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Abstract: Two large-scale subsurface constructed wetland pilot plants were designed, implemented and operated for almost three years for the treatment of a real municipal wastewater. One unit was running in a horizontal flow (HFCW) with a surface area of 654.5m2, while the other one was a sub-tidal vertical flow (VFCW) with 457.6m2 surface area. The two wetland units were operated at a hydraulic load of 20m3/day for each unit and at temperature ranged from 15 to 30°C. The organic loading rate was 2.02kg BOD/day. The two pilot units were planted with three kinds of plants namely; Canna, Phragmites and Cyperus. Monitoring and evaluation of the performance of the two pilot units were carried out through regular physico-chemical as well as biological analysis of the inlet and outlet wastewater. In addition, nutrient uptake in the plants was also measured. The results indicated significant removals of different pollutants in both HFCW and VFCW in terms of COD, BOD and TSS. The average removal efficiencies of COD, BOD and TSS in HFCW were 91.5%, 92.8% and 92.3%, while it reached 92.9%, 93.6% and 94% in VFCW. However, VFCW proved to be more efficient than HFCW not only in COD, BOD removals but also for nitrification because of the tidal vertical flow, which allows the penetration of more oxygen, beside its small size and long detention time. The removal rate of ammonia due to nitrification reached 62.3% in VFCW, while in HFCW it reached 57.1%. In addition, the results indicated that most of the plants survived for almost 12 months and their growth depend on the type of constructed wetlands (CW) used. In conclusion VFCW proved to be more effective for wastewater treatment than HFCW due to its smaller size, high quality effluent and better nitrification. [Copyright &y& Elsevier]

Abstract: A pilot scale vertical flow constructed wetland unit (VFCW) with a surface area of 457.56m2 was built within the vicinity of a wastewater treatment plant, North Cairo, Egypt. The wetland unit was planted with three kinds of plants namely; Canna, Phragmites australis and Cyprus papyrus. The wetland unit was fed with primary treated municipal wastewater at influent flow rate of 20m3/day and surface loading rate ranged between 26.2kgBODha−1 day−1 and 76.5kgBODha−1 day−1 and a detention time of 7.7 days. The efficiency of VFCW after two years operation was evaluated in terms of both mass removal and water quality improvement, both physico-chemically and biologically. The biological analysis was carried out for total coliform, fecal coliform, and Escherichia coli. The accumulation of the elements in the plants organs and their uptake with the harvested macrophyte were also measured. The results obtained showed that the average removal efficiency of COD, BOD and TSS in the final effluent were 88%, 90%, 92%, respectively with corresponding residual values of 30.60mg/l, 13.20mg/l and 8.50mg/l. The amount of nutrients accumulated in the plants which represented by total phosphorus and total kjeldahl nitrogen were 32.55g/m2 and 68.10g/m2. Also, significant reduction of total coliform, fecal coliform were achieved. To conclude, the quality of treated effluent proved that the use of VFCW as a post treatment step is an effective technology for wastewater treatment and use for irrigation in rural areas and small communities. [Copyright &y& Elsevier]

Abstract: In 2007, a constructed wetland system was implemented on the tourist island of Koh Phi Phi in Southern Thailand. This paper presents the process of planning, designing and implementing the system and discusses the performance and operational issues 3 years after implementation. The system is an international lighthouse project showing the potential for aesthetical integration of constructed wetland systems in the built environment. The system comprises a wastewater collection system for the main business and hotel area of the island, a pumping station and a pressure pipe system to the treatment facility, a multi-stage constructed wetland system, and a system for reuse of treated wastewater. The treatment chains consist of vertical-flow, horizontal subsurface flow and free water surface flow units. Because the treatment system is located at the centre of the island, surrounded by resorts, restaurants and shops, the systems are designed with terrains as scenic landscaping. The wastewater is treated to meet the Thai effluent standards for total suspended solids and nitrogen, but because of inadequate pre-treatment and removal of oil and grease prior to the system, the standards for oil and grease and BOD are not met. A number of challenges during construction and operation have caused problems with clogging of the vertical flow constructed wetlands and given rise to odour problems. Safeguards were prepared, but not effectively activated, mainly because no key-person or key-authority took responsibility for managing the system. [Copyright &y& Elsevier]

Abstract: Constructed wetlands are becoming increasingly popular worldwide for removing contaminants from domestic wastewater. This study investigated the removal efficiency of nitrogen (N) and phosphorus (P) from wastewater with the simulated vertical-flow constructed wetlands (VFCWs) under three different substrates (i.e., BFAS or blast furnace artificial slag, CBAS or coal burn artificial slag, and MSAS or midsized sand artificial slag), hydraulic loading rates (i.e., 7, 14, and 21cmd−1), and wetland operational periods (0.5, 1, and 2 years) as well as with and without planting Canna indica L. The wastewater was collected from the campus of South China Agricultural University, Guangzhou, China. Results show that the percent removal of total P (TP) and ammonium N (NH4 +-N) by the substrates was BFAS>CBAS>MSAS due to the high contents of Ca and Al in substrate BFAS. In contrast, the percent removal of total N (TN) by the substrates was CBAS>MSAS>BFAS due to the complicated nitrification/denitrification processes. The percent removal of nutrients by all of the substrates was TP>NH4 +-N>TN. About 10% more TN was removed from the wastewater after planting Canna indica L. A lower hydraulic loading rate or longer hydraulic retention time (HRT) resulted in a higher removal of TP, NH4 +-N, and TN because of more contacts and interactions among nutrients, substrates, and roots under the longer HRT. Removal of NO3 −N from the simulated VFCWs is a complex process. A high concentration of NO3 −N in the effluent was observed under the high hydraulic loading rate because more NH4 +-N and oxygen were available for nitrification and a shorter HRT was unfavorable for denitrification. In general, a longer operational period had a highest removal rate for nutrients in the VFCWs. [Copyright &y& Elsevier]

Abstract: Constructed wetlands have a good potential for wastewater treatment in developing countries due to the simple operation and low implementation costs. Ornamental plants like Canna and Heliconia are used in the wetlands to increase their aesthetic value and these two species were compared in this study. Six pilot scale horizontal subsurface flow constructed wetland units were constructed at the Asian Institute of Technology (AIT) campus in Bangkok, Thailand, of which three were planted with Heliconia psittacorum L.f.× H. Spathocircinata (Aristeguieta) and three with Canna × generalis L. Bailey. The beds were loaded with domestic wastewater in four trials with hydraulic loading rates ranging from 55 to 440mmd−1 corresponding to nominal detention times between 12h and 4 days. Both plant species grew well in the systems and especially Canna had high growth rates (3100±470gDWm−2 yr−1) compared to Heliconia (550±90gDWm−2 yr−1). TSS mass removal rates were very high with efficiencies >88% even at hydraulic loading rates of 440mmd−1. COD mass removal rates varied between 42 and 83% depending on the loading rates. The removal rate constants for COD as fitted by the first-order k–C * model were estimated to be 0.283 and 0.271md−1 for Canna and Heliconia beds, respectively (C * =28.1 and 26.7mgl−1). Removals of nitrogen (N) and phosphorus (P) were low compared to the loading rates, but removal of total-N was higher in the beds planted with Canna than in beds with Heliconia because of the higher growth rate of Canna. It is concluded that ornamental species like Canna and Heliconia can be used to enhance the aesthetic appearance and hence the public acceptance of wastewater treatment systems in tropical climates. Canna is the preferred species from a treatment perspective because of its more vigorous growth, but since Heliconia has an economic potential as cut flowers may be preferred in many cases. [Copyright &y& Elsevier]