Algae R&D Centre, School of Environmental and Conservation Sciences, Murdoch University, WA 6150, Australia; Centre for Water, Energy and Waste, Harry Butler Institute, Murdoch University, Murdoch, WA 6150, Australia.
The UWA Institute of Agriculture, And UWA School of Agriculture and Environment, The University of Western Australia, Perth, 6009, Australia.
J Environ Manage. 2023 Oct 15;344:118467. doi: 10.1016/j.jenvman.2023.118467. Epub 2023 Jul 6.
The use of microalgae for nutrient recovery from wastewater and subsequent conversion of the harvested biomass into fertilizers offers a sustainable approach towards creating a circular economy. Nonetheless, the process of drying the harvested microalgae represents an additional cost, and its impact on soil nutrient cycling compared to wet algal biomass is not thoroughly understood. To investigate this, a 56-day soil incubation experiment was conducted to compare the effects of wet and dried Scenedesmus sp. microalgae on soil chemistry, microbial biomass, CO respiration, and bacterial community diversity. The experiment also included control treatments with glucose, glucose + ammonium nitrate, and no fertilizer addition. The Illumina Mi-Seq platform was used to profile the bacterial community and in-silico analysis was performed to assess the functional genes involved in N and C cycling processes. The maximum CO respiration and microbial biomass carbon (MBC) concentration of dried microalgae treatment were 17% and 38% higher than those of paste microalgae treatment, respectively. NH and NO released slowly and through decomposition of microalgae by soil microorganisms as compared to synthetic fertilizer control. The results indicate that heterotrophic nitrification may contribute to nitrate production for both microalgae amendments, as evidenced by low amoA gene abundance and a decrease in ammonium with an increase in nitrate concentration. Additionally, dissimilatory nitrate reduction to ammonium (DNRA) may be contributing to ammonium production in the wet microalgae amendment, as indicated by an increase in nrfA gene and ammonium concentration. This is a significant finding because DNRA leads to N retention in agricultural soils instead of N loss via nitrification and denitrification. Thus, further processing the microalgae through drying or dewetting may not be favorable for fertilizer production as the wet microalgae appeared to promote DNRA and N retention.
利用微藻从废水中回收营养物质，然后将收获的生物质转化为肥料，为创建循环经济提供了一种可持续的方法。然而，收获的微藻干燥过程会增加额外的成本，并且其对土壤养分循环的影响与湿藻生物质相比还没有得到充分的了解。为了研究这一点，进行了一项为期 56 天的土壤培养实验，比较了湿和干 Scenedesmus sp.微藻对土壤化学、微生物生物量、CO 呼吸和细菌群落多样性的影响。实验还包括葡萄糖、葡萄糖+硝酸铵和不添加肥料的对照处理。使用 Illumina Mi-Seq 平台对细菌群落进行分析，并进行了计算机分析，以评估参与 N 和 C 循环过程的功能基因。干微藻处理的最大 CO 呼吸和微生物生物量碳 (MBC) 浓度分别比湿微藻处理高 17%和 38%。与合成肥料对照相比，NH 和 NO 通过土壤微生物分解微藻缓慢释放。结果表明，与微藻添加剂相比，异养硝化可能有助于硝酸盐的产生，这可以从amoA 基因丰度低和铵浓度随硝酸盐浓度增加而降低得到证明。此外，异化硝酸盐还原为铵（DNRA）可能有助于湿微藻添加剂中铵的产生，这可以从 nrfA 基因和铵浓度的增加得到证明。这是一个重要的发现，因为 DNRA 导致氮在农业土壤中的保留，而不是通过硝化和反硝化导致氮损失。因此，通过干燥或脱湿进一步加工微藻可能不利于肥料生产，因为湿微藻似乎促进了 DNRA 和氮的保留。
