Insights into the succession of the bacterial microbiota during biodrying of storage sludge mixed with beer lees: Studies on its biodiversity, structure, associations, and functionality

Thermophilic bacterial agent inoculation enhances biodrying of kitchen waste: Insights into process properties, organic degradation, bacterial communities and metabolic pathways

The high moisture content of kitchen waste (KW) restricts the future treatment and resource utilization. Biodrying is an effective approach to remove the water of KW. However, conventional biodrying only uses the heat generated by the indigenous microorganisms to remove water, which has long treatment cycle and low moisture removal rate. Microbial bioaugmentation is an emerging approach to improve the biodrying efficiency of KW. In this study, a thermophilic bacterial agent (TBA) composed of Bacillus, Geobacillus and Acinetobacter was used to promote water evaporation during the biodrying process. Based on the results, the moisture removal rate of experimental group inoculated with TBA was 82.20 %, which was notably higher than CK group without inoculation. Moreover, TBA significantly increased the amount of organic matter degradation. Microbial community analysis revealed that TBA could promote the proliferation of thermophilic bacteria and make bacterial community more tolerant to high temperature environment. Further analysis of metabolic pathways showed that quorum sensing and glyoxylate and dicarboxylate metabolism were enhanced by TBA inoculation, which can help microorganisms to better adapt to high temperature environment and release more energy to facilitate the water evaporation. This study offers a fresh approach to improve the water removal efficiency in biodrying process.

Effectiveness of biological drying for citric acid dewatered sludge: Evaluating the impact of energy-efficient ventilation strategies

The effectiveness of dehydration and utilization processes for citric acid dewatered sludge is hampered by its high concentrations of polysaccharides, proteins, and water-binding properties of microbial extracellular polymers (EPS). This research explores the efficacy and mechanisms involved in extracting water from this type of sludge using biological drying technology, with varying rates of ventilation. Especially pertinent was the use of low ventilation rates as control variables. Our results suggest that a scheduled intermittent ventilation at lower rates allows for the most efficient removal of water, achieving a rate of 41.71 % within eight days, according to the zero-order kinetic model. Remarkably, the peak temperature registered was 60 °C, reaching this threshold in just 0.1 days and maintaining high temperatures for approximately 5.9 days. Component analysis of organic matter illustrated a preferential degradation process for lipids under these ventilation conditions which is pivotal for releasing and transforming bound water for efficient extraction, as well as facilitating the breakdown of easily hydrolysable materials. Further, polysaccharide/protein (EPS) decomposition contributed to water removal, though less significantly. The periodic ventilation strategy allowed for the maximum cumulative temperature to be sustained, demonstrating superior efficiency in harnessing bio-generated heat (82.77 % for water evaporation), resulting in dry sludge suitable for self-sustained combustion at relatively low cost ($26.61/t). Highlighted by this study is the considerable potential of energy-efficient ventilation methods in the biological drying treatment of citric acid fermented sludge and similar industrial waste materials.

Synergistic effects of chemical additives and mature compost on reducing H2S emission during kitchen waste composting

Additives could improve composting performance and reduce gaseous emission, but few studies have explored the synergistic of additives on H2S emission and compost maturity. This research aims to make an investigation about the effects of chemical additives and mature compost on H2S emission and compost maturity of kitchen waste composting. The results showed that additives increased the germination index value and H2S emission reduction over 15 days and the treatment with both chemical additives and mature compost achieved highest germination index value and H2S emission reduction (85%). Except for the treatment with only chemical additives, the total sulfur content increased during the kitchen waste composting. The proportion of effective sulfur was higher with the addition of chemical additives, compared with other groups. The relative abundance of H2S-formation bacterial (Desulfovibrio) was reduced and the relative abundance of bacterial (Pseudomonas and Paracoccus), which could convert sulfur-containing substances and H2S to sulfate was improved with additives. In the composting process with both chemical additives and mature compost, the relative abundance of Desulfovibrio was lowest, while the relative abundance of Pseudomonas and Paracoccus was highest. Taken together, the chemical additives and mature compost achieved H2S emission reduction by regulating the dynamics of microbial community.

Mechanisms of total phosphorus removal and reduction of β-lactam antibiotic resistance genes by exogenous fungal combination activated sludge

This study utilized Trichoderma and activated sludge to construct combined activated sludge (TAS). The metagenomic approach was employed to examine the shifts in microbial community structure and function of TAS under amoxicillin stress and investigate the mechanism underlying the reduction of β-lactam antibiotic resistance genes (β-ARGs). The findings demonstrated that the elevated aundance of glpa, glpd, ugpq, glpq, and glpb were primarily responsible for the reduction in total phosphorus (TP) removal by TAS. The increased abundance of Proteobacteria and Verrucomicrobia led to enhanced expression of ugpb, phnd, and phne, thereby improving the TP removal of TAS. Furthermore, antibiotic inactivation has gradually become the primary antibiotic resistance mechanism in TAS. Specifically, an increase in the abundance of OXA-309 in TAS will decrease the probability of amoxicillin accumulation in TAS. A decrease in β-ARGs diversity confirmed this. This study presents a novel approach to reducing antibiotic and ARG accumulation in sludge.

