The Research On Removal Of Nitrogen And Phosphate From Water By Constructed Wetland Intensified With Calcium Silicate Hydrate And Zeolite

This study relys on the early nutrition of the lake (Erhai) water pollution prevention technology and engineering demonstration project which belong to the National Major Science and Technology Program for Water Pollution and Treatment-Lake Theme(2009ZX07105-003-03). The project is aim at using ecological water treatment technology and engineering demonstration to purifying the upstream into to river, of which the nutrient is in low concentration. In order to resolve problems caused by the low concentration of the nurtrient, this study combines the matrix-silicate hydrate calcium and zeolite which can enrich the nutrient and constructed wetland technology, which is supposed to intensify the purification of the constructed wetland.In this paper the main research content include: (1) The phosphate oval capacity of calcium silicate hydrate, including the effect of particle size, the dosage, time, pH and interfering ions; (2)Design 4 columns filled with different proportion of calcium silicate hydrate and zeolite, analyses the remove rate of the phosphate and nitrogen; (3)Design the constructed wetland, separate the plant and matrix districts and, analyses the removal of phosphate and nitrogen;(4)Design the conventional full-matrix subsurface flow constructed wetland, research the effects of different substrate mixture of nitrogen and phosphorus, COD removal efficiency, etc.Studies have shown that highly hydrated calcium silicate and phosphorus removal capabilities, even at the low concentrations of phosphorus condition (0.5mg/L), could also be reached 0.38mg/g, making the phosphorus concentration in micro-polluted water containing less than 0.05mg/L. In terms of interfering ions, NH4+ ions concentration exceeded a certain value would be good for calcium silicate hydrate removal of phosphorus, mainly due to the formation of MgNH4PO4·6H2O. Dynamic filter columns experiments, mixing up a single column filter compensated the shortcomings of weak load changes. Set in the hydraulic retention time of 24 hours, zeolite and hydrated calcium silicate ratio of 1:1 could remove the phosphate and ammonia, with the highest phosphate removal up to 98.46%, and NH4+ removal rate up to 82.43%. On small constructed wetland studies showed that when the hydraulic retention time of 312.5mm/d, the NO.1 device on phosphate removal rates could achieve to 86.62% and 89.11% on average, and the NH4+ removal rate could achieve to 71.85% and 85.62% on average. The TN removal rate could achieve to 23.69% and 30% on average, and the most important was that the separate of plant and matrix was much less prone to clogging. Furthermore the harvest plant would not cause a deterioration of water quality, but bring out the economic benefits. The studies on traditional full-matrix-based constructed wetland have shown that the one filled with hydrated calcium silicate and zeolite matrix could remove around 51.35% of COD, and the effluent concentration was less than the 10mg/L, which was under the blow ofⅡlevel of surface water. For TN and NH4+-N, the device with hydrate calcium silicate and zeolite had a much better performance than the one filled with gravel, which met the requirement ofⅢlevel. For the removal of TP, the former had a much better performance, and the TP removal rate was able to reach 80%, with the effluent concentration between surface water standardⅢandⅣ.