Abstract：
Water outages caused by elevated ammonium (NH4+-N) levels are a prevalent problem faced by conventional raw water treatment plants in developing countries. A treatment solution requires a short hydraulic retention time (HRT) to overcome nitrification rate limitation in oligotrophic conditions. In this study, the performance of polluted raw water treatment using a green downflow sponge biofilm (DSB) technology was evaluated. We operated two DSB reactors, DSB-1 and DSB-2 under different NH4+-N concentration ranges (DSB-1: 3.2-5.0 mg L-1; DSB-2: 1.7-2.6 mg L-1) over 360 days and monitored their performance under short HRT (60 min, 30 min, 20 min, and 15 min). The experimental results revealed vertical segregation of organic removal in the upper reactor depths and nitrification in the lower depths. Under the shortest HRT of 15 min, both DSB reactors achieved stable NH4+-N and chemical oxygen demand removal (≥95%) and produced minimal effluent nitrite (NO2--N). DSB system could facilitate complete NH4+-N oxidation to nitrate (NO3--N) without external aeration energy requirement. The 16S rRNA sequencing data revealed that nitrifying bacteria Nitrosomonas and Nitrospira in the reactor were stratified. Putative comammox bacteria with high ammonia affinity was successfully enriched in DSB-2 operating at a lower NH4+-N loading rate, which is advantageous in oligotrophic treatment. This study suggests that a high hydraulic rate DSB system with efficient ammonia removal could incorporate ammonia treatment capability into polluted raw water treatment process and ensure safe water supply in many developing countries.
摘要：
由升高的铵（NH4-N）水平引起的停水是发展中国家常规原水处理厂面临的普遍问题。处理溶液需要短的水力停留时间(HRT)以克服在寡养条件下的硝化速率限制。在这项研究中,评估了使用绿色下流式海绵生物膜（DSB）技术处理污染原水的性能。我们操作了两个DSB反应堆,DSB-1和DSB-2在不同的NH4-N浓度范围（DSB-1：3.2-5.0mgL-1；DSB-2：1.7-2.6mgL-1）下360天，并监测其在短HRT下的表现（60分钟，30分钟,20分钟,和15分钟）。实验结果表明，在较高的反应器深度中，有机去除的垂直偏析和较低的深度中的硝化作用。在15分钟的最短HRT下，两个DSB反应器均实现了稳定的NH4-N和化学需氧量去除（≥95％），并产生了最少的亚硝酸盐（NO2--N）。DSB系统可以促进NH4-N完全氧化为硝酸盐（NO3--N），而无需外部曝气能量。16SrRNA测序数据显示，反应器中的硝化细菌亚硝基单胞菌和亚硝基螺旋体被分层。具有高氨亲和力的推定的Comammox细菌成功地富集在以较低的NH4-N负载率运行的DSB-2中，这在寡营养治疗中是有利的。这项研究表明，具有高效氨去除功能的高水力DSB系统可以将氨处理能力纳入污染原水处理工艺，并确保许多发展中国家的安全供水。
