Anaerobic digestion (AD) and dewatering are the most common and widely applied sludge treatment methods in wastewater treatment plants (WWTPs). However, sludge dewatering has been recognised as one of the most expensive and least understood processes. Therefore, this study investigated the dewatering performance of synthetic sludge in comparison with anaerobically digested sludge when conditioned with chitosan, organic polyelectrolytes and inorganic metal cations. Capillary suction time (CST), turbidity, electrical conductivity, zeta potential, cake solids content and particle size were used to assess sludge dewatering performance and to determine the optimum conditioner dose. The effectiveness of sludge conditioning was evaluated by batch experiments using a series of 250-mL jar test beakers. Both synthetic sludge and AD sludge exhibited similar trend but little different extent of dewaterability when conditioned with low molecular weight (MW) chitosan. The low MW and medium MW chitosans, commercial cationic polyelectrolytes and trivalent metal cations (Al³⁺, Fe³⁺) demonstrated as effective conditioning agents with good sludge dewaterability. When assessing the dewaterability measurement parameters using synthetic sludge, the optimal dosage was found at the range of 15 to 20 g-chitosan/kg-dry sludge where the values of CST, turbidity and cake solids content were attained between 6.6 and 11.0 s, 35.4–40.6 NTU, and 24.3–25.3%, respectively. The application of cationic polyelectrolytes and trivalent metal cations generally improved the sludge dewaterability via charge neutralisation and polymer bridging. This study also demonstrated that less complex chemically controlled synthetic sludge can be used for studying the final properties of complex real digested sludge.

Dissipation rates of copper following algaecide treatments resulting in pulse exposures can be accurately modeled if the component dissipation rates are known. Scaled experiments (in situ, laboratory and mesocosm) were used to parse and rank dominant processes from concurrent processes affecting copper fate in pulse exposures. Copper dissipation rates were measured cumulatively in situ and in mesocosms as well as individually in laboratory experiments. Predictions of the influence of individual dissipation rates on the cumulative dissipation rate were assessed mathematically. In situ aqueous copper dissipated rapidly following an algaecide treatment, with a measured half-life of 0.03 days. Based on laboratory experiments, the most rapid copper fate process was dilution with a half-life of 0.03 days, followed by sediment sorption with a half-life of approximately 3 days. Mesocosm experiments incorporating physical characteristics of the site (i.e., dilution, sediment, algae, and site water) resulted in similar copper dissipation rates (0.02 days) relative to the in situ copper dissipation rate. Prediction of the fate of copper from algaecide treatments requires incorporation of accurate estimates of dominant fate processes that can be determined physically and mathematically.

The effect of solids retention time (SRT) on volatile fatty acids (VFAs) accumulation and microbial community evolutions in enzymolysis-pretreated waste activated sludge (WAS) fermentation process was investigated. SRT played important roles on VFA accumulation efficiency and composition with a best performance of over 2200 mg COD/L at an SRT of 8 days. Volatile suspended solids (VSS)/total suspended solids (TSS) of fermentative sludge decreased obviously during the fermentation tests at various SRTs. Distribution spread index (DSI) of fermentative WAS augmented from 1.175 to 1.218 in accordance with SRT rising from 6 to 11 days. SRT changes led to microbial community (bacterial and archaeal) shifts clearly as well as the community diversity in the fermentation system. Bacterial community evenness tended to be more uneven at an SRT of 8 days compared to SRTs of 6 and 11 days, which indicated that high dominance of bacterial community could be formed at 8 days SRT with more VFA accumulation in WAS fermentation system. RDA inferred that microbial consortia could be driven by the preponderant individual VFA accumulation (acetate, propionate, and N-butyrate) with getting to a relative balance level by SRT optimization in the system.

