Thermophilic-mesophilic biodegradation: An optimized dual-stage biodegradation technique for expeditious stabilization of sewage sludge

Role of cow dung and sawdust during the bioconversion of swine waste through the rotary drum composting process

The demand for strategic and environment-friendly swine waste (SW) management is critical in the northeastern states of India, which account for 46.7% of the country's total swine population. This paper examines nutrient-rich compost production from SW with minimal negative environmental fallout, using cow dung microbiological inoculum and sawdust bulking agent for expeditious rotary drum composting. Aerobic biodegradation conducted in a rotary drum composter (RDC), raised the feedstock temperature to > 40 °C in just 24 h, which stimulated thermophilic decomposition. The thermophilic phase remained for 16 days in the cow dung-amended 10:1:1 (swine waste:cow dung:sawdust) trial (RDC1) versus 7 days for the sawdust-amended 10:1 (swine waste:sawdust) trial (RDC2). After 20 days, the RDC1 product exhibited superior nutritional characteristics, with a total nitrogen content of 2.52%, a significantly reduced coliform population, and an overall weight loss of 25%. These findings highlight that incorporating cow dung (10% w/w) into SW and bulking agents through RDC produces high-quality compost in just 20 days. Thus, the livestock industry benefits significantly from this laboratory-scale method of improved waste management by producing valuable bioproducts via RDC.

Bacterial dispersal enhances the elimination of active fecal coliforms during vermicomposting of fruit and vegetable wastes: The overlooked role of earthworm mucus

Earthworms play a pivotal role in the elimination of fecal coliforms during vermicomposting of fruit and vegetable waste (FVWs). However, the specific mechanisms underlying the action of earthworm mucus remain unclear. This study investigated the mechanisms of fecal coliform reduction related to earthworm mucus during FVWs vermicomposting by comparing treatments with and without earthworms. The results show that the secretion of earthworm mucus decreased by 13.93 % during the startup phase, but significantly (P < 0.001) increased by 57.80 % during the degradation phase. Compared to the control without earthworms, vermicomposting led to a significant (P < 0.05) 1.22 -fold increase in the population of active bacteria, with a strong positive correlation between mucus characteristics and dominant bacterial phyla. As the dominant fecal coliforms, Escherichia coli and Klebsiella pneumoniae significantly (P < 0.05) declined by 86.20 % and 93.38 %, respectively, in the vermi-reactor relative to the control. Bacterial dispersal limitation served as a key factor constraining the elimination of E. coli (r = 0.73, P < 0.01) and K. pneumoniae (r = 0.77, P < 0.001) during vermicomposting. This study suggests that earthworm mucus increases the active bacterial abundance and cooperation by weakening the bacterial dispersal limitation, thus intensifying competition and antagonism between fecal coliforms and other bacteria.

Bioconversion of Eichhornia crassipes into vermicompost on a large scale through improving operational aspects of in-vessel biodegradation process: Microbial dynamics

Eichhornia crassipes is a common, abundant aquatic weed biomass found globally. The present study examined optimum biodegradation procedures through batch studies (550 L rotating drum composter) and the resulting best combination on a large scale (5000 L rotary drum composter). The pilot scale rotary drum reactor was commenced with cow manure and then treated for 3 months with 250 kg/day of homogenously mixed E. crassipes and dry leaves. The rotary drum's inlet and outlet temperatures were 60 °C and 39 °C, respectively, suggesting thermophilic conditions with a 7-day waste retention duration. Eisenia fetida was used for vermicomposting the outlet material for 20 days, raising the nitrogen content to 3.2%. Bacterial diversity (16S-rRNA) sequencing revealed that Proteobacteria and Euryarchaeota are the most predominant. After 27 days, the volume dropped by 71%, and the product was stable and soil-safe. Large-scale optimised biodegradation may be a better way to handle aquatic weed biomass.