Biodegradable plastics have been introduced and widely used as a promising alternative to traditional nondegradable plastics. However, the differences in sorption behavior of pesticides on nondegradable and biodegradable microplastics has been insufficiently studied. Here, four types of nondegradable [polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), polypropylene (PP)] and two types of biodegradable [polylactic acid (PLA), polybutylene succinate (PBS)] microplastics were selected to investigate the sorption mechanism of fipronil based on their sorption kinetics and isotherms. The results indicated that the sorption rates of PLA and PBS were much higher than those of PE, PP, PVC and PS and that the sorption capacities of fipronil on microplastics followed the order of PBS > PLA > PP > PE > PS > PVC. The sorption kinetics followed a pseudo-second-order kinetics model (R² = 0.953–0.998) for all tested microplastics. External mass transport and intraparticle diffusion were the main rate controlling steps of the sorption of fipronil on microplastics. Furthermore, isotherm results indicated that a Langmuir model provided the best fit for fipronil sorption on PE, PS, PVC and PP (R² = 0.997–0.999), while a Freundlich model was the most appropriate model for PLA and PBS (R² = 0.998–0.999). The presence of surface O-containing functional groups and the spatial arrangement of rubbery domains are likely to affect the sorption process. The results from this work suggest that microplastics, especially biodegradable ones, may play an important role in the fate and transport of pesticides, and their effects on soil organisms (e.g., earthworms) require further investigation.

Although fertilization plays an important role in determining the contents of soil dissolved organic matters or water-extractable organic matter (DOM, WEOM), knowledge regarding the dynamics, biodegradability, and microbial community shifts of WEOM in response to different fertilization treatments is very limited, particularly in rice–wheat cropping soil. Thus, in the present study, we performed biodegradation experiments using WEOM extracted from samples of soil that had been subjected to four different fertilization treatments: unfertilized control (CK), chemical fertilizer (CF), 50% chemical fertilizer plus pig manure (PMCF), and 100% chemical fertilizer plus rice straw (SRCF). UV spectrum and fluorescence 3D excitation–emission matrix analyses applied to investigate the chemical composition of WEOM revealed that all examined WEOMs were derived from microbial activity and the dominant portion comprised humic acid-like compounds. After the incubation, 31.17, 31.63, 43.47, and 33.01% of soil WEOM from CK, CF, PMCF, and SRCF treatments, respectively, were biodegraded. PMCF- derived WEOM had the highest biodegradation rate. High-throughput sequencing analyses performed to determine the microbial community before and after the incubation indicated that Sphingomonas, Bacillus, and Flavisolibacter were the predominant bacterial genera in the original inoculum derived from the four fertilization treatments. Following biodegradation, we observed that the dominant bacteria differed according to fertilization treatments: Curvibacter (43.25%) and Sphingobium (10.47%) for CK, Curvibacter (29.68%) and Caulobacter (20.00%) for CF, Azospirillum (23.68%) and Caulobacter (13.29%) for PMCF, and Ralstonia (51.75%) for SRCF. Canonical correspondence analysis revealed that, shifts in the microbial community were closely correlated with pH and specific UV absorbance at 254 nm. We speculated that the inherent traits of different WEOM and the properties of soil solutions under different fertilization treatments shaped the soil microbial community structure, thereby influencing the biodegradation of WEOM.

Growth of textile industries led to production of enormous dye varieties. These textile dyes are largely used, chemically stable and easy to synthesize. But they are recalcitrant and persist as less biodegradable pollutants when discharged into waterbodies. Potential use of enzyme-linked bioremediation of textile dyes will control their toxicity in waterbodies. Bioinformatics and Molecular docking tool provides an insight into remediation mechanism by predicting susceptibility of dye degradation using oxidoreductive enzymes. In this study, six dyes, Reactive Red F3B, Remazol Red RGB, Joyfix Red RB, Joyfix Yellow MR, Remazol Blue RGB and Turquoise CL-5B of azo, anthraquinone and phthalocyanine molecular class were identified as potential targets for degradation by laccase and azoreductase of Aeromonas hydrophila in addition to Lysinibacillus sphaericus through in silico docking tool BioSolveIT-FlexX. Azoreductase breaks azo bonds by ping-pong mechanism whereas laccase decolorizes dyes by free radical mechanism which is not specific in nature. Results were analyzed based on parameters like stability, catalytic action and selectivity for enzyme-dye interactions. Amino acids of enzymes interacted with several dyes substantiating variations in active site for enzyme-ligand binding affinity. This suggests the role of enzymes in decolorizing an extensive variety of textile dyes, thereby, aiding in understanding the enzyme mechanisms in Bioremediation.

