Abstract
The substrate in the constructed wetlands (CW) plays an important role in wastewater treatment. The resource utilization of drinking water treatment sludge (DWTS) has good application prospects, but its powder form is not an ideal substrate and may cause blockage. This paper studies granulated DWTS by loading powdered DWTS on zeolite (DWTS@ZEOLITE). Results show that there should be 1 g of thickener, 5 mL of binder, and 0.15 g of DWTS for the best removal effect. The adsorption process of DWTS@ZEOLITE on phosphorus conforms to the Langmuir model, and the theoretical saturated adsorption capacity is 21.8 mg/g. pseudo-second-order kinetics can be used to fit the adsorption behavior and the adsorption of phosphorus with the DWTS@ZEOLITE was a spontaneous exothermic process. Acidic conditions and humic acid can increase the amount of adsorbed phosphorus, while CO32- inhibits the removal of PO43- due to competitive adsorption. The adsorbed products of DWTS@ZEOLITE after saturation were analyzed, and the main combinations were Fe-P and Al-P. The DWTS@ZEOLITE was characterized by Brunauer Emmett Teller (BET), X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), X-ray spectroscopy (SEM-EDS) etc. BET results show that the specific surface area of DWTS@ZEOLITE is 4.2751 m2/g. SEM-EDS results show that the surface of DWTS@ZEOLITE is rough and has obvious phosphorus peaks after reacting with phosphorus. Both XRD and XPS results indicated that the reaction of DWTS@ZEOLITE with phosphorus showed characteristic peaks of FePO4, AlPO4 and Ca(H2PO4)2. The Fe, Al, and Ca elements contained in DWTS@ZEOLITE are exchanged with phosphate ligands to achieve adsorption. Finally, Dynamic experiments show that DWTS@ZEOLITE has a good effect on phosphorus, and the saturated adsorption capacity can reach 1774.5 mg/kg. DWTS@ZEOLITE provides a method for the granulation of DWTS) and realizes the resource utilization of DWTSand zeolite.
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