigment synthesis, elevated proline accumulation, and increased cellular injury. Ion analysis showed excessive Na⁺ accumulation under higher effluent concentrations, whereas the 25% dilution maintained a comparatively balanced ionic status by enhancing K⁺ and Ca²⁺ uptake. Overall, the findings suggest that properly diluted wastewater, particularly at 25%, may support rice growth and serve as an alternative irrigation resource. However, untreated or highly concentrated effluents may adversely affect plant physiology and productivity. Further investigations on heavy metal accumulation, grain quality, and long-term environmental impacts are necessary before recommending wastewater irrigation for sustainable agricultural practices.