Applications of aluminium (Al) salt or lanthanum (La) modified bentonite (LMB) have become popular methodologies for immobilizing phosphorus (P) in eutrophic lakes. The presence of humic substances, has been shown to inhibit this form of treatment due to the complexation with La/Al. However, the effects of other dissolved organic matter (DOM), especially that derived from phytoplankton (the dominant source in eutrophic lakes) are unknown. In this study, the interaction with La/Al of Suwannee River Standard Humic Acid Standard II (SRHA) and algae-derived DOM (ADOM) were investigated and compared. Differed to SRHA which was dominated by polyphenol-like component (76.8%, C1-SRHA), majority in ADOM were protein-like substance, including 41.9% tryptophan-like component (C2-ADOM) and 21.0% tyrosine-like component (C3-ADOM). Two reactions of complexation and coprecipitation were observed between SRHA/ADOM and La/Al. Complexation dominated at low metal inputs less than 10 μM and coprecipitation was the main reaction at higher metal inputs. For ADOM, the tryptophan-like component (C2-ADOM) was the important component to react with metal. The reaction rate for C2-ADOM with La were about two-third of that for C1-SRHA, indicating that the influence of C2-ADOM was significant during the P immobilization by La/Al-based treatment in eutrophic lakes. The P removal data in the presence of ADOM confirmed the significant inhibition of ADOM. In addition, based on the composition of coprecipitates and relatively biodegradable character of tryptophan-like substances (C2-ADOM), the coprecipitation of ADOM was assumed to reduce the stability of precipitated P in eutrophic lakes. The release of P from the potential biodegradation of the coprecipitates and thus the possible decline of the performance of P immobilization by La/Al-based treatments is an important work in the future.

Bacterial antibiotic resistance (BAR) is profoundly important to human health, but the environmental reservoirs of resistance determinants are poorly understood. BAR of biofilm and tap water were analyzed by using a water distribution simulator where different doses of chlorine and chloramine were used in this study. The results revealed that the disinfectants (≥2 mg/L) suppressed antibiotic resistant bacteria (ARB) in tap water and biofilms, while disinfected water and biofilms had a high relative abundance of ARB. The difference of ARB concentration and ARB percentage between the samples obtained from a disinfected pipeline and a non-disinfected pipeline became smaller over time. Because the water supply system is a unidirectional process, it is unclear how planktonic bacteria in water transfer BAR over time, although biofilm is suspected to play a role in this process. Compared with the biofilm samples without disinfectant, the disinfected biofilm had lower ICC and HPC/ICC percentage, lower AOC and AOC/TOC percentage, indicating that the disinfectant inhibited the bacteria growth in biofilm, and the disinfected biofilm had high proportion of non-culturable bacteria and low biodegradability, which affected BAR in biofilms. High throughput sequencing showed that in biofilms, the relative abundance of genera (uncultured_f_Rhodocyclaceae, Brevundimonas, and Brevibacillus in chlorinated systems, and Brevundimonas, Brevibacillus in chloraminated systems) with multiple antibiotic resistance and high abundance (up to 78.5%), were positively associated with disinfectant concentration and ARB percentage. The major prevalent genera in biofilms were also detected in tap water, suggesting that biofilm growth or biofilm detachment caused by external environmental factors will allow the movement of biofilm clusters with higher ARB concentration and percentage into bulk water, thereby increasing the antibiotic resistance of bacteria in tap water.

Integrated systems with appropriate bio-filters can be used to treat aquaculture effluents. However, the information on bio-filters that alters the ecological functions of the bacterioplankton community (BC) in biodegradation of the aquaculture effluents remains controversial. In this study, we implemented a comprehensive restoration technology combined with bio-filters [biofilm, clam (Tegillarca granosa), and macrophytes (Spartina anglica)] to investigate their influence on the stability of the BC and nutrient removal. We found that the diversity of BC was linked with biogeochemical factors in processing and upcycling nitrogen-rich effluents into high-value biomass. The BC exhibited significant distinct patterns in the bio-filter areas. Potential biomarkers for constrained harmfully algae-bacteria (Nitriliruptoraceae, Bacillales, and Rhodobacteraceae) and nutrient removal were significantly higher in the bio-filters areas. The bio-filters significantly promoted the restoration effects of N and P balance by reducing 82.34% of total nitrogen (TN) and 81.64% of total phosphorus (TP) loads at the water interface. The main mechanisms for TN and TP removal and nutrient transformation were achieved by assimilation and absorption by the emergent macrophytes (Spartina anglica). The bio-filters significantly influenced the biodegradability and resolvability of particulate organic matter through ammonification, nitrification, and denitrification of microbes, which meliorated the nutrient removal. Beside bio-filter effects, the BC was significantly controlled by abiotic factors [nitrate (NO₃⁻-N), dissolved oxygen (DO), total nitrogen (TN), and water temperature (WT)], and biotic factors (chlorophyll ɑ and green algae). Our study revealed that the co-existence system with bio-filters may greatly improve our understanding on the ecological functions of the BC in aquaculture systems. Overall, combined bio-filters provide an opportunity for the development of efficient and optimized aquaculture wastewater treatment technology.

