Study On The Removal Of DOM In Landfill Concentrated Leachate During Coagulation Process And The Effect On Scaling

As a kind of hazardous wastewater with high salt and high concentration organic matter,landfill concentrated leachate will lead to serious environmental pollution problems if it is not treated properly.Some conventional biological methods and chemical methods are difficult to be applied on a large scale in industry due to their treatment effects and economic costs,at present,the industrial treatment of the landfill concentrated leachate is mainly by evaporation.However,the scaling of heat exchanger will inevitably occur during the evaporation process.Most of the previous studies have studied the effect of scaling from the aspects of heat exchanger design parameters and calcium and magnesium ions.In the current study,we compared several different treatments of landfill concentrated leachate by using laboratory-made flocculant,The composition and properties of landfill concentrated leachate and DOM after flocculation were characterized by UV-visible spectroscopy,three-dimension fluorescence spectroscopy and electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry(ESI FT-ICR MS),and to study the influence of organic matter on scaling.In this paper,DOM in the landfill concentrated leachate and the landfill concentrated leachate after different flocculation treatments were characterized.It was found that the landfill concentrated leachate mainly contained humic acid and fulvic acid substances.At the molecular level,it mainly contained CHO,CHON,CHONS and CHOS.After different flocculation treatment methods,it was found that the removal effect of liquid coagulant on protein and CHOS was poor,while the mixed treatment of solid coagulant and liquid coagulant could remove all organic matter in the concentrated membrane solution.According to the characterization of the organic matter in landfill concentrated leachate,three typical organic matter-BSA,SSA and HA were taken to simulate protein,polysaccharide and humic to study their effects on the crystallization rate,crystal shape and morphology of calcium carbonate and calcium sulfate.BSA has little effect on the crystallization rate of calcium carbonate,while HA and SSA can significantly inhibit the formation of calcium carbonate,and these three kinds of organic matter can change the crystal shape and morphology of calcium carbonate.These three organic substances have obvious inhibitory effects on the crystallization rate of calcium sulfate,and can change the morphology of calcium sulfate,but basically have no effect on the crystal form of calcium sulfate.Finally,take the landfill concentrated leachate and the landfill concentrated leachate after flocculation treatment as the research objects to study its influence on the scaling of calcium carbonate and calcium sulfate.It was found that the crystallization rate of calcium sulfate and calcium carbonate was inhibited only in the original solution and the concentrated solution treated with liquid flocculant,but there was little inhibition in the other four concentrated solutions.By comparing the effects of solutions under six conditions on the crystal morphology of calcium carbonate and calcium sulfate,it is found that these six solutions can change calcium carbonate from calcite to spherical aragonite,and the morphology of calcium sulfate can make it grow longer.The strips become flakes,but the crystal shape has no effect.