Mechanism Research On The Influence Of Calcium Silicate Hydrate-Macrophyte System On Phosphorous Migration And Transformation In Sediment

Eutrophication is a crucial problem in our modern society. Since phosphorous has been considered the main factor of eutrophication and accumulation of endogenous phosphorous in sediment which has brought a huge potential risk to lake eutrophication, it is a essential to reduce the amount of endogenous phosphorous and control its release from the sediment. The phytoremediation has been widely used in endogenous phosphorous control in recent years. However, problems of low remediation efficiency have gradually come out in some practical applications. In order to enhance the efficiency, a newly-developed phosphorus removal material, Calcium Silicate Hydrates (CSH) is applied in the phytoremediation as the seed of crystallization, which can also promote the growth of plants and improve to control the endogenous phosphorous releasing from the sediment.In this paper, the phosphorous removal ability of this newly-developed material CSH and its principle were studied, with the effect to control the phosphorous releasing from the sediment. Phosphorous from sediment was examined to analyze the influence of CSH on phosphorous transformation in sediment. On the basis, crystallization was combined with phytoremediation. The effect of CSH-macrophyte system on phosphorous release from sediment and phosphorous transformation in sediment was also studied.It is revealed that the phosphorous removal ability of CSH is extremely high, which could arrive 194.11mg/g for each unit. It also can prevent phosphorous releasing from the sediment. In static states, the phosphorous releasing amount of the group which 100g CSH was added was only 1/10 of the group without CSH after 50 days. The reason is that Fe-P and Al-P which is easy to release can be transformed to Ca-P and Ex-P with CSH, and mainly in the existence of stable Ca-P. When adding 50mg CSH, the proportion of Al-P and Fe-P in total phosphorous of the sediment was decreased by 26%, while that of Ca-P was increased by 24%.Study also showed that the dosage of CSH can promote Myriophyllum Spicarum absorbing Ex-P from the sediment, phosphorous transferring from sediment to plant and the growth of the plant. The phosphorous amount in plant of the group with CSH is 76% higher than that of the group without CSH after 35 days. Meanwhile, the height and biomass of the group with CSH are also much higher.Moreover, CSH dosage can make the pH of cover water increase. In static states, pH arrived 9.3. However, the plant can reduce this affection and maintain pH around 8.5~8.9. On the contrary, the increase of pH can improve phosphorous removal ability of crystallization. It is verified that high pH is the premise for CSH to remove phosphorous.