The co-management of different wastewater matrices can lead to synergistic effects in terms of pollutants removal. Here, the co-treatment of real municipal wastewater (MWW) and acid mine drainage ...(AMD) is comprehensively examined. Under the identified optimum co-treatment condition, i.e., 15 min contact time, 1:7 AMD to MWW liquid-to-liquid ratio, and ambient temperature and pH, the metal content of AMD (e.g., Al, Fe, Mn, Zn) was grossly (~95%) reduced along with sulphate (~92%), while MWW’s phosphate content was practically removed (≥99%). The PHREEQC geochemical model predicted the formation of (oxy)-hydroxides, (oxy)-hydro-sulphates, metals hydroxides, and other mineral phases in the produced sludge, which were confirmed using state-of-the-art analytical techniques such as FE-SEM-EDS and XRD. The key mechanisms governing pollutants removal include dilution, precipitation, co-precipitation, adsorption, and crystallization. Beneficiation and valorisation of the produced sludge and co-treated effluent could promote resource recovery paradigms in wastewater management. Overall, the co-treatment of AMD and MWW appear to be feasible, yet not practical due to the excessive volume of MWW that is required to attain the desired treatment quality. Future research could focus on chemical addition for the control of the pH and the use of (photo)-Fenton for enhancing treatment efficiency.
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•The co-treatment of acid mine drainage and municipal wastewater was successfully performed.•Optimum mixing ratios for the treatment of two wastewater streams were duly determined.•PHREEQC geochemical model and simulations were used to complement experimental results.•Advanced and state of art analytical techniques were used to verify the fate of chemical species.
Wave energy is a nascent industry characterized by high capital costs, which impede technological development and industry expansion. For this reason, new strategies are required to improve ...sustainability, reduce cost and enable wave energy harnessing even in low energy seas. Six new strategies that can make commercialization of wave energy more appealing are studied. These comprise the integration of wave energy converters (WECs) in coastal defence; tourism; desalination technology; offshore aquaculture; energy security; and power plants. WECs can axe erosion by half, or even more, in sandy beaches by creating wave shadows in their lee. Therefore, an innovative way to offset WEC high initial capital expenditure is their incorporation in coastal defence, with the added benefit of electricity production. Also, WECs can directly provide pressurized seawater for reverse osmosis desalination plants, thus achieving significant energy, cost and environmental footprint reductions. The touristic trade could also benefit from educational and interpretive displays of the wave energy technology, whilst ecotourism opportunities may arise that could address tourism seasonality. Combined offshore aquaculture facilities with WECs would benefit for reduced installation, operation, and maintenance costs, as well as addressing fossil fuel dependence in aquaculture. Moreover, WECs could be used for mitigating the intermittency of established renewables (solar and wind) and advance their penetration; while a combined WEC- pump hydropower storage scheme could secure the energy supply in remote coastal areas and islands. Finally, WECs could directly supply cooling water intake structures, such as power plants, with the huge amounts of seawater they require for cooling purposes. WEC are also able to provide high purity sterile water for core cooling in nuclear reactors and also support its circulation. For example, WECs can be introduced in coastal nuclear power plants, as to minimize the loss of coolant accident and prevent disasters similar to Fukushima’s 2011.