Because of their adverse effects, such as their toxicity and carcinogenicity, volatile organic compounds (VOCs) are the most important and common pollutants produced by urbanization and industrial processes that contaminate air and water streams. VOCs, commonly originating from many industrial syntheses, and their derivatives, especially halogen, produce an unpleasant odor in the air when present in excess. All the issues related to VOCs make them a severe threat to whole ecosystems and environments as well as humans. Globally growing environmental awareness and knowledge have resulted in strict regulations to control VOC emissions into the air. It is necessary for each component of emitted VOCs to be controlled or removed from the air. NaZSM-5 and HZSM-5, having high ratios of SiO₂/Al₂O₃ (50), which are necessary for good adsorbents of organics, were prepared. Characterization of the prepared materials was done by XRD, SEM, FTIR, N₂ adsorption, NH₃-TPD, ²⁷Al-NMR, and TGA analysis. The adsorptive removal of VOCs from the air by Na-ZSM-5 and H-ZSM-5 was explored. These adsorption materials were tested with respect to the adsorption capacity, renewability, and selectivity for benzene, toluene, ethylbenzene, and xylene. The effects of the contact time, adsorbent dose, and initial concentration of pollutant on the adsorption process were also studied. Finally, the adsorption data were applied to Langmuir, Freundlich, and Temkin isotherms and two different kinetic models.

Increasing concentrations of tropospheric ozone and reactive nitrogen threaten the composition and function of semi-natural plant communities. Using a free-air fumigation system, we investigated the effects of elevated ozone (1.73 × ambient concentration; +O₃) and nitrogen (+50 k g N ha year⁻¹; +N) deposition on growth of juveniles of three subalpine grassland species and their colonization by arbuscular mycorrhizal fungi (AMF) in situ. In a subsample, the extra-radical mycelium was regularly disrupted to determine the effect of AMF on the plants’ pollutant sensitivity. The plants reacted sensitively to the pollutants: +N increased shoot growth in Festuca rubra, while +O₃ decreased root growth in Trifolium alpinum and F. rubra. Colonization with AMF was stimulated by N in Leontodon helveticus and was strongly reduced by O₃ in F. rubra and L. helveticus, probably due to lower carbon allocation belowground. Conversely, AMF did not protect plants from O₃ neither did they increase the species’ responsiveness to N. Our results indicate that irrespective of AMF colonization, juvenile plants are highly sensitive to O₃ stress, probably since their growth is primarily limited by carbon assimilation.

Despite recent regulations, atmospheric ammonia (NH₃) emissions have not changed much over the last decades and excessive nitrogen remains as one of the major drivers for biodiversity changes. To prevent deleterious effects on species and ecosystems, it is very important to establish safety thresholds, such as those defined by the Critical Level (CLE) concept, “the concentration above which direct adverse effects on receptors may occur, based on present knowledge.” Empirical critical levels of atmospheric NH₃ have mainly been reported for temperate forests and there is a lack of information for Mediterranean forests. Here, we provide a case study on NH₃ CLEs for a typical Mediterranean ecosystem, the holm-oak (Quercus ilex) forest. To derive the CLE value, we measured NH₃ concentrations for 1 year at a distance gradient in the forest surrounding a point source (cattle farm) and used diversity changes of lichen functional groups to indicate the onset of adverse effects. We estimate a NH₃ CLE threshold of 2.6 μg m⁻³, a value that is higher than that reported in other Mediterranean ecosystems and suggests that the site has been already impacted by NH₃ pollution in the past. In a more general context, this study confirms the validity of lichen functional groups to derive CLEs in Mediterranean forests and woodlands and contribute to the body of knowledge regarding the impacts of NH₃ on ecosystems.

Air sparging (AS) is one of the most efficient techniques for remediating saturated soils and groundwater contaminated with volatile organic compounds. Most studies have focused on how the subsurface conditions control the AS process; however, the “side-effects” of AS that feed back to subsurface environment have not been well addressed. This paper studied the perturbation of porous media induced by AS and the consequent multi-parameter changes with the support of Miller soil box and resistivity test, and Darcy experiment and tracer breakthrough test. The Miller soil box test shows that the resistivity response can be credibly used as a non-intrusive method to indicate the porosity change, and that the porosity-resistivity data can be well fitted using Archie equation (R ² > 0.98). Based upon the electricity measurement and above quantitive relationship, it was found that the porosity increased near the air injection point and decreased near the upper boundary of the column due to the upward-transport of particles during air sparging. The changes in porosity were found to be directly proportional to the air injection rate, and the maximum absolute variation of porosity was up to 0.104 at the air flow rate of 20 ml/min, while it did not change in the absence of AS. Both the hydraulic conductivity and dispersion coefficient increased after AS perturbation as the preferential flow pathway formed. The two parameters changed from 3.40 m/d and 0.110 to 6.13 m/d and 0.288, respectively, at 20 ml/min. This work provides useful insight into the changes in flow and transport properties of porous media induced by AS, which then help to understand the instability of air flow and the parameter-uncertainty analysis in related AS model.

