实验室双介质过滤试验在直接过滤模式下进行，使用浊度适中、溶解有机碳含量较低的原水模型，并在常规过滤模式下处理浊度适中、溶解有机碳含量较高的原水。在常规和高过滤速率下，研究了化学预处理对过滤器性能的影响。本研究结果表明，直接过滤系统比传统系统对混凝剂剂量更敏感。在直接过滤模式下，明矾用量的增加在改善过滤器性能的同时，也显示出一些缺点，包括水头损失的快速发展，从而缩短了过滤器的使用时间。 直接过滤中的次优剂量显著降低了过滤器的性能。在传统模式下，明矾用量对过滤器性能的影响虽然明显，但不像直接过滤那样显著。实验室罐试验为直接过滤或常规过滤模式下的最佳过滤剂量提供了有用的估计。常规过滤结果与使用标准凝固和沉淀程序的罐试验结果一致。采用48小时延长絮凝的Jar试验确定了直接过滤试验的最佳明矾用量，并证明这是一个合理的近似值。颗粒去除的成熟早于浊度的成熟，在大多数情况下，颗粒的突破早于浊度的突破。 这些结果表明，浊度可以作为成熟期过滤器性能的更好或更保守的监测指标，而颗粒浓度测量可以被视为突破期过滤器性能恶化的早期指标。在双介质过滤中，当无烟煤层的性能无效时，下部砂层充当颗粒的多重屏障。当化学预处理不充分时，通过无烟煤层的颗粒会到达砂层，如果混凝剂用量不太低，则可以去除，因为介质颗粒的尺寸较小。通过充分的预处理，当无烟煤的性能开始突破时，从无烟煤介质中排出的颗粒在较低的砂介质中被有效去除。 在直接过滤中，有效过滤性能的最佳明矾用量随着凝固pH值的降低而降低。高过滤速率在一定程度上降低了过滤器的效率，而水头损失发展、浊度和颗粒去除的总体趋势与低过滤速率下的趋势一致。包括3个参考文献、表格和图表。

Laboratory dual media filtration experiments were conducted in direct filtration mode using a model raw water moderate in turbidity and low in dissolved organic carbon, and were also conducted in conventional filtration mode treating a watermoderate in turbidity and high in dissolved organic carbon. Effects of chemical pretreatment on the filter performance were investigated at conventional and high filtration rates. The results of this research indicated that direct filtration systems are much more sensitive to coagulant dose than are conventional systems. An increase in alum dosage in direct filtration mode, while improving filter performance, also showed some disadvantages including rapid development of head loss and, consequently, shorter filter service time. Suboptimal dosage in direct filtration significantly impaired the filter performance. In conventional mode, the effect of alum dosage on the filter performance, while obvious, was not as dramatic as in direct filtration. Laboratory jar tests provided useful estimates for the optimum dosage for the filtration in either direct filtration orconventional filtration mode. The conventional filtration results agreed with the jar test results using standard coagulation and sedimentation procedures. Jar tests with 48 hour extended flocculation were used in determining the optimum alum dosage for direct filtration experiments and proved to be a reasonable approximation. Ripening of particle removal occurred earlier than that of turbidity and, in most cases, breakthrough of particles started earlier than breakthrough of turbidity. These results suggest that turbidity can be used as a better or more conservative monitor of filter performance during the ripening period, while particle concentration measurements can be considered an earlier indicator of deteriorating filter performance during the breakthrough period. In dual media filtration, the lower sand layer serves as a multiple barrier for particles when the performance of the anthracite layer is not effective. When chemical pretreatment is inadequate, particles that pass through the anthracite layer reach the sand layer and if the coagulant dosage is not too low, can be removed due to the smaller size of the media particles. With adequate pretreatment, when the performance of the anthracite starts to break through, the particles dislodged from the anthracite media are effectively removed in the lower sand media. The optimal alum dosage for effective filter performance in direct filtration decreased as the pH of coagulation decreased. High filtration rates somewhat reduced the efficiency of the filter, while the general trends of the head loss development and turbidity and particle removals were consistent with those at low filtration rates. Includes 3 references, tables, figures.