Search Results (25)

This study investigated the efficiency of two advanced oxidation processes (AOPs), ozonation (O₃), and electrochemical oxidation (EO), applied individually or in combination, in the removal of contaminants of emerging concern (CECs) contained in hospital wastewaters, focusing on pharmaceuticals. The optimisation of the single technologies was performed using synthetic wastewater composed of four refractory pharmaceuticals, (carbamazepine-CBZ, lorazepam-LZP, ketoprofen-KTP, 10,11-epoxicarbamazepine-E-CBZ), first alone and then in mixture, in an initial concentration of 1 mg L⁻¹ each. Once the best operational conditions for EO and O₃ were defined, their combination (both simultaneous and sequential) was evaluated for the mixture of the selected pharmaceuticals. The treatment solution that showed the best performance was the simultaneous combination of O₃ and EO. This treatment was validated using real hospital wastewater previously treated through a moving bed biofilm reactor (MBBR), evaluating its viability by testing the toxicity of the final effluent via Vibrio fischeri inhibition tests. The obtained results showed that the simultaneous combination of O₃ and EO as the polishing step after a biological treatment is a very promising solution for hospital wastewater treatment, allowing for obtaining a non-toxic effluent and full degradation of refractory compounds. The disinfection potential of the proposed AOP was also assessed by determining Escherichia coli inactivation potential. Full article

Marimo is a type of microalgal-bacterial granular sludge (MBGS) that exists in natural water bodies. For the first time, this paper explored the feasibility of marimo in real wastewater effluent polishing, focusing on nutrient removal as compared with MBGS. The results showed that the color of marimo gradually darkened during a 21-day experiment, and the chlorophyll content increased significantly. Although marimo and MBGS showed fairly similar removal performance in terms of NO₃⁻-N and TN, marimo exhibited better phosphate removal as compared to MBGS. Marimo and MBGS contained different algae but the same bacterial phylum of Proteobacteria, including denitrifiers. In addition, marimo had a higher relative abundance of nitrite reductase than MBGS, suggesting that the denitrification process might also happen in addition to assimilation. This study is expected to initiate the application of marimo for wastewater effluent polishing and reclamation, shedding light on nature-based wastewater self-purification technology in the era of carbon neutrality. Full article

Since the conventional processes employed in most wastewater treatment plants (WWTPs) worldwide are not designed to entirely remove or oxidize emerging pollutants, which, due to their incidence and persistence, can cause damage to both the environment and human health, several options for their degradation and removal have emerged. Coupling the advanced Fenton oxidation process as a polishing or tertiary wastewater treatment alternative within conventional WWTP processes stands out among the treatment options. Therefore, the main objective of this research was to evaluate, at the laboratory level, the ability of the advanced Fenton oxidation process to oxidize triclosan, ibuprofen, DEET (N, N-diethyl-meta-toluamide), carbamazepine, caffeine, and acesulfame-K, which represent several groups of emerging pollutants in real wastewater from the second settling tank of a municipal WWTP. The compound used as a catalyst (Fe²⁺) supplier in the advanced Fenton oxidation process was ferrous sulfate heptahydrate (FeSO₄•7H₂O). The results obtained upon application showed that the advanced Fenton oxidation process could simultaneously oxidize and remove practically the total concentration of the above-mentioned emerging pollutants, except for DEET (85.21%), in conjunction with the chemical oxygen demand (COD), total suspended solids (TSS), and fecal coliforms (FC, pathogen group) in the effluent generated by the advanced Fenton oxidation process. Full article

Palm oil mill effluent (POME) is considered the most environmentally harmful when discharged without proper treatment. In addition to conventional biological treatment methods, physicochemical treatment techniques are considered alternative methods to treat POME as polishing or post-treatment techniques to meet the discharge water quality standards set by authorities. Recently, electroflotation (EF) has gained popularity in wastewater treatment owing to its high efficiency, no harmful by-products, and ease of operation. However, EF has limitations on energy consumption because high current density and long electrolysis time are often used to increase the density of gas bubbles and metallic ions produced in the EF system used in pollutant removal. Polyaluminum chloride (PAC) and cationic polyacrylamide (CPAM) are used as alternative options for the production of coagulants instead of using a sacrificial anode in EF. In this study, we hypothesized that PAC and CPAM could enhance the efficiency and reduce the specific energy consumption of EF by minimizing the electrolysis time used in POME treatment. The effects of electrolysis time, current density, and coagulant dosage on POME treatment were investigated. EF treatment at a current density of 2.5 mA/cm² has achieved 82% of turbidity and 47% of chemical oxygen demand (COD) removal after 45 min electrolysis time, consuming 0.014 kWh of specific energy for the treatment of one gram of COD. There was no improvement in terms of turbidity removal when the current density was increased from 2.5 to 5 mA/cm²; however, the COD removal efficiency was increased up to 52% at 5 mA/cm². When EF was performed at 1 A combined with PAC at a dosage of 40 mg/L and CPAM at a dosage of 20 mg/L, it was noticed that turbidity and COD removal increased up to 96% and 54%, respectively, within 15 min electrolysis. Subsequently, the specific energy consumption was reduced to 0.004 kWh (by 71%) per one gram of COD treatment. Results confirmed that the chemical coagulants could increase the POME treatment efficiency and reduce the specific energy consumption of EF. However, this method can be improved aiming at further reduction of COD by mineralizing the dissolved organic compounds to fulfill the POME discharge quality standards. Full article

