Treatment of wastewater by natural systems

Experimental results from a pilot-scale constructed wetland (CW) treatment plant have been described. The study was conducted at two different systems: continuous and batch. In the continuous system, the treatment yields were monitored in different loading conditions in 1-year period. The pilot plant consists of two serially connected tanks settled up with fillers; Cyperus was used as treatment media and wastewater between the two tanks was recycled periodically. Chemical oxygen demand (COD) and suspended solid (SS) removal efficiencies were obtained as 90% and 95%, respectively. The effluent COD concentration at an average loading of 122 g COD/m(2) day was satisfactory for the Turkish Water Pollution Control Regulation. This means that a 0.8 m(2) of garden area per person is required. Other removal values for the same conditions were as follows: total Kjeldahl nitrogen (TKN) was 77%, total nitrogen (TN) was 61%, and PO43--P was 39%: The batch experimental systems consist of 12 pairs of serially connected tanks, with each pair having a surface area of 1 m(2). Each set was filled with sewage once a day, and the wastewater between the paired tanks was recycled periodically by the pump. Each pair of tanks was filled with materials such as gravel, peat, and perlite. Seven of them were vegetated with Phragmites, Cyperus, Rush, Iris, Lolium, Canna, and Paspalum, while the other five were not seeded. The best performances were obtained by Iris for COD (% 94), by Canna for ammonia nitrogen (% 98), and by Iris for total nitrogen (% 90) and phosphorus (% 55) removal. (C) 2001 Elsevier Science Ltd. All rights reserved.