Surface characteristics, physicochemical properties, functional groups, and bioactive compounds of microalgal biomass (MB) samples harvested from various wastewater treatment facilities (WTFs) were investigated to evaluate the reuse feasibility of MB as a potential renewable source of plant biostimulation. Mixtures of the microalgae cells and fine particles (i.e., silt, clay, suspended solids, extracellular organic matter, humus substances, natural organic matter, etc.) were complexed inside MB samples. MB samples harvested and air-dried under natural conditions investigated in this study can have relatively well-preserved cellular morphology as well as chemical substances such as carbohydrates, proteins, and fatty acids based on SEM-EDS analysis. A broad form of the amorphous cellulose rather than a distinct crystalline was observed from FTIR analysis, indicating that the middle spectrum of glucose and starch hydrolysate exist in MB samples. A wide array of chemicals (i.e., Undecane; Heptadecane; Hexadecanoic acid, methyl ester; and Methyl stearate, phenolics, and fatty acids) extracted from MB samples were involved in signaling plant response to abiotic stress, plant growth and biomass with MB samples were greater than those without MB samples. Thus, mixtures of nutrients, minerals and algal biomass in wet and dried MB samples can be beneficially reused as biostimulants in agricultural area after simple processes such as composting, microbial fermentation, and extraction. Further study is warranted to elucidate the effect of useful ingredients in MB harvested from on-site coagulation/flocculation processes on the soil environment as bio-fertilizers.

中文翻译：

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从不同的水处理设施收获的微藻生物质—其特性和潜在用途作为植物生物刺激的可再生来源

研究了从各种废水处理设施（WTF）收集的微藻生物质（MB）样品的表面特征，理化性质，官能团和生物活性化合物，以评估MB作为植物生物刺激的潜在可再生资源的再利用可行性。微藻细胞和细颗粒（即泥沙，粘土，悬浮固体，细胞外有机物，腐殖质，天然有机物等）的混合物被复合在MB样品内。在本研究中研究的在自然条件下收获和风干的MB样品，根据SEM-EDS分析，可以具有相对保存完好的细胞形态以及化学物质，例如碳水化合物，蛋白质和脂肪酸。从FTIR分析观察到广泛形式的无定形纤维素而不是明显的结晶，表明MB样品中存在葡萄糖和淀粉水解产物的中谱。从MB样品中提取的各种化学物质（即十一烷，十七烷，十六烷酸，甲酯和硬脂酸甲酯，酚和脂肪酸）与植物对非生物胁迫，植物生长和生物量的信号传递有关。比没有MB样本的样本大。因此，经过简单的处理（例如堆肥，微生物发酵和提取）后，湿的和干的MB样品中的养分，矿物质和藻类生物质的混合物可以有益地在农业领域重新用作生物刺激剂。