人工湿地填料除砷效率及影响因素试验研究

人工湿地是净化含砷水体的重要途径之一,而填料是决定人工湿地除砷效果的关键因素。通过填料如砾石、锰砂、沸石和陶粒的理化性质的测定,以及各种填料的吸附动力学、吸附等温线和吸附影响因素试验,研究了填料的除砷性能及影响因素。结果表明:4种填料均能在24 h内达到吸附平衡,一级动力学方程和二级动力学方程能很好地拟合其吸附过程;锰砂、陶粒、沸石和砾石最大吸附容量依次为36.62,25.39,11.96,7.04 mg/kg,Freundlich方程能较好地拟合填料的等温吸附过程;在0.25~0.50 mm范围内,粒径对锰砂和陶粒吸附砷影响不显著;溶液中氨氮浓度在0.50~2.50 mg/L范围内几乎不影响填料对砷的吸附;当砷初始浓度低于0.4 mg/L时,磷酸盐在0.25~0.50 mg/L范围内对填料吸附砷的影响不显著;砷初始浓度高于0.4 mg/L时,随着磷酸盐浓度从0.25 mg/L增加至0.50 mg/L时,陶粒对砷的最大吸附量降低了2.57 mg/kg,对锰砂的吸附量降低了1.85 mg/kg。

Efficiency and Influence Factors of Arsenic Removal by Constructed Wetland Substrates

Constructed wetland is an important approach of removing arsenic in water,and substrates are key factors determining the removal efficiency.We researched the efficiency and impact factors of arsenic removal through ad-sorption experiments (adsorption kinetics,adsorption isotherm,and influence factors)on four substrates (gravel, manganese sand,zeolite,and ceramsite).Results reveal that the arsenic adsorption is time-dependent and could reach equilibrium in 24 hours for all the four substrates.The adsorption process consists with the pseudo-first-order kinetic model and pseudo-second-order kinetic model.The maximum arsenic adsorption capacity are as follows:manganese sand (36.62 mg/kg),ceramsite(25.39 mg/kg),zeolite (11.96 mg/kg),and gravel (7.04 mg/kg).The arsenic adsorption capacity of all tested substrates could best explained by the Freundlich adsorption iso-therm.Given the range from 0.25mm to 0.50mm,the grain size of substrate has insignificant impact on the adsorp-tion capacity of manganese sand and zeolite.The presence of ammonia-nitrogen (concentration 0.50-2.50 mg/L) shows negligible effect on arsenic adsorption capability.When the arsenic concentration is lower than 0.4 mg/L, the effect of phosphate (concentration 0.25-0.50 mg/L)is insignificant;when arsenic concentration is higher than 0.4 mg/L,the maximum arsenic adsorption capacity decreased significantly (ceramsite decreased 2.57 mg/kg and manganese sand decreased 1 .85 mg/kg)when phosphate concentration rose from 0.25 mg/L to 0.50 mg/L.