The accumulation of ash, heavy metals, and polycyclic aromatic hydrocarbons (collectively called potential accumulating substances, PAS) was evaluated to ascertain the stability of lysis–cryptic growth sludge reduction process (LSRP) for municipal sludge treatment. One sequencing batch reactor (SBR) incorporated with homogenization was run to test the LSRP and another SBR as a control. The continuous monitoring results for 2 months showed that the ash and heavy metals slightly increased, and the polycyclic aromatic hydrocarbons decreased by 18.0%, indicating that there may be negligible accumulations during the LSRP. Their accumulations met pattern I, as demonstrated by statistical analysis, proving no PAS accumulation for LSRP. This was further confirmed by sludge activity and system performance. Moreover, the mechanism for no PAS accumulation was discussed. It was concluded that the LSRP was stable with no worries about PAS accumulation under the operational conditions.

Agricultural practices and industrial growth have contaminated the environment with heavy metals and many other harmful compounds. Arsenic (As) has been highlighted as a major heavy metal affecting growth and development of plants as well as causing severe human health hazards through food chain contamination. Most studies of heavy metal impacts address only one of these aspects, overlooking the effect of pollution on the plant as a whole. In this work, our objective was to determine the effect of arsenic stress on physiological, biochemical, and morphological characteristics in seedlings of two cultivars of maize with different arsenic tolerance. This study investigated the effects of varying levels of arsenic (As) stress on growth, enzymatic characteristics, and cell ultrastructure in seedlings of As-sensitive and As-tolerant maize cultivars (Shiyu No. 9 and Dongdan90, respectively) grown in hydroponic culture. Compared to Shiyu No. 9 at the same As concentration, Dongdan90 maintained higher values of biomass, shoot length, root length, and activity of superoxide dismutase, peroxidases, and catalase, but had lower malondialdehyde content, As accumulation, and non-protein thiol. High As concentrations inhibited the growth of both cultivars, while lower concentrations stimulated it. The As-tolerant cultivar also maintained the structural integrity of cells and tissues more efficiently under As stress. These findings demonstrate a link between the physiological and physical impacts of heavy metals on crop plants that paves the way for improved interventions to deal with heavy metal pollution.

The objective of this study was to examine the degradation of pharmaceutical compounds diclofenac, ketoprofen, and carbamazepine in a bench-scale batch type advanced oxidation treatment system combining non-thermal plasma and UV photocatalysis. The key factors affecting pollutant decomposition were studied in a dielectric barrier discharge (DBD) plasma reactor. This was followed by the comparative assessment of various advanced oxidation processes (O₃; UV+O₃; TiO₂+O₃; TiO₂+UV+O₃) in a UV-photocatalysis reactor. The overall effectiveness of the treatment process was established according to the decomposition efficiency of the individual compound determined by high-performance liquid chromatography with ultraviolet detection (HPLC/UV), removal of total organic carbon (TOC), energy consumption, and acute toxicity test with Chironomus sp. larvae. Depending on the pharmaceutical compound and oxidation system, complete decomposition of the target compound was reached within 3–6 min. The TOC removal ranged between 25 and 100% with energy consumption varying 3.1–10.6 MJ/g. TiO₂+UV+O₃ revealed slightly higher toxicity of treated water as compared to TiO₂+O₃ (22–50% vs 17–33% mortality rate of Chironomus sp. larvae). TiO₂+O₃ and TiO₂+UV+O₃ systems proved as an efficient combination of AO processes for the decomposition of pharmaceuticals in water, as long as the treatment duration is sufficient to fully mineralize organic substances.

This work is dedicated to study the potential application of char byproducts obtained in the gasification of rice husk (RG char) and rice husk blended with corn cob (RCG char) as removal agents of two emergent aquatic contaminants: tetracycline and caffeine. The chars presented high ash contents (59.5–81.5%), being their mineral content mainly composed of silicon (as silica) and potassium. The samples presented a strong basic character, which was related to its higher mineral oxides content. RCG char presented better textural properties with a higher apparent surface area (144 m² g⁻¹) and higher micropore content (V ₘᵢcᵣₒ = 0.05 cm³ g⁻¹). The alkaline character of both chars promoted high ecotoxicity levels on their aqueous eluates; however, the ecotoxic behaviour was eliminated after pH correction. Adsorption experiments showed that RG char presented higher uptake capacity for both tetracycline (12.9 mg g⁻¹) and caffeine (8.0 mg g⁻¹), indicating that textural properties did not play a major role in the adsorption process. For tetracycline, the underlying adsorption mechanism was complexation or ion exchange reactions with the mineral elements of chars. The higher affinity of RG char to caffeine was associated with the higher alkaline character presented by this char.