Biomass-derived biochar is considered as a promising heavy metal adsorbent, due to its favorable physicochemical properties, from aqueous solution as compared with other adsorbents. However, there is a limited number of studies on the effects of biochar produced from different feedstocks and pyrolytic temperatures on metal removal from metal-contaminated water. So in this study, the removal of the most prevalent heavy metals [(lead (Pb(II)), cadmium (Cd), and chromium (Cr)] by green waste biochar (GWB) and popular twigs biochar (PTB), produced at different pyrolytic temperatures, i.e., low 350 and high 650 °C, has been investigated, following the determination of physical and chemical properties of biochar. The efficiency of heavy metals removal of biochar was studied at different concentrations of heavy metals (10 and 100 μg mL⁻¹), biochar types and treatment duration (3, 6, 9, and 12 h) at isothermic condition of aqueous solution. Results revealed that both feedstock type and pyrolytic temperature to produce biochar significantly affected its metal sorption capacity. The maximum sorption capacities of all three metals, i.e., Pb (II), Cd, and Cr were determined in the GWB produced at low pyrolytic temperature 350 °C after 9 h of treatment duration at both high and low metal concentrations. This highest sorption capacity of all metals by low pyrolytic temperature produced GWB was due to its better physicochemical properties especially high surface area, cation exchange capacity, and oxygen-containing functional groups as compared with woody feedstock based high pyrolytic temperature produced PTB. Conclusively, low pyrolytic temperature produced GWB was evaluated as a potential adsorbent to efficiently reduced heavy metal concentration in metal-contaminated water.

The main objective of the present paper is to evaluate the use of Moringa oleifera (MO) as a natural coagulant in coagulation/flocculation/sedimentation (CFS) followed by the microfiltration (MF) or nanofiltration (NF) process in dairy wastewater treatment, focusing on determining the best association of treatments that can generate wastewater for reuse purposes. The association of CFS-MF-NF treatments showed a high removal efficiency for chemical oxygen demand (COD) (mean of 96%), turbidity, and color (mean of 99%) meeting water reuse standards, allowing the reutilization of the wastewater, in relation to the analyzed parameters. The results indicate a lower membrane fouling rate (63%), an increase in permeate flow, and better quality of the permeate, proving that the CFS-MF-NF treatment is the most suitable among all the tested treatments. Finally, the treated wastewater obtained with this process presents better quality than the wastewater obtained with the conventional treatments.

Amphibians are the most threatened vertebrate group with a third of currently known species endangered with extinction, as a result of climate change, habitat loss, disease-introduced exotic species, and pollution. Because of their vulnerability, they have often been used as environmental quality indicators, as well as laboratory models for toxicological research. Given the sensitivity of amphibians to changes in their surrounding environment, including pollution, it was deemed important to define a non-lethal technique based on the evaluation of a set of biomarkers in different tissues of neotenic individuals of Ambystoma velasci. The levels of acetylcholinesterase (AChE), butyrylcholinesterase (BChE), carboxylesterase (CaE), alkaline and acid phosphatases (ALP, ACP), glutathione s-transferase (GST), 7-ethoxyresorufin-O-deethylase (EROD), and superoxide dismutase (SOD) activities, as well as the oxygen radical absorption capacity (ORAC) were measured in tail, gills, liver, plasma, and brain samples. Significant tissue-specific differences were observed for all biomarkers with the exception of ACP. The highest values of specific activity for most biomarkers were detected in the liver. However, the levels measured in gills were very close to those observed in the liver and showed fewer variations than other tissues. These findings suggest that the sampling of gills could be used to evaluate pollution biomarkers in salamanders without apparent harm, as this tissue quickly regenerates.