Chromium (Cr(VI)) causes serious impacts on the environment and human. In this study, the commercial activated carbon-loaded silver nanoparticle (AgNPs-AC) was used as a new adsorbent to remove Cr(VI) from the aqueous solution. Batch adsorption experiments were conducted to evaluate the effects of pH, the initial concentration of Cr(VI), contact time, and dose of AgNPs-AC upon removal of Cr(VI) from the aqueous solution. The results showed that at pH of 4, the contact time of 150 min, 40 mg/L of initial Cr(VI), and dosage of 20 mg AgNPs-AC/25 mL were the most suitable condition for absorption of Cr(VI) onto AgNPs-AC from the aqueous solution. The maximum adsorption capacity achieved at abovementioned conditions was 27.70 mg/g. Meanwhile, the adsorption capacity of commercial activated carbon from a coconut shell obtained only 7.61 mg/g in the case where the initial Cr(VI) concentration is 10 mg/L and the contact time is 60 min. The adsorption kinetic data were found to fit best to the pseudo-second-order model with a high correlation coefficient (R² = 0.9597). The adsorption process was controlled by chemisorption due to the appearance of new chemical species on the adsorbent surface. The positively charged functional groups rapidly reduced Cr(VI) to Cr(III), and Cr(III) was subsequently adsorbed by the carboxyl group on the adsorbent’s surface. From this study, it can be concluded that AgNPs-AC is a fully promising, low-cost adsorbent in the removal of Cr(VI) from the aqueous solution.

The use of bioscrubber is attracting increasing attention for exhaust gas treatment in intensive pig farming. However, the challenge is to improve the methane (CH₄) removal efficiency as well as the possibility of pig house wastewater treatment. Three laboratory-scale bioscrubbers, each equipped with different recirculation water types, livestock wastewater (10-times-diluted pig house wastewater supernatant), a methanotroph growth medium (10-times-diluted), and tap water, were established to evaluate the performance of CH₄ removal and wastewater treatment. The results showed that enhanced CH₄ removal efficiency (25%) can be rapidly achieved with improved methanotrophic activity due to extra nutrient support from the wastewater. The majority of the CH₄ was removed in the middle to end part of the bioscrubbers, which indicated that CH₄ removal could be potentially optimised by extending the length of the reactor. Moreover, 52–86% of the ammonium (NH₄⁺-N), total organic carbon (TOC), and phosphate (PO₄³⁻-P) removal were simultaneously achieved with CH₄ removal in the present study. Based on these results, this study introduces a low-cost and simple-to-operate method to improve CH₄ removal and simultaneously treat pig farm wastewater in bioscrubbers.

Natural free estrogens found in animal manures are potent endocrine-disrupting compounds. Environmental detections can be caused by such processes as physical and chemical non-equilibrium and colloidal or conjugate facilitate transport. Antecedent or “legacy” concentrations of estrogens resident in soil may also contribute significantly to environmental detections. The objective of this study was to measure and understand the dominant causes contributing to estrogen detections in the environment from a grazed system. To achieve this objective, the effluent of undisturbed lysimeters constructed from soils of fields grazed by dairy cows (Bos taurus) was monitored for free and conjugated estrogens. Four lysimeters were dosed with urine (Urine) and four only received water (Control). Water transfer for all lysimeters was similar, and all lysimeters were near field capacity for the duration of the experiment. Rapid transport of a conservative bromide tracer suggested that preferential flow was an important physical non-equilibrium transport process. Free estrogens and conjugated estrogens (17β-estradiol (E2), estrone (E1), 17β-estradiol-17-sulfate (E2-17S), 17β-estradiol-3-glucuronide (E2-3G), estrone-sulfate (E1-S)) were detected in the source urine (E2 = 17,248 ng/L, E1 = 1006 ng/L, E2-3G = 967 ng/L, E2-17S = 886,456 ng/L, E1-S = 1730 ng/L). These same free and conjugated estrogens, in addition to estriol (E3), were all detected frequently in both Control and Urine lysimeters (detection concentration ranks: E3 > E2-17S = E2 > E2-3G = E1 = E1-3S). Total potential estrogenicity in the effluent of the Control and Urine was also similar, indicating the presence of antecedent estrogens was the dominant contribution to estrogenic detections. Additionally, the frequent detection of conjugates in the lysimeter effluent was important, because it indicated that conjugates were stable in soil but had greater potential mobility than free estrogens.