Pig slurry contains sufficient amount of nitrogen, phosphorus, and potassium for plant growth. If appropriately administered, this could substitute significant amounts of fertilizer. However, excessive fertilization with slurry causes environmental problems. To reduce environmental issues, solid-liquid separation or anaerobic digestion is needed to obtain a better distribution of nutrients. Solid-liquid separation produces a solid fraction rich in phosphorus and a liquid fraction containing ammonia, potassium, and high water content. Therefore, further concentration of ammonia is desired for any practical use. In this study, ammonia membrane stripping was carried out using polypropylene membranes and the impact of temperature, flow velocities, and liquid fraction pretreatment on the membrane contactor performance was tested. Sieved liquid effluents from a decanter centrifuge, a screw press, an AL-2 system (flocculation and filtration), and an anaerobic digester were tested. Since the properties of these liquid effluents vary, they might affect ammonia recovery. Thus, it is essential to investigate which effluent is most suitable as a feed for a membrane contactor and what is the cost of preprocessing. The mean ammonia mass transfer coefficient at 30 °C was found to be equal to 17 ± 2 × 10⁻³ m h⁻¹. At 50 °C, it was found to be equal to 29 ± 2 × 10⁻³ m h⁻¹ for all the tested effluents. This means that sieving after slurry separation or anaerobic digestion alleviates the influence the solid-liquid separation has on ammonia membrane stripping. However, the cost evaluation showed that solid-liquid separation using a decanter centrifuge followed by sieve draining is the cheapest of the methods investigated.

Thermally robust hydroxylated biochar (HBC) and sulphonated biochar (SBC) were synthesised from paper and pulp sludge (PPS) and used for the adsorption of Zn²⁺ from synthetic wastewater through batch experiments. FTIR analyses proved successful incorporation of the hydroxyl and sulphonic functional groups in HBC and SBC, respectively. The effects of initial solution pH, initial Zn²⁺ concentration, solution temperature and equilibrium contact time were investigated. The removal efficiency of Zn²⁺ increased with increase in both solution temperature and initial Zn²⁺ concentration. Adsorption of Zn²⁺ was greatest at pH 3. HBC and SBC removed 38–99% and 68–90% of Zn²⁺ from solution, respectively. Zn²⁺ adsorption on SBC followed both Langmuir (R ² = 0.994) and Freundlich isotherm models (R ² = 0.999), while adsorption on HBC followed the Freundlich model (R ² = 0.989). Zn²⁺ adsorption on both biosorbents followed pseudo-second-order kinetics (R ² = 0.994–0.999). The increase in enthalpy of adsorption indicated the adsorption process was endothermic and a decrease in Gibbs free energy signified the spontaneity of adsorption. Positive entropy change values imply that the adsorbed Zn²⁺ ions are randomly distributed over the adsorbent surface. The research demonstrated that although their adsorption mechanisms had salient differences, HBC and SBC can effectively remove Zn²⁺ from wastewater. Development of HBC and SBC from PPS provides potential low-cost biosorbents for water and wastewater, while simultaneously minimising the environmental and public health risks associated with current disposal practices of PPS.

Phthalates are considered as dangerous priority pollutants, several effects being attributed to them: foetal deformations, cancers, and endocrine disruptions. Activated carbons are highly efficient materials for the adsorption of numerous organic molecules. Before their use, it is important first to determine both textural and chemical properties and to study kinetics and thermodynamics adsorption, to understand and to optimize the interactions between material and molecules. The aim of this work was to study the kinetics and the adsorption isotherms of three phthalates (dimethylphthalate, diethylphthalate, and diethylhexylphthalate) currently found in industrial effluents, on two different activated carbons. The co-adsorption of these molecules in a synthetic mix and in complex matrices was modeled. The kinetic study and adsorption isotherms of dimethylphthalate and diethylphthalate in monosolute and bisolute were first investigated, followed by a similar study with a mix of the three molecules in complex matrices (surface water (Loire and Loiret Rivers near Orléans city) and municipal wastewater treatment plant outflow). The pseudo-second-order kinetic model was used to determine the kinetic adsorption parameters. The Langmuir equation was used to calculate the surface occupied. Results showed that non-electrostatic interactions are predominant in phthalate adsorption in complex matrices, mainly due to dispersion forces and hydrophobic interactions.

