Study On Deep Treatment Of Tannery Wastewater By Eichhornia Crassipes And Alligator Alternanthera Herb

Tan wastewater is a kind of hard-dealing industrial waste water, because the wastewater yield and water quality is extremely uneven, and the concentration of COD、BOD5、SS、NH3-N in water is very high.This paper describes the characteristics of the tan wastewater, introduces the traditional processing mode of tan wastewater and phytoremediation technology appling to heavy metal waste water research. According to the second pond water quality characteristics of the YongXinXian leather sewage treatment plant, selecting Eichhornia crassipes and Alligator Alternanthera Herb as the main material of treatment system, a series of laboratory experiments were made. In the support of the experimental results, experiments were made in the YongXinXian leather sewage treatment plant and Jiangxi Dadeli Co.LTD.Reasearch was made from the number of plants, the concentration of total chromium and different plants, which provide the theory basis and the practical experience for promoting plant floating island to process low concentration tan wastewater. The main conclusions of this paper are as follows:(1) The effects to tan wastewater treatment of different plants island are different. The experiment set three groups:single Eichhornia crassipes, single Alligator Alternanthera Herb, Eichhornia crassipes and Alligator Alternanthera Herb mixing, to deal with waste water of different concentration of total chromium, the results showing that:mixing group slightly higher than the single Eichhornia crassipes and a single Alligator Alternanthera Herb group in the removal efficiency of NH3-N, but the removal efficiency of COD and total chromium was superseded the single Eichhornia crassipes group, higher than the single Alligator Alternanthera Herb group. Therefore, the mixing group can be choosed for the water of NH3-N required, but for general Cr-containing wastewater treatment, the single Eichhornia crassipes group is the better choice.(2)The number of plants in the system can affect the treatment influence of chromium-containing wastewater.Maintaining other factors to constant,and changing the number of plants will affect the treatment effect. Comparing the experimental results of experiment I and experiment II, increasing the number of floating-island plants can improve removal rate.However, because of the floating island plants itself multipling fast and needing certain reserved space to give it to grow,1/2water area was suggested to be reserved,and1/2water area for the experiment was advisable.(3) The results of actual wastewater experiment and laboratory simulation experiment were different. By setting up Eichhornia crassipes group in the second pond, adjusting-pool and chromium-pool, the result showed that the treatment effect was worse than in laboratory simulation experiment;however, the total removal trend is consistent, just increasing at the first and then droping finally tend to level. The reasons of difference were practical wastewater was more complex and diverser than the laboratory simulation wastewater and the difference of relative time.Therefore, plant-floating island had the important applications in the actual technology.(4) The treatment effect for wastewater of secondary Eichhornia crassipes group was better than primary Eichhornia crassipes group. The second pond water can achieve the requirements of Comprehensive Sewage Discharge Standard (GB8978-1996) after processing of secondary Eichhornia crassipes group;and the total removal rate of COD、NH3-N and total chromium of the wastewater in regulation-pond and chromium-pool were above50%, which shows that removal efficiency can be increased through changing plant regularly to set multi-level plant processing system.(5) Plants can enrich chromium obviously at different chromium concentration. Plants’ roots and leaves all has the function of enriching chrome.When the concentration of total chromium is8.00mg/L, the highest content of chromium in Eichhornia crassipes’ root, Alligator Alternanthera Herb’ root, mixing root, Eichhornia crassipes’leaves, Alligator Alternanthera Herb’leaves, mixing leaves were3023.74mg/kg,2104.61mg/kg,2567.78mg/kg,513.71mg/kg,276.20mg/kg,381.70mg/kg. As the chromium concentration in waste water increasing,the chrome content of plants’roots and leaves enriching also increased, and ability of plants’ roots enriching chromium is far outweigh the plants’leaves.