Brown Trevor J, Emelko Monica B
Department of Civil and Environmental Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1, Canada.
Water Res. 2009 Feb;43(2):331-8. doi: 10.1016/j.watres.2008.10.035. Epub 2008 Oct 26.
Maintenance of appropriate chemical pretreatment is a critical component of ensuring proper filtration performance. Pilot-scale in-line filtration studies were performed to investigate the relative impacts of chitosan, alum, and FeCl(3) coagulation on the removal of Cryptosporidium parvum oocysts and oocyst-sized polystyrene microspheres by granular media filtration. Similar removals of oocysts and microspheres were achieved when optimal coagulant doses were utilized. Sub-optimal alum and FeCl(3) coagulation resulted in a deterioration filter effluent turbidity (0.2-0.3NTU) and total particle counts (30-100 total particles > or =2microm/mL) that were accompanied by reduced (by approximately 2-3-log) median oocyst and microsphere removals by filtration. At all doses investigated, chitosan coagulation resulted in excellent turbidity and particle reductions by filtration. Nonetheless, chitosan coagulation at doses of 0.1, 0.5, and 1.0mg/L did not result in appreciable improvements in C. parvum oocyst removal relative to complete coagulation failure (median oocyst removals were < approximately 1-log). As well, oocyst-sized polystyrene microspheres appear to be reasonable indicators of C. parvum oocyst removal by in-line filtration preceded by alum and FeCl(3) coagulation, but not chitosan coagulation.
维持适当的化学预处理是确保正确过滤性能的关键组成部分。进行了中试规模的在线过滤研究，以调查壳聚糖、明矾和FeCl₃混凝对颗粒介质过滤去除微小隐孢子虫卵囊和卵囊大小的聚苯乙烯微球的相对影响。当使用最佳混凝剂剂量时，卵囊和微球的去除效果相似。次优的明矾和FeCl₃混凝导致过滤后出水浊度（0.2 - 0.3NTU）和总颗粒数（30 - 100个总颗粒≥2微米/毫升）恶化，同时过滤对卵囊和微球的中位去除率降低（约2 - 3个对数）。在所研究的所有剂量下，壳聚糖混凝通过过滤可实现出色的浊度和颗粒去除。尽管如此，相对于完全混凝失败（中位卵囊去除率<约1个对数），0.1、0.5和1.0毫克/升剂量的壳聚糖混凝并未导致微小隐孢子虫卵囊去除率有明显提高。此外，卵囊大小的聚苯乙烯微球似乎是明矾和FeCl₃混凝后在线过滤去除微小隐孢子虫卵囊的合理指标，但不是壳聚糖混凝的指标。