Industrial processes typically produce large wastewater volumes, which, if left untreated, greatly affect receiving ecosystems. However, wastewater treatment can be costly and energy-intensive, with ...the developing world particularly struggling with wastewater management. As such, simple and cost-effective solutions are urgently required with the passive (no energy or reagents) co-treatment of different wastewater matrices holding great promise. Here, wastewater from a phosphorus recovery system (chemical precipitation) was co-treated with acid mine drainage (AMD). Specifically, phosphorus-rich municipal wastewater was treated with hydrated lime, as to synthesize a wastewater-derived phosphorus product, i.e., calcium phosphate (Ca3(PO4)2), also producing a phosphorous-depleted alkaline effluent. The feasibility of valorising this effluent is examined here by using it for the passive co-treatment of real AMD. Different liquid-to-liquid (v/v) ratios were considered, with the optimum ratio (AMD to phosphate-depleted wastewater) being 1:9. The pH of the co-treated effluent was adjusted to 8.4 (from an initial value of 11.5 in the phosphorus-depleted wastewater and 2.2 in AMD), while metals (∼100% reduction of Fe, Mn, Ni, Cu, Pb, ≥99.5 for Al, Zn, and Mg, 80% for Cr, and 75% for As) and sulphate (89.26% reduction) contained in AMD were greatly removed. This was also the case for the remaining orthophosphate that was contained in the phosphorus-depleted wastewater (93.75% reduction). The electrical conductivity was also reduced in both the AMD (88.75%) and the phosphorus-depleted wastewater (69.21%), suggesting the removal of contaminants from both matrices. Results were underpinned by state-of-the-art analytical techniques, including FE-SEM/FIB/EDX, FTIR, and XRD, along with geochemical modelling (PHREEQC). Contaminants were removed through complexation, (co)adsorption, crystallization, and (co)precipitation. Overall, results suggest that the co-treatment of these wastewater matrices is feasible and could be directly scaled up (e.g., using waste stabilization ponds), while opportunities for the beneficiation of the produced sludge and for water reclamation (e.g., through membrane filtration) could also arise, further promoting the sustainably of this passive co-treatment method.
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•Acid mine drainage was passively co-treated with phosphate-depleted municipal wastewater.•No energy or reagents were consumed during their co-treatment.•The optimum liquid-to-liquid (v/v) ratio was 1:9 (AMD to phosphate-depleted wastewater).•Complexation/(co)adsorption, crystallization, and (co)precipitation was the treatment modality.•Beneficiation opportunities for the generated sludge and for water reclamation are available.
This study includes an environmental analysis of a membrane bioreactor (MBR), the objective being to quantitatively define the inventory of the resources consumed and estimate the emissions produced ...during its construction, operation and end-of-life deconstruction. The environmental analysis was done by the life cycle assessment (LCA) methodology, in order to establish with a broad perspective and in a rigorous and objective way the environmental footprint and the main environmental hotspots of the examined technology. Raw materials, equipment, transportation, energy use, as well as air- and waterborne emissions were quantified using as a functional unit, 1m3 of urban wastewater. SimaPro 8.0.3.14 was used as the LCA analysis tool, and two impact assessment methods, i.e. IPCC 2013 version 1.00 and ReCiPe version 1.10, were employed. The main environmental hotspots of the MBR pilot unit were identified to be the following: (i) the energy demand, which is by far the most crucial parameter that affects the sustainability of the whole process, and (ii) the material of the membrane units. Overall, the MBR technology was found to be a sustainable solution for urban wastewater treatment, with the construction phase having a minimal environmental impact, compared to the operational phase. Moreover, several alternative scenarios and areas of potential improvement, such as the diversification of the electricity mix and the material of the membrane units, were examined, in order to minimize as much as possible the overall environmental footprint of this MBR system. It was shown that the energy mix can significantly affect the overall sustainability of the MBR pilot unit (i.e. up to 95% reduction of the total greenhouse gas emissions was achieved with the use of an environmentally friendly energy mix), and the contribution of the construction and operational phase to the overall environmental footprint of the system.
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•The environmental sustainability of an MBR pilot unit was examined.•The functional unit of this study was the treatment of 1m3 of urban wastewater.•MBR environmental impacts are attributed mainly to the energy consumption.•The second environmental hotspot of the MBR is the membrane unit's material.•MBR environmental footprint is directly associated to the energy mix used.
