Performance and modeling of a vertical flow constructed wetland-maturation pond system.
ABSTRACT A 32-month monitoring program is presented in a vertical flow constructed wetland facility, located in North Greece. The monitoring campaigns were organized every 15 days. Water quality samples were collected at the inlet, at four intermediate points (i.e., at the end of each treatment stage) and at the outlet of the system. Temperature, electrical conductivity, pH and dissolved oxygen (DO) were measured in-situ with the use of appropriate instruments at the same points of water sample collection. Water samples were analyzed for biochemical oxygen demand (BOD), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), ammonia, nitrate, nitrite, total phosphorus (TP), ortho-phosphate (OP), total suspended solids (TSS) and total coliforms (TC). Mean removal efficiencies for the monitoring period were: 90.8% for BOD, 89.0% for COD, 83.9% for TKN, 83.8% for ammonia, 38.8% for TP, 17.4% for OP, 90.4% for TSS and 99.9% for TC, indicating, for most pollutant, excellent performance of this constructed wetland (CW) system under Mediterranean climate conditions. Results showed that organic matter, TSS, TKN, ammonia, TP, OP and TC removal is not significantly affected by temperature. The collected removal data were used to produce appropriate parameter values for first-order k-C* models and develop simple models based on stepwise multiple linear regression (SMLR) analysis, in an effort to predict CW performance. These models were verified using data from another facility located in the same region. The results showed that the predictions correlate well with measured values, leading to the conclusion that the first-order models and the developed SMLR models are useful tools in the design of vertical flow (VF) CWs.
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ABSTRACT: Nine pilot wetlands (eight free water surface and one subsurface flow) have been constructed in Queensland as joint projects between the State and Local Governments, to treat municipal wastewater. The wetlands are in several geographical locations which include tropical, subtropical and arid climates. Each wetland is a different configuration and contains a variety of macrophyte types and species. Most species are native and were collected in the locality or self colonised. This paper examines the performance efficiency of the wetlands and nutrient bioaccumulation in wetland plants. Biochemical oxygen demand concentrations were reduced by 17–89% and suspended solids concentrations by 14–77% to produce wetland effluent with BOD less than 12 mg l−1 and suspended solids less than 22 mg l−1. Reduction in total nitrogen concentrations ranged from 18 to 86%, ammonia nitrogen from 8 to 95% and oxidised nitrogen from 55 to 98%, producing effluent with total nitrogen between 1.6 and 18 mg l−1. Reduction in reactive phosphorus concentration was less than 13% in the free water surface systems with concentration in the effluent exceeding the influent in many of the systems over long term operation. In contrast reduction through the single household subsurface system was 65%. Nutrient bioaccumulation was investigated in 60 species. Submerged (Ceratophyllum) and free floating species (duckweed) had the highest tissue nutrient concentrations, followed by the waterlily (Nymphoides indica), aquatic vines (Ipomoea spp., Ludwigia peploides), and waterferns (Ceratopteris, Marsilea). All these species remove nutrients from the water column. Emergent species had lower nutrient concentrations with the highest nutrients occurring in the exotic sedge Cyperus involucratus. Aquatic grasses including Phragmites had higher nutrient content than the sedges. Nitrogen concentrations were higher in leaf/stem tissue compared to the root/rhizome, whereas phosphorus was higher in root/rhizome tissue. Emergent species had a greater biomass than submerged or free floating species and were therefore able to store more nutrients per unit area of wetland. Cropping the shoots of emergent species increased nutrient content in new shoot growth.Ecological Engineering. 01/1999;
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ABSTRACT: A small-scale horizontal subsurface flow constructed wetland, located in North Greece, was designed and constructed to treat wastewater from a single-family residence. A three-year monitoring program was undertaken to evaluate the performance of this system. The monitoring campaigns were organized every 7 days. Water quality samples were collected at the inlet, at intermediate points (i.e. at the end of each treatment stage) and at the outlet of the system. Temperature, electrical conductivity, pH and DO were measured in-situ with the use of appropriate instruments at the same points of water sample collection. Water samples were analyzed for BOD, COD, TKN, ammonia, nitrate, nitrite, total phosphorus (TP), ortho-phosphate (OP), total suspended solids (TSS) and total coliforms (TC). Mean removal efficiencies for the monitoring period were: 86.5% for BOD, 84.6% for COD, 83.7% for TKN, 82.2% for ammonia, 63.1% for OP, 63.3% for TP, 79.3% for TSS and 99.9% for TC. Furthermore, based on statistical testing, TKN, ammonia and TP removal efficiencies showed dependence on temperature. The paper presents facility description, study details and monitoring results. The study shows that the use of constructed wetlands in wastewater treatment is a good option for single-family residences in rural areas.Water Science & Technology 01/2010; 62(3):603-14. · 1.10 Impact Factor
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ABSTRACT: In order to investigate the effect of temperature, hydraulic residence time (HRT), vegetation type, substrate material and wetland shape on the performance of free-water surface (FWS) constructed wetlands treating wastewater, 5 pilot-scale units were constructed and operated continuously from December 2004 until March 2007 in parallel experiments. Four of the units (A, B, C, D) were rectangular in plan view with dimensions 3.40 m in length and 0.85 m in width, and contained substrate material at a thickness of 0.45 m. The fifth unit (E) had a trapezoidal plan view shape, with a width at the inlet of 1.15 m and at the outlet of 0.55 m, while the length and the thickness of the substrate were the same as in the other four. All units operated at a water depth of 0.10 m. Units B–E contained clay substrate and unit A contained sand. The four units with clay were planted as follows: two with cattails (B and E), one with common reeds (C), and one with giant reeds (D). Unit A, containing sand, was planted with cattails. Planting and substrate material combinations were appropriate for comparison of the effect of vegetation and material type on the function of the system. Synthetic wastewater was introduced in the units. During the operation period four HRTs (i.e., 6 days, 8 days, 14 days and 20 days) were used, while wastewater temperatures varied from about 0.0 °C to 29.1 °C. The removal performance of the five constructed wetland units was good, since it reached on the average 77.5%, 67.9%, 60.4%, 53.9%, 56.0% and 51.7% for BOD, COD, TKN, ammonia (NH4-N), ortho-phosphate (PO4-P) and total phosphorus (TP), respectively. BOD and phosphorus removal efficiencies showed dependence on temperature in most units. The 14-day HRT was found adequate for acceptable removal of organic matter, nitrogen and phosphorus for most temperatures. A 20-day HRT is recommended for acceptable removal of BOD and PO4-P in the cold season. The unit with the trapezoidal plan view shape showed the best performance, with mean removals of 80.1%, 73.5%, 70.4%, 68.6%, 64.7% and 63.5% for BOD, COD, TKN, NH4-N, PO4-P and TP, respectively. The cattail was found statistically more efficient than the other two plants in COD and PO4-P removal. The unit that contained the clay substrate was found statistically more efficient in phosphorus removal than the unit containing sand. HSF CW units were found more efficient than FWS units in removal of most pollutant.Ecological Engineering. 01/2010;