Use of EmBio to reduce toxic and odorous compound from sewage sludge and analysis of volatile compound using Mass Spectrometry Gas Cromatography.

In recent decades, great attention has been devoted to the recovery of nutrients from secondary resources and their reuse in sustainable agriculture, driven by the growing food demand of a rising global population and the water–energy–food nexus challenges of climate change and resource depletion. Transitioning to a circular economy hinge on technologies that reclaim valuable compounds while minimizing natural resource consumption. Following this principle, Centro Agricoltura Ambiente “Giorgio Nicoli” (C.A.A.) has pioneered treatments at its Crevalcore (BO) facilities where sewage sludge is accumulated and processed[DD2.1], the sludge is kept in fifteen tons tanks and constantly mixed to avoid anaerobic fermentation since is transported to other facilities for its disposal. Although sludge is rich in water and organic matter, with the potential to be a rich soil amendment, it often harbours contaminants and malodorous volatiles, that pose environmental and health risks. In the EU alone, 6–9 million tons of dry sludge are generated annually, typically managed via landfilling or incineration, practices that highly impact the true potential of this waste product. This project aims to reduce sludge derived odorous molecules (aliphatic and aromatic hydrocarbons, sulphur‐ and nitrogen‐based volatiles) and degrade hazardous organic pollutants by applying a commercial product (EMbio) containing a consortium of the so called Effective Microorganisms (EM), and by developing a new microbial consortium able to process this complex organic matrix with degradation capabilities on pollutants and odorigenic compounds. The experimental design was as follows: two tanks of untreated sludge (sample V8) ascontrol, two tanks were inoculated with a single EmBio treatment (sample V7), and two tanks were inoculated with a double EmBio treatmen[DD3.1]t (sample V7 DT). After one month from the inoculum the sludge was sampled collecting three grams of material, in vial for gas chromatography, from three different layer of the tank, and was conditioned adding 15 uL of 4-methyl-2-pentanol at a final concentration of 50 ppm (mg/L) as standard. The volatile organic profiles were analyzed by HS-SPME GC-MS on the three treatments and the results obtained showed that single EmBio dosing (V7) achieved drastic reductions in high impact aromatics: 4-methylphenol fell from 122.1 ± 4.6 ppm eq. to 2.7 ppm eq., indole from 4.3 ± 0.3 ppm eq. to 0.7 ± 1.2 ppm eq., and 5-methylindole from 51.1 ± 9.6 ppm eq. to 5.7 ± 8.5 ppm eq. After a second EmBio application (V7 DT), toluene dropped by ~300-fold to near 1 ppm eq. and all aromatics fell below detection limits (< 1 ppm eq.). Linear and branched alkanes (C10–C16) exhibited partial decreases only in V7 DT. Microbial plate counts highlighted a surge in viable bacteria post EmBio treatment: aerobic CFUs rose from 6.5×10^5 UFC/g (V8) to 5.9×10^6 UFC/g (V7) and 5.4×10^6 UFC/g (V7 DT) while anaerobic CFUs from 2.3×10^6 UFC/g to 4.3×10^7 UFC/g and 9.5×10^7 UFC/g, respectively. With the anaerobic medium Wilkins-Chalgren the agar counts showed similar trends: 3.4×10^6 UFC/g (V8) versus 8.5×10^7 and 6.7×10^7 UFC/g. These results confirm that EmBio fosters microbial proliferation while modifying the volatile compound profile toward odour mitigation and reduction of organic and inorganic pollutants. The EmBIO treatment reduces phenolic and indolic odorants and lowers hydrocarbon loads, improving the social acceptance of land-applied sludge and potentially mitigating greenhouse gas emissions from conventional disposal practices. Field applications benefit from a microbially active amendment, which may contribute to nutrient cycling, organic matter stabilization, and disease suppression. A better-characterized and readily testable microbial co-culture would enhance process control and treatment reliability, offering opportunities to align wastewater management with circular and climate-smart agricultural strategies.