Experimental Study Of Phosphorus Adsorption By Water Plant Alum Sludge

The main purpose of the research is to reuse the water works sludge and removephosphor in the waste water. We researched the sludge discharged by a precipitating tankof a large water supply work in Beijing and analyzed it’s composition feature. As afurther research, we set static test and dynamic test on the dewatered Al-containingsludge to evaluate the phosphorus in the water.The physicochemical property of the dewatered sludge shows that the main compositionof the sludge is Al₂O₃, Fe₂O₃, CaO, MgO and SiO₂,besides, Al₂O₃takes up32.2%,andFe₂O₃accounts for0.76%. The porosity of the sludge is0.62and the density is1.84kg/L.The static adsorption test was set to research influence of1)the pH of the adsorbatessolution2) the particles size of the adsorbent3) the temperature of the solution in theadsorption process4) the contact time of the adsorbate and the adsorbent to the adsorptioneffect. the date ofphosphorus adsorption onto dewatered alum sludge are found to fit bothLangmuir isotherm and Freundlich isotherm well，however，the Freundlich isothermyields a better fit than the Langmuir isotherm while its saturation adsorption capacity is15.74mg/g when initial phosphorus concentration is10mg/g.The adsorption wasinfluenced by particle size and initial phosphorus concentration but slightly afected bytemperature．Particle size is less than2.00mm by decreased to0.074mm, removal rateincreased from38.3%to97. The quality of initial phosphorus concentration by15mg/Lincreased to50mg/L, adsorption by20.74mg/g increases to54.32mg/g.And the dynamic test evaluated the different adsorption effect in different filtering layerthickness and filtering velocities: filtering velocity has a large impact on adsorption effect.Leakages may take place when the filtering velocity is too fast the adsorption velocityrise with the rising of the filtering velocity and get to the equilibration point at a propervelocity. The adsorption capacity of the equilibration point is about30.7mg/g,which islightly smaller than the adsorption capacity on the condition that the initial concentrationis50mg/L and the equilibrium concentration is20mg/L.