Assessing the Efficacy of Waste Organic Solids as Carbon Sources in Denitrification Bio-filters for Abating Nitrate Toxicity from Wastewater

Abstract

Wastewater treatment is used to preserve the quality of scarce freshwater resources and improve their usability. Solid-phase denitrification is a method that has the potential to improve nitrate removal from wastewater. Being heterotrophic by nature, the source of organic carbon determines how well the denitrification process proceeds because both a lack of and an abundance of organic carbon cause disruptions in the heterotrophic denitrifiers’ usual metabolism. So, choosing the right carbon source is crucial for the best denitrification process. Therefore, the purpose of this study is to evaluate a few locally available waste organic solids as potential carbon source for heterotrophic denitrifiers. The primary research variables included in this project were the influent flow rate, influent nitrate concentration, and amount of carbon source and its effect on denitrification rate. Batch and continuous mode of experiments were used to thoroughly study and assess the denitrification potential of agricultural wastes, namely rice straw (RS), wheat straw (WS), tender coconut shells (CS) and mix of the three. Maximum denitrification efficiency of 96.13% was achieved in continuous mode of operation, surpassing the efficiency of each individual carbon source of 72.6% (WS), 60.3% (CS), and 58.6%. (RS). When the physical features of the organic wastes were examined using SEM, FTIR, and EDS, the findings showed significant morphological changes in samples after denitrification as compared to original samples. The nitrate reduction ability of the microbial strains isolated from the denitrifying column as confirmed by biochemical characterization validated the experimental evidences of this study. These results provide a theoretical framework for effectively using agricultural waste as a solid carbon source and improving denitrification efficiency in wastewater treatments.