Plant-scale hyperthermophilic composting of sewage sludge shifts bacterial community and promotes the removal of organic pollutants

Extreme thermophilic microbial inoculation for reducing NH3 and N2O emissions in hyperthermophilic aerobic composting of refinery waste activated sludge

Ammonia (NH3) and nitrous oxide (N2O) release are the main causes of nitrogen loss during aerobic composting. In this study, hyperthermophilic aerobic composting of refinery waste activated sludge (RWAS) was performed by adding extreme thermophilic bacteria, and the effects of inoculation on NH3 and N2O emissions were systematically studied. The results revealed that inoculation achieved hyperthermophilic aerobic composting (T group), increased maturity, and reduced NH3 and N2O emissions by 32.36% and 10.17%, respectively. The results of microbial network analysis and structural equation modeling revealed that inoculation altered the mechanisms influencing NH3 and N2O release. Nitrogen genes and dominant bacteria were positively correlated with NH3 and N2O release during conventional composting (CK group), whereas dominant bacteria and physicochemical factors were the main factors affecting NH3 and N2O release during hyperthermophilic composting(T group). The correlation between the dominant bacteria and the release of NH3 and N2O was weakened in the hyperthermophilic aerobic composting system, resulting in a decrease in the release of the above gases.

Thermophilic bacteria contributing to humus accumulation in hyperthermophilic aerobic fermentation of mushroom residue

The purpose of this study is to clarify the roles of thermophilic bacteria in humification during hyperthermophilic composting (HTC) of organic wastes mainly composed of mushroom residue. Results showed that HTC with a long hyperthermophilic (>80°C) period lasting for 18 days produced 83 mg/g of humus in compost on day 27, significantly higher than that of thermophilic composting (TC, 9.7 mg/g). Machine learning models identified that the dominant thermophiles belonging to Bacillaceae, Sporolactobacillaceae, Thermaerobacteraceae, Paenibacillaceae families and the unique thermophiles (Thermus and Calditerricola) in HTC played important roles in accumulating stubborn and soluble humus including humic acid and fulvic acid. Hyperthermophilic fermentation not only recruited and enriched these thermophilic bacteria to rapidly degrade organic matter into bioavailable nutrients, but also upregulated the metabolic pathways relevant to the generation and oxidation of precursors including amino acids that would be polymerized into humus, thus efficiently converting organic waste into humus-rich compost.

The activation of Parageobacillus toebii in hyperthermophilic composting was depended on the bioavailability of raw materials

Hyperthermophilic composting (HTC) with excellent disposal effect is a novel composting technology by inoculating exogenous thermophilic microorganisms. However, the role of exogenous thermophilic microorganisms in HTC remains debated, especially for the applicability of different compost feedstocks. In this study, the role of Parageobacillus toebii during HTC using chicken and pig manure was investigated. The addition of P. toebii could raise the maximum temperature to 78.2 °C and obviously enhanced maturation effect in chicken manure composting. However, the enhancement effect of P. toebii was weaker in pig manure compost, and the maximum temperature only reached 73 °C. Addition of P. toebii could stimulated functional microbial communities for C&N transformation, increased temperature, and promoted the growth of thermophilic microorganisms in chicken manure composting. Component analyses showed that chicken manure had higher bioavailability compared to pig manure. Correlation analysis indicated that P. toebii activated as a "leader", stimulating metabolic activity among functional microbial communities and enhancing organic matter degradation for heat release, while its activation depended on the bioavailability of the raw material. This study provides important insights into the role and application of exogenous microorganisms in promoting HTC.

Emerging organic contaminants in sewage sludge: Current status, technological challenges and regulatory perspectives

Sewage sludge is the source and sink of pollutants. It accumulates a large number of organic contaminants such as endocrine disrupting compounds (EDCs), persistent organic pollutants (POPs), microplastics (MPs) and pharmaceuticals and personal care products (PPCPs), thus posing threats to the ecological environment and human health. The harmlessness of sludge provides the possibility to realize the recycling of resources. In this study, the VOSviewer software is used to visualize published papers related to organic contaminants in sewage sludge. The sources and hazards of emerging pollutants in sewage sludge are outlined, as well as the current state of research on composting, hydrothermal treatment, electrochemical technology, and advanced oxidation processes applied to this area. Key challenges facing this field include the low mineralization rate of contaminants, the ecological risks posed by degradation products, reasonableness of regulations, and effectiveness of enforcement. In conclusion, the integration of existing removal technologies, exploration of degradation pathways, and toxicity assessment of degradation products are the key to achieving the harmlessness and resource utilization of sewage sludge. Additionally, it is also necessary to strengthen the international consensus on the prevention and control of emerging organic contaminants in sewage sludge, improve regulatory frameworks, enhance law enforcement, and implement comprehensive management strategies.

