Laboratory of Microbiology, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands; Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911 MA Leeuwarden, The Netherlands.
Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911 MA Leeuwarden, The Netherlands.
Water Res. 2021 Jun 15;198:117163. doi: 10.1016/j.watres.2021.117163. Epub 2021 Apr 18.
Pure culture studies have shown that biofilm dispersal can be triggered if the nutrient supply is discontinued by stopping the flow. Stimulating biofilm dispersal in this manner would provide a sustainable manner to control unwanted biofilm growth in industrial settings, for instance on synthetic membranes used to purify water. The response of multispecies biofilms to nutrient limitation has not been thoroughly studied. To assess biomass dispersal during nutrient limitation it is common practise to flush the biofilm after a stop-period. Hence, flow-stop-induced biomass removal could occur as a response to nutrient limitation followed by mechanical removal due to biofilm flushing (e.g. biofilm detachment). Here, we investigated the feasibility to reduce membrane biofouling by stopping the flow and flushing the membrane. Using a membrane fouling simulator, biomass removal from synthetic membranes after different stop-periods was determined, as well as biomass removal at different cross flow velocities. Biomass removal from membrane surfaces depended on the nutrient limiting period and on the flow velocity during the biofilm flush. When flushed at a low flow velocity (0.1 m.s), the duration of the stop-period had a large effect on the biomass removal rate, but when the flow velocity was increased to 0.2 m.s, the length of the stop period became less considerable. The flow velocity during membrane flushing has an effect on the bacterial community that colonized the membranes afterwards. Repetition of the stop-period and biofilm flushing after three repetitive biofouling cycles led to a stable bacterial community. The increase in bacterial community stability coincided with a decrease in cleaning effectivity to restore membrane performance. This shows that membrane cleaning comes at the costs of a more stable bacterial community that is increasingly difficult to remove.
纯培养研究表明，如果通过停止流动来中断营养供应，生物膜的分散可以被触发。以这种方式刺激生物膜的分散将为控制工业环境中不需要的生物膜生长提供一种可持续的方法，例如在用于净化水的合成膜上。多物种生物膜对营养限制的反应尚未得到彻底研究。为了评估营养限制期间生物量的分散，通常在停止期后冲洗生物膜。因此，由于生物膜冲洗（例如生物膜脱落）而发生的流动停止诱导的生物量去除可能是对营养限制的响应。在这里，我们研究了通过停止流动和冲洗膜来减少膜生物污染的可行性。使用膜污染模拟器，确定了在不同停止期后从合成膜中去除生物量，以及在不同的横流速度下去除生物量。从膜表面去除生物量取决于营养限制期和生物膜冲洗期间的流速。当以低流速（0.1 m.s）冲洗时，停止期的持续时间对生物量去除率有很大影响，但当流速增加到 0.2 m.s 时，停止期的长度变得不那么重要。膜冲洗期间的流速会影响随后定植在膜上的细菌群落。在三个重复的生物污染循环后重复停止期和生物膜冲洗会导致细菌群落稳定。细菌群落稳定性的增加与恢复膜性能的清洁效果降低相对应。这表明膜清洁是以更稳定的细菌群落为代价的，而这些细菌群落越来越难以去除。
