Evaluating the Efficiency of Bioreactor with Triangular Cross Section to Remove Nitrate from Agricultural Wastewater

Nitrate is one of the most important pollutants in drainage water in agricultural lands. Biological removal or reduction of nitrate has recently been considered in different parts of the world. The bioreactor with the denitrification process is one of the newest solutions for this purpose. Scientific and local experience is needed to optimally use the bioreactor. Due to the existence of Moghan irrigation and drainage network and a high volume of effluent, this study was conducted to evaluate the efficiency of bioreactor for removal of nitrate at Moghan plain conditions. The cross-section of bioreactor was triangular and water retention times were 12, 16 and 24 hours. The bioreactor core was selected from wood chip, wheat straw and corn chips as carbon-based and treated substrates, and each treatment had three replicates. Results of 12 hours retention time showed that, on average, the wood chip reduced the initial nitrate by 29.84%, which had the highest nitrate depletion among the organic matters. The performance of the two other organic matters was not significantly different according to Duncan test. In 16 hours retention time, the performance of bioreactors with different organic matters was statistically different for nitrate removal and the wood chip, wheat straw and corn stalk treatments were prioritized with 40.1, 35.23 and 28% nitrate removal, respectively. In 24 hours retention time, although all three treatments had the same performance for nitrate removal from agricultural wastewater, the wood chip treatment with 46.75% removal efficiency was the best. The results also showed that the percentage of nitrate removal increased with increasing the retention time for all three treatments.