Studies On Phytoremediation Of COD And Ammonia-Nitrogen In Coking Wastewate By Six Aquatic Plants

Coal is one of the most important energy sources in China and even in the world. Coking industry plays a significant role in the national economic development. However, the discharge of wastewater is also increasing with the rapid development of the coking industry. The coking wastewater has high COD and phenol value and some ammonia-nitrogen. In addition, the wastewater is a kind of typical organic, refractory substance with high density. The discharge in large amount not only pollutes the environment severely, but also gives bad effect to the agricultural and industrial manufacture or human life. The treatment of the wastewater has been concerned widely by public.Aquatic plants, with a great diversity and present in a variety of water bodies, can grow in long period and reproduce rapidly. The plants have pollution resistibility and wide temperature scale of adaptation (4℃-30℃) and need little sunshine, thus they have been widely used for the wastewater purification because of above characteristics.This study mainly addresses the purification and restoration of the coking wastewater by means of the aquatic plants that include Chara contraria, Nasturium officinale, Cladophora fracta, Potamogeton crispus, Polygonum orientale and Phragmites australis. Six aquatic plants were respectively treated with dichromate potassium or nessler's reagent colorimetric method to test the removal results of COD or ammonia-nitrogen from the coking wastewater under the experimental condition. The results indicated that the COD or ammonia-nitrogen removal efficiency of the six aquatic plants in water samples without dilution were best, followed by the dilution ratio 3:1 and 2:2, and worst in the water samples of the dilution ratio 1:3.By comparison of the six plants, it was found that the COD removal capacity was P. australis, C. contraria, N. officinale, P. orientale, C. fracta and P. crispus from the strong one to the weak. The COD removal ability of P. australis was the highest in water samples and the rate went up to 84.7%, higher than P. crispus (40.3%) by 44.4%.As for the ammonia-nitrogen treatment, the order was C. contraria, P. australis, N.officinale, C. fracta, P. orientale and P. crispus in turn. The removal capacity of C. contraria was the best for ammonia-nitrogen with a percentage of 14.3% from water samples, higher than P. crispus (7.9%) by 6.4% for ammonia-nitrogen from the wastewater.