The effect of the Geometric Shape of Bioreactors and Organic Matter on the Efficiency of Nitrate Removal from Drainage Water

Abstract

Denitrification bioreactors for nitrate removal from agricultural water effluents have improved in recent years due to their low cost and ease of use. Scientific results and local experience are required for the optimal use of bioreactors. This study aimed to study nitrate removal efficiency and the effectiveness of each of these factors. Thus, 27 pilot bioreactors had the same volume and depth with different cross-sections in a randomized statistical design. Three geometric shapes of the trapezoid, rectangle, and triangle for the cross-section bioreactors and three organic matters including wood chips, corn stem chips, and wheat straw in 3 replications were used. Nitrate concentration at the inlet of the reactor and their outlet was measured at hydraulic retention times of 3, 6, 12, 16, and 24 hours. According to the average nitrate removal from the effluent, wood chips, wheat straw, and corn stem chips with 31.3, 28.6, and 27%, respectively, were prioritized during the 24-hour hydraulic retention time. Therefore, wood chips are the most suitable organic matter for nitrate removal from drainage water in actual biological reactors compared to other organic materials used in this study. The results demonstrated nitrate removal the 25.6, 30.1, and 35.3% for triangular, rectangular, and trapezoidal geometric shapes, respectively, for wood chips organic matters. Also, reactors with trapezoidal cross-sections have higher efficiency. In sum, this study showed that where there is a limit to the supply of wood chips, wheat straw and corn stalk chips can be used in bioreactors to remove nitrate.