Hijnen W A M, Schijven J F, Bonné P, Visser A, Medema G J
Kiwa Water Research Ltd, 3430 BB Nieuwegein, the Netherlands.
Water Sci Technol. 2004;50(1):147-54.
The decimal elimination capacity (DEC) of slow sand filters (SSF) for viruses, bacteria and oocysts of Cryptosporidium has been assessed from full-scale data and pilot plant and laboratory experiments. DEC for viruses calculated from experimental data with MS2-bacteriophages in the pilot plant filters was 1.5-2 log10. E. coli and thermotolerant coliforms (Coli44) were removed at full-scale and in the pilot plant with 2-3 log10. At full-scale, Campylobacter bacteria removal was 1 log10 more than removal of Coli44, which indicated that Coli44 was a conservative surrogate for these pathogenic bacteria. Laboratory experiments with sand columns showed 2-3 and >5-6 log10 removal of spiked spores of sulphite-reducing clostridia (SSRC; C. perfringens) and oocysts of Cryptosporidium respectively. Consequently, SSRC was not a good surrogate to quantify oocyst removal by SSF. Removal of indigenous SSRC by full-scale filters was less efficient than observed in the laboratory columns, probably due to continuous loading of these filter beds with spores, accumulation and retarded transport. It remains to be investigated if this also applies to oocyst removal by SSF. The results additionally showed that the schmutzdecke and accumulation of (in)organic charged compounds in the sand increased the elimination of microorganisms. Removal of the schmutzdecke reduced DEC for bacteria by +/-2 log10, but did not affect removal of phages. This clearly indicated that, besides biological activity, both straining and adsorption were important removal mechanisms in the filter bed for microorganisms larger than viruses.
已通过实际规模数据、中试装置及实验室实验评估了慢砂滤池（SSF）对病毒、细菌和隐孢子虫卵囊的十进制去除能力（DEC）。根据中试装置滤池中MS2噬菌体的实验数据计算得出，病毒的DEC为1.5 - 2个对数10。在实际规模和中试装置中，大肠杆菌和耐热大肠菌群（Coli44）的去除率为2 - 3个对数10。在实际规模下，弯曲杆菌的去除率比Coli44高1个对数10，这表明Coli44是这些致病细菌的保守替代指标。砂柱实验室实验表明，亚硫酸盐还原梭菌（SSRC；产气荚膜梭菌）的加标孢子和隐孢子虫卵囊的去除率分别为2 - 3个对数10和>5 - 6个对数10。因此，SSRC不是量化慢砂滤池对卵囊去除效果的良好替代指标。实际规模滤池对本地SSRC的去除效率低于实验室砂柱中的观察结果，这可能是由于这些滤床持续受到孢子的负载、积累和运输受阻。慢砂滤池对卵囊的去除是否也如此仍有待研究。结果还表明，砂层中的泥膜以及（有机）带电化合物的积累增加了微生物的去除率。去除泥膜使细菌的DEC降低了约2个对数10，但不影响噬菌体的去除。这清楚地表明，除了生物活性外，筛分和吸附对于滤床中大于病毒的微生物来说都是重要的去除机制。
