Optimization of a Novel Engineered Ecosystem Integrating Carbon, Nitrogen, Phosphorus, and Sulfur Biotransformation for Saline Wastewater Treatment Using an Interpretable Machine Learning Approach.

The denitrifying sulfur (S) conversion-associated enhanced biological phosphorus removal (DS-EBPR) process for treating saline wastewater is characterized by its unique microbial ecology that integrates carbon (C), nitrogen (N), phosphorus (P), and S biotransformation. However, operational instability arises due to the numerous parameters and intricates bacterial interactions. This study introduces a two-stage interpretable machine learning approach to predict S conversion-driven P removal efficiency and optimize DS-EBPR process. Stage one utilized the XGBoost regression model, achieving an R2 value of 0.948 for predicting sulfate reduction (SR) intensity from anaerobic parameters with feature engineering. Stage two involved the CatBoost classification and regression model integrating anoxic parameters with the predicted SR values for predicting P removal, reaching an accuracy of 94% and an R2 value of 0.93, respectively. This study identified key environmental factors, including SR intensity (20-45 mg S/L), influent P concentration (<9.0 mg P/L), mixed liquor volatile suspended solids (MLVSS)/mixed liquor suspended solids (MLSS) ratio (0.55-0.72), influent C/S ratio (0.5-1.0), anoxic reaction time (5-6 h), and MLSS concentration (>6.50 g/L). A user-friendly graphic interface was developed to facilitate easier optimization and control. This approach streamlines the determination of optimal conditions for enhancing P removal in the DS-EBPR process.

Thiosulfate/FeCl3 pre-treatment enhances short-chain fatty acid production and mitigates H2S generation during anaerobic fermentation of waste activated sludge: Performance, microbial community and ecological analyses.

Anaerobic fermentation (AF) has been identified as a promising method of transforming waste activated sludge (WAS) into high-value products (e.g., short-chain fatty acids (SCFAs)). This study developed thiosulfate/FeCl3 pre-treatment and investigated the effects of different thiosulfate/FeCl3 ratios (S:Fe = 3:1, 3:2, 1:1, 3:4 and 3:5) on SCFA production and sulfur transformation during the AF of WAS. At a S:Fe ratio of 1:1, the maximal SCFA yield (933.3 mg COD/L) and efficient H2S removal (96.5 %) were obtained. S:Fe ratios ≤ 1:1 not only benefited hydrolysis and acidification but largely mitigated H2S generation. These results were supported by the enriched acidogens and reduced sulfur-reducing bacteria (SRB). Molecular ecological network analysis further revealed that the keystone taxon (g_Saccharimonadales) was found in S:Fe = 1:1, together with reductions in associations among methanogens, acidogens and SRB. This work provides a strategy for enhancing high-value product recovery from WAS and minimising H2S emissions.

Optimizing parameters for the preparation of low viscosity rubber asphalt incorporating waste engine oil using response surface methodology.

Due to the high viscosity, rubber asphalt displays poor construction workability, which ultimately compromises the comfort and safety of pavement. In this study, specified control variates were used to study the effect of the waste engine oil (WEO) addition sequence on the properties of rubber asphalt while ensuring the consistency of other preparation parameters. Initially, in order to evaluate their compatibility, the storage stability and aging properties of the three groups of samples were determined. The variation of asphalt viscosity was then analyzed using a low-field nuclear magnetic resonance (LF-NMR) test, by predicting the fluidity of each sample. Subsequently, the results showed that the rubber asphalt prepared by premixing WEO and crumb rubber (CR) had the best properties of low temperature, compatibility, and fluidity. On this basis, the effects of WEO content, shear rate, shear temperature, and shear time on the properties of low viscosity rubber asphalt were investigated separately through response surface methodology (RSM). Quantitative data from the basic performance experiment were used to fit the high precision regression equation, thereby correlating a more precise level of factors with experimental results. The response surface model prediction analysis showed that the optimal preparation parameters of the low viscosity rubber asphalt were 60 min shear time, 180 °C shear temperature, and 5000 r/min shear rate. Simultaneously, the addition of 3.5% of WEO showed great potential as an asphalt viscosity reducer. Ultimately, this study provides an accurate method for determining the optimum preparation parameters of asphalt.

Effect of different waste plastic modifiers on conventional asphalt performance: optimal preparation parameters determination and mechanism analysis.