Tannery wastewater (TWW) is a toxic and hazardous effluent that causes great harm to receiving ecosystems if released untreated. Here, magnesium oxide nanoparticles (MgO-NPs), synthesized from ...low-cost and readily available magnesite, were used for the treatment of real TWW under batch laboratory conditions. The optimum treatment conditions were 90 min contact time and 10 g MgO-NPs dosage per L of real TWW, under ambient pH and temperature. Results were underpinned by state-of-the-art analytical techniques, including ICP-OES, XRD, XRF, and FIB/EDS-SEM, along with geochemical modelling (PHREEQC). The removal efficiency for the main contaminants that are typically found in TWW was, from higher to lower score, Fe ≥ U ≥ Cr ≥ Mn ≥ Al ≥ Sb ≥ Cu ≥ Ni ≥ TOC ≥ COD≥ SO42−. The removal percentages for these contaminants were ≥99%, aside from Ni (97%), TOC (71%), COD (69%) and particularly SO42− (21%). The underlying mechanism for contaminants removal is linked to the scavenging of metals by the MgO-NPs, forming complexes, in combination with alkalinity addition (through MgO dissolution) that lead to contaminants precipitation. The PHREEQC geochemical model confirmed the existence of divalent, trivalent, oxyanions, and multivalent chemical species in MgO-NPs/TWW solution, including complexes. Contaminants attenuation was achieved through precipitation, co-precipitation, adsorption, and co-adsorption, while these were removed as hydroxides, sulfides, carbonates, oxide, and oxyhydrosulfates. Overall, results highlight the great potential of MgO-NPs for the sustainable management of real TWW.
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•MgO nanoparticles were successfully used for real tannery wastewater treatment.•Optimum conditions for the treatment of tannery wastewater were determined.•PHREEQC geochemical model was used to complement experimental results.•The state-of-the-art analytical techniques were used to verify the fate of pollutants.
Phosphate and nitrate enrichment largely impair aquatic ecosystem functions and services, thus comprising an emerging problem of environmental concern. The problem pertains to developing countries ...where their discharge to surface water is on the rise due to a rapid growth in population. Herein, these pollutants (phosphate and ammonia) were removed from real municipal wastewater using a simple, fast, and cost-effective process. Raw cryptocrystalline magnesite, a mineral abundant in South Africa, was simply milled and calcined (mechano-thermo processing) in order to produce the activated magnesite (feed). The feed was then used in batch processing for pollutants adsorption and precipitation from real wastewater. The process was optimised by varying the treatment or contact time, feed dosage, concentration, pH, and temperature. The feed and product mineral (produced sludge) were characterised using X-ray Diffraction (XRD), field emission scanning electron microscopy (FESEM) compatible with energy dispersive spectroscopy (EDS), and Fourier Transform Infrared Spectrometer (FTIR). It was identified that the optimal conditions differed for each pollutant, highlighting the importance of tailoring the process to fit the local wastewater characteristics and as part of a treatment train system. Specifically, maximum P removal was achieved after 5 min of mixing, using 1 g L−1 of feed, 123 mg L−1 initial phosphate concentration, pH 8 – 10, and was not affected by temperature variations; whereas, for ammonia removal, optimal conditions were 180 min, 16 g L−1 feed dosage, 80 mg L−1 initial concentration, pH 10 and temperature > 45 °C. The optimal conditions for the removal of both pollutants from real wastewater were 30 min, 6 g L−1 dosage, and ambient temperature and pH. Furthermore, Mg and Ca concentration was found to influence the process. Reduction in total dissolved solids (TDS) and electrical conductivity (EC) suggest an attenuation of chemical species. Characterisation revealed that the product mineral obtained under the optimal conditions for pollutants removal is rich in quartz, periclase, brucite, calcite, magnesite, and struvite. This was further supported by the FTIR results, which indicated the presence of Mg–O, PO43−, N–H and OH stretches. In addition, the EDS verified the presence of Mg, Ca and P in product mineral. Results are suggestive of the high efficiency of the mechano-thermo activated magnesite treatment process for phosphate and ammonia removal and struvite crystallization. Thus, this technology could valorise municipal wastewater effluents and open new horizons for the effective and sustainable management of wastewater effluents, since struvite can replace the mined phosphate fertilizers, which are rapidly depleting, in the agriculture industry.
