两种新型涂铁改性砂的过滤性能及反冲洗条件研究

以两种新型涂铁改性石英砂(纳米氧化铁改性砂,Nano-OCS;氧化铁改性砂,IOCS)及普通石英砂(RQS)为研究对象,考察了两种新型改性砂对沉后水腐殖酸及浊度的直接过滤效果,对其反冲洗条件进行优化研究,并对3种滤料的过滤效果进行了比较.结果表明,1滤层厚度为45 cm时,最佳滤速为6 m·h-1;3种滤料对腐殖酸和浊度的直接过滤效果依次为:Nano-OCSIOCSRQS,其中两种涂铁砂对腐殖酸的去除率分别为71.70%和61.61%;2Nano-OCS和IOCS滤柱的反冲洗流程分4步,对应的流程及最佳操作条件为:首先,用0.5 mol·L-1NaOH的溶液浸泡,气冲强度13 L·s-1·m-2,气冲时间6 min;然后,用0.075 mol·L-1的NaOH溶液与空气同时反冲洗,NaOH溶液冲洗强度为8 L·s-1·m-2,气冲强度13 L·s-1·m-2,冲洗时间3 min;接着用0.015 mol·L-1的FeCl3溶液与空气同时反冲洗,FeCl3溶液冲洗强度为8 L·s-1·m-2,气冲强度13L·s-1·m-2,冲洗时间2 min;最后,用清水冲洗,冲洗强度8 L·s-1·m-2,冲洗时间4 min.两种涂铁砂反冲洗前后表面形态结构更加复杂、粗糙度增加,对腐殖酸去除率进一步提高.3当滤层厚度由45 cm增加到80 cm时,Nano-OCS对腐殖酸直接过滤的最高去除率由74.6%提高至80.3%,平均去除率由57.9%提高至68.5%.

Filtration performance and backwashing conditions of two types of modified sand materials

We investigated the filtration efficiencies of two types of coated iron oxide sand prepared in the laboratory, Nano-Iron Oxide Coated Sand (Nano-OCS) and Iron Oxide Coated Sand (IOCS), to humic acid (HA) and turbidity and optimum backwashing conditions. Their filtration and backwashing properties were compared with those of Raw Quartz Sand (RQS). The results are: 1 When thickness of filter media layer is 45 cm, the optimal filtration velocity is 6 m·h^-1, and their filtration efficiency to HA and turbidity is in the following order: Nano-OCS > IOCS > RQS. The removal efficiency of Nano-OCS and IOCS to HA is 71.70% and 61.61%, respectively. 2 For Nano-OCS and IOCS, there are four steps in the process of backwashing. The optimum operations are: First, sands are kept soaking in NaOH solution with concentration 0.5 mol·L^-1 and backwashing intensity with air of 13 L·s^-1·m^-2 for 6mins; Second, backwashing with NaOH solution of 0.075 mol·L^-1 and air at the same time. Their backwashing intensity is 8 L·s^-1·m^-2 and 13 L·s^-1·m^-2, respectively, with 3 mins of backwashing time; Third, backwashing with air and 0.015 mol·L^-1 of FeCl₃ solution together; Their backwashing intensity is 8 L·s^-1·m^-2 and 13 L·s^-1·m^-2, respectively, with 2 mins of backwashing time; Finally, backwashing with clean water with intensity of 8 L·s^-1·m^-2 for 4 mins. For Nano-OCS and IOCS, their surface morphological structures are more complex and rough, and the porosity on the surface increases after backwashing compared with those on the surface of RQS. Removal efficiency to HA is enhanced. 3 When the thickness of the filter media layer increases from 45 cm to 80 cm, the highest direct filtration efficiency of Nano-OCS to HA is improved from 74.6% to 80.3%, and the average removal rate is enhanced from 57.9% to 68.5%.