铁盐絮凝法对阳宗海湖泊水体的除砷效果及底泥的稳定性考察

Removal of Arsenic in Yangzonghai Lake by Ferric Salt Coagulation Method and the Stability of Its Precipitate in Sediment

2008年,昆明阳宗海受到严重砷污染,砷浓度高达0.134 mg/L。项目组充分考虑其受污染水体容量大、砷浓度低的实际情况,提出了安全、廉价、高效的Fe Cl3絮凝法治理方案。实验室小试结果表明,提出的Fe Cl3絮凝法对As(Ⅲ)及As(V)均有理想的去除效果,并且湖水中大量存在的阴离子HCO-3可使治理过程中水体p H值基本保持不变。因此该方案摒弃了文献普遍报道所需要的预氧化及调节p H值的工艺步骤,将固体Fe Cl3·6H2O溶解、用湖水稀释后通过喷洒船将最终浓度为1%左右的Fe Cl3水溶液喷洒到湖面上,使湖水中的As O3-4及As O-2与Fe Cl3水解过程产生的Fe(OH)3胶体絮凝形成稳定的沉淀物被固定于底泥中。在对阳宗海进行降砷工程化治理期间,2009年11月—2010年9月砷浓度从0.117 mg/L快速下降到0.021 mg/L并可持续达到Ⅱ-Ⅲ类水标准(<0.05 mg/L),总除砷率高达82.05%。沉积物中的As绝大部分以残渣态的形式被固定在沉积物中,生态风险很低。

Yangzonghai Lake in Kunm^ng was heavily polluted by arsenic with concentration up to U. 134 mg/L. Through taking full account of the larg water storage capacity and the low arsenic concentration, a facile generic strategy of removal of arsenic by ferric salt was proposed. The strategy was of great advantage for high efficien- cy, low cost and ecological safety. Experiments in the laboratory scale demonstrated that FeC13 coagulation can remove both As （ ]Ⅱ） and As （ V ） efficiently. Meanwhile, pH value of the water was kept constant after the co- agulation process. Therefore, the pretreatment operations of pre-oxidation and adjusting pH value, which were widely employed in literature, were omitted in the treatment engineering for arsenic contamination of Yangzong- hal Lake. Solid of FeC13＋ 6H2O was dissolved and diluted to prepare FeC13 solution with concentration of 1% FeC13, which was sprayed into the lake. Colloid of Fe （OH） 3 formed in the FeC13 hydrolysis process would co- precipitate with ions of AsO-and AsO2- in the lake and the stable precipitate was fixed in the sediment of the lake. During the treatment engineering for arsenic contamination of Yangzonghai Lake, the arsenic concentration was decreased from 0. 117 mg/L to 0. 021 mg/L in the period of November 2009 to September 2010. The con- centration of arsenic could be kept below the national standard of category Ⅱ - Ⅲ（ 〈0.05 mg/L） and the re- moval ratio of arsenic was up to 82. 05 %. Residual fraction was the overwhelming arsenic form in the lake sedi- ment and its ecological risk was quite low due to its high stability.