As potassium ferrate(VI) is an important kind of water treatment agent which has a high efficiency in algal removal, its effects on the cell substance are rarely discussed. The changing of the protein and enzyme was analyzed here to deeply understand the oxidation of Fe on the protein in the algae. The result of the research showed the inactivation on growth and the biochemical process of the algal cell were all inhibited by Fe, including the function of the photosynthesis system. During the process, SOD (superoxide dismutase), CAT (catalase), POD (peroxidase), and GST (glutathione S-transferase) played cooperative roles to prevent the injury on the cells from destructive oxidation stress. The lipid peroxidation strengthened the defense system. The damage was intensified with the increase of ferrate concentration.

Mine waste contaminated soils are classified as degraded soils with poor conditions such as low soil pH, low organic matter and high metal concentrations. This study evaluated the potential of fly ash enriched vermicompost in improving poor soil conditions in mine waste affected soils. The soils were amended with the vermicompost to supply 0, 10, 20, 40 and 80 mg of phosphorus per kg and incubated for 8 weeks. The soil pH increased from the original acidic range of 3.7–5.3 to 6.8–7.6. Available P significantly improved (P < 0.001) to yield the target P levels; however, at the end of incubation period, 80 mg-P/kg treatment had lower Olsen P relative to the 40 mg-P/kg treatment. Nitrogen mineralisation was enhanced with addition of the vermicompost as reflected by an average increase of 51% in NO₂/NO₃⁻-N while NH₄⁺-N decreased over time. The Mn, Zn and Pb solubility was reduced with addition of the vermicompost, with 20 mg-P/kg resulting in the most reduced solubility. However, concentrations at 20 mg-P/kg treatment were generally not different to 40 mg-P/kg. Solubility of Cu significantly increased in proportion to increase in amendment rate but did not exceed maximum permissible limits. Solubility of Cd and Cr also increased during the incubation study; however, this could not be attributed to the different vermicompost treatments but the soil properties. Therefore, in conclusion, application of fly ash enriched vermicompost at 40 mg-P/kg was found to be optimum for a balanced supply of essential nutrients and reduced metal solubility.

The brewing industry is an important sector in the world economy, and its production process generates a large amount of wastewater. It is essential the proper treatment of this wastewater and a significant amount of biomass may be recovered by coagulation/flocculation process. When using vegetable tannin as an organic flocculant, biomass can be used in the preparation of organic fertilizer, unlike what would occur if a metal base flocculant was used, some of which are considered to be toxic. This work presents a study on the use of vegetable tannin as flocculant agent (Tanfloc SL) for the treatment of brewery wastewater, which also contains microalgae originated from an aerated pond of a local brewery industry. Experiments of coagulation/flocculation and sedimentation were carried out using jar test equipment. A sequential 2² factorial design and two-factor Doehlert design were used to determine the optimum levels of pH and tannin concentration for turbidity and apparent color removals from the wastewater. The higher efficiency results in the biomass separation were obtained by employing 0.23 mL L⁻¹ of vegetable tannin at pH = 4.9, resulting in the substantial removal of approximately 99% of turbidity and apparent color. The removals of biomass and nutrient components were also evaluated: N-NH⁴⁺ (80.8%), N-NO₂- (83.6%), N-NO₃ (56.9%), total phosphorus (82.3%), orthophosphate (76.2%), COD (96.5%), BOD (69.4%), and total solids (40.8%). The Tanfloc SL showed to be efficient in flocculation of the brewery effluent, allowing the reuse of water in industry and the recovered biomass material containing nutrients in agriculture.

The toxic impacts of CuO nanoparticles (NPs) on the marine phytoplankton Nannochloropsis oculata were evaluated by measuring a number of biological parameters. Exposure to different concentrations of CuO-NPs (5–200 mg/L) significantly decreased the growth and content of chlorophyll a of N. oculata. The results showed that CuO-NPs were toxic to this microalga with a half maximal effective concentration (EC50) of 116.981 mg/L. Exposure to CuO-NPs increased the hydrogen peroxide (H₂O₂) content and induced the membrane damages. Moreover, the concentration of phenolic compounds was increased, while the levels of carotenoids were markedly decreased in comparison to the control sample. The activity of catalase (CAT), ascorbate peroxidase (APX), polyphenol oxidase (PPO) and lactate dehydrogenase (LDH) enzymes significantly was increased in response to CuO-NPs treatments. These results indicated that CuO-NPs stimulated the antioxidant defense system in N. oculata to protect the cells against the oxidative damages. The Fourier-transform infrared spectroscopy (FTIR) analyses showed that the main functional groups (C=O and C–O–C) interacted with CuO-NPs. The images of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed the cell membrane damage and the change of cell wall structure which may be contributed to the nanotoxicity. These findings may provide additional insights into the mechanisms of cytotoxicity induced by CuO-NPs.

A consortium of highly degrading microorganisms was used in an integrated bioaugmentation/electrocoagulation process for treating olive mill wastewater. The system was investigated for treating 1 m³ day⁻¹, at a pilot scale, for 2 years; hydraulic loading rate and organic loading rate were 2880 l m⁻² day⁻¹ and 37,930 g COD m⁻² day⁻¹, respectively. Average removal efficiency for COD, oils, and total phenols was 63.9%, 85.2%, and 43.6%, respectively. The olive mill consortium, OMC, consisted of seven actinomycete strains. The strains were confirmed, by 16S rDNA analysis, to belong to five Streptomyces, one Kitasatospora, and one Micromonospora strains, at 100–99.06% similarities. Hydrolytic enzyme activities of OMC strains were remarkably higher for degrading cellulosic and lipid constituents (enzyme-cumulative indices, 14–16.1), than the phenolic constituents (indices, 4.1–6.5). The establishment of actinomycetes in the treatment system was indicated by their increased counts in the biofilm at the end of the biofilter, reaching 13-fold higher than that in the control bed. The treated effluent was toxic to the seedlings of Jatropha curcas (Jatropha) and Simmondsia chinensis (Jojoba). Though its application in irrigation of 3-year-old Jatropha shrubs, significantly, enhanced the fruit yield up to 1.85-fold higher than the control, without affecting the seed oil content, after 3-month application, the irrigated soil showed insignificant changes in its biochemical properties. This developed bioaugmentation/electrocoagulation process can treat wastewater with extremely high organic strength, while its approximate construction and operational costs are limited to 0.03 and 0.51 US$ m⁻³, respectively. It produces a treated effluent that can be reused in irrigation of specific plants. Graphical abstract

