随着工业发展和工业废水防治政策日益严格，零排放已成为工业废水处理和资源回收的首要目标。纳滤（nanofiltration, NF）和反渗透（reverse osmosis, RO）是应用广泛的零排放技术。在废水膜处理过程中，膜污染是限制NF/ RO长效稳定运行的主要瓶颈，而膜无机结垢和膜生物污染的相互作用影响机制尚不明确。本研究采用石膏为模式结垢，铜绿假单胞菌（Pseudomonas aeruginosa, PA）为模式微生物，探索了无机‒微生物复合膜污染形成的关键影响因素，以及其在不同形成阶段的膜表面理化性质特点和膜阻组成，进而揭示微生物增殖和无机结垢的相互作用、微生物及微生物胞外聚合物（extracellular polymeric substances, EPS）与复合污染膜之间界面作用的动态变化过程；探究了不同剂量阻垢剂2-膦酸丁烷-1,2,4-三羧酸（2-phosphonobutane-1,2,4-tricarboxylic acid, PBTCA）对PA生长代谢的影响，进而揭示其对无机‒微生物和无机-有机物（微生物EPS）复合膜污染的调控效果及作用机制。

（1）探究了NF/ RO中，操作压力、结垢离子（CaCl₂和Na₂SO₄）浓度和膜表面理化性质对无机‒微生物复合膜污染的形成影响。在高浓度结垢离子（35 mM CaCl₂ + 20 mM Na₂SO₄）条件下，生物污染在低压（4 bar）时占主导；而在高压（8 bar）时，无机结垢是导致膜通量下降的主要因素。低浓度结垢离子（7 mM CaCl₂ + 4 mM Na₂SO₄）促进PA生长，在培养后期提高了多糖和总有机碳（total organic carbon, TOC）的分泌；而高浓度结垢离子抑制PA生长活性以及多糖、TOC分泌。结垢离子均促进蛋白分泌，在低浓度下将蛋白分泌提高25.1% ~ 46.4%。膜表面石膏晶体的（021）面是导致结垢形成和膜通量下降的关键晶面。PA及其营养组分中的柠檬酸钠通过抑制石膏晶体的（020）、（021）和（041）面，并促进（-221）和（150）面生长，导致石膏由杆状堆叠的花簇构型变为六边形片状结构，减小了水流阻力，膜通量下降速度减慢。Pearson相关性分析表明，膜表面亲疏水性和粗糙度比电性对无机‒微生物复合膜污染形成的影响更大。表面疏水且粗糙的NF/ RO膜有利于EPS富集而不利于结垢形成，复合膜污染的通量下降程度更小。

（2）揭示了RO中无机‒微生物复合膜污染的膜表面理化性质动态变化过程，以及微生物与膜表面的界面作用变化。微生物粘附和浓差极化是RO中无机–微生物复合膜污染初期通量下降的主要原因，随后结垢逐渐形成。结垢离子的清洗效率（Ca²⁺和SO₄^2-分别为57.0% ~ 84.8%和~ 85.0%）远高于多糖和蛋白组分（分别为10.1% ~ 32.3%和4.2% ~ 12.6%），因此导致无机‒微生物复合膜污染的可逆膜污染阻力占总膜阻的比例由初期的32%提高到54%。微生物溶解性产物（Ⅳ区）是无机–微生物复合污染膜表面的主要荧光物质（占比~ 40%），但是色氨酸类简单芳香族蛋白（Ⅱ区）和富里酸类物质（Ⅲ区）更容易在膜表面富集，在清洗后的膜表面占比约41% ~ 53%和19% ~ 24%。结垢离子一方面促进进水PA和EPS团聚，增大进水污染物尺寸；另一方面通过形成结垢层，逐渐增强膜表面亲水性并将PA粘附量降低16.2% ~ 29.8%，提高无机–微生物复合膜污染中PA与膜表面的排斥作用，进而增强了结垢在复合膜污染后期的形成。

（3）探究了NF/ RO中，阻垢剂对无机‒微生物和无机-有机物（微生物EPS）复合膜污染的调控效果及作用机制。低剂量（5 mg/L）阻垢剂PBTCA略微促进微生物生长和EPS分泌；而高剂量（50 mg/L）阻垢剂相反。阻垢剂和海藻酸钠（sodium alginate, SA）、牛血清蛋白（bovine serum albumin, BSA）通过抑制石膏晶体的（021）面并促进（020）面生长，使石膏晶体由光滑杆状晶体聚集成的花簇状形貌变为边缘粗糙、细小且零散的杆状和棱柱状形貌，进而缓解了4.6% ~ 42.9%的通量下降。模拟多糖组分的SA在高浓度（20 mg/L）下与Ca²⁺在膜表面形成凝胶层并加剧膜污染，导致的通量下降程度高于模拟蛋白组分的BSA。阻垢剂通过抑制结垢缓解无机-有机物（微生物EPS）复合膜污染，但是缓解效果比单一结垢低33% ~ 43%，尤其在高有机物浓度（20 mg/L）情况下。

本论文揭示了NF/ RO中无机–微生物复合膜污染形成的影响因素和机制，阐述了其形成过程以及结垢和生物污染的动态变化，并探索了商品化阻垢剂PBTCA对无机–微生物、无机-有机物（微生物EPS）复合膜污染的调控效果和作用机制，为工业废水膜法零排放中的无机–微生物复合膜污染控制提供了理论依据。