A fast sol-dipping-gel method was applied to load Ag and TiO₂ nanoparticles on the surface of crayfish shell biochar to make an inexpensive and novel nanocomposite. Tetra-n-butyl titanate (Ti(OC₄H₉)₄) and silver nitrate (AgNO₃) were used as the nanoparticle precursors. Crayfish shell was pyrolyzed to produce the biochar host. Paper-disk diffusion method was applied to measure antibacterial activities of the nanocomposites to E. coli. The maximum loading rate of TiO₂ and Ag nanoparticles on the biochar reached 7.54% and 3.20%, respectively. Results of long-term antibacterial effect experiment showed that the Ag-TiO₂-biochar had robust antibacterial activity and could be reused for multiple times. The inactivation of E. coli of initial concentration of 10⁵ CFU/mL by Ag-TiO₂-biochar under solar light reached around 99% of sterilization ratio in 5 min. In addition, the antibacterial ability of the nanocomposite was better in light than that in dark due to the presence of TiO₂. Findings of this study suggest that the novel nanocomposite is a promising material for water treatment units and household water purifiers.

Textile effluents contain a series of dyes and salts, and their decolorization is strongly affected by salinity. In this work, the influence of salinity on methylene blue (MB) adsorption by comminuted raw avocado seeds was investigated. The adsorbent was firstly characterized. The optimal conditions for MB adsorption on the avocado seeds were determined by response surface methodology (RSM). Subsequently, the influence of ten salts in MB adsorption was evaluated using kinetic and equilibrium studies. The optimal conditions for MB adsorption on the avocado seeds were pH = 10 and adsorbent dosage = 1 g L⁻¹. General order model was able to describe the kinetic profile, and its parameters showed that the adsorption rate and capacity were affected by the presence of salts. The equilibrium was adequately represented by the Sips model. The maximum adsorption capacity without the presence of salts was 97.97 mg g⁻¹. The maximum adsorption capacity was found in the presence of sodium carbonate, which was 103.13 mg g⁻¹. The presence of sodium citrate reduced the adsorption capacity to 80.42 mg g⁻¹. Therefore, even in the presence of salts, comminuted raw avocado seeds demonstrated great potential to treat colored effluents containing MB dye.

In order to further understand the status of the water quality of Min River’s sea-entry section, the index systems for water environmental quality assessment was built based on twenty evaluation parameters including dissolved oxygen (DO), permanganate index (CODMₙ), chemical oxygen demand (CODCᵣ), biochemical oxygen demand (BOD₅), ammonia (NH₃-N), total phosphorus (TP), and total nitrogen (TN). Water environmental quality of Min River’s sea-entry section in 2015–2017 was evaluated by utilizing the entire-array-polygon synthesis illustration method, accompanied by the time-dependent trend analysis. The results demonstrated that the water environmental quality of Min River’s sea-entry section was between the levels I and II of the Environmental Quality Standards for Surface Water (EQSSW, GB3838-2002) in 2015–2017, indicating a generally good water quality. The water quality was affected by both natural factors (such as temperature, rainfall, and runoff) and human factors and had a tendency to deteriorate at the duration of 2015–2017. The research results are of great significance for further understanding of the discharge of pollutants from the Min River basin and will be a strong support for the scientific decision-making of marine management in Fujian Province.

The effects of increased mining of seafloor massive sulfide deposits on marine ecosystems have not been characterized. In this study, the impact of leaching metals from a hydrothermal sulfide on photosynthetic protist and cyanobacterial communities in marine environments was investigated by amplicon analyses of small subunit rDNA (SSU rDNA) and rRNA (SSU rRNA). Seawater samples collected from the Iheya North region and Suruga Bay, Japan, were incubated with or without a leachate containing zinc, copper, cadmium, and manganese, of the actual seafloor hydrothermal sulfide from the Hakurei site in the Izena Hole region. The relative abundances of prasinophytes, diatom protists, and the cyanobacteria Synechococcus decreased substantially during incubation with leachate, indicating the vulnerability of these lineages to the leachate. Phylogenetic analysis based on the cyanobacterial phycocyanin cpcBA/rpcBA operon obtained from samples incubated with or without leachate indicated that the individual lineages of Synechococcus can determine sensitivity to heavy metals in different marine regions as well as particular clades and ecotypes.