This study aimed to explore the nitrogen and phosphorus removal performance of the horizontal submerged constructed wetland (HSCW) with Ti-bearing blast furnace slag (T). Another two HSCWs, with the converter steelmaking slag (G) and the stone (S) as wetland substrates, respectively, were simultaneously running as control. The results showed that the nitrogen and phosphorus removal capacities of the T-HSCW were generally better than those of another two HSCWs. When the hydraulic retention time (HRT) was 6 days, the effluent concentrations of ammonia nitrogen (NH₄⁺-N) and total nitrogen (TN) were 6.66 mg L⁻¹ and 14.02 mg L⁻¹, respectively, and the removal rates of NH₄⁺-N and TN reached 77.54% and 71.07%, respectively. The T-HSCW had better removal efficiency of phosphorus. The effluent concentration of total phosphorus (TP) was lower than 0.3 mg L⁻¹, and the maximum removal rate could reach 98%. Through the characterization of the three substrates before and after experiments, it was found that the removal of nitrogen and phosphorus by T and G mainly relied on chemical adsorption, while S mainly relied on physical adsorption. Ti could also promote the absorption of nitrogen by plants and increase the nitrogen removal capacity of T-HSCWs.

Inorganic and organic constituents present in textile effluents have a noticeable effect on the performance of Fenton processes. However, studies have been focused on simple wastewater matrices that do not offer enough information to stakeholders to evaluate their real potential in large-scale facilities. Chemical auxiliaries, commonly present in textile wastewaters (NaCl = 30 g/L, Na₂CO₃ = 5 g/L, and CH₃COONa = 1 g/L), affect both the economic and environmental performance of the process because they increase the treatment time (from 0.5 to 24 h) and the consumption of H₂SO₄ (657%) and NaOH (148%) during conditioning steps. The life cycle assessment (LCA) performed with the IPCC-2013 method revealed that dyeing auxiliaries increase from 1.06 to 3.73 (252%) the emissions of carbon dioxide equivalent (CO₂-Eqv/m³). Electricity consumption can be considered an environmental hotspot because it represents 60% of the carbon footprint of the Fenton process. Also, the presence of auxiliaries is critical for the process because it results in the increase of the relative impact (between 50 and 80%) in all environmental categories considered by the ReCiPe-2008 method. Chemical auxiliaries increased the costs of the treatment process in 178% (US$2.22/m³) due to the higher energy consumption and the additional reagent requirements. It is worthwhile mentioning that the technical simplicity of the Fenton process and its low economic and environmental costs turn this process into an attractive alternative for the treatment of textile effluents in emerging economies.

Full-scale application of heterogeneous photocatalysis for industrial wastewater treatment remains a challenge because of the complex nature of these matrices and the potential to form toxic by-products during treatment. A recent unsuccessful attempt to find adequate conditions for TiO₂/UV treatment of a cotton dyeing textile mill led to this study on the treatability of mixtures of the dyes used in the greatest amounts at the mill and therefore most likely to be present in mill effluent. Four reactive and three vat dyes were mixed in different combinations and treated (10 mg/L of each dye, 0.5 mg/L TiO₂, pH 4) to evaluate the influence of the different dyes on ADMI color, chemical oxygen demand (COD), and acute toxicity. While ADMI color removal was similar in all dye mixtures, COD removal was higher when vat dyes were absent. When treated individually, vat dyes exhibited greater recalcitrance, with no ADMI color removal and COD removals of less than 30%. Toxicity to Daphnia similis was decreased or eliminated from dye mixtures that exhibited the highest COD removals and corresponded to those in which reactive dyes were partially degraded. For raw textile mill effluent, photocatalysis reduced but did not eliminate treated effluent toxicity (EC50 = 26.8%).

With increasing metal prices and declining ore grades, new mines are getting larger and mine waste disposal and management have become more difficult, particularly from an environmental perspective. While technologies keep on improving, the available space for terrestrial mine waste disposal is limited. Thus, several coastal countries still consider deep-sea tailings placement (DSTP) as a viable option. This brief review compares the environmental impacts of DSTP versus on-land disposal and suggests several factors to consider in selecting the most suitable options for mine waste disposal.

Iron-incorporated silica (Fe/SiO₂) with different Fe/Si molar ratio was successfully prepared from rice husk pyrolytic residues (RHR) through alkali pretreatment, co-precipitation, and calcination. Various characterization methods indicated that the Fe/SiO₂ samples possessed mesoporous structure with Fe species incorporated into the framework of silica. The obtained materials were applied in the treatment of hazardous banknote printing wastewater, and under the optimal conditions, colored pollutants, humic acid-like and soluble microbial by-product-like organics were removed significantly. It was found that Fe/SiO₂ acted as both flocculant and catalyst, and the framework iron species catalyzed the oxidative degradation of refractory organics in the presence of H₂O₂. A heterogeneous Fenton-like system was formed in the wastewater treatment process.