COD and NH₄-N Removal in Two-Stage Batch-Flow Constructed Wetland

Abstract:

Research was conducted on pilot-scale, two-stage batch-flow constructed wetland systems for domestic wastewater treatment. Synthetic domestic wastewater was treated in a pre-acidification reactor with a hydraulic retention time (HRT) of 3 hours and the average removal rate of chemical oxygen demand (COD) and ammonia-nitrogen (NH₄-N) reached 30% and 13.6%, respectively. The first-stage constructed wetland operated with up-flow and batch feed and drain. One cycle was 12h, including 6h feed and 6h drain. With HRT of 3 days, the effluent COD concentrations fluctuated from 32.5 mg/L to 103.4 mg/L, removal rates varied from 60% to 88%; effluent NH₄-N concentrations were in the range of 4.8 mg/L to 10.8 mg/L, removal rates varied from 50% to 70%. The second-stage constructed wetland operated with down-flow, which one cycle was 24h, including 12h feed and 12h drain. With HRT of 1 day, effluent COD concentrations varied from 15.7 mg/L to 48.7 mg/L, removal averaged 53.2%; effluent NH₄-N concentrations ranged from 0 mg/L to 0.4 mg/L, average removal exceeded 99%. The spatial variation of COD and NH₄-N in the first-stage constructed wetland demonstrated that entrainment of air during draining of constructed wetland could strengthen the removal of COD and NH₄-N. Temperature had no significant effect on COD degradation while obviously affected the removal of NH₄-N.

• Periodical: Applied Mechanics and Materials (Volumes 448-453)
• Pages: 604-607
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.448-453.604
• Online since: October 2013
• Authors: Hong Jie Sun, Xin Nan Deng, Rui Chen
• Keywords: Ammonia-Nitrogen, Batch Load, Chemical Oxygen Demand, Constructed Wetland, Wastewater

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