title: Effects of step-feeding and intermittent aeration on organics and nitrogen removal in a horizontal subsurface flow constructed wetland.
abstract: The effect of step feed strategy and intermittent aeration on removal of chemical oxygen demand (COD) and nitrogen was investigated in a laboratory scale horizontal subsurface flow constructed wetland (HSSFCW). Wetland was divided into four zones along the length (zone I to IV), and influent was introduced into first and third zones by step feeding. Continuous study was carried out in four phases. In phases I to III, 30% of influent was bypassed to zone III for denitrification along with organics removal. Intermittent aeration was provided only in zone II at 2.5 L/min for 4 h/day, during phases II, III and IV. In phase I, 87% COD and 43% NH4+-N (ammonia-nitrogen) removal were obtained from influents of 331 and 30 mg/L, respectively. In phase II study, external aeration resulted in 97% COD and 71% NH4+-N removal in the wetland. In phase IV, 40% of feed was delivered to zone III. Higher supply of organic in zone III resulted in higher denitrification, and total nitrogen removal rate increased to 70% from 56%. In the final effluent, concentration of NO3--N was 9-11 mg/L in phase I to III and decreased to 4 mg/L in phase IV. Batch study showed that COD and NH4+-N removal followed first order kinetics in different zones of wetland.
authors.affiliation: a Department of Civil Engineering , Indian Institute of Technology Guwahati , Assam , India.
authors.forename: Sagar
authors.initials: S
authors.lastname: Patil
authors.affiliation: a Department of Civil Engineering , Indian Institute of Technology Guwahati , Assam , India.
authors.forename: Saswati
authors.initials: S
authors.lastname: Chakraborty
mesh_terms: D001673:Biodegradation, Environmental; D057919:Biological Oxygen Demand Analysis; D058440:Denitrification; D052918:Environmental Restoration and Remediation / Q000379:methods*; D009584:Nitrogen / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry*; D062065:Wastewater / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*; D053833:Wetlands
chemical_list: D009584:Nitrogen; D009930:Organic Chemicals; D062065:Wastewater
keywords: Denitrification; external aeration; nitrification; step feeding; total nitrogen removal