The typical treatment of waste plastics has become a global environmental problem. In light of recent developments, waste plastics used as asphalt modifiers offer an efficient approach to solve this problem. This paper studied the effects of three kinds of waste plastic-modified asphalts (WPMA), with polypropylene (PP), polyethylene (PE) and ethylene-vinyl acetate copolymer (EVA) as their respective modifiers, on the conventional asphalt performance. Furthermore, an orthogonal experimental design (OED) was used to determine the preparation parameters of WPMA. Thereafter, thermogravimetric-differential scanning calorimetry (TG-DSC) and Fourier transform infrared spectroscopy (FTIR) were employed to expound the mechanism of WPMA. It was then subsequently ascertained that the optimum preparation parameters of PP-modified asphalt (PPMA) and PE-modified asphalt (PEMA) were 170 °C, 3000 rpm, and 30 min, while the optimum preparation parameters of EVA-modified asphalt (EVAMA) were 180 °C, 3000 rpm, and 30 min. In addition, WPMA displayed better high-temperature performance and are inherently more suitable for pavement in high-temperature regions. Ultimately, this study will effectively solve the disposal of waste plastic and promote the research and application of WPMA in the future.

Analysis of the Influence of Production Method, Plastic Content on the Basic Performance of Waste Plastic Modified Asphalt.

The sustainable reuse of waste plastic as an alternative construction material has numerous environmental and economic advantages. New opportunities to recycle waste plastic in asphalt for road construction would mitigate landfill issues and significantly reduce global carbon emissions. With a clear aim to contribute to a more efficient reuse of waste plastic, this paper reutilized two types of waste plastic (polypropylene (PP) and polyethylene (PE)) as asphalt modifiers to improve the performance of asphalt pavement as well as to achieve the purpose of sustainable recycling waste plastic. Therefore, the optimal preparation parameters of plastic-modified asphalt were recommended by the orthogonal test. Then, the dispersion and modification mechanisms of plastic particles in plastic-modified asphalt were further studied by Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Differential Scanning Calorimetry (TG-DSC). The results show that the asphalt containing PP and PE shows better overall performance at high temperatures compared with the base asphalt. Furthermore, PE-modified asphalt and PP-modified asphalt exhibited optimal properties when prepared at 3000 rpm for 30 min at 170 °C. Moreover, the results of the expansion mechanism show that the main reaction process of plastic asphalt is a physical change. Finally, PP-modified asphalt and PE-modified asphalt generally perform well and are suitable for high-temperature areas. Consequentially, the results of this research promote the recycling of waste plastic, ultimately advocating the recycling of waste materials and environmental protection of pavement construction.

[Composition Characteristics and Construction Mechanism of Microbial Community on Microplastic Surface in Typical Redox Environments].

Microplastics are widely distributed in the biogeochemical cycle driven by microbes. Their surface is enriched with unique microbial communities, called plastispheres. Various redox environments that exist widely in the natural environment can affect the microbial composition in the plastisphere and the fate of the microplastics. To explore the microbial community composition and construction mechanism on the surface of microplastics in typical redox environments, three microplastics, PHA (polyhydroxyalkanoates), PLA (polylactic acid), and PVC (polyvinyl chloride), were placed in five specific redox environments:aerobic, nitrate reduction, iron oxide reduction, sulfate reduction, and methane production. The culture experiment simulated the microcosm, which was inoculum by sludge. The results showed that microplastic factors affected 18.94% and 46.67% of the microbial communities on the plastisphere in taxonomy and phylogeny, respectively. Redox factors affected 31.04% and 90.00% of the microbial communities on the plastisphere in taxonomy and phylogeny, respectively. Compared with that in sludge, the microbial community richness and diversity were reduced on the three microplastics. The most apparent reduction was found on the plastisphere of more degradable PHA. At the same time, microbial communities on the refractory PLA and PVC surfaces remained similar. Anaerocolumna (26.44%) was the dominant genus on the surface of PHA microplastics, whereas microbes related to the redox reaction were less enriched. Clostridium_sensu_stricto_7 (15.49% and 11.87%) was the dominant strain on PLA and PVC microplastics, and the microbes related to the redox reaction were significantly enriched. Thus, characteristic microbes involved in the redox reaction will be enriched in the surface of refractory microplastics, and microplastics may affect the rate of biogeochemical cycling.