Algal Technology Program, Center for Sustainable Development, College of Arts and Sciences, Qatar University, Doha, 2713, Qatar.
Algal Technology Program, Center for Sustainable Development, College of Arts and Sciences, Qatar University, Doha, 2713, Qatar.
Sci Total Environ. 2020 May 1;715:136775. doi: 10.1016/j.scitotenv.2020.136775. Epub 2020 Jan 23.
Hydrothermal Liquefaction (HTL) could be a promising and better alternative to other techniques for energy recovery from municipal sewage sludge (MSS). However, the nutrients (i.e., N, and P) recovery potential from the byproducts, generated in the HTL of MSS, needs to be studied so that a comprehensive sludge management practice could be adopted. In this study, HTL process temperature (275-400 °C), and reaction time (30-120 min) were first investigated for biocrude yield and release of the nutrients to the aqueous phase liquid (APL) and biochar. The maximum energy recovery (i.e., 59%) and maximum energy return on investment (i.e., 3.5) were obtained at 350 °C and 60 min of holding time. With the increase in HTL reaction time, the concentration of nitrogen in the APL increased (5.1 to 6.8 mg/L) while the concentration of phosphorus decreased (0.89 to 0.22 mg/L); the opposite was observed for the biochar. The nutrient recycling efficiency from the APL using microalgae was found to be strain-specific; nitrogen recycling efficiency by Picochlorum sp. and Chlorella sp. were 95.4 and 58.6%, respectively. The APL, derived from 1 kg MSS, could potentially produce 0.49 kg microalgal biomass. Since the concentrations of various metals in the biochar samples were substantially lower compared to their concentrations in raw MSS, the application of biochar as a soil conditioner could be very promising. Overall, net positive energy could be recovered from MSS using the HTL process, while the nutrients in the APL could be used to cultivate specific microalgae, and biochar could be applied to enhance the soil quality.
水热液化 (HTL) 可能是从城市污水污泥 (MSS) 中回收能源的一种有前途且更好的替代技术。然而，需要研究从 MSS 的 HTL 中产生的副产物中回收营养物质（即 N 和 P）的潜力，以便采用综合的污泥管理实践。在这项研究中，首先研究了 HTL 工艺温度（275-400°C）和反应时间（30-120 分钟）对生物原油产量和营养物质向水相液体（APL）和生物炭的释放的影响。在 350°C 和 60 分钟的保持时间下，获得了最大的能量回收（即 59%）和投资能源回报（即 3.5）。随着 HTL 反应时间的增加，APL 中氮的浓度增加（从 5.1 增加到 6.8mg/L），而磷的浓度降低（从 0.89 减少到 0.22mg/L）；生物炭则相反。使用微藻从 APL 中回收营养物质的效率因菌株而异；Picochlorum sp. 和 Chlorella sp. 的氮回收效率分别为 95.4%和 58.6%。从 1kg MSS 中提取的 APL 理论上可以产生 0.49kg 微藻生物质。由于生物炭样品中各种金属的浓度与 raw MSS 相比大幅降低，因此生物炭作为土壤改良剂的应用非常有前景。总体而言，HTL 工艺可以从 MSS 中回收净正能量，而 APL 中的营养物质可以用来培养特定的微藻，生物炭可以用来提高土壤质量。