Influence of microbial community succession on biodegradation of municipal sludge during biodrying coupled with photocatalysis

A 20-day sludge biodrying process was coupled with photocatalysis to improve biodrying efficiency and investigate the effect of photocatalysis on biodegradation. After biodrying, the moisture content in the coupled photocatalytic group (TCA) and the control group (TUCA) decreased from 63.61% to 50.82% and 52.94%, respectively, and the volatile solids content decreased from 73.18% to 63.42% and 64.39%, respectively. Neutral proteinase activity decreased by 9.38% and 28.69%, and lipase activity decreased by 6.12% and 26.17%, respectively, indicating that photocatalysis helped maintain neutral proteinase and lipase activities. The Chao1 and Shannon indices showed that photocatalysis increased fungal diversity and reduced bacterial richness and diversity. The β diversity clustering analysis indicated that the bacterial community structure during the thermophilic phase in TCA differed from that in TUCA. The Kyoto Encyclopedia of Genes and Genomes annotation showed that photocatalysis has the potential to promote the synthesis and degradation of ketone bodies. Biodrying coupled with photocatalysis can improve the dewatering of sludge without negatively affecting biodegradation.

Performance changes in the anammox process under the stress of rare-earth element Ce(III) and the evolution of microbial community and functional genes

The high Ce(III) content in ionic rare-earth tailings wastewater has hindered the application of anammox process in this field. Here, the effect of Ce(III) on the performance of anammox processes was investigated, and the evolution of microbial communities and functional genes was explored using metagenomic sequencing. The results showed that the reactor nitrogen removal rate decreased when the Ce(III) concentration reached 25 mg/L, although ammonia nitrogen removal (92.31%) and nitrogen removal efficiency (81.33%) remained at a high level; however, both showed a significant decreasing trend. The relative abundance of anammox bacteria increased continuously from P1-P5, reaching 48.81%, whereas the relative abundance of Candidatus jettenia reached 33.71% at P5, which surpassed that of Candidatus brocadia as the most abundant anammox bacteria, and further analysis of functional genes and metabolic pathways revealed that Candidatus brocadia was richer in biochemical metabolic genes, whereas Candidatus jettenia had richer efflux genes.

Effects of chemical additives and mature compost on reducing nitrogen loss during food waste composting

This study is aimed at adding different types of mature compost and sulfur powder, as additives into food waste composting to investigate the effect on nitrogen loss and compost maturity. The composting experiment used the in-vessel composting method and was conducted continuously for 15 days. High-throughput sequencing was used to analyze the bacterial community during composting. Results showed that the secondary fermentation mature compost mixed with sulfur powder group had the most reduction of ammonia emission (56%) and the primary fermentation mature compost amendments were the most effective for nitrous oxide emission reduction (37%). The temperature, pH, and nitrogen forms of transformation of the pile significantly affect the nitrogen loss during composting. Firmicutes helped to promote the rapid warming of the pile, and Actinobacteria and Proteobacteria played an important role in decomposition of organic matter. Thermobifida and Ureibacillus had a main contribution to the rapid degradation of organic matter in the process of composting. The relative abundance of nitrogen-fixing bacteria was higher, and the relative abundance of predominantly ammonifying and denitrifying bacteria was lower than the control group, with the addition of different additives.

Insights into the effect mechanism of back-mixing inoculation on sewage sludge biodrying process: Biodrying characteristics and microbial community succession

Back mixing was frequently used to replace conventional bulking agenting, however, however, the internal effect mechanism was unclear. This study compared four bulking agents: mushroom residue (MR), MR + primary BM (BM-P), BM-P, and secondary BM (BM-S). The effect mechanism of back mixing (BM) inoculation was assessed based on biodrying performance and microbial community succession. Four trials (Trial A, Trial B, Trial C, and Trial D) reached maximum temperatures of 61.9, 68.8, 73.7, and 69.9 °C on days 6, 3, 2, and 2, respectively. Application of BM increased pile warming rate and resulted in higher temperatures. Temperature changes and microbial competition lead to decline in microbial diversity and richness during the biodrying process. Microbial diversity increased of four biodried products. The number of microorganisms shared by Trial A, Trial B, Trial C, and Trial D were 90, 119, 224, and 300, respectively. The addition of BM improved microbial community stability, and facilitating the initiation of biodrying process. Microbial genera that played an important role in the biodrying process included Ureibacillus, Bacillus, Sphaerobacter, and Tepidimicrobium. Based on these results, it was concluded that BM was efficient method to enhanced the microbial activity and reduced the usage of bulking agent.