The presence of urban surface pollutants washed off by stormwater is a growing concern due to their adverse effects on receiving water quality. The stormwater quality mitigation strategies, therefore, should be based on the knowledge of the distribution and source apportionment of pollutants on urban surfaces. This study showcases the distribution of particulate-associated PAHs as a function of surface characteristic. Samples were obtained from six sites in the city of Dresden, Germany, using a wet vacuum sample-taking method. Both surface load (mg/m²) and solid-phase concentration (mg/g) of PAHs were determined. Results show that the highest surface load of ∑₁₆PAHs was found at a natural stone-paved pedestrian path with 34.5 μg/m². By contrast, the highest solid-phase concentration occurred at a high traffic load road with 36 mg/kg. Through a combined qualitative diagnostic ratio and quantitative principal component analysis with stepwise multiple linear regression (PCA-MLR) source apportionment, two significant contributors to PAH at vehicular roads were primarily identified as pyrogenic and petrogenic sources; 81.6% of the PAH burden was ascribed to pyrogenic sources including vehicle emission, coal, and wood combustions; 18.4% was attributed to petrogenic sources, such as spilled engine oil and vehicular tire debris. To minimize the adverse influence of surface sediments adsorbed PAHs to the receiving waters via stormwater runoff, a surface pavement-based city street sweeping strategy could be planned and optimized to remove hazardous materials from the impervious urban surfaces.

The effect of different Cr and Zn concentrations in the soil on the development of Albares wheat and Pedrezuela barley plants at the physiological, biochemical, and structural levels was evaluated during the crop cycle in a greenhouse assay, as well as their potential use in phytoremediation strategies. The accumulation of Cr and Zn in plants was dose-dependent for both cultivars. The highest contents were found in root and the lowest in grain. In the Cr treatments, the decrease with respect to the control in the biomass, relative water content (RWC), chlorophyll content (Chl), and chlorophyll fluorescence values (Fv/Fm) was more pronounced in wheat than in barley. For the Zn treatments, the behavior was the opposite. Barley showed less tolerance to Zn concentrations although its higher translocation factor (TF) and greater biomass make this plant adequate to use in phytoremediation process in soil contaminated with Zn. The electron microscopy studies showed evidence that treatment with both Cr and Zn produced alterations in the cellular ultrastructure of the plant leaves. Cr and Zn induced the production of malondialdehyde (MDA) in both cultivars; the highest concentrations were observed in barley leaves. In general, the ascorbate peroxidase activity (APX) was higher in the plants exposed to metal treatments. The catalase activity (CAT) showed a different behavior depending on the metal studied. These results highlight the potential capacity of Albares wheat for use in the phytoremediation of soils contaminated by Zn and of Pedrezuela barley for use in Cr- and Zn-contaminated soils.

Singapore is an island city state with an economy dependent on petrochemicals and shipping, but with severely limited water resources. This study aimed to establish a suitable methodology specifically for the translation of a laboratory-scale system to an industrial scale for the treatment of phenol-contaminated wastewater. A habitat-specific microbial consortium was developed and reconstituted from 22 pure cultures dominated by Acinetobacter sp., Bacillus sp. and Pseudomonas sp. to form a synthetic biofilm-forming community with the capacity to degrade phenol-contaminated wastewater. The laboratory experiment was scaled-up to 400 m³ by using biotrickling reactors to reduce the phenol level from 407 mg L⁻¹ to below detection limit over 104 days incubation. The results showed that the microbial consortia could also reduce the toxicity of the wastewater while degrading the phenol and lowering the wastewater COD. Further, this approach could be translated into the field without the need for a purpose-built primary treatment facility preventing the generation of excessive biomass and eliminating the need for sludge disposal.