Enhanced wastewater nutrients removal in vertical subsurface flow constructed wetland: Effect of biochar addition and tidal flow operation. (January 2022)

• Record Type: Journal Article
• Authors: Chand, Naveen; Kumar, Kapil; Suthar, Surindra
• Is Part Of: Chemosphere. Volume 286:Part 2(2022)
• Publication Date: 2022-01
• Subjects: Wastewater treatment -- COD -- N load in wastewater -- Cattle dung -- Nitrification; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2021.131742
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Dissolved oxygen (DO) and carbon stock in substrate medium play a vital role in the nutrient removal mechanism in a constructed wetland (CW). This study compiles the results of dynamics of DO, ammonium N (NH4 + -N), nitrate (NO3 –N), sulfate (SO4 −2 ), phosphate (PO4 −3 ), chemical oxygen demand (COD), in three setups of vertical-flow constructed wetlands (TFCWs) (SB: substrate + biochar; SBP: substrate + biochar + Colocasia esculenta plantation; SP: substrate + Colocasia esculenta (SP), operated with tidal flow cycles. Experimental analyses illustrated the continuous high DO level (2.743–5.66 mg L −1 ) in SB and SBP after the I and II cycle of tidal flow (72 h flooding and 24 h dry phase). COD reduction efficiencies increased from 15.75 – 61.86% to 48.55–96.80% after tidal operation among operating TFCWs. N (NH4 + -N) and N (NO3 –N) removal were found to be 88.16%, and 76.02%; 49.32, and 57.85%; and 40.23%, and 48.94 % in SBP, SP and SB, respectively. The theory of improved nitrification and adsorption through biochar amended substratum was proposed for TFCW systems. PO4 −3 and SO4 −2 removal improved from 22.63 to 80.50%, and 19.69 to 75.20%, respectively after first tidal operation in all TFCWs. The microbial inhabitation on porous biochar could promote the transformation of available P into microbial biomass and also helped by the plant uptake process while SO4 −2 reduction in TFCWs could be mainly due to sulfate-reducing bacterial activity and nitrate reduction process, mainly facilitated by high DO and biochar addition in such setups. The study suggests that effluent re-circulation through tidal operation and biochar supplementation in the substratum could be an effective mechanism for the improvement of the working efficiencies of CWs operated with low energy input systems. Highlights: Tidal flow operation with effluent re-circulation improved DO load remarkably. The tidal flow with biochar addition improved COD (96.08%) and NH4 + -N (88.16%) removals. Improved oxidation and adsorption were the main pathways for nutrient removals.