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Ecological effectiveness of constructed wetlands in treating oil refined wastewater

2003; Elsevier BV; Volume: 23; Issue: 7 Linguagem: Inglês

1000-0933

Xia Hanping, Ke Honghua, Deng Zhaoping, Tan Peng, Shizhong Liu,

Wetland Management and Conservation

Wastewater produced from the oil refinery of the Maoming Petro-Chemical Company, China Petro-Chemical Corporation contains high concentrations of organic and inorganic pollutants, therefore it cannot be discharged directly into river or sea unless being treated first. Four plant species, Vetiveria zizanioides, Phragmites australis, Typha latifolia, and Lepironia articutala we re planted in large containers as a ver tical flow wetland to test their effic iencies in the purif ication of oil refined wa stewa ter a nd their grow th in wetla nds soaked with oil r efine d wastewater. The results f rom a 2-month treatment indica ted that the purifying rates of constructed wetlands for oil-refined wastewater were all very high at the beginning. Results included the re moval of 97.7% of ammonia N, 78.2% of COD, 91.4% of BOD, and 95.3% of oil in the first batch of highly-concentrated wastewater (HCW), and 97.1% of ammonia N, 71.5% of COD, 73.7% of BOD, and 89.8% of oil in the first batch of low -conc entra ted w astew ater (LCW). The performance of wetlands however was decreased and became basically stable as time passed. The efficiency of wetlands in removing the pollutants was always in order of ammonia N > oil > BOD > COD, but the net removal from plants was ranked as COD > BOD > oil and ammonia N. In the beginning, the purifying function of plants was quite weak, but it gradually increased with the acceleration of plants growth. However, there was almost no significant difference in the removal efficiencies among the four species. The four tested species produced better growth in wetlands (HCW or LCW) than with clean water, but V. zizanioides, P. australis, T. latifolia produced fewer tillers in HCW than those in LCW, while this was contrary to L. articutala. This could infer HCW might damage the first three species, and promote the growth of L. articutala During the period of clean water cultivation before the start of the trial, the new tiller producing rate of V. zizanioides was the lowest among the four species, but it gradually rose during the period of water soak treatment, while the tiller-producing rates of the other three species were distinctly lowered. It was therefore suggested that V. zizanioides might have a stronger adaptation to the harsh environment than other species tested in the experiment, especially in the situation of long time of adaptation to the environment. However, the above results remains to be further verified due to the limited observation time of only two months.