Revolutionizing sanitation: Valorizing fecal slags through co-digesting food waste at high-solid content and dosing metallic nanomaterials for anaerobic digestion stability.

To achieve the UN Sustainable Development Goals (SDGs) and the China Toilet Revolution on a global scale, it is crucial to implement a decentralized sanitation management system in developing countries. Fecal slags (FS) generated from septic tanks of toilets pose a challenge for remote villages. This study sought to resourcefully utilize FS through co-digesting with food waste (FW) under high-solid anaerobic co-digestion (HSAD). Besides, two metallic nanomaterials, nano-zerovalent iron (nZVI) and magnetite (Fe3O4), were employed to demonstrate the practical improvement of HSAD. The results showed that nZVI-dosed digesters produced the highest cumulative methane of 295.72 mL/gVS, 371.36 mL/gVS, 360.53 mL/gVS and 296.64 mL/gVS in 10%, 15%, 20% and 25% TS content, respectively, which was 1.15, 1.22, 1.16, 1.12 times higher than Fe3O4 dosed digesters. This increment could be ascribed to the simultaneous production of H2 from Fe2+ release from nZVI and the enrichment of homoacetogen. Changes in carbon degradation and methanogenic pathways, which facilitated stability under high TS contents, were observed. At low solid digestion (10% TS), Syntrophomonas cooperated with Methanosarcina and Methanobacterium to metabolize butyrate and propionate. However, due to the buildup of total ammonia nitrogen and volatile fatty acids, acetoclastic methanogens were inhibited in the high-solid digesters (15%, 20% and 25% TS). Consequently, a more resilient and highly tolerant Syntrophaceticus, alongside hydrogenotrophic methanogens such as Methanoculleus and Methanobrevibacter, maintained stability in the harsh environment.

Tackling fat, oil, and grease (FOG) build-up in sewers: Insights into deposit formation and sustainable in-sewer management techniques.

The increasing global demand for fatty products, population growth, and the expansion of food service establishments (FSEs) present significant challenges for the wastewater industry. This is often due to the build-up of fat, oil and grease (FOG) in sewers, which reduces capacity and leads to sanitary sewer overflows. It is crucial to develop economic and sustainable in-sewer FOG management techniques to minimise maintenance costs and service disruptions caused by the removal of FOG deposits from sewers. This study aims to understand the process of FOG deposit formation in both concrete and non-concrete sewers. Compared to fresh cooking oil, disposal of used cooking oil in households and FSE sinks results in the formation of highly adhesive and viscous FOG deposits. This occurs due to hydrolysis during frying, which increases the concentration of fatty acids, particularly palmitic acid, in the used cooking oil. Furthermore, metal ions from food waste, wastewater, and dishwashing detergents contribute to the saponification and aggregation reactions which cause FOG deposition in both concrete and non-concrete sewers. However, the leaching of Ca2+ ions exacerbates FOG deposition in cement-concrete sewers. The article concludes by suggesting future research perspectives and proposes implementation strategies for microbially induced concrete corrosion (MICC) control to manage FOG deposition in sewers. One such strategy involves applying superhydrophobic coating materials with low surface free energy and high surface roughness to the interior surfaces of the sewer. This approach would help repel wastewater carrying FOG deposit components, potentially disrupting the interaction between FOG components, and reducing the adhesion of FOG deposits to sewer surfaces.

Semi-solid anaerobic co-digestion of source-separated fecal slag and food waste: focusing on methane production, ecological risk assessment, and quality evaluation as fertilizer.

Toilet revolution is driven by the urgent need for solutions to improve sanitation and access to high-quality organic fertilizer for rural areas, which is tagged "resource recovery from human waste." This study provides a possible solution via semi-solid anaerobic co-digestion (Aco-D) of source-separated fecal slag (SFS) and food waste (FW) (3:1). A comprehensive investigation of Aco-D at different inoculum/substrate ratios (ISR) was conducted. Results revealed that the reactor with ISR of 1:4 reached the highest methane yield (255.05 mL/gVS), which enhanced Methanosaetaceae, Methanomicrobiales, and Syntrophomonas. Additionally, the reactor with low feedstock (ISR of 1:2) showed higher removal efficiency of antibiotics (74.75%). The ecological risk of digestate decreased to an insignificant hazard quotient level, and the contents of nutrients and heavy metals were in line with the standard requirement for fertilizer. This study could serve as an alternative technology to support further research in SFS management and digestate utilization as fertilizer.