Photoelectrocatalysis (PEC) has been already proposed as a polishing treatment for wastewater treatment plants (WWTPs) effluents. In this work, the impact of polarization reversal during PEC process has been studied and evaluated on the basis of the removal of organic substance and color, biodegradability of the matrix, and inactivation of the catalyst. Effluents were sampled from a full-scale WWTP and alternatively treated by electrochemical oxidation (EC), photolysis (PL), photocatalysis (PC), photoelectrocatalysis, and photoelectrocatalysis with reverse polarization (PECr). The efficiency and the kinetics of the process, in terms of removal of organic substance and color, were not affected by reverse polarization and very similar results were obtained by PEC and PECr. The biodegradability of the effluents strongly increased both by PECr (RSBR: 0.84 ± 0.07), and by PEC and PL (0.89 ± 0.11, and 0.78 ± 0.02, respectively). In the selected polarization reversal mode (100 s at −0.1 V every 500 s at 4 V, cell voltage), a similar photocurrent loss after PEC and PECr was observed, suggesting no effect on the activity of the TiO₂ mesh. This study can serve as a base for future research on polarization reversal to optimize operation parameters and exploit the procedure to preventing fouling and inactivation of the catalyst. Full article

Water pollution is a severe health concern. Several studies have recently demonstrated the efficacy of various approaches for treating wastewater from anthropogenic activities. Wastewater treatment is an artificial procedure that removes contaminants and impurities from wastewater or sewage before discharging the effluent back into the environment. It can also be recycled by being further treated or polished to provide safe quality water for use, such as potable water. Municipal and industrial wastewater treatment systems are designed to create effluent discharged to the surrounding environments and must comply with various authorities’ environmental discharge quality rules. An effective, low-cost, environmentally friendly, and long-term wastewater treatment system is critical to protecting our unique and finite water supplies. Moreover, this paper discusses water pollution classification and the three traditional treatment methods of precipitation/encapsulation, adsorption, and membrane technologies, such as electrodialysis, nanofiltration, reverse osmosis, and other artificial intelligence technology. The treatment performances in terms of application and variables have been fully addressed. The ultimate purpose of wastewater treatment is to protect the environment that is compatible with public health and socioeconomic considerations. Realization of the nature of wastewater is the guiding concept for designing a practical and advanced treatment technology to assure the treated wastewater’s productivity, safety, and quality. Full article

Domestic and industrial wastewater discharges harbor rich bacterial communities, including both pathogenic and commensal organisms that are antibiotic-resistant (AR). AR pathogens pose a potential threat to human and animal health. In wastewater treatment plants (WWTP), bacteria encounter environments suitable for horizontal gene transfer, providing an opportunity for bacterial cells to acquire new antibiotic-resistant genes. With many entry points to environmental components, especially water and soil, WWTPs are considered a critical control point for antibiotic resistance. The primary and secondary units of conventional WWTPs are not designed for the reduction of resistant microbes. Constructed wetlands (CWs) are viable wastewater treatment options with the potential for mitigating AR bacteria, their genes, pathogens, and general pollutants. Encouraging performance for the removal of AR (2–4 logs) has highlighted the applicability of CW on fields. Their low cost of construction, operation and maintenance makes them well suited for applications across the globe, especially in developing and low-income countries. The present review highlights a better understanding of the performance efficiency of conventional treatment plants and CWs for the elimination/reduction of AR from wastewater. They are viable alternatives that can be used for secondary/tertiary treatment or effluent polishing in combination with WWTP or in a decentralized manner. Full article

