Substrate phosphorus removal for contaminated water treatment in constructed wetlands by integrating static adsorption experiments with seepage sand tank tests

doi:10.7523/j.issn.2095-6134.2021.04.006

Abstract

Abstract: In order to solve the problem of decreasing for the removal rate of phosphorus and consider the optimal design and maintenance of the substrate structure in constructed wetlands, it is necessary to understand the phosphorus adsorption characteristics for different substrates and obtain the evolution trend and law regarding the actual dephosphorization effect for specific phosphorus-containing wastewater. In this study, three substrates including zeolite, medical stone, and magnetite, were selected, which are commonly used in constructed wetlands with good phosphorus removal performance, to study their adsorption kinetics and isothermal adsorption characteristics of phosphorus and to investigate the effects of different substrates and particle sizes on phosphorus adsorption. Further, zeolite with the best phosphorus adsorption performance among the three substrates was selected to carry out the seepage sand tank test for phosphorus removal, so as to simulate and obtain the phosphorus removal and purification effects of the subsurface flow wetland. By integrating the static experiment with seepage sand tank test for the phosphorus removal, the mechanisms of dephosphorization and the evolution trend and law of actual dephosphorization effects of the zeolite substrates with different particle sizes were identified. The results show that the adsorption process of phosphorus on the three substrates consists of the fast adsorption, slow adsorption, and gradual equilibrium. Furthermore, the Langmuir equation can accurately describes the isothermal process of phosphorus adsorption on the substrates. The adsorption phosphorus removal efficiency and the overall phosphorus removal efficiency of the zeolite substrate with different particle sizes are significantly different. Additionally, the phosphorus removal efficiency of the zeolite substrates fluctuates with the particle size, and the overall phosphorus removal efficiency initially increases and then decreases considerably. The analysis of the achieved data sets indicates that, in addition to the significant mechanism of phosphorus adsorption removal, the microbial effect is also considerable on the phosphorus removal. Based on this type of integrated investigations, the phosphorus removal mechanisms with their relative importance and the overall phosphorus removal efficiency can be identified.

Key words: substrate, phosphorus, adsorption, physical model simulation, phosphorus removal efficiency

CLC Number:

X703

WANG Di, WANG Mingyu. Substrate phosphorus removal for contaminated water treatment in constructed wetlands by integrating static adsorption experiments with seepage sand tank tests[J]. Journal of University of Chinese Academy of Sciences, 2021, 38(4): 478-485.

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