The low ammonium concentration, low temperature, presence of organic matter, and large variation of influent ammonium load pose serious challenges for the application of PN/AMX (partial nitrification-anammox) reactor in the mainstream wastewater treatment. Previous mathematical simulation studies of PN/AMX granule reactor mainly concentrated on the steady-state modeling. The steady-state simulation cannot be used for developing control strategies under dynamic condition. In this study, four control strategies were evaluated on their abilities to minimize the impact of feed disturbances on autotrophic nitrogen removal in mainstream wastewater. The four control strategies included are the following: (A) direct airflow adjustment to maintain the fixed NH₄ ⁺ set point, (B) fixed NH₄ ⁺ set point control manipulated by DO concentration with DO limit, (C) constant DO control strategy, and (D) adaptive change of NH₄ ⁺ set point control based on the feed disturbance (NH₄ ⁺ set point value achieved by DO concentration manipulation with DO limit). The results indicated that the control strategy A successfully implemented for high NH₄ ⁺ strength wastewater treatment cannot be directly transferred into the mainstream wastewater treatment, in which high NO₂ ⁻ accumulation was resulted during the NH₄ ⁺ peaks at the low-temperature period. Satisfactory TN removal could be achieved by maintaining either fixed or variable bulk NH₄ ⁺ set point values calculated based on the feed disturbances (control strategies B and D). The DO limit imposed on the DO concentration manipulation to derive the desired NH₄ ⁺ set point values was essential for the successful implementation of control strategies B and D. The control strategy C with constant DO concentration was not feasible for the PN/AMX process under dynamic feed disturbances. The control simulation results and the control variable sensitivity analysis indicated that the NH₄ ⁺ concentration was a better control variable than the DO concentration.

Hospitals consume a large volume of water to carry out their activities and, hence, generate a large volume of effluent that is commonly discharged into the local sewage system without any treatment. Among the various sectors of healthcare facilities, the laundry is responsible for the majority of water consumption and generates a highly complex effluent. Although several advanced oxidation processes (AOPs) are currently under investigation on the degradation of a variety of contaminants, few of them are based on real wastewater samples. In this paper, the UV/H₂O₂ AOP was evaluated on the treatment of a hospital laundry wastewater, after the application of a physicochemical pretreatment composed of coagulation-flocculation and anthracite filtration. For the UV/H₂O₂ process, a photoreactor equipped with a low-pressure UV-C lamp was used and the effects of initial pH and [H₂O₂]/chemical oxygen demand (COD) ratio on COD removal were investigated through a randomized factorial block design that considered the batches of effluent as blocks. The results indicated that the initial pH had no significant effect on the COD removal, and the process was favored by the increase in [H₂O₂]/COD ratio. Color and turbidity were satisfactorily reduced after the application of the physicochemical pretreatment, and COD was completely removed by the UV/H₂O₂ process under suitable conditions. The results of this study show that the UV/H₂O₂ AOP is a promising candidate for hospital laundry wastewater treatment and should be explored to enable wastewater reuse in the washing process.

This study was conducted to investigate the capability of moso bamboo grown alone and in combination with Sedum plumbizincicola to remediate heavy metals. Monoculture of moso bamboo (MM), intercropping of moso bamboo × S. plumbizincicola (IMS), and control (uncultivated, CK) were established in Cu-, Zn-, and Cd-contaminated soil. Soil properties and heavy metal removal capacity were assessed. Results showed that the available and total heavy metal contents in soil (0–20 and 20–40 cm soil layers) were ranked IMS < MM < CK. Available Cu, Zn, and Cd contents were 65.0, 28.7, and 48.4% lower in the IMS and 52.8, 24.8, and 45.5% lower in the MM than those in the CK, respectively. In plants, Cu contents in bamboo rhizomes, branches, and leaves and those of Zn and Cd in all bamboo tissues were significantly higher in the IMS than in the MM. The bioconcentration and translocation factors of bamboo tissues showed an obviously increasing tendency from MM to IMS. Moso bamboo possessed the properties of endurance to heavy metals and high biomass production. Phytoremediation by moso bamboo in association with S. plumbizincicola is an economical strategy to promote heavy metal removal from metal-contaminated soil.