Effects of nitrile compounds on the structure and function of soil microbial communities as revealed by metagenomes

The proliferation of nitrile mixtures has significantly exacerbated environmental pollution. This study employed metagenomic analysis to investigate the short-term effects of nitrile mixtures on soil microbial communities and their metabolic functions. It also examined the responses of indigenous microorganisms and their functional metabolic genes across various land use types to different nitrile stressors. The nitrile compound treatments in this study resulted in an increase in the abundance of Proteobacteria, Actinobacteria, and Firmicutes, while simultaneously reducing overall microbial diversity. The key genes involved in the denitrification process, namely, nirK, nosZ, and hao, were down-regulated, and NO3--N, NO2--N, and NH4+-N concentrations decreased by 7.7%-12.3%, 11.1%-21.3%, and 11.3%-30.9%, respectively. Notably, pond sludge samples exhibited a significant increase in the abundance of nitrogen fixation-related genes nifH, vnfK, vnfH, and vnfG following exposure to nitrile compounds. Furthermore, the fumarase gene fumD, which is responsible for catalyzing fumaric acid into malic acid in the tricarboxylic acid cycle, showed a substantial increase of 7.2-10.6-fold upon nitrile addition. Enzyme genes associated with the catechol pathway, including benB-xylY, dmpB, dmpC, dmpH, and mhpD, displayed increased abundance, whereas genes related to the benzoyl-coenzyme A pathway, such as bcrA, dch, had, oah, and gcdA, were notably reduced. In summary, complex nitrile compounds were found to significantly reduce the species diversity of soil microorganisms. Nitrile-tolerant microorganisms demonstrated the ability to degrade and adapt to nitrile pollutants by enhancing functional enzymes involved in the catechol pathway and fenugreek conversion pathway. This study offers insights into the specific responses of microorganisms to compound nitrile contamination, as well as valuable information for screening nitrile-degrading microorganisms and identifying nitrile metabolic enzymes.

Arsenic-contaminated soil remediation with hyperthermophilic compost: Effects on arsenic bioavailability, soil fertility and bacterial community

Soil arsenic (As) contamination has posed a significant global environmental challenge seriously threatening human health. Compost has attracted broad interests as a kind of eco-friendly and versatile amendment. However, hyperthermophilic compost (HTC), which is newly-developed and more advantageous to environment, has not yet been widely utilized to remediate As-contaminated soil, and its effectiveness remains unclear. Herein, the effects of HTC amendment on soil fertility, As bioavailability, plant growth and soil bacterial community were investigated. After amended with HTC, soil nutrient content and enzyme activity were improved. Concurrently, the content of both total As and available As in soil was reduced, partially due to the formation of organo-As complex with the presence of humic acid and fulvic acid in HTC. Notably, Chinese white cabbage (Brassica campestris L. ssp. chinensis Makino) cultivated in HTC-treated soil exhibited better growth and less As uptake, but showed enhanced translocation of As from the below-ground part to the above-ground part. In particular, the lowest HTC addition ratio (HTC:Soil = 1:10, v:v) proved to be the most optimal, increasing the height, width and biomass of Chinese white cabbage from 9.92 ± 0.72 cm, 6.76 ± 0.31 cm and 4.43 ± 0.49 g, to 21.29 ± 0.48 cm, 19.3 ± 1.44 cm and 23.27 ± 2.45 g, respectively. The results of soil bacterial community analysis revealed that HTC amendment stimulated the growth and metabolism of soil microbes, augmenting the richness and diversity of bacteria related to the methylation and volatilization of As and plant growth. This work suggests that HTC can serve as an effective amendment for As-contaminated soil remediation, and a superior alternative to compound fertilizer for plant cultivation, displaying promising potential for agricultural applications.

