不同填埋年龄期垃圾渗滤液对HDPE管材结垢影响

Effect of Leachate of Different Landfill Age on HDPE Pipe Scaling

垃圾渗滤液含有大量复杂且有害成分,在其收集和输运过程中极易引起管道系统的腐蚀和结垢.HDPE管材已广泛应用于填埋场设计,以其作为研究对象,制备成HDPE样片分别浸置于幼龄期渗滤液(1#渗滤液)和老龄期渗滤液(2#渗滤液)中,研究结垢特点.通过监测渗滤液中ρ(Ca^(2+))、ρ(Mg^(2+))、ρ(Cl-)、ORP(氧化还原电位)、pH等水质参数指标的变化,结合HDPE样片的SEM分析及其质量变化,推断了引起管道结垢的主要原因.结果表明:①渗滤液中ρ(Ca^(2+))、ρ(Mg^(2+))随试验周期推进显著下降,且ρ(Ca^(2+))降低较快,试验50 d内1#渗滤液ρ(Ca^(2+))降低了85%,2#渗滤液降低了75%.②HDPE样片对渗滤液的水质产生了一定的介入影响,试验初期对ρ(Ca^(2+))、ρ(Cl-)及ORP影响较大,中后期则对pH影响显著.③1#渗滤液和2#渗滤液中HDPE样片结垢量分别为1.10和0.682 mg/cm^(2),管材在1#渗滤液中结垢更严重.④渗滤液中ρ(Ca^(2+))和ρ(Mg^(2+))与结垢量均呈显著负相关(P<0.05),其中ρ(Ca^(2+))是引起结垢的关键因素(P<0.01);温度、pH和ORP与结垢量均呈正相关,ρ(Cl-)与结垢量呈负相关.⑤通过材料表面形貌表征,试验初期主要是规则的结晶垢,试验后期则为多孔隙沉积垢.研究显示,1#渗滤液对管材结垢影响更明显,Mg^(2+)、Ca^(2+)沉淀是管材结垢的主导因素,控制二者浓度是减缓管材结垢的关键.

Landfill leachate may cause pipe corrosion and scaling during its collection and transportation due to its complex and harmful components.High-density polyethylene(HDPE)has been widely used as pipe materials in landfill design.In this study,HDPE samples were placed in young leachate(1#leachate)and old leachate(2#leachate)to study their scaling potentials and characteristics.Through periodical monitoring the water quality parameters of the leachates,including Ca^(2+),Mg^(2+),Cl-,ORP and pH,and analysis of weight changes of the samples and SEM morphology,the possible causes of pipe scaling was inferred.The results show that:(1)With the implementation of experiment,the concentration of calcium and magnesium ions in the leachate decrease significantly,among which Ca^(2+)varies significantly.The concentration of Ca^(2+)in the 1#leachate decreases by 85%while that in the 2#leachate decreases by about 75%after 50 days of the experiment.(2)The immersion of HDPE pipe material affect the leachate quality.In the initial stage of the experiment,it has an impact on Ca^(2+),Cl-and ORP,while it causes an increase of pH at the middle and late stages.(3)The scale on the HDPE samples placed into the 1#leachate and 2#leachate is 1.10 and 0.682 mg cm^(2),respectively,indicating that the scaling occurs more serious in the 1#leachate.(4)The concentrations of Ca^(2+)and Mg^(2+)are negatively correlated with the scaling(P<0.05),and the Ca^(2+)is identified as the key influencing factor(P<0.01).Temperature,pH and ORP are positively correlated with the scaling,whilst Cl-is negatively correlated.(5)In the early stage of the experiment,the scale formation was identified as chemical crystallization and precipitation,whilst the scales were gradually transformed into amorphous sediments in the later stage.In conclusion,the scaling is more serious when placing the pipe samples into the 1#leachate.Ca^(2+)and Mg^(2+)are identified as the dominant influencing factors.Monitoring and controlling their concentrations is critical to mitigate pipe scaling during the leachate collection and transportation.