Ecological effectiveness of constructed wetlands in treating oil refined wastewater
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 were planted in large containers as constructed vertical flow wetland to test their efficiencies in the purification of oil refined wastewater and their growth in wetlands soaked with oil refined wastewater. The results gotten from a 2-month treatment indicated that the purifying rates of constructed wetlands for oil refined wastewater were all very high at the beginning, which removed 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-concentrated wastewater (LCW). But the performance of wetlands 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 of plants to them 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 with 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 inferred that HCW might damage the first three species, and promote the growth of L. articutala. During the period of clean water cultivation, the new tiller producing rate of V. zizanioides was the lowest among the four species, but it gradually rose during the period of treatment water soak, 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.
国家科技期刊平台
NSTL
万方数据
维普
