Enhance nitrogen removal in bioretention cells with addition of hydrothermal pre-treated pine barks as external carbon source

Abstract

The problem of poor carbon source is a common factor limiting the nutrients removal in bioretention cells (BRCs). This study aimed to investigate the feasibility of using modified biomass in BRCs filled with a mixture of fly ash ceramsite and pumice fillers to enhance nitrogen removal. Different pretreatment methods (hydrothermal-treated, acid-treated and alkali-treated) were attempted, and hydrothermal pretreatment showed a best performance in carbon release ability. The scanning electron microscopy showed that the lignin in hydrothermal pretreated pine barks (H-PBs) was destroyed, and the fiber structure became thinner with more irregular folds, which improved the accessibility of cellulose and attachment of microorganisms. The addition of H-PBs significantly enhanced the nutrients removal in BRCs, and the removal rates of TN and NO3−-N increased by 23.25% and 38.22% compared with those in BRC-A (without external carbon source), but the removal rate of NH4+-N was inferior to BRC-A. Besides, the large carbon release amount of H-PBs did not deteriorate the effluent quality, with COD removal rate of 87.98% in the 48 d. These results indicate that the BRCs by adding H-PBs could intensify the denitrification process.

Nutrient Removal Efficiencies in a Bioretention Cell Using Pre-Treated Coconut By-Product as Carbon Source

“…Therefore, enhancing the soil composition recommended by MSMA through the inclusion of carbon sources as additives has been discovered to efficiently improve nutrient removal, especially for nitrogen species (NH4+, TN, NO3-, NO4-), TP, COD and TSS from the contaminated stormwater. Previous studies have recorded that carbon sources such as pine bark [4], fly ash [5], corn cob, rice straw, rice husk [6], and sawdust [7], are suitable for this application.…”