Performance evaluation and microbial community succession analysis of co-composting treatment of refinery waste activated sludge

Refinery waste activated sludge (RWAS) is riched in organic matter with energy recovery value, while unique petroleum components in RWAS may pose challenges to the recycling process. Aerobic composting technology is an effective means of organic solid waste resource treatment, which can convert organic solid waste into fertilizer for agriculture. This study explores the effect of petroleum components on the performance of RWAS composting by co-composting it with chicken manure. The results showed that more than 65% of petroleum was removed by aerobic composting. After composting, germination index (GI) exceeded 80%, and a humic acid to fulvic acid ratio (HA/FA) was greater than 1. These results signified that the petroleum components slightly affect the harmless and recycling of RWAS. The microbial community succession found that Firmicutes (54.11-91.96%) and Ascomycota (82.35-97.21%) emerged as the dominant phyla during the thermophilic phase of composting. Thermobifida, norank_f__Limnochordaceae and Kernia were the key microorganism in the degradation of petroleum and the humification of composting, and reduced the phytotoxicity of composting products. Redundancy analysis found that the degradation of petroleum was conducive to the formation of humic acid. These findings indicate that aerobic composting technology can remove petroleum components in RWAS and convert them into composted fertilizers, providing key technical support for managing RWAS in a sustainable and environmentally friendly manner.

Effect of initial moisture content, resulting from different ratios of vegetable waste to maize straw, on compost was mediated by composting temperatures and microbial communities at low temperatures

Owing to the huge amounts and perishable character of vegetable wastes, composting is one of the best options for recycling vegetable wastes post-harvest. The initial moisture content (MC) is critical for optimizing composting process, but the effect of high MC in undehydrated vegetable wastes on composting was rarely reported. For this, the plant-scale windrows were prepared by mixing cauliflower waste and maize straw at different ratios to control initial MC of 70 % (T1-70) and 80 % (T2-80), respectively, and composted in winter. As composting progressed, substantial organic matter degradation, progressive humification, decreases in electrical conductivity and increases of pH and germination index (GI) were observed in both treatments. Nonetheless, T1-70 accelerated heating rate early during composting, prolonged high temperature period (>50 °C) by 30 d, thus increased the harmless level of composting, and significantly improved the humification of end-products compared to T2-80. Results also revealed that T1-70 activated more indigenous microbes and enhanced microbial interactions early during composting, with the fungi enriched in T1-70 playing an important role in accelerating the composting process. Remarkably, the difference in composting temperatures, humification degree, and microbial communities between the two treatments was most significant during the maturation phase. In this phase, MWH_CFBk5, Planktosalinus, Pseudopedobacter, and Luteimonas enriched in T1-70 were positively correlated with humification indices. It is suggested that the effect of initial MC, resulting from different ratios of vegetable waste to maize straw, on their composting was mediated by the composting temperature and microbial communities at low temperatures.

Spartina alterniflora invasion altered phosphorus retention and microbial phosphate solubilization of the Minjiang estuary wetland in southeastern China

Spartina alterniflora invasion is considered a critical event affecting sediment phosphorus (P) availability and stock. However, P retention and microbial phosphate solubilization in the sediments invaded with or without S. alterniflora have not been fully investigated. In this study, a sequential fractionation method and high-throughput sequencing were used to analyze P transformation and the underlying microbial mechanisms in the sediments of no plant (NP) zone, transition (T) zone, and plant (P) zone. Results showed that except for organic phosphate (OP), total phosphate (TP), inorganic phosphate (IP), and available phosphate (AP) all followed a significant decrease trend from the NP site to the T site, and to the P site. The vertical decrease of TP, IP, and AP was also observed with an increase in soil depth. Among the six IP fractions, Fe-P, Oc-P, and Ca10-P were the predominant forms, while the presence of S. alterniflora resulted in an obvious P depletion except for Ca8-P and Al-P. Although S. alterniflora invasion did not significantly alter the alpha diversity of phosphate-solubilizing bacteria (PSB) harboring phoD gene, several PSB belonging to p_Proteobacteria, p_Planctomycetes, and p_Cyanobacteriota showed close correlations with P speciation and IP fractions. Further correlation analysis revealed that the reduced soil pH, soil TN and soil EC, and the increased soil TOC mediated by the invasion of S. alterniflora also significantly correlated to these PSB. Overall, this study elucidates the linkage between PSB and P speciation and provides new insights into understanding P retention and microbial P transformation in the coastal sediment invaded by S. alterniflora.

