Research On Absorption Of Nitrogen And Phospaorus And Purifying Effect In Swine Wastewater By Pasplum Distichum L.

With the increasing development of swine industry and the enlarging scale of piggery, the discharge amount of piggery slurry aggravated environmental pollution. A large amount of wastewater from piggery farm is mostly discharged directly without appropriate treatments, which can bring about a serious pollution to the water environment. Thompsmgrass (Pasplum distichum L.) is a kind of wild grasses that commonly founded in rice fields and wet ditch in south China. With the advantages of strong adaptability, good tolerance, great amount of biomass, rapid growth and so on, Thompsmgrass can be used as purifying plant of post-processing swine wastewater. The study used Thompsmgrass as purifying plant, river sand as substrate that conducted to 30-day hydroponic experiment for 25%,50%,75%,100% of four different concentrations of wastewater from the May 23,2009 to June 22 and for 255mg/L,510mg/L,765mg/L,1020mg/L of four nitrogen-content wastewater from July 23,2009 to August 22 respectively, researched on the absorption of nitrogen and phosphorus and the purification effects of nitrogen, phosphorus. The results were as follows:1.Thompsmgrass grown well in swine wastewater, and plant height of thompsmgrass grown in wastewater were significantly higher than that of control group (CK). But the difference were not significant for plant height of thompsmgrass grown in different concentration wastewater. Compared with the control, root growth was inhibited when the sewage concentration is 100%. Biomass of above ground parts increased with the increase of the sewage concentration, whereas biomass of under ground parts increased when the sewage concentration increased from 25% to 75%. and decreased when the sewage concentration increased from 75% to 100%. and thompsmgrass in 75% concentrations of wastewater has highest underground biomass.Thompsmgrass purified sewage with different nitrogen content to a certain extant. Plant height of thompsmgrass significantly reduced after the nitrogen content of wastewater increased. Root growth was inhibited in different nitrogen-content of wastewater. Biomass of above and under ground parts increased when the nitrogen content of wastewater increased from 255to 510 mg/L, and decreased when the nitrogen content of wastewater increased from 510 to 1020 mg/L, and biomass of above and under ground parts was the highest when the nitrogen content of 510mg/L.2. After thompsmgrass purified different concentrations wastewater, nitrogen and phosphorus of above and under ground parts increased with the increasng of the sewage concentration. The nitrogen contents above ground parts were significantly higher than that under ground parts. When the concentratin of wastewater was lower than 75%, the phosphorus contents of above ground parts was lower than the under ground parts. When the concentratin of wastewater was 100%. the phosphorus contents of above ground parts was higher than the under ground parts.Thompsmgrass purified sewage with different nitrogen content, the nitrogen content of above and under ground parts, and the phosphorus of under ground parts all increased with the increase of the nitrogen-content of wastewater, but the phosphorus of above ground parts increased from 255 to 510 mg/L, and decreased when the nitrogen content of wastewater increased from 510 to 1020 mg/L, phosphorus of above ground parts was the highest wnen the nitrogen content of 510mg/L.3. After the purified treatment by thompsmgrass or natural standing, the total nitrogen, total phosphorus, ammonia nitrogen and organic contents in piggery wastewater decreased significantly. The purification effects with thompsmgrass was better than that of natural standing. The removal rates of total nitrogen, ammonia nitrogen and total phosphorus increased with the passage of time. The removal rates of all the test group was over 98.75%, 99.66% and 96.54% respectively, on the first 30 days. However, COD removal rate of different concentrations of wastewater was not significant difference compared with control on the first 30 days.After thompsmgrass purified different nitrogen content of sewage, the removal rates of ammonia nitrogen and total phosphorus increased with the passage of time, the removal rates of all the test group was over 94.13% and 88.78% on the 30 days. The total nitrogen removal rate reached the highest when nitrogen content of sewage is 510mg/L and 765mg/L on the 24 days, the removal rates of total nitrogen increased with the passage of time in 255mg/L and 510mg/L of nitrogen content, the removal rates ranged from 71.26% to 93.03%. COD removal rate of different concentrations of wastewater was significantly different compared with control in the first 30 days, and the removal rates of COD decreased with the increasing of nitrogen content.4. After thompsmgrass purified different concentrations of wastewater. the absorptive amount of nitrogen and phosphorus and of removal amount of nitrogen and phosphorus of sewage increased as the increase of wasterwater concentrations.The nitrogen and phosphorus of absoiptive amount and amount of removal of sewage increased increased from 0 to 510 mg/L. and decreased when the nitrogen content of wastewater increased from 510 to 1020 mg/L. The 510mg/L nitrogen content of sewage has the largest amount of nitrogen and phosphorus absorption.Considering these factors of the growth status of thompsmgrass in sewage, and purification of nitrogen, phosphorus, organic compounds, as well as absorptive amount of nitrogen and phosphorus, comprehensively, we can draw a conclusion that the optimum concentration for thompsmgrass to purify the piggery wastewater was the concentration of 100%.