The present work assesses the production rate of cell phone e-waste in Kuwait by comparing the number of clients in three telecommunication service providers like Zain, Ooredoo, and Viva in the state of Kuwait over a period of 7 years from 2008 to 2015. An online survey was conducted to evaluate the growth in the number of clients in three cell phone companies, and the data analysis was carried out using statistical package for the social sciences (SPSS) software. The prediction of the growth percentage of the number of clients in each telecommunication company was analyzed using analysis of variance (ANOVA) test and followed by the regression model. The study shows that there is an increase in the number of clients in all three companies (Zain, Ooredoo, and Viva) between year 2008 and 2015, and it was estimated that approximately 7.9 million cell phone users would be achieved in the first quarter of 2015. Based on this predicted number of cell phone users, the production of e-waste would be 3 kt per year with an average growth of 12.7%.

This paper investigates a new test method to assess the photocatalytic activity of plasterboards coated with a TiO₂ dispersion under real-world conditions. The degradation of nitrogen oxides NO ₓ (NO and NO₂) is studied and the photocatalytic efficiency under UV illumination is evaluated in a 10-m³ room after a constant gas injection. Two ultrafine TiO₂ dispersions are used: 0.85% TiO₂ and 5% TiO₂, and three types of gas are tested: an NO/NO₂ mixture (8/8 mol-ppm), NO (45 mol-ppm) and NO₂ (45 mol-ppm). The test method presented here is midway between laboratory and real-scale procedures and allows better control of the experimental parameters than a real field experiment. Testing a mixture of NO and NO₂ is a way to get closer to real-world conditions as air is polluted by various gases. This study focuses on the degradation of NO and NO₂ under UV illumination when two types of TiO₂ dispersions are used and highlights the difference in behaviour between these two molecules in terms of photocatalytic degradation. The results show that photocatalytic activity does not appear to be efficient to degrade NO₂ molecules. Another mechanism seems to be responsible for the reduction of the concentration of NO₂, namely adsorption. Encouraging results are obtained with NO molecules, which can be degraded by photocatalysis. The degradation observed is even greater with the more concentrated TiO₂ dispersion.

A novel magnetically recoverable, visible light active TiO₂-WO₃ composite (Fe₃O₄@SiO₂@TiO₂-WO₃) was prepared to enable the photocatalyst recovery after the degradation of bisphenol A (BPA) under simulated solar light. For comparison, the photocatalytic activity of other materials such as non-magnetic TiO₂-WO₃, Fe₃O₄@SiO₂@TiO₂, TiO₂, and the commercial TiO₂ P25 was also evaluated under the studied experimental conditions. The structure and morphology of the synthesized materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and electron dispersion spectroscopy (EDS). Moreover, Brunauer-Emmett-Teller (BET) surface area and magnetic properties of the samples were determined. The Fe₃O₄@SiO₂@TiO₂-WO₃ and TiO₂-WO₃ led to a BPA degradation of 17.50 and 27.92 %, respectively, after 2 h of the simulated solar light irradiation. Even though their activity was lower than that of P25, which degraded completely BPA after 1 h, our catalysts were magnetically separable for their further reuse in the treatment. Furthermore, the influence of the water matrix in the photocatalytic activity of the samples was studied in municipal wastewater. Finally, the identification of reaction intermediates was performed and a possible BPA degradation pathway was proposed to provide a better understanding of the degradation process. Graphical abstract ᅟ

