Abstract
This study conducted two experiments to evaluate the effects of two cheap adsorbents, including bentofeed (a commercial name of bentonite) and Persian melon peel biochar (PMPB) on the decolorization of water contaminated by methylene blue (MB) and ruminal fermentation pattern. The decolorization efficiency of bentofeed and PMPB at three levels of 0, 4, and 8 mg per 10 ml of 0, 3, 6, and 9 mg/L MB solutions mg/L after 3 and 24 h of incubation was evaluated by its absorbance at 660 nm. At all dye concentrations, PMPB, and bentofeed showed high potential in removing MB from water with an efficiency of 60%-99.5%. In both incubation times, the addition of 8 mg bentofeed had the highest effect on the removal efficiency when the dye concentration was 6 or 9 mg/L. However, the removal efficiency was declined with increasing MB concentration (p <0.05). Experiment two evaluated the effects of various levels (same as experiment one) of MB, bentofeed, and PMPB on in vitro gas production (GP) and volatile fatty acids (VFA) in two individual 4×3 factorial experiments. The potential GP (b), rate constant of gas production (c), metabolizable energy, organic matter digestibility, and total VFA were significantly decreased with increasing MB in the medium (p <0.05), while all parameters were increased when bentofeed or PMPB was added to the medium containing MB (p <0.05). The amounts of acetic, propionic, and butyric acids were not affected by PMPB; however, they changed when bentofeed was added to the medium (p <0.05). The NH3-N concentration was decreased significantly following the increase of MB; moreover, it was increased when PMPB and bentofeed were added to the medium. MB, as a water contaminant agent, had negative effects on ruminal fermentation parameters. Both adsorbents (i.e., PMPB and specially bentofeed) were efficiently able to remove MB from the water. The negative effects of MB on fermentation parameters were also alleviated as a result of using bentofeed or PMPB. It seems that bentofeed has the higher adsorption property of MB, compared to that of the PMPB.