Removal of Solids and Oxygen Demand from Aquaculture Wastewater with a Constructed Wetland System in the Start-Up Phase

• Published in: Water environment research 2002-03, Vol.74 (2), p.136-141
• Main Authors: Lin, Ying-Feng, Jing, Shuh-Ren, Lee, Der-Yuan, Wang, Tze-Wen
• Format: Article
• Language: English
• Subjects: ALGAE; Applied sciences; Aquaculture; AQUACULTURE WASTEWATER; artificial wetlands; Biodegradation, Environmental; Biological and medical sciences; Biological treatment of waters; Biotechnology; Capital costs; Chemical oxygen demand; Chlorophyll; Cod; CONSTRUCTED WETLANDS; Ecosystem; Effluents; Energy consumption; Environment and pollution; Eukaryota; Exact sciences and technology; Filtration; Fish culture; Fundamental and applied biological sciences. Psychology; Hydraulics; Industrial applications and implications. Economical aspects; Loading rate; Other wastewaters; Oxygen - metabolism; OXYGEN DEMAND; Particle Size; Pollutants; Pollution; Research Papers; Sedimentation & deposition; SUSPENDED SOLIDS; Waste Disposal, Fluid - methods; Wastewater; Wastewater treatment; Wastewaters; Water Movements; Water Purification - methods; Water treatment; Water treatment and pollution; Wetlands
• ISSN: 1061-4303; 1554-7531
• DOI: 10.2175/106143002X139848

A pilot-scale, constructed wetland system consisting of a free water surface (FWS) and a subsurface flow (SF) wetland operated in series was set up for treating aquaculture farm wastewater. This study examined the system start-up phenomena and evaluated its performance in removing suspended solids, algae, and chemical oxygen demand (COD) under various hydraulic loading rates (1.8 to 13.5 cm/d). The SF wetland achieved stable effluent qualities without an adaptation period, while the FWS wetland required approximately 5 months to reach consistent removal levels for suspended solids and algae. Macrophyte density was a critical factor affecting the reduction of suspended solids and chlorophyll for the FWS wetland, but not for the SF wetland. Suspended solids removals in both of the wetlands and the combined system (47 to 86%) decreased significantly as the hydraulic loading rate increased, strongly following the first-order mass-decrease equation. Phytoplankton solids (biomass and detritus) were a primary source of suspended solids in the aquaculture wastewater. Both chlorophyll reduction (76 to 95%) and COD removal (25 to 55%) in the constructed wetland system were apparently not affected by hydraulic loading. While algae died out because of limited sunlight in both wetlands, algae detritus probably still contributed fine particles that were difficult to remove from the water by either filtering or settling out. Removed suspended solids did not result in the increase of COD and nutrients, indicating that further solids stabilization occurred in the wetland system.