A review of the influence of heat drying, alkaline treatment, and composting on biosolids characteristics and their impacts on nitrogen dynamics in biosolids-amended soils

Application of biosolids to agricultural land has gained increasing attention due to their rich nutrient content. There are a variety of treatment processes for converting sewage sludge to biosolids. Different treatment processes can change the physicochemical properties of the raw sewage sludge and affect the dynamics of nutrient release in biosolids-amended soils. This paper reviews heat drying, alkaline treatment, and composting as biosolids treatment processes and discusses the effects of these treatments on biosolid nitrogen (N) content and availability. Most N in the biosolids remain in organic forms, regardless of biosolids treatment type but considerable variation exists in the mean values of total N and mineralizable N across different types of biosolids. The highest mean total N content was recorded in heat-dried biosolids (HDB) (4.92%), followed by composted biosolids (CB) (2.25%) and alkaline-treated biosolids (ATB) (2.14%). The mean mineralizable N value was similar between HDB and ATB, with a broader range of mineralizable N in ATB. The lowest N availability was observed in CB. Although many models have been extensively studied for predicting potential N mineralization in soils amended with organic amendments, limited research has attempted to model soil N mineralization following biosolids application. With biosolids being a popular, economical, and eco-friendly alternative to chemical N-fertilizers, understanding biosolids treatment effects on biosolids properties is important for developing a sound biosolids management system. Moreover, modeling N mineralization in biosolids-amended soils is essential for the adoption of sustainable farming practices that maximize the agronomic value of all types of biosolids.

Acceleration of the biodegradation of cationic polyacrylamide by the coupling effect of thermophilic microorganisms and high temperature in hyperthermophilic composting

As a flocculant of sewage sludge, cationic polyacrylamide (CPAM) enters the environment with sludge and exists for a long time, posing serious threats to the environment. Due to the environmental friendliness and high efficiency in the process of organic solid waste treatment, hyperthermophilic composting (HTC) has received increasing attention. However, it is still unclear whether the HTC process can effectively remove CPAM from sludge. In this study, the effects of HTC and conventional thermophilic composting (CTC) on CPAM in sludge were compared and analyzed. At the end of HTC and CTC, the concentrations of CPAM were 278.96 mg kg-1 and 533.89 mg kg-1, respectively, and the removal rates were 72.17% and 46.61%, respectively. The coupling effect of thermophilic microorganisms and high temperature improved the efficiency of HTC and accelerated the biodegradation of CPAM. The diversity and composition of microbial community changed dramatically during HTC. Geobacillus, Thermobispora, Pseudomonas, Brevundimonas, and Bacillus were the dominant bacteria responsible for the high HTC efficiency. To our knowledge, this is the first study in which CPAM-containing sludge is treated using HTC. The ideal performance and the presence of key microorganisms revealed that HTC is feasible for the treatment of CPAM-containing sludge.

Novel process for organic wastewater treatment using aerobic composting technology: Shifting from pollutant removal towards resource recovery

In this study, an organic wastewater treatment process based on aerobic composting technology was developed in order to explore the transition of wastewater treatment from pollutants removal to resource recovery. The novelty of the process focuses towards the microbial metabolic heat that is often ignored during the composting, and taking advantage of this heat for wastewater evaporation to achieve zero-discharge treatment. Meanwhile, this process can retain the wastewater's nutrients in the composting substrate to realize the recovery of resources. This study determined the optimum condition for the process (initial water content of 50 %, C/N ratio of 25:1, ventilation rate of 3 m3/h), and 69.9 % of the total heat generated by composting was used for wastewater treatment under the condition. The HA/FA ratio of composting substrate increased from 0.07 to 0.53 after wastewater treatment, and the retention ratio of TOC and TN was 52.3 % and 61.7 %, respectively, which proved the high recycling value of the composting products. Thermoduric and thermophilic bacteria accounted for 44.3 % of the community structure at the maturation stage, which played a pivotal role in both pollutant removal and resource recovery.