A Fenton like advanced oxidation process (AOP) employing scrap zerovalent iron (SZVI) and hydrogen peroxide (H2O2) was studied for industrial textile wastewater treatment from a textile manufacturing plant located at Medellín, Colombia (South America). The wastewater effluent studied contains a mixture of organic compounds resistant to conventional treatments. The effect of initial pH and SZVI concentration and H2O2 concentration were studied by a response surface methodology (RSM) Box-Behnken design of experiment (BBD). The combined SZVI/H2O2 process led to reductions of 95% color, 76% of chemical oxygen demand (COD) and 71% of total organic carbon (TOC) at optimal operating conditions of pH = 3, SZVI = 2000 mg/L and [H2O2] = 24.5 mM. Molecular weight distribution measurement (MWD), ultraviolet–visible (UV–Vis) spectroscopy, HPLC, biodegradability and toxicity were used to characterize the pollutants after the treatment process finding that the resulting effluent was polluted mostly by low molecular weight carboxylic acids. A remarkable biodegradability enhancement of the effluent was evidenced by a BOD5/COD ratio increase from 0.22 to 0.4; also, the SZVI/H2O2 process successfully reduced the toxicity from 60% to 20% of dead A. Salina crustaceans.

Biodegradation assays involve both biodegradation and analytical processes which can be affected by systematic errors, among others. These errors can affect all the environmentally relevant parameters related to biodegradability, enantioselectivity (in the case of chiral compounds), kinetic parameters and persistence of chemicals. However, such impacts have never been well-characterized. In this work, calculations and models used for a long time are studied by simulating systematic errors at the 5% level, which affect independently the analytical calibration step and the biodegradation process. The impact of these errors is also compared with those obtained from an alternative approach: recently proposed equations and a novel model (a Monod modified version) developed in this work. All simulations are compatible with an environmentally relevant pollutant concentration. The results suggest a high degree of minimization (or even cancelation) of the systematic error impact using the alternative approach respect to the conventional one. These findings can be interpreted either in view of achiral or chiral pollutants. The present work can have a positive impact in the area of risk assessment of new pollutants and hazardous materials.

There is a reasonably extensive body of literature recording mass loss of polyhydroxyalkanoates (PHAs) (a class of biodegradable plastics) in the natural marine environment. However, to date, this research has been very disparate. Thus, it remains unclear what the timeframe for the biodegradation of such marine biodegradable plastics actually is. The aim of this work was to determine the rate of biodegradation of PHA in the marine environment and apply this to the lifetime estimation of PHA products. This provides the clarification required as to what ‘marine biodegradation of PHA’ means in practicality and allows the risks and benefits of using PHA to be transparently discussed. It was determined that the mean rate of biodegradation of PHA in the marine environment is 0.04–0.09 mg·day⁻¹·cm⁻² (p = 0.05) and that, for example, a PHA water bottle could be expected to take between 1.5 and 3.5 years to completely biodegrade.

The ozonation process is efficient in degrading aromatic substances and substances with unsaturated bonds, but cannot effectively destroy small-molecule organic compounds, which accumulate. Likewise, the Fenton process is a classic wastewater treatment method, but requires strict pH control and produces secondary pollution when the concentration of organic substances is high. In this study, we applied a 1stO₃-2ndFenton sequential process to treat diazodinitrophenol (DDNP) industrial wastewater and provide suitable reaction conditions for Fenton process. For the 1stOzone process, organics removal increased as O₃ dosage increased. At optimized operation, the 1stO₃ process provided an acidic effluent (pH = 3) and reduced the organics concentration to a level suitable for the 2ndFenton process. Benzene ring substances as well as nitro group and diazo group compounds were greatly degraded in the 1stO₃ process and were further mineralized in the 2ndFenton process. Additionally, the biodegradability of DDNP industrial wastewater was greatly improved. This is the first reported time that ozonation and the Fenton process have been integrated sequentially to treat an explosive production wastewater. The study provides a feasible chemical oxidation method for treating DDNP industrial wastewater by simply combining two classic treatment processes.