Nutrient limitation is a biofouling control strategy in reverse osmosis (RO) membrane systems. In seawater, the assimilable organic carbon content available for bacterial growth ranges from about 50 to 400 μg C·L⁻¹, while the phosphorus concentration ranges from 3 to 11 μg P·L⁻¹. Several studies monitored biofouling development, limiting either carbon or phosphorus. The effect of carbon to phosphorus ratio and the restriction of both nutrients on membrane system performance have not yet been investigated.

This study examines the impact of reduced phosphorus concentration (from 25 μg P·L⁻¹ and 3 μg P·L⁻¹, to a low concentration of ≤0.3 μg P·L⁻¹), combined with two different carbon concentrations (250 C L⁻¹ and 30 μg C·L⁻¹), on biofilm development in an RO system. Feed channel pressure drop was measured to determine the effect of the developed biofilm on system performance. The morphology of the accumulated biomass for both carbon concentrations was characterized by optical coherence tomography (OCT) and the biomass amount and composition was quantified by measuring total organic carbon (TOC), adenosine triphosphate (ATP), total cell counts (TCC), and extracellular polymeric substances (EPS) concentration for the developed biofilms under phosphorus restricted (P-restricted) and dosed (P-dosed) conditions.

For both carbon concentrations, P-restricted conditions (≤0.3 μg P·L⁻¹) limited bacterial growth (lower values of ATP, TCC). A faster pressure drop increase was observed for P-restricted conditions compared to P-dosed conditions when 250 μg C·L⁻¹ was dosed. This faster pressure drop increase can be explained by a higher area covered by biofilm in the flow channel and a higher amount of produced EPS. Conversely, a slower pressure drop increase was observed for P-restricted conditions compared to P-dosed conditions when 30 μg C·L⁻¹ was dosed. Results of this study demonstrate that P-limitation delayed biofilm formation effectively when combined with low assimilable organic carbon concentration and thereby, lengthening the overall membrane system performance.

营养限制是反渗透（RO）膜系统中的生物污染控制策略。在海水中，可用于细菌生长的可吸收有机碳含量范围为约50至400μgC·L ^-1，而磷浓度范围为3至11μgP·L ^-1。一些研究监测了生物污垢的发展，限制了碳或磷。尚未研究碳磷比和两种养分对膜系统性能的影响。

本研究考察了降低的磷浓度（从25μgP·L ^-1和3μgP·L ^-1到≤0.3μgP·L ^-1的低浓度），以及两种不同的碳浓度（250）的影响。 CL ^-1和30μgC·L ^-1），有关反渗透系统中生物膜的开发。测量进料通道的压降以确定所形成的生物膜对系统性能的影响。通过光学相干断层扫描（OCT）对两种碳浓度下的累积生物量形态进行表征，并通过测量总有机碳（TOC），三磷酸腺苷（ATP），总细胞数（TCC）和生物量来定量生物量和组成。在磷限制（P限制）和剂量（P剂量）条件下，已开发生物膜的细胞外聚合物质（EPS）浓度。

对于这两种碳浓度，P限制条件（≤0.3μgP·L ^-1）都限制了细菌的生长（较低的ATP，TCC值）。与剂量为250μgC ·L ^-1的P限制条件相比，P限制条件观察到了更快的压降增加。这种更快的压降增加可以解释为流道中生物膜覆盖的面积更大，产生的EPS量也更大。相反，与P剂量条件相比，当P剂量限制条件为30μgC·L ^-1时，压降增加较慢。这项研究的结果表明，与低同化有机碳浓度结合使用时，P限制有效地延迟了生物膜的形成，从而延长了整个膜系统的性能。