A review of the definition, influencing factors, and mechanisms of rapid composting of organic waste

Composting is a traditional method of treating organic waste. A growing number of studies have been focusing on accelerating the process to achieve "rapid composting." However, the specific definition and influencing factors of rapid composting remain unclear. Therefore, we aimed to gather more insight into the features of rapid composting by reviewing the literature concerning organic waste composting published in the Web of Science database in the past 5 years. We selected 1615 sample studies with "composting" as the subject word and analyzed the effective composting time stated in each study. We defined rapid composting within 15 days using the median test and quartile method. Based on this definition, we summarized the influencing factors of "rapid composting," namely materials, reactors, temperature, and microorganisms. Finally, we summarized two mechanisms related to humus formation during organic waste rapid composting: high temperature-promoting maturation and microbial driving mechanisms. This literature review compiled useful references to help promote the development of rapid composting technology and related equipment.

Influence of leachate microenvironment on the occurrence of phthalate esters in landfills

Phthalate esters (PAEs) are added to various products as plasticizers. Plastic waste containing PAEs enters landfills as they age with use. However, the influence of microenvironmental changes on the occurrence of PAEs during landfill stabilization is still unknown. In this study, we evaluated the relationship between the physical and chemical properties of leachate, the structure of bacterial communities and the chemical structure of dissolved organic matter (DOM), and the occurrence of PAEs and the mechanism underlying their responses to changes. Landfill leachate in different stabilization states had high Cl- and NH4+ contents and its metal element (Cr, Pb, and Zn) contents generally decreased with the increase in landfill ages. Proteobacteria, Bacteroidetes, and Firmicutes were important phyla and had an average relative abundance of 68.63%. The lignin/carboxylate-rich alicyclic molecule structure was the main component of DOM (56%-64%). Of the 6-priority controlled PAEs in leachate, di-n-butyl phthalate was the most abundant (1046 μg L-1), while butyl phthalate was not detected. The results showed that pH, the relative abundance of Chloroflexi, and the value of SUVA254 can directly influence the occurrence of PAEs in leachate. The positive and negative effects vary depending on the PAE content and molecular weight. DBP and DEHP have higher environmental risks in the aquatic system. These results are intended to provide a scientific basis for the evolutionary characterization of the microenvironment in complex environmental systems and the control of novel contaminants, such as PAEs.

Synergistic effects of biochar derived from different sources on greenhouse gas emissions and microplastics mitigation during sewage sludge composting

This study aimed to investigate the effects of biochar derived from different sources (wheat straw, sawdust and pig manure) on greenhouse gas and microplastics (MPs) mitigation during sewage sludge composting. Compared to the control, all biochar significantly reduced the N2O by 28.91-41.23%, while having no apparent effect on CH4. Sawdust biochar and pig manure biochar significantly reduced the NH3 by 12.53-23.53%. Adding biochar decreased the global warming potential during composting, especially pig manure biochar (177.48 g/kg CO2-eq.). The concentration of MPs significantly increased in the control (43736.86 particles/kg) compared to the initial mixtures, while the addition of biochar promoted the oxidation and degradation of MPs (15896.06-23225.11 particles/kg), with sawdust biochar and manure biochar were more effective. Additionally, biochar significantly reduced the abundance of small-sized (10-100 μm) MPs compared to the control. Moreover, biochar might regulate specific microbes (e.g., Thermobifida, Bacillus and Ureibacillus) to mitigate greenhouse gas emissions and MPs degradation.

Identify the potential driving mechanism of reconstructed bacterial community in reduce CO2 emissions and promote humus formation during cow manure composting

The mineralization of organic components releases CO2 during composting, which not only leads to the loss of organic carbon, but has a direct negative impact on the environment. Malonic acid as a competitive inhibitor of succinate dehydrogenase could affect the tricarboxylic acid (TCA) cycle and reduce CO2 emissions. However, the bacterial interaction and organic component transformation has less known how to malonic acid reduce CO2 and improve of humus synthesis in complex composting. The aim of this study was to investigated the malonic acid on organic carbon sequestration and transforming cow manure waste into products with high humus content. Humus content was elevated by 16.8% and cumulative CO2 emissions (30 d)d reduced by 13.6% after malonic acid addition compared to the CK. SparCC analysis of bacterial interaction presented that the network complexity and stability was more higher with malonic acid addition, while a greater concentration of keystones and their ecological metabolic functions was observed, suggesting they weaken the influence of TCA cycle inhibition by enhancing interactions. PICRUSt predictions indicate that malonic acid might enhance humus content by promoting the synthesis of polyphenols and polymerization with amino acids. This study investigated the potential mechanism of regulators to enhance quality and reduce emissions during humification process, providing a new strategy for the resource utilization of organic solid waste.