Beer lees and ceramsite amendments enhance the two-stage co-composting of green waste

Composting is a major way to process green waste (GW), and amendments are important in GW composting. In this study of the two-stage co-composting of GW, beer lees (0, 25, 30%) and/or ceramsite (0, 10, 15%) were assessed as amendments. Changes in bulk density, porosity, temperature, pH, gaseous emissions, dissolved organic carbon (DOC) and nitrogen (DON), lignocellulose degradation, microbial abundances, and phytotoxicity were assessed during GW composting with the amendments. Treatments with a combination of beer lees and ceramsite had positive effects, and 25% beer lees and 15% ceramsite optimized all compost parameters. The optimal combination of amendments extended the thermophilic phase, enhanced the lignocellulose decomposition, and generated a stable and mature product in 20 days. Consequently, the best final compost was not phytotoxic (germination index: 164%), was mature (void space ratio: 48.48, pH: 7.20, and DOC/DON ratio: 0.51), and nutrient-rich (especially for N: 5.13%, P: 1.84%, and K: 0.68%).

The change of water content and role of microbe in the sludge drying process

In this study, the pure terephthalic acid sludge was treated by a drying process which was an economical and environmentally method. The water change and metabolic pathways for bacterial community function prediction were analyzed. The microbial community changes were studied by high-throughput sequencing to draw the dynamic succession model. Then multiple statistics was used to determine the key factors of the reduction. The results showed that the main stage of water loss in the PTA sludge drying process was the high temperature period where the water lost by evaporation accounted for more than 90% of the total removal. The main metabolic pathways for bacterial community function were amino acid (7.72%-8.71% of Kyoto encyclopedia of genes and genomes relative abundance and 8.26%-9.51% of Cluster of orthologous groups of proteins relative abundance) and carbohydrate metabolism. The model describing the dynamic succession of microbial communities showed that the dominant bacteria changed from Nitrospira, Novosphingobium and Azohydromonas to Pseudomonas, Paeniglutamicibac and Pelotomaculum. The key factors for water loss were Gemmatimonas, Novosphingobium and Azohydromonas with the correlation coefficients of 0.887, 0.772, 0.783, respectively; the key factors for dry matter loss were Pelotomaculum, total organic matter, dissovlved organic carbon and carbon/nitrogen ratio; the key factors for toxic substance loss were Brevundimonas, Novosphingobium and Gemmatimonas. These results provided theoretical support for the application and demonstration for hazardous waste sludge reduction.

Microbial succession and degradation during kitchen waste biodrying, highlighting the thermophilic phase

Biodrying in conjunction with compound stone amendment was used to treat kitchen waste, which improved biodrying. After 16 days, the pile moisture content decreased from 68.8% to 23.0%. Lignin, cellulose and hemicellulose concentrations decreased from 104.6 mg g^-1 d.b., 322.9 mg g^-1 d.b. and 155.9 mg g^-1 d.b., respectively, to 74.0 mg g^-1 d.b., 224.8 mg g^-1 d.b. and 134.5 mg g^-1 d.b., respectively. The Shannon index for bacteria increased from 2.5 to 3.1, while for fungi, it decreased from 4.6 to 0.6. The relative abundances of Amino Acid Metabolism and Carbohydrate Metabolism exceeded 7%. The thermophilic phase during the process inactivated the pathogenic microorganisms, increased the bacterial diversity, decreased the fungal diversity, and potentially improved the metabolism of nutrients, including amino acids, carbohydrates, lipids and vitamins. The biomarker analysis and predicated protein sequences provide genetic evidence to elucidate why the thermophilic phase is the peak time for nutrient metabolism.

Adaptation, restoration and collapse of anammox process to La(III) stress: Performance, microbial community, metabolic function and network analysis

During the mining of rare earth mineral, the use of lanthanum-containing fertilizers, and the disposal of lanthanum-containing electronic products, the content of lanthanum (La(III)) in typical ammonia wastewater with low carbon to nitrogen ratio is increasing day by day. Here, effects of La(III) on anammox process in performance, microbial community structure, metabolic function, and microbial co-occurrence network were investigated. The results shown that the nitrogen removal efficiency was declines briefly and then gradually recovers after low dosage (1-5 mg/L) La(III) treatment and the decrease to low level (24.25 ± 1.74%) under high La(III) dosage (10 mg/L). La(III) in the range of 1-5 mg/L significantly promoted the relative abundance of Anammoxoglobus (0.024% to 9.762%). The blocking of key metabolic pathways was confirmed to cause the breakdown of anammox by PICRUSt. Furthermore, network analysis revealed that lack of cooperation bacteria limits the activity of Anammoxoglobus.