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•Phosphate and ammonia were effectively removed from real municipal wastewater.•An integrated process based on mechano-thermo activated magnesite was employed.•Magnesium ammonium phosphate (struvite) was recovered as a process co-product.•The treatment time, feed dosage, concentration, pH, and temperature were examined.•The process was optimised and could be used for treating and valorising wastewater.
The efficacy of magnesium oxide (MgO)-bentonite clay nanocomposite particles (MgO nanoparticles embedded in powdered bentonite clay) for water and wastewater treatment applications is examined ...herein. Congo red (CR), a widely used azo dye, was used as the model contaminant. For CR concentrations ≤120 mg/L, the optimum nanocomposite dosage was ≤1 g/L, achieving CR removal ≥99% for contact times (mixing durations) ≤10 min, whereas temperature and pH had no significant effect on the treatment process. The removal of CR dye followed the pseudo-second-order model than the first order model. Furthermore, adsorption isotherms followed the Langmuir adsorption isotherm rather than the Freundlich adsorption isotherm (R2 ≥ 0.99), hence confirming monolayer homogenous adsorption. The surface morphological and physicochemical characteristics of the nanocomposite were also identified, and results suggest that CR removal was governed by electrostatic attraction between the protonated hydroxyl groups (i.e., -OH2+), embedded on the nanocomposite surface, and the negatively charged –SO3-groups of the CR dye. When used for the treatment of real printing ink wastewater, CR was practically removed (⁓100%), whereas for real printing and dyeing wastewater (PDW), a more challenging effluent that also contains salts and other contaminants, CR removal was ≥80%. Overall, the produced MgO-bentonite clay nanocomposite hold great promise for sustainable CR removal, a typical contaminant that is released by many industries including printing, tannery and textile, paper, plastic, and paint and coatings.
The wave energy potential in the Mediterranean has been estimated using numerical models. However, the veracity of these estimates in the nearshore, where wave energy harnessing is likely to take ...place, remains largely unknown. This paper compares measured wave data (AWAC/ADCP) with estimates of the third-generation spectral WAve Model (WAM), in Varkiza, Athens, a typical south facing nearshore Greek locale. Overall, good agreement in the mean wave power (Pmean) was found, but WAM overestimated the peak Pmax and had an overall error of ∼19° when estimating the mean wave direction (Mdir). The results are suggestive that WAM could act as a screening tool to identify nearshore wave energy hotspots and avoid areas with extreme sea states. Nonetheless, in-situ wave measurements are required to determine the wave energy power potential and the direction of wave propagation so as to select the appropriate conversion technology that better fits local conditions. Finally, it is suggested that existing wave energy technology should be, redesigned, downscaled and optimized to suit the milder Mediterranean wave regime, thus enacting wave energy development in Greece.
•Nearshore wave power was measured with AWAC and compared to WAM numerical model estimates.•WAM (1.16 kW/m) was in good agreement with AWAC (1.13 kW/m) when estimating mean wave power (Pmean).•Uncertainty in maximum wave power (Pmax) and mean wave direction (Mdir) was identified.•Numerical models can be used at best, as a screening tool for nearshore wave energy “hotspots”.•Field measurements are required for wave energy converters (WECs) emplacement.