Advanced approaches for resource recovery from wastewater and activated sludge: A review

Due to resource scarcity, current industrial systems are switching from waste treatment, such as wastewater treatment and biomass, to resource recovery (RR). Biofuels, manure, pesticides, organic acids, and other bioproducts with a great market value can be produced from wastewater and activated sludge (AS). This will not only help in the transition from a linear economy to a circular economy, but also contribute to sustainable development. However, the cost of recovering resources from wastewater and AS to produce value-added products is quite high as compared to conventional treatment methods. In addition, most antioxidant technologies remain at the laboratory scale that have not yet reached the level at industrial scale. In order to promote the innovation of resource recovery technology, the various methods of treating wastewater and AS to produce biofuels, nutrients and energy are reviewed, including biochemistry, thermochemistry and chemical stabilization. The limitations of wastewater and AS treatment methods are prospected from biochemical characteristics, economic and environmental factors. The biofuels derived from third generation feedstocks, such as wastewater are more sustainable. Microalgal biomass are being used to produce biodiesel, bioethanol, biohydrogen, biogas, biooils, bioplastics, biofertilizers, biochar and biopesticides. New technologies and policies can promote a circular economy based on biological materials.

Di-n-butyl phthalate stress hampers compost multifunctionality by reducing microbial biomass, diversity and network complexity

Phthalates are common pollutants in agriculture. Here, the influence of di-n-butyl phthalate (DBP) on multifunctionality of composting was assessed. Results indicated that DBP stress (100 mg/kg) hampered multifunctionality from the thermophilic phase onwards and resulted in a 6.5 % reduction of all assessed functions. DBP stress also significantly reduced microbial biomass (P < 0.05), altered microbial composition (P < 0.05), and decreased network complexity (P < 0.01). Multifunctionality was found to be strongly correlated (P < 0.001) with microbial biomass, diversity, and network complexity. In addition, keystone taxa responsive to DBP were identified as Streptomyces, Thermoactinomyces, Mycothermus, and Lutispora. These taxa were significantly (P < 0.001) affected by DBP stress, and a correlation between them and multifunctionality was shown. This study contributes to a better understanding of the negative implications of phthalates during composting processes, which is of great significance to the development of new treatment strategies for agricultural waste.

Critical review of biochemical pathways to transformation of waste and biomass into bioenergy

In recent years, biofuel or biogas have become the primary source of bio-energy, providing an alternative to conventionally used energy that can meet the growing energy demand for people all over the world while reducing greenhouse gas emissions. Enzyme hydrolysis in bioethanol production is a critical step in obtaining sugars fermented during the final fermentation process. More efficient enzymes are being researched to provide a more cost-effective technique during enzymatic hydrolysis. The exploitation of microbial catabolic biochemical reactions to produce electric energy can be used for complex renewable biomasses and organic wastes in microbial fuel cells. In hydrolysis methods, a variety of diverse enzyme strategies are used to promote efficient bioethanol production from various lignocellulosic biomasses like agricultural wastes, wood feedstocks, and sea algae. This paper investigates the most recent enzyme hydrolysis pathways, microbial fermentation, microbial fuel cells, and anaerobic digestion in the manufacture of bioethanol/bioenergy from lignocellulose biomass.