Many organochlorine pesticides (OCPs) are considerably high toxic, and have bioaccumulation potential and chronic adverse impact on both wildlife and human. This study focuses on the fate and metabolic degradation, which is the potential to be more efficient, economic, and safe compared to the aforementioned conventional methods. By these positive attributes, the present work then investigates the capability of newly isolated pathogenic yeast Pichia kluyveri FM012 for biodegradation of DDT in aquatic culture. Pichia kluyveri FM012 mycelia were cultured in a mineral liquid medium consisting of the solution of DDT (40 mg/l) with some experimental conditions such as the initial pH of the culture (5–8), agitation speed (0–150 rpm), and various carbon and nitrogen sources. The highest biodegradation of DDT by Pichia kluyveri FM012 was shown in the culture with pH 5 and 150 rpm agitation. Moreover, the use of glucose and yeast offers the best performance for the degradation compared to other carbon and nitrogen sources. The highest enzyme activity during the decolorization process was dioxygenase. Fourier-transform infrared spectroscopy (FTIR), UV-Vis spectrophotometer, and GC-MS profile showed that the transformation of DDT has occurred. The present DDE and DDD as metabolites of DDT were confirmed by GCMS at a retention time of 17.8 and 16.6 min. The outcomes of this study have several important implications for future practice, for instance in providing an alternative biodegradation agent to remove some organochlorine pollutants.

Diclofenac (DCF) is one of the most widely used non-steroidal anti-inflammatory drugs worldwide, and several studies have reported adverse effects on the environment, in plants and animals; so, it is classified as an emerging pollutant. There are several alternatives for its removal; however, it is necessary to study the way in which the DCF is degrading to offer more effective removal techniques, since the traditional ones such as chlorination, activated sludge, and biofiltration offer low removal efficiency (20–40%). This work analyzes the kinetic behavior of the photodegradation of DCF and the thermodynamic parameters of the reaction under UV-C-type light radiation. The results obtained indicate that it presents a first-order kinetic promoted by the increase of the temperature. Also, within the evaluated interval (273 to 308 K), the values of the kinetic coefficient (k) range between 0.05 and 0.20 min⁻¹ and the half-life ranges from 3 to 9 min. The reaction is exothermic and spontaneous and gives way to the formation of approximately 6 byproducts, being two with the greatest presence and stability. This suggests that its decomposition route occurs through the dechlorination of the molecule and originate compounds known as carbazoles that have been detected in previous works. It was also found that this mixture of byproducts remained after the degradation of the drug, which is released to the environment, so it is necessary to extend a study on its properties and its possible environmental impact.

In perspective of the issue of how to begin simultaneous nitrification, anammox, and denitrification (SNAD) rapidly, the sequencing batch biofilm reactor (SBBR) was adopted to enrich ammonia-oxidizing bacteria (AOB) and anammox bacteria (AnAOB) rapidly and to inhibit nitrite-oxidizing bacteria (NOB) after three phases (67 days) of culture, and the impacts of different low carbon-nitrogen ratios (COD/N) on denitrification performance of the process were investigated. The results showed that preventing the accumulation of nitrite (NO₂⁻-N) was the key to start SNAD successfully. The removal efficiencies of ammonia nitrogen (NH₄⁺-N) and total nitrogen (TN) in the system can reach more than 99% and 90%, respectively. Corresponding to COD/N = 0, 1 and 2, removal efficiencies of NH₄⁺-N were 99.6%, 99.5%, and 98.5% respectively and removal efficiencies of TN were 93.8%, 97.2%, and 98.1%, respectively; the total nitrogen removal rate (TNRR) was greater than 0.29 kg N m⁻³ day⁻¹. It indicates that the presence of a small amount of COD is beneficial to the denitrification of NO₃⁻-N without affecting the effect of simultaneous nitrification and anaerobic ammonium oxidation, which further improves the efficiency of nitrogen removal. High-throughput sequencing analysis showed that the ratios of AOB, AnAOB, and denitrifying bacteria were 7.3%, 20.1%, and 7.66%, respectively. Candidatus Kuenenia was the only genus of the SNAD reactor with anaerobic ammonium oxidation. AOB, Anammox, and heterotrophic denitrifying bacteria were present in the system, while ammonia oxidation and anaerobic ammonium oxidation played a dominant role in the denitrification process.