With the development of industry and the increasingly stringent industrial wastewater control policies, zero liquid discharge (ZLD) has become the primary goal of industrial wastewater treatment and resource recovery. Nanofiltration (NF) and reverse osmosis (RO) are widely used ZLD technologies. However, membrane fouling is the bottleneck limiting the long-term operation of NF/ RO in the treatment of industrial wastewater, and the interaction mechanisms between membrane inorganic scaling and biofouling remain unclear. In this research, gypsum and Pseudomonas aeruginosa (PA) were selected as the model scalant and model microorganism, respectively. The key factors affecting the formation of combined scaling–biofouling were explored. The physiochemical characteristics and membrane resistance distribution of membranes fouled by combined scaling–biofouling at different filtration time were clarified, and then the interactions between membrane scaling and biofouling, as well as interfacial interactions among microorganisms, extracellular polymeric substances (EPS) and fouled membranes were revealed. The effects of 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) with different dosages on the growth and metabolism of PA were explored, and the regulatory effect and mechanism of combined scaling–biofouling and combined scaling–organic (EPS) fouling were elucidated.

(1) In NF/ RO, the influence of pressure, concentration of scaling ions (CaCl₂ and Na₂SO₄), and physiochemical properties of the membrane on the formation of combined scaling–biofouling was explored. Under high concentration of scaling ions (35 mM CaCl₂ + 20 mM Na₂SO₄), biofouling and inorganic scaling dominated combined scaling–biofouling under low (4 bar) and high (8 bar) pressure, respectively. Low concentration of scaling ions (7 mM CaCl₂ + 4 mM Na₂SO₄) promoted the propagation of PA, and increased the secretion of polysaccharide and total organic carbon (TOC) from PA at the later stage of incubation. High concentration of scaling ions inhibited the growth and activity of PA, and the secretion of polysaccharide and TOC. Scaling ions stimulated protein secretion, with the improvement of 25.1% ‒ 46.4% at low concentrations. The (021) plane of gypsum crystal was key to scale formation and decrease of membrane flux. PA and sodium citrate (the nutrient for microbial growth) inhibited (020), (021) and (041) planes, while augmented the growth of (‒221) and (150) planes in gypsum crystals, altering its structures from rod-stacked blossoms configurations to hexagonal prism sheets, therefore reducing the permeate resistance and alleviating membrane flux decline. Pearson correlation analysis revealed that, in comparison with the electrical property, the hydrophilicity and roughness of the membrane surface had greater impacts on the formation of combined scaling–biofouling. NF/ RO membranes with hydrophobic and rough surface were conducive to EPS enrichment, but unfavorable to scale formation, and thus led to lighter flux decline in combined scaling–biofouling.

(2) The variation of physiochemical properties of RO membranes during combined scaling–biofouling and the interactions between microbes and the fouled membranes were illustrated. Microbial adhesion and concentration polarization were the main reasons for the initial flux decline of combined scaling–biofouling, and then membrane scaling gradually formed. The physical cleaning efficiencies of scaling ions (Ca²⁺: 57.0% ‒ 84.8%, and SO₄^2-: ~ 85.0%) were much higher than that of polysaccharide and protein (10.1% ‒ 32.3% and 4.2% ‒ 12.6%, respectively), therefore elevating the proportion of reversible fouling resistance from 32% at the initial stage to 54%. Among the fluorescent substances on the membranes fouled by combined scaling–biofouling, the microbial soluble products (region Ⅳ) (~ 40%) were dominant, but tryptophan proteins with simple structures (region Ⅱ) and fulvic acids (region Ⅲ) were more easily deposited on the membrane surface, and were more recalcitrant to membrane cleaning (taking up 41% ‒ 53% and 19% ‒ 24% after flushing, respectively). On the one hand, scaling ions promoted the aggregation of influent microorganisms and EPS, increasing the size of pollutants in feed water; on the other hand, they gradually enhanced the hydrophilicity of membranes fouled by combined scaling–biofouling through forming scaling layers, thus reduced 16.2% ‒ 29.8% of PA adhesion and improved the repulsion between PA and membrane surface, and finally enhanced scaling formation in the later stage of combined scaling–biofouling.

(3) In NF/ RO, the regulation effect and mechanisms of antiscalant on combined scaling–biofouling and combined scaling–organic (EPS) fouling were explored. Antiscalant (PBTCA) at low dosage (5 mg/L) slightly enhanced microbial growth and EPS secretion; while that at high dosage (50 mg/L) was on the contrary. By inhibiting (021) plane and enhancing the growth of (020) plane, antiscalant, sodium alginate (SA) as well as bovine serum albumin (BSA) altered the gypsum morphology of smooth rod crystals into rough, fine and scattered rod or prismatic morphology, therefore alleviated 4.6% ‒ 42.9% flux decline. SA, the simulant of polysaccharide, formed gel layers with Ca²⁺ and aggravated membrane fouling at high concentration (20 mg/L), causing severer flux decline compared with combined scaling–organic (EPS) fouling formed by BSA, the simulant of protein. Antiscalant relieved combined scaling–organic (EPS) fouling through scale inhibition effect, while its efficiency was 33% ‒ 43% lower than treating inorganic scaling alone, especially in the presence of organic matter with high concentration (20 mg/L).

This research revealed the influencing factors and formation mechanisms of combined scaling–biofouling in NF/ RO, elaborated its formation process and the dynamic succession of membrane scaling and biofouling, and explored the efficiency and mechanisms of commercial antiscalant PBTCA for the control of combined scaling–biofouling and combined scaling–organic (EPS) fouling. Our research provided a theoretical basis for the control of combined scaling–biofouling in membrane-based ZLD technologies for the treatment of industrial wastewater.