Effects of biochar on the degradation of organophosphate esters in sewage sludge aerobic composting

In this study, the impact of biochar on the degradation of organophosphate esters (OPEs) during the aerobic composting of sewage sludge was investigated. Three treatments were conducted with different percentages of biochar in the compost, including 5 %, 10 %, and 20 %. The treatment with 10 % of biochar showed the longest thermophilic phase compared to that of 5 % and 20 % of biochar, which greatly promoted the decomposition of organic matter. In addition, the degradation rate of the hard-to-degrade chlorinated-OPEs was significantly increased by 10 % biochar, reaching to 57.2 %. Correspondingly, approximately 43.6 % of the total concentration of OPEs (Σ₆OPEs) was eliminated in the presence of 10 % of biochar, which was higher than the treatments with 5 % and 20 % of biochar. Biochar significantly influenced the microbial community structure of compost, but the previously reported organophosphorus-degrading bacteria did not play a major role in the degradation of OPEs. The redox ability of the increased oxygen-containing functional groups such as quinone on the surface of biochar and the biochar-mediated electron transfer ability may play an essential role in the degradation of OPEs during the composting process.

Composting and green technologies for remediation of phthalate (PAE)-contaminated soil: Current status and future perspectives

Phthalate esters (PAEs) are hazardous organic compounds that are widely added to plastics to enhance their flexibility, temperature, and acidic tolerance. The increase in global consumption and the corresponding environmental pollution of PAEs has caused broad public concerns. As most PAEs accumulate in soil due to their high hydrophobicity, composting is a robust remediation technology for PAE-contaminated soil (efficiency 25%-100%), where microbial activity plays an important role. This review summarized the roles of the microbial community, biodegradation pathways, and specific enzymes involved in the PAE degradation. Also, other green technologies, including biochar adsorption, bioaugmentation, and phytoremediation, for PAE degradation were also presented, compared, and discussed. Composting combined with these technologies significantly enhanced removal efficiency; yet, the properties and roles of each bacterial strain in the degradation, upscaling, and economic feasibility should be clarified in future research.

Role of multistage inoculation on the co-composting of food waste and biogas residue

Effect of diverse Lactobacillus amylophilus, Geobacillus thermoleovorans, and Bacillus subtilis inoculation patterns on the co-composting performance of food waste and biogas residue was explored. Experimental results revealed that, compared to the single-stage inoculation and non-inoculation groups, the multistage inoculation pattern prolonged the thermophilic period during composting, consequently improving organic matter decomposition and humification [with a high germination index (120.9%)]. In addition, it could promote the development of humic substances [with a high humus index (4.3) and biological index (1.4)] and lower emissions of carbon dioxide (CO₂), methane (CH₄), and ammonia (NH₃). Additionally, it could improve the microbial variety and the amounts of functional bacteria (i.e., Chloroflexi) in compost, which might be advantageous for the decomposition of refractory organic materials and plant growth. Therefore, the multistage inoculation pattern is recommended for organic waste composting in terms of its gas emissions, compost quality and efficacy benefits.

Exploring the influence mechanisms of polystyrene-microplastics on sewage sludge composting

To explore the influence mechanisms of polystyrene-microplastics (PS-MPs) on sewage sludge composting and put forward relevant composting adjustment strategies, a 30-day sewage sludge (SS) composting experiment was conducted by adding 0%, 0.5%, and 1% (w/w) PS-MPs. The addition of PS-MPs reduced compost temperature, microbial biomass carbon (MBC), and the degradation of volatile solids (2.6%-4.8%), and inhibited the activities of key enzymes (β-glucosidase and alkaline phosphatase) but increased urease activity in the thermophilic phase. Moreover, PS-MPs altered the relative abundance of dominant bacteria and changed the relevance of main enzymes and bacterial communities. Moreover, high levels of PS-MPs inhibited the contribution of dominant bacterial to alkaline phosphatase and β-glucosidase. Redundancy analysis revealed that PS-MPs affected the composting process mainly through reduced MBC at the mesophilic phase and temperature at the thermophilic phase. Thus, regulating MBC and temperature in specific phases could help overcome the adverse effects of PS-MPs on composting.

Advances in bioremediation of emerging contaminants from industrial wastewater by oxidoreductase enzymes

The bioremediation of emerging recalcitrant pollutants in wastewater via enzyme biotechnology has been evolving as cost-effective with an input of low-energy technological approach. However, the enzyme based bioremediation technology is still not fully developed at a commercial level. The oxidoreductases being the domineering biocatalysts are promising candidates for wastewater treatments. Henceforth, comprehending their global market and biotransformation efficacy is mandatory for establishing these techno-economic bio-enzymes in commercial scale. The biocatalytic strategy can be established as a combinatorial approach with existing treatment technology to achieve towering bioremediation and effective removal of emerging pollutants from wastewater. This review provides a novel insight on the toxicological xenobiotics released from industries such as paper and pulps, soap and detergents, pharmaceuticals, textiles, pesticides, explosives and aptitude of peroxidases, nitroreductase and cellobiose dehydrogenase in their bio-based treatment. Moreover, the review comprehensively covers environmental relevance of wastewater pollution and the critical challenges based on remediation achieved through biocatalysts for future prospectives.

