Zhao Xinsheng

Influence of substrate depth and particle size on phosphorus removal in a surface flow constructed wetland

Substrate adsorption is one of the main processes by which redundant phosphorus is removed from wastewater in surface flow constructed wetlands (SFCWs). The physical properties of the substrate, such as depth and particle size, will influence the amount of phosphorus adsorption. This study was carried out in a long-running intermittent inflow constructed wetland that covered a total area of 940.4 m2 in the Shunyi District of Beijing, China. We investigated how the concentrations of four phosphorus fractions, namely calcium phosphate (CaP), iron phosphate (FeP), adsorbed phosphorus (AdsP), and organic phosphorus (OP), varied between the surface (0-10 cm) and subsurface (10-20 cm) substrate and among the different substrate particle sizes. The total phosphorus concentrations in the substrate ranged from 154.97 to 194.69 mg/kg; CaP accounted for more than 80% of the total phosphorus content. The concentrations of OP were significantly higher in the surface layer than in the subsurface layer, but the concentrations of inorganic phosphorus were not significantly different between the two layers. The CaP, AdsP, and OP adsorption capacities were greater for small-sized substrate particles than for large-sized substrate particles. The results from this study provide a theoretical basis for the construction of constructed wetlands.

Different wetland plant roles of removing nitrogen and phosphorus on sewage water

Five kinds of wetland plants,including reed(Phragmites australis),oriental cattail(Typha orientalis),calamus(Zizania aquatica),wildrice stem(Acorus calamus),Iris(Iris tenuifolia),and one kind of shrub of willow(Salix viminalis) were selected to study the growth characteristics of plants and the role of removing nitrogen and phosphorus in severe eutrophic waters.The study showed that the six kinds of plants in experiments grew well and steadily.After 105 days,the total biomass ranged from 424 to 1772g/m2.Ratios of most plant biomass above/below ground(A/U) varied between 0.63 and 1.49,except for oriental cattail(A/U: 3.23).Concentrations of nitrogen and phosphorus in the biomass of above ground ranged from 13.12 to 28.83mg/g and from 1.55 to 3.77mg/g,respectively.Concentrations of nitrogen and phosphorus in the biomass below ground ranged from 7.76 to 15.60mg/g and from 1.70 to 2.71mg/g,respectively.The concentrations of nitrogen and phosphorus between above and below ground biomass differed significantly.The average plant accumulations of nitrogen and phosphorus were 20.60g/m2 and 3.08g/m2,which the above ground accounted for 66.60% and 58.22%,respectively.Purification effect of the plants on different pollutants was different.The best purification effects for TN in Iris and TP in reed were found.Plant accumulations of nitrogen and phosphorus displayed significantly positive linear correlation with plant biomass and concentrations of nitrogen and phosphorus.