This paper presents a brief survey of the Hungarian constructed wetland types that have been established for wastewater treatment in the last thirty years, and gives an analysis of the design and performance of those reed ponds that have been constructed for the polishing of petrochemical wastewaters. Natural treatment processes are in great demand because they are protective of the environment and have low operation costs and satisfactory purification efficiency. Three major types of treatment wetlands are utilized in Hungary: free water surface system, subsurface flow system, and artificial floating meadow system. Since the 1970s, the petrochemical industry has utilized sewage treatment systems consisting of ponds of emergent and/or submerged macrophyte vegetation that operate as free water surface systems. In the wastewater treatment system of Nyirbogdány, the average COD removal efficiency is around 60%, while the reed-submerged weeds pond has an efficiency of 25%. In the reed pond of the TIFO post-treatment pond system, the total phosphorus removal averaged 40% for several years, while the nitrogen removal efficiency has not exceeded 35%. For both constructed wetlands, the nutrient stabilising and heavy metal accumulating role of the aquatic plant-periphyton complex has been quantified, and the biological water quality has been found to be typical of any other natural water bodies.

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