The life cycle assessment of several zinc oxide (ZnO) nanostructures, fabricated by a facile microwave technique, is presented. Key synthesis parameters such as annealing temperature, varied from ...90°C to 220°C, and microwave power, varied from 110W to 710W, are assessed. The effect of these parameters on both the structural characteristics and the environmental sustainability of the nanostructures is examined. The nanostructures were characterized by means of X-ray diffraction (XRD), focused ion beam scanning electron microscopy (FIB-SEM), ultraviolet–visible spectroscopy (UV–Vis), Photoluminescence (PL) and Brunauer–Emmett–Teller (BET) analysis. Crystalline size was found to be 22.40nm at 110W microwave power, 24.83nm at 310W, and 24.01nm at 710W. Microwave power and synthesis temperature were both directly proportional to the surface area. At 110W the surface area was 10.44m2/g, at 310W 12.88m2/g, and at 710W 14.60m2/g; while it was found to be 11.64m2/g at 150°C and 18.09m2/g at 220°C. Based on these, a life cycle analysis (LCA) of the produced ZnO nanoparticles was carried out, using the ZnO surface area (1m2/g) as the functional unit. It was found that the main environmental weaknesses identified during the production process were; (a) the use of ethanol for purifying the produced nanomaterials and (b) the electricity consumption for the ZnO calcination, provided by South Africa's fossil-fuel dependent electricity source. When the effect of the key synthesis parameters on environmental sustainability was examined it was found that an increase of either microwave power (from 110 to 710W) or synthesis temperatures (from 90 to 220°C), results in higher sustainability, with the environmental footprint reduced by 27% and 41%, respectively. Through a sensitivity analysis, it was observed that an electricity mix based on renewable energy could improve the environmental sustainability of the nanoparticles by 25%.
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•Temperature and power influences nanomaterials grain size and surface area.•An increase of the surface area results in an environmentally friendlier product.•Ethanol use and electricity consumption are the main environmental weaknesses.•The use of renewable energy minimizes the nanostructures environmental impact.
This dataset manuscript describes the preparation procedure and lists the preconcentration efficiency of 112 ligands, immobilized on solid-state polymer membranes, for pollutants/elements monitoring ...in tap water and in environmentally relevant water matrices. Specifically, the energy dispersive X-ray fluorescence (EDXRF) spectra are presented, along with the preconcentration efficiency of each ligand in tap water. The main materials required for membrane preparation include the membrane matrix, a plasticizer, an ionophore, a catalyst (used only when producing anion-selective membranes), and a complexing agent, i.e. ligand. These are simply mixed, applied on a desired surface, here on a BoPET (biaxially-oriented polyethylene terephthalate) film (Mylar®), and left to dry and solidify, producing anion- or cation-selective membranes. Once the membranes are produced, they can be used even by non-specialised personnel directly on the field, which could be of particular importance for low and middle income countries (LMIC) and for remote or insular areas. The membranes can be functionalised with different ligands, suggesting that they can be used for identifying a vast array of different pollutants/elements in water matrices. Here a dataset of 112 ligands, immobilized on anion-selective membranes, are presented in terms of calcium (Ca), iron (Fe), nickel (Ni), zinc (Zn), antimony (Sb), lanthanum (La), uranium (U), copper (Cu), and gold (Au) preconcentration in tap water. Strontium (Sr) was also attempted to be measured, however, quantifiable results were not obtained. Furthermore, data for mercury (Hg) preconcentration, in cation-selective membranes, are also given. The enclosed data show that the most promising ligand for Hg, Ca, Fe, Ni, Zn, Sr, La, U, Cu, and Au preconcentration were 4-(2-Pyridylazo)resorcinol, Eriochrome Black T, di-Ammonium hydrogen citrate, 1,5-Diphenylcarbazide, dithizone, 1,1'-Carbonyldiimidazole, Bis(cyclopentadienyl)titanium dichloride, sodium dibenzyldithiocarbamate, calconcarbonsaure, and dibenzoylmethane, respectively. Interpretation of the data can be found in our previous work 1. Overall, the main intention of this dataset manuscript is to communicate and promote the adoption of the proposed method by researchers and the water industry alike. This could further advance the method and encourage the assessment of additional ligands or/and pollutants/elements, including heavy metals which are typically found in water.
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