Study On The Ability Of Water Hyacinth For Purifying Eutrophic Water

Water eutrophication has become a serious environmental problem because of industry and daily life sewage disposal to natural aquatic system. How to improve the quality of water and decrease the water eutrophication level has become an issue. Water hyacinth, as a floating plant, has a good ability for significantly decreasing water eutrophication. At present, there has been a large amount of research about the ability of water hyacinth on decreasing water eutrophication, but little on the dynamic interaction between water hyacinth growth and water. Thus, we conducted a systematic and dynamic experiment to investigate the ability of water hyacinth on purifying eutrophic water and the growth traits of water hyacinth in2009. The main results are as follows:1. Different concentrations of sewage had a significant effect on the physiological characteristics of water hyacinth. The fresh biomass of water hyacinth increased by104.1%,99.0%,94.3%in the T1, T2,T3treatments during the whole growth period. In the sewage with T1, T2, and T3concentrations, the number of ramet was25,23,21respectively. Accompanied by the decreasing concentration of sewage, the average growth rate of water hyacinth in the three treatments were36g/day,16g/day,15g/day at the end of the experiment. At the end of the experiment, the ratio of root to stem of water hyacinth was0.34,0.41,0.44and the accumulation of the dry matter was114.5g,72.8g,57.1g in the three treatments, respectively.2. Sewage applications with different nutrient concentrations had a significant impact on the N, P and K contents of the water hyacinth. The N, P, K contents in roots and stems of water hyacinth in Tl treatment both increased first and then decreased with the uptake of N, P and K being6.42g/m2,1.32g/m2and2.69g/m2. In T2treatment, the N content in root was decreased all the time, while the N, P and K contents in stem and leaf, and the P, K contents in root all increased first and then decreased. In the end the N, P, K uptakes of water hyacinth in T2treatment were3.27g/m2,0.74g/m2and2.3g/m2. The nutrients dynamics in T3treatment were the same as those in T1. At the end of stocking, the total uptakes of N, P and K were2.77g/m2,0.23g/m2and1.87g/m2. 3After the harvest of water hyacinth, the total N, P and K contents in different concentrations of sewages were significantly decreased. The total N in the three treatments with high, medium and low nutrient concentrations decreased85%,72%,84%, total P94%,88%,89%and total K96%,95%,95%, respectively.Our results showed that the water hyacinth could significantly remove the nutrients in the eutrophic water, while the sewage within certain ranges of nutrient concentrations could also promote the growth and reproduction of water hyacinth. Therefore, if the occurrence of water hyacinth can be controlled effectively in a given region, it will alleviate or eliminate the nutrients in the eutrophic water, thus achieving an ecological purification of water by the biological method with the lowest risk.