Judd S J, Hillis P
School of Water Sciences, University of Cranfield, Bedfordshire, UK.
Water Res. 2001 Aug;35(12):2895-904. doi: 10.1016/s0043-1354(00)00586-8.
The effect of upstream coagulant dosing for full-flow microfiltration of an upland-reservoir water has been investigated. The process, run under conditions of constant flux and pH and based on a ferric salt, is compared with a published study of another full-flow process based on alum dosing and operated at constant pressure and coagulant concentration. The current study includes data for the residual deposit remaining following backflushing by reverse flow. Results are presented in terms of the specific-cake resistance (R'o, m(-2)) as a function of pH or coagulant dose. Reasonable correlation with classical cake filtration theory was obtained, such that R' was assumed to be independent of run time and cake thickness. The following trends have been noted: The optimum pH for the alum-based system appears to be between 7.5 and 8 on the basis of cake resistance. The effect of coagulant dose between 18 and 71 microM Fe3+ is much more significant than a change in pH between 5 and 9 for the alum system: a 53-fold increase in specific flux compared with a 7-fold increase with reference to the limiting R'o values at pH 4.8 and 7.7. A low coagulant dose (0.018mM, 1.0 mg l(-1) Fe3+) appears to have a slightly detrimental effect on downstream microfiltration operation. The low coagulant doses apparently cause incomplete aggregation of colloidal particles such that internal fouling of the membrane takes place. The residual (cleaning cycle) deposit resistance followed roughly the same trend as the backflush cycle-cake resistance with coagulant concentration, but with a much reduced value (about 16 times lower, on average). An optimum coagulant dose of 0.055 mM (3.1 mg/l) Fe3+ can be identified on the basis of operational cost based on coagulant cost and cake resistance, all other aspects of the system being substantially unchanged. It is concluded that coagulation with downstream microfiltration offers a cost-effective means of removing natural organic matter, achieving a THMFP removal of around 80% at the optimum dose.
研究了上游投加混凝剂对山地水库水全流微滤的影响。该工艺在恒通量和pH条件下运行，以铁盐为基础，与另一项已发表的基于投加明矾且在恒压和混凝剂浓度下运行的全流工艺研究进行了比较。当前研究包括逆流反冲洗后残留沉积物的数据。结果以比滤饼阻力（R'o，m(-2)）作为pH或混凝剂剂量的函数呈现。与经典滤饼过滤理论获得了合理的相关性，因此假设R'与运行时间和滤饼厚度无关。已注意到以下趋势：基于滤饼阻力，明矾基系统的最佳pH似乎在7.5至8之间。对于明矾系统，18至71 microM Fe3+之间的混凝剂剂量影响比pH在5至9之间的变化更为显著：与pH 4.8和7.7时的极限R'o值相比，比通量增加了53倍，而pH变化时增加了7倍。低混凝剂剂量（0.018 mM，1.0 mg l(-1) Fe3+）似乎对下游微滤操作有轻微不利影响。低混凝剂剂量显然会导致胶体颗粒不完全聚集，从而发生膜的内部污染。残留（清洗周期）沉积物阻力与反冲洗周期滤饼阻力随混凝剂浓度的变化趋势大致相同，但值大幅降低（平均约低16倍）。基于混凝剂成本和滤饼阻力的运行成本，可以确定最佳混凝剂剂量为0.055 mM（3.1 mg/l）Fe3+，系统的所有其他方面基本不变。得出的结论是，混凝与下游微滤相结合提供了一种具有成本效益的去除天然有机物的方法，在最佳剂量下可实现约80%的三卤甲烷前体物去除率。