Chloropicrin fumigation alters the soil phosphorus and the composition of the encoding alkaline phosphatase PhoD gene microbial community

The transformation of phosphorus (P) compounds in soil depends largely on soil microbial communities and is sensitive to agricultural practices. However, the effects of soil fumigation on soil P, and microbes involved in P transformation, are unknown. Our results showed that chloropicrin (CP) fumigation significantly increased the available-P, Leached-P and active-P fractionation (inorganic P extracted from H₂O, NaHCO₃ and NaOH) in Shangdong and Miyun soils in the early stages of culture, while soil alkaline phosphatase (ALP) activity and phoD gene abundance decreased significantly. Leached-P in fumigated soil was positively correlated with increased active-P fractionation, indicating that it was an important source of soil Leached-P after fumigation. The changes in P-fractionation, Leached-P and ALP after fumigation were also significantly correlated with the composition of the microbial communities. CP fumigation briefly stimulated an increase in the abundance and diversity of phoD-harboring microbial communities and promoted the mineralization process of soil P. PICRUSt metagenomic analysis showed an increase in the relative abundance of microorganisms with involved in carbohydrate/lipid transport and metabolism functions after fumigation. These results suggest CP fumigation altered soil P transformation and phoD-harboring microbes that might lead to an increased risk of P enrichment in waterways.

Multivariate insights of bulking agents influence on co-biodrying of sewage sludge and food waste: Process performance, organics degradation and microbial community

As a prerequisite additive, bulking agent played an essential role on organic wastes biodrying by affecting the organics degradation and microbial consortia. In this study, a series of experiments were conducted to explore the relationships among the type of bulking agents, organics degradation and microbial community evolution. In line with the excellent physiochemical properties, corncob was found to be more desirable for biodrying with more water removal (62.13% vs. 53.70% for sawdust and 51.72% for straw) and higher energy efficiency. Furthermore, different bulking agents showed different biodegradability and affected co-existed organics degradation. In detail, corncob upgraded the amylase and lipase activities, thus promoting the degradation of readily degradable carbohydrates and lipids in feedstocks, which accounted for >60% of the bio-heat sources for water evaporation. In addition, pyrosequencing analysis revealed that Bacillus (>50%) and Ochrobactrum (>40%) were the dominant genera in thermophilic and cooling phases, with degradation capacities of readily degradable substrate and lignocellulose, respectively. And the pathogens, e.g., E. coli and K. pneumonia, were seriously inhibited by high matrix temperatures in corncob trial. These results not only suggested the corncob was a promising bulking agent, but the potential microbial mechanisms for organics degradation were also revealed.

Feasibility of dry anaerobic digestion of beer lees for methane production and biochar enhanced performance at mesophilic and thermophilic temperature

This study investigated the feasibility of dry anaerobic digestion using beer lees as substrate and the effect of cow manure-derived biochar addition on dry anaerobic digestion performance at mesophilic and thermophilic temperature, respectively. With TS content of 25%, maximum cumulative methane production and yield were achieved to be 5230 ± 91 mL d^-1 and 220.1 ± 7.7 mL g^-1 VS at mesophilic condition and 7386 ± 134 mL d^-1 and 310.4 ± 9.2 mL g^-1 VS at thermophilic condition in the control cultures. The biochar addition has a positive effect in improving dry anaerobic digestion performance. The maximum cumulative methane production and yield in the cultures with 10 g L^-1 biochar were substantially improved by 82.9% and 82.6% at mesophilic condition and 47.2% and 46.8% at mesophilic condition when compared to the control.

Exploiting community structure, interactions and functional characteristics of fungi involved in the biodrying of storage sludge and beer lees

In this study, the dynamic changes in fungal biodiversity, community structure, fungal associations and functional characteristics were investigated in the biodrying of storage sludge and beer lees by using high throughput sequencing, network and correlation matrix analyses, and FUNGuild database. Additionally, a hypothetical model was provided to better understand the biodrying system. The results showed that fungal diversity decreased after biodrying, while community richness increased in the mesophilic stage and decreased as biodrying progressed. Fungal communities differed in different stages of the biodrying process. Ascomycota and Basidiomycota were the dominant phyla throughout the biodrying process, while Pichia was the dominant genus in the thermophilic stage. Network and correlation matrix analyses provided useful tools for insight into the fungal interactions, allowing us to propose a conceptual model of how succession in fungal associations regulates the dynamics of biodrying systems. Biodrying treatment had a significant effect on fungal trophic modes, with most pathogenic fungi fading away over the process, illustrating that biodrying is an effective bio-treatment method to eliminate pathogenic fungi. These findings provide information that elucidates the fungal interactions and functional characteristics during the biodrying process.