Effect of scleral protein shell amendment on bacterial community succession during the pig manure composting

The impact of scleral protein shell (SPS) amendment on bacterial community succession during pig manure (PM) composting were evaluated in the present work. Five treatments representing different dry weight dosage of SPS [0 % (T1), 2.5 % (T2), 5 % (T3), 7.5 % (T4), 10 % (T5) and 12 % (T6)] were applied with initial mixture of raw materials (Wheat straw along with the PM) and composted for 42 days. Results indicated that the dominant of phyla were Proteobacteria, Actinobacteria, Bacteroidetes and Firmicutes. The relative abundance (RA) of genus un-identified, Ruminofilibacter, Thermovum, Longispora and Pseudomonas were greater among the all treatments but interestingly genus Ruminofilibacter was also higher in control treatment. The network analysis was confirmed that T6 treatment with higher dosage of SPS amendment could enhance the bacterial population and rate of organic matter mineralization. Compared with T1, the T5 has greater potential impact to enhance the bacterial population and significant correlation among the pH and temperature.

Treatment and novel resource-utilization methods for shale gas oil based drill cuttings - A review

The oil exploration and production (E&P) industry has made outstanding contributions to gross domestic product (GDP) growth in many countries. In recent years, the gap between energy supply and demand has widened, and, simultaneously, demand for clean energy has gradually increased. As an emerging clean energy source, shale gas has received extensive attention. However, the environmental problems caused by oil and gas extraction and production should not be underestimated. Oil-based drill cuttings (OBDC) are typical hazardous solid wastes produced during oil/gas exploration and production processes. In addition, oil-based drill cuttings ash (OBDCA) is the main product of treated OBDC and should be further utilized to avoid pollution and waste of resources. This review describes relevant policies and regulations for the OBDC. The main treatment methods for OBDC have been systematically summarized. Compared to the standard method for resource utilization of OBDCA, a novel approach was proposed to utilize OBDCA as an environment-friendly functional material for environmental remediation. The future development prospects for OBDC were envisioned to achieve sustainable development goals.

Biochar addition stabilized soil carbon sequestration by reducing temperature sensitivity of mineralization and altering the microbial community in a greenhouse vegetable field

Biochar is widely used for soil carbon sequestration and fertility improvement. However, the effects of biochar interacted with nitrogen (N) on the mineralization of soil organic carbon (SOC) and microbial community have not been thoroughly understood, particularly no reports have been published on the long term effects of biochar in vegetable field. Here, we examined soil properties, SOC mineralization and microbial community affecting by biochar (0, 20 and 40 t ha^-1; C0, C1 and C2, respectively), N (0 or 240 t ha^-1; N0 or N1, respectively) and their interaction in a greenhouse vegetable field. Results indicated that biochar addition increased soil pH, SOC, recalcitrant C pool, especially for the 40 t ha^-1 treatment. Biochar addition generally decreased soil C-cycling enzyme activity while increasing N and P-cycling enzyme and oxidase activities. Biochar combined with N addition reduced SOC mineralization rate and metabolic quotient (qCO₂) by 10.2-22.0% and 6.85-30.4%, respectively, across 15-35 °C and the temperature sensitivity (Q₁₀) by 0.96-4.70%, except for the N1C2 at 25-35 °C. Apparent changes in bacterial alpha diversity and community structures were observed among treatments. Besides, biochar mixed with N application significantly enhanced the relative abundance of Proteobacteria and decreased Acidobacteria, while did not result in significant differences in fungal diversity and community composition. Redundancy analysis indicated that the microbial community composition shifts induced by the interaction between N and biochar were attributed to the changes in soil chemical properties, such as pH and SOC. Overall, the combination of biochar and N fertilizer is recommended to improve SOC sequestration potential and regulate bacterial community diversity and composition in vegetable field for sustainable intensification.