Microcosm Wetlands for Wastewater Treatment with Different Hydraulic Loading Rates and Macrophytes

Abstract

Constructed wetlands (CW) usually require large land areas for treating wastewater. This study evaluated the feasibility of applying CW with less land requirement by operating a group of microcosm wetlands at a hydraulic retention time (HRT) of less than 4 d in southern Taiwan. An artificial wastewater, simulating municipal wastewater containing 200 mg L(-1) of chemical oxygen demand (COD), 20 mg L(-1) of NH4+-N (AN), and 20 mg L(-1) of PO4(3-)-P (OP), was the inflow source. Three emergent plants [reed, Phragmites australis (Cav.) Trin. ex Steud.; water primrose, Ludwigia octovalvis (Jacq.) P.H. Raven; and dayflower, Commelina communis L.] and two floating plants [water spinach, Ipomoea aquatica Forssk.; and water lettuce, Pistia stratiotes L.] plants were tested. The planted systems showed more nutrient removal than unplanted systems; however, the type of macrophytes in CW did not make a major difference in treatment. At the HRTs of 2 to 4 d, the planted system maintained greater than 72,80, and 46% removal for COD, AN, and OP, respectively. For AN and OP removal, the highest efficiencies occurred at the HRT of 3 d, whereas maximum removal rates for AN and OP occurred at the HRT of 2 d. Both removal rates and efficiencies were reduced drastically at the HRT of 1 d. Removals of COD, OP, and AN followed first-order reactions within the HRTs of 1 to 4 d. The efficient removals of these constituents obtained with HRT between 2 and 4 d indicated the possibility of using a CW system for wastewater treatment with less land requirement.

Performance of Tropical Vertical Subsurface Flow Constructed Wetlands at Different Hydraulic Loading Rates

“…Contaminant REs were estimated as the percentage change in concentration after treatment using Equation . Following this, relevant mass loading rate (MLR) and mass removal rate (MRR) in g*P/m 2 /day (P = pollutant concentration) for BOD 5 , TSS, NH 4 + ‐N, NO 3 − ‐N, and PO 4 3− as well as coliform unit removal in CFU/m 2 /day (CFU = colony forming units) for FC and TC were calculated using Equations and , respectively . where, C i = Influent concentration of the wastewater parameter; and C o = Effluent concentration of the wastewater parameter.…”

“…This approach has been adopted for wastewater management in many parts of the world due to easy construction, low cost, simple operation, efficient and robust treatment , low sludge production , and superior ecological values . Many researchers have reported that CWs could remove a wide variety of pollutants effectively from wastewater including suspended solids, organic matter, nutrients, and heavy metals . Furthermore, it has been found that CWs can tolerate high variability of influent wastewater load .…”

“…Of these, the VSSF CWs are gaining popularity due to their greater oxygen transfer capacity and smaller land requirements . However, the treatment performance of contaminants in these wetland systems depends largely upon the wetland design, and is a function of the characteristics of wastewater, inflow pollutant concentrations, land availability, hydraulic regime, and the climatic conditions .…”

Designing a Constructed Wetland for the Detention of Agricultural Runoff for Water Quality Improvement

“…4. Cross-sectional diagram of the constructed wetland system design. are often used to predict the breakdown of pesticides and nutrients as well as the removal of pathogenic microorganisms (Alvord and Kadlec, 1996;Jamieson et al, 2007;Jing et al, 2002;Kadlec, 1999;Khatiwada and Polprasert, 1999;Moore et al, 2001):…”

Improvement of Sand Filter and Constructed Wetland Design using an Environmental Decision Support System

“…Several technologies for upgrading the quality of WSP effl uent have been studied (Harris et al, 1977;Middlebrooks, 1995;Saidam et al, 1995;Neder et al, 2002;Kim et al, 2003;Wang et al, 2005), among which intermittent sand fi lters (ISFs) and vertical fl ow constructed wetlands (VFCWs) have been successfully applied. Th e performance of these combined technologies is not completely understood because many variables, such as wastewater pretreatment, fi ltration media, planted macrophyte, hydraulic and organic loading rates, wastewater temperature, and dosing technique and frequency, aff ect the treatment effi ciency (Anderson et al, 1985;Jing et al, 2002).To increase the knowledge on the variables aff ecting the effi ciency of these treatment systems, a wastewater treatment plant (WWTP) combining WSP and ISF, and WSP and VFCW was built in the small community (300 population equivalents [PE]) of Aurignac, France. Th e experts participating in this project defi ned a protocol to collect data and knowledge from a 2-yr experimental operation of the Aurignac WWTP (Torrens et al, 2006).…”