The Research On Conditions And Effects Of Constructed Wetland Simulated System To Phosphorus Removal

With the development of agriculture and industry around Lake Chaohu, a plenty of pollutant which contain phosphorus has been discharged into it. The pollution is becoming more and more serious which has lead to the frequent cyanobacterial bloom. Constructed wetland treatment system is one of the most important treatments applied in lakes. This paper is based on the substrates, aquatic plants and land raw plants around Lake Chaohu. In the experiment we designed the indoor adsorption column to simulate constructed wetland system in order to explore the effect of matrix thickness, the inlet concentration ratio of carbon and phosphorus, the composition of complex matrix and the retention time on phosphorus removal. This study will provide technical support for the treatment of low pollution water in Lake Chaohu. The main results are as follows.(1) For soil I(collected in Huang Lintou town), adding five kinds of plant powder or scrap extracts will not contribute to the sorption of phosphorus and it has a negative effect on the contrary. For soil II(connected in Qing Long Zui town), adding five kinds of plant powder extracts will inhibit the sorption of phosphorus in solution, but adding the scrap extracts can obviously improve it on the contrary.(2) For the choice of substrate thickness, we found that the SRP removal rates of the columns were similar in 70 cm and 50 cm layer, the average rates of which were around 55%, and there was no significant difference between them. But they were significantly higher than that of 30 cm layer, the phosphorus removal rate of which is only 44%, P<0.01. There was no significant difference between the average DTP removal rates of the 3 kinds of thickness, and the thickness of 50 cm will be the best choice.(3) For the choice of concentration ratio of carbon and phosphorus(C/P), when the SRP removal rate of each column tended to be stable, the SRP removal rate of the column without glucose(C/P=0/1) was the lowest which was 50%. While, the SRP removal rates of the columns with the C/P of 50/1 or 100/1 were around 70%, and the SRP removal rates of the 150/1 and 200/1 were around 80%, and the SRP removal rates of the 250/1 was the highest which was about 95%. The differences between the columns with or without glucose were significant, and the DTP removal of each column was similar to SRP. Therefore, in a certain concentration range, the higher the concentration of C/P is, the higher the removal of phosphorus will be. So, the best choice of the concentration of C/P should be 250/1.(4) For the choice of combined matrix, after 12 weeks of continuous experiment, we found that the SRP removal rate of the column which was consist of CK+IM or CK+TP+IM was significantly higher than that of CK+AP or CK+AL. While, at the 13 th week, they were of no significant difference. And the DTP removal of each column is similar to that of SRP. Therefore, CK+IM should be the best choice for the combined matrix.(5) For the retention time, comparing the SRP and DTP removal rates of the columns made of 7 main combined matrix under the retention time of 3h, 6h, 9h and 12 h, we found that the phosphorus removal rate of the column which was under 3h was significantly higher or equal to the other retention times. Therefore, considering the actual treatment capacity of wastewater in unit time, 3h should be the best retention time.