Heavy metal soil contamination from mining and smelting has been reported in several regions around the world, and phytoextraction, using plants to accumulate risk elements in aboveground harvestable organs, is a useful method of substantially reducing this contamination. In our 3-year experiment, we tested the hypothesis that phytoextraction can be successful in local soil conditions without external fertilizer input. The phytoextraction efficiency of 15 high-yielding crop species was assessed in a field experiment performed at the Litavka River alluvium in the Příbram region of Czechia. This area is heavily polluted by Cd, Zn, and Pb from smelter installations which also polluted the river water and flood sediments. Heavy metal concentrations were analyzed in the herbaceous plants’ aboveground and belowground biomass and in woody plants’ leaves and branches. The highest Cd and Zn mean concentrations in the aboveground biomass were recorded in Salix x fragilis L. (10.14 and 343 mg kg⁻¹ in twigs and 16.74 and 1188 mg kg⁻¹ in leaves, respectively). The heavy metal content in woody plants was significantly higher in leaves than in twigs. In addition, Malva verticillata L. had the highest Cd, Pb, and Zn concentrations in herbaceous species (6.26, 12.44, and 207 mg kg⁻¹, respectively). The calculated heavy metal removal capacities in this study proved high phytoextraction efficiency in woody species; especially for Salix × fragilis L. In other tested plants, Sorghum bicolor L., Helianthus tuberosus L., Miscanthus sinensis Andersson, and Phalaris arundinacea L. species are also recommended for phytoextraction.

The spatial–temporal changing characteristics and potential ecological risk combined with local policies and industrial status were analyzed. The metal contamination was studied by sediment quality guidelines (SQGs), potential ecological risk index (PERI), and geoaccumulation index (I gₑₒ) of metals (Hg, Cr, Cd, As, Pb, and Cu) in the sediments of Xiaoqing River in Jinan from 1996 to 2014. Results showed that the concentrations of metals were in fluctuation and had a decreasing trend in the past 19 years, which was influenced by industry and policy. The concentrations of metals from upstream to downstream presented a change from low to high and then a gradual decrease which were mainly related to anthropogenic activities. The assessment suggested that Hg presented the highest levels of I gₑₒ and was the largest contributor to RI, while Cd was the second contributor. This finding indicated that Hg and Cd had a strong effect on potential ecological risk. Damatou had the largest pollution level and potential ecological risk, whereas Mulizhuang was the least polluted area. SQGs indicated that Cd was below the TEC while it was the second contributor to potential ecological risk. Indeed, the pollution control of Xiaoqing River had a certain effect, but it needs long-term effective management measures and a strengthened source control. The suggestions of targeted management have been proposed in the paper.

The study was intended to investigate heavy metal contamination levels in the rice grown in the vicinity of the mining areas of Singhbhum Copper Belt, India. The concentrations of the metals were below the Indian maximum allowable concentrations for food except for Pb, Ni, and Zn at some locations. Principal component analysis extracted three factors explaining 79.1% of the data variability. The extracted factors suggested that the sources of metals in the rice can be attributed to soil, irrigating water, and atmospheric dust deposition. High potential health risks of metal exposure from rice consumption were illustrated based on estimated daily intake (EDI) and target hazard quotient (THQ). The daily intakes of heavy metals for local adults were higher than the tolerable daily intakes provided by WHO in some samples for Cr, Fe, Ni, and V. Considering the geometric mean of the metals in rice samples of the study area, the hazard index (HI) for adult was above unity (3.09). Pb, Cu, and Cr were the key components contributing to potential non-carcinogenic risk. The HI varied from 2.24 to 12.7 among the locations indicating an appreciable heath risk to the consumers of the locally grown rice around the mining areas.

The destruction of persistent organic pollutants (POPs) is a large challenge in particular in developing and emerging economies. To date, a detailed assessment of non-combustion technologies with respect to formation of dioxins is lacking. In this study, an assessment of mechanochemical (MC) destruction technology for polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in contaminated soil remediation was conducted. Actual applied conditions of pilot-scale MC POPs destruction process indicates that the temperature increase inside the ball mills has the potential to form high levels of toxic polybrominated and polychlorinated dibenzo-p-dioxins and dibenzofurans (PXDD/Fs) when dioxin precursors are present. Therefore, the MC technology was modified for treatment of the PCB and PBDE containing soil including an efficient cooling system which could prevent the formation of PXDD/F during the destruction of PCBs and PBDEs. This is likely relevant for all contaminated soils containing relevant dioxin precursor and need to be considered for treatment of soils with MC and probably other non-combustion technologies. Graphical abstract ᅟ