The Study Of Treatment Effects And Resistance With Cong Red By Elodea Densa (Planch.) Casp.

For a long time, printing and dyeing wastewater is one of the main sources of industrial effluents. Printing and dyeing wastewater is featured by high COD, complex composition, refractory compounds, high colority and biological toxicity. At present, the wastewater has been treated by different physical, chemical and biological technologies. However, each method, due to the limitations with its own technical and economic conditions, has some limitations. It is still a major problem to select a cost-effective technology for the wastewater treatment. Therefore, there is still important theoretical and practical significance to develop bioremediation technique.The research that purifies water by using aquatic plants is one of the hottest areas in recent years. Aquatic plants play a crucial role in the treatment of water eutrophication and heavy mental pollution. This technology, which has been widely favored, has such advantages as esthetics value, low treatment cost and avoiding secondary pollution. Treatment of dyeing wastewater by aquatic plant is developed on this background.In the process of the production and use, there will be some dye loss into the environment with wastewater. Based on the characteristics of printing and dyeing wastewater, the use of submerged plants to treat the wastewater is concluded in this paper. Elodea densa (Planch.) Casp. was taken as the object of study in the laboratory. Then the treatment effects were investigated by the plant with Congo red solution, and the plant resistance was also considered. Ceratophyllum demersum L. was taken as the control group. The purpose of these researches is to develop a technology with highly effective, energy-saving, low-cost and environment-friendly. Besides, it can also provide some experience and theoretical basis for the in-situ remediation of the wastewater by using of constructed wetlands. The research fruits are summed up as follow:1. In the controlled trials, the average removal of dye from Congo red solution in25,50mg·L-1was95.45%and94.12%by50g Egeria densa. The CODcr decreased to48.74and67.13mg·L-1, and the color decreased to67.73and86.73. The CODcr and the color were reached or approached to the standard of Discharge Standard of Water Pollutants for Dyeing and Finishing of Textile Industry (GB4287-92). However, the average removal rate of the same solution was34.72%and29.96%by Ceratophyllum demersum. After treatment, the CODcr was still as high as425.02and850.33mg·L-1, and the color reached up to222.73and423.07. Egeria densa is much better than Ceratophyllum demersum on the treatment effects of wastewater.2. Two kinds of isothermal adsorption equation were fitted to the data of removing dyes. Both of them can get good results. Altogether, the effect was more suitable to Freundlich isotherm equation (R2=0.987). The theoretical adsorption capacity of Congo red (Qmax=9.63mg-g-1) can be calculated by Langmuir isotherm equation (R2=0.931).3. In Congo red solution, the chlorophyll content declined firstly, while the lowest average level was0.433mg-g-1, then the content would be gradual recovery. Meanwhile, the plant would accumulate free praline, and the maximum level reached up to328.10%of the initial value. The POD activity was inhibited at an early stage, and the lowest average level was only37.36%of the initial value. Then, the POD enzyme system of the plant would adjust immediately to reduce the damage. These showed that the physiological indicators would be inhibited when the plant received the strees. However, they could adapt quickly to the stress environments because of the strong resistance.4. Egeria densa was still able to maintain good effects on highly concentrated solution of Congo red. This showed the plant could adapt to the dramatically change of the water quality, which the concentration range was25-200mg·L-1in this study. Meanwhile, keeping the density of the plant would not only to improve the effects of the treatment, but also to promote the resistance of the negative effects from stress environment. Putting75g Egeria densa into2L solution could get the best effect.