Comprehensive screening and prediction of effective and lasting water purification and phosphorus removal substrates

In order to select effective and lasting phosphorus removal substrates, eight kinds of substrates, including tourmaline ceramsite, red mud ceramsite, attapulgite, silica gel, sponge iron, activated carbon, volcanic rock and zeolite, were taken for phosphorus static adsorption experiments. Three substrates were selected for single-substrate columnar phosphorus removal percolation experiment and microstructure characterization, to obtain the phosphorus removal characteristics of each substrate, and to predict their long-term phosphorus removal effect by modeling based on percolation experimental data. The investigation results showed that the adsorption capacities of the eight substrates for phosphorus were quite different, the top three of which were tourmaline ceramsite, red clay ceramsite, and zeolite in order. In the seepage experiment, the phosphorus removal rate of tourmaline ceramsite remained at 67% after 111 days, while that of red mud ceramsite dropped to 37%. The total phosphorus concentration of effluent from different substrates presented differently over time, and the pertinent statistical models showed good predictability. It was predicted by the models that the phosphorus removal rate of tourmaline ceramsite would drop to 50% in about 160 days, and the adsorption saturation would be reached in about 300 days. In comparison, the red mud ceramsite would be saturated on adsorption in about 150 days. The microstructure of the substrates, including their specific surface area and surface characteristics, and their chemical element composition had a significant effect on the removal rate.