Low-energy sponge-core bioreactor for reducing total nitrogen and antibiotic resistance burden in domestic wastewater

Inadequate sanitation can lead to the spread of infectious diseases and antimicrobial resistance (AMR) via contaminated water. Unfortunately, wastewater treatment is not universal in many developing and emerging countries, especially in rural and peri-urban locations that are remote from central sewers. As such, small-scale, more sustainable treatment options are needed, such as aerobic-Denitrifying Downflow Hanging Sponge (DDHS) bioreactors. In this study, DDHS reactors were assessed for such applications, and achieved over 79% and 84% removal of Chemical Oxygen Demand and Ammonium, respectively, and up to 71% removal of Total Nitrogen (TN) from domestic wastes. Elevated TN removals were achieved via bypassing a fraction of raw wastewater around the top layer of the DDHS system to promote denitrification. However, it was not known how this bypass impacts AMR gene (ARG) and mobile genetic element (MGE) levels in treated effluents. High-throughput qPCR was used to quantify ARG and MGE levels in DDHS bioreactors as a function of percent bypass (0, 10, 20 and 30% by volume). All systems obtained over 90% ARG reductions, although effluent ARG and TN levels differed among bypass regimes, with co-optimal reductions occurring at ~20% bypass. ARG removal paralleled bacterial removal rate, although effluent bacteria tended to have greater genetic plasticity based on higher apparent MGE levels per cell. Overall, TN removal increased and ARG removal decreased with increasing bypass, therefore co-optimization is needed in each DDHS application to achieve locally targeted TN and AMR effluent levels.

不充分的卫生条件可能导致通过受污染的水源传播传染性疾病和抗菌药物耐药性（AMR）。遗憾的是，在许多发展中国家和新兴国家，尤其是在远离中心下水道的农村和近郊地区，废水处理并未得到普遍实施。因此，迫切需要小型化、可持续的处理方案，例如好氧-反硝化向下流悬挂海绵（DDHS）生物反应器。在本研究中，对DDHS生物反应器进行了相关应用评估，并实现了对化学需氧量（COD）和铵的分别超过79%和84%的去除率，以及对家庭废物中总氮（TN）高达71%的去除率。通过绕过DDHS系统顶部一部分原废水以促进反硝化作用，实现了更高的TN去除率。然而，尚不清楚这种绕行对处理后的废水中的抗菌药物耐药基因（ARG）和移动遗传元件（MGE）水平的影响。本研究采用高通量qPCR技术，以绕行百分比（0%、10%、20%和30%的体积）作为函数，对DDHS生物反应器中的ARG和MGE水平进行量化。所有系统均实现了超过90%的ARG减少，尽管在不同绕行方案中，排放废水中的ARG和TN水平存在差异，而在约20%绕行时达到协同最优的减少。ARG的去除与细菌的去除速率相一致，尽管排放细菌的遗传可塑性较高，这基于每个细胞中更高的MGE水平。总体而言，随着绕行比例的增加，TN的去除率上升，而ARG的去除率下降，因此在每个DDHS应用中都需要实现TN和AMR排放水平的协同优化。