Environmental RNA (eRNA) analysis has emerged as a promising tool for assessing the physiological status of macro-organisms in aquatic environments. However, existing eRNA analysis for physiological assessments has been limited to laboratory experiments. To explore the potential of eRNA under non-laboratory conditions, this study re-analyzed two published metatranscriptome datasets from an aquaculture facility and an aquarium. The re-analysis revealed that functional genes, such as tlr4, lrp12, and elovl1, were detected as eRNA from Pacific oyster (Magallana gigas), whale shark (Rhincodon typus), zebra shark (Stegostoma tigrinum), and green sea turtle (Chelonia mydas). This result highlights the feasibility of using eRNA to assess biological processes, including immune responses and fatty acid metabolism. Despite these successes, challenges such as the dominance of microbial RNA, low sequencing depth, and RNA degradation were identified. Strategies to overcome these challenges were discussed as pathways for advancing eRNA analysis. This study provides a foundational direction for developing eRNA analysis as a non-invasive tool for ecological monitoring and the management of aquatic organisms in non-laboratory environments.

Microalgal biomass is a promising renewable feedstock for producing biofuels and bioplastics. The use of wastewater or food industrial organic waste as a cultivation medium is an economical and sustainable approach to microalgal biomass production. However, the biomass productivity of diverse microalgae cultured in different wastewaters or organic wastes is still not fully understood. This study aimed to confirm the biomass production of various microalgae using different culture media, two wastewaters and an organic waste medium, and to identify an ideal combination of microalgae and wastewater/organic waste medium. The four microalgae Chlorella vulgaris, Chlorella sorokiniana, Euglena gracilis, and Chlamydomonas reinhardtii grew well in sewage, 10% anaerobic digestion effluent, and 5 g/L corn steep liquor (CSL). The four microalgae utilized nitrogen from their culture media for biomass production. Biomass production rates ranged from 0.020 to 0.180 g-dry weight (dw)/L/d. The biomass production rates of the four microalgae species were generally higher in 5 g/L CSL and 10% anaerobic digestion effluent, which contained more nitrogen than sewage. CSL and diluted anaerobic digestion effluent were considered suitable for microalgal cultivation. C. sorokiniana cultured in 5 g/L CSL showed the highest biomass production rate (0.180 g-dw/L/d) in this study.

To recover the soluble nutrients from the anaerobic digestate liquor into the concentrate, which could be recycled to the materials of chemical fertilisers, the sets of batch tests were conducted using the lab-scale electrodialysis apparatus. The ammonium nitrogen, potassium and phosphate were recovered from the liquor by about 70%, 63%, and 40%, respectively, with an acceptable current efficiency of about 83% and power consumption in the optimised scheme. A small amount of organic foulant was formed on the surface of the anion-exchange membranes in the dilute compartments, whereas cationic inorganic deposits were not noticeably precipitated in the concentrate compartments. The development of the foulant was successfully controlled by activating the electrodialysis in an intermittent manner associated with the maintained liquid streams. During the idling stage, a part of the foulant was eroded by the hydraulic shear stress, and removed from the membrane surfaces. The experiments revealed that the most optimised intermittent operation would save the electricity by about 50% and the system size by 20% compared to the continuous operation without idling, respectively. The experimental performance was equivalent to an ammonium-based nutrient recovery of about 5.0 kWh kg-N⁻¹, which might outcompete with the pricing of urea in recent commercial trades.