The management and treatment of hospital wastewater are issues of great concern worldwide. Both in the case of a dedicated treatment or co-treatment with urban wastewater, hospital effluent is generally subjected to pre-treatments followed by a biological step. A polishing treatment is suggested to promote (and guarantee) the removal of micropollutants still present and to reduce the total pollutant load released. Activated carbon-based technologies and advanced oxidation processes have been widely investigated from technical and economic viewpoints and applied in many cases. In this study, the potential exploitation of these technologies for the polishing treatment of hospital effluent is investigated by combining a Strengths, Weaknesses, Opportunities and Threats (SWOT) analysis with a Strategic Orientation (SOR) analysis. This approach allows a coherent strategy to be extracted from the SWOT-SOR data, increasing the chances of success of each technology. It emerges that both technologies present relevant and sometimes similar strengths and can present opportunities. At the same time, activated carbon-based technologies are more likely to contain the main identified threats than O₃/UV technology. The study also finds that, for both technologies, further research and development could improve their potential applications in the treatment of hospital wastewater. Full article

Located in a semi-arid to arid region, Morocco is confronting increasing water scarcity challenges. In the circular economy paradigm, the reuse of treated wastewater in agriculture is currently considered a possible solution to mitigate water shortage and pollution problems. In recent years, Morocco has made significative progress in urban wastewater treatment under the National Wastewater Program (PNA). However, rural sanitation has undergone significant delays. Therefore, an alternative technology for wastewater treatment and reuse in rural areas is investigated in this review, considering the region’s economic, social, and regulatory characteristics. Constructed wetlands (CWs) are a simple, sustainable, and cost-effective technology that has yet to be fully explored in Morocco. CWs, indeed, appear to be suitable for the treatment and reuse of wastewater in remote rural areas if they can produce effluent that meets the standards of agricultural irrigation. In this review, 29 studies covering 16 countries and different types of wastewater were collected and studied to assess the treatment efficiency of different types of CWs under different design and operational parameters, as well as their potential application in agricultural reuse. The results demonstrated that the removal efficiency of conventional contamination such as organic matter and suspended solids is generally high. CWs also demonstrated a remarkable capacity to remove heavy metals and emerging contaminants such as pharmaceuticals, care products, etc. The removal of microbial contamination, on the other hand, is challenging, and does not satisfy the standards all the time. However, it can be improved using hybrid constructed wetlands or by adding polishing treatment. In addition, several studies reported that CWs managed to produce effluent that met the requirements of wastewater reuse in agriculture of different countries or organisations including Morocco. Full article

Microalgae immobilisation can be a long-term solution for effective wastewater post-treatment. This study was conducted to evaluate the ability of immobilised Chlorococcum oleofaciens to remove contaminants from palm oil mill effluent (POME) until it complies with the POME discharge standard. First, the native dominating green microalga was isolated from a polishing POME treatment pond. Then, the microalgae cells were immobilised on sodium alginate beads and cultivated in a lab-scale-treated POME to treat it further. The immobilised microalgae cells demonstrated a high removal of total phosphorus, total nitrogen, ammonia nitrogen, and soluble chemical oxygen demand with 90.43%, 93.51%, 91.26%, and 50.72% of reduction, respectively. Furthermore, the growth rate of the microalgae fitted nicely with the Verhulst logistical model with r² of more than 0.99, indicating the model’s suitability in modelling the growth. Thus, we concluded that the species can be used for post-treatment of effluents to remove TP, TN, and ammonia nitrogen from palm oil mills until it complies with the POME effluent discharge standard. However, during the process, degradation of the beads occurred and the COD value increased. Therefore, it is not suitable to be used for COD removal. Full article

Alkaline chlorination, an efficient but high chemical cost process, is commonly employed for cyanide (CN⁻) removal from CN-rich wastewater streams. CN⁻ removal and recovery through the precipitation of Prussian Blue (Fe₄^III[Fe^II(CN)₆]₃, PB) or Turnbull’s Blue (Fe₃^II[Fe^III(CN)₆]₂, TB) were realized using iron salts, leading to a cost-effective and sustainable process producing a valuable recovery product. However, the precipitation of PB and TB is highly affected by pH and dissolved oxygen (DO). CN⁻ removal and recovery from CN-containing water by crystallization of PB and/or TB were investigated using dissolved iron that was electrochemically generated from a sacrificial iron anode under various pH values, initial CN⁻ levels (10 to100 mg/L) and DO levels (aeration, mechanical mixing, and N₂ purging). It was shown that the complexation of CN⁻ with Fe ions prevented the vaporization of HCN under acidic pH. At pH of 7 and initial CN⁻ concentration of 10 mg/L, CN⁻ removal efficiency increases linearly with increasing Fe:CN⁻ molar ratios, reaching 80% at the Fe:CN⁻ molar ratio of 5. A clear blue precipitate was observed between the pH range of 5–7. CN⁻ removal increases with increasing initial CN⁻ concentration, resulting in residual CN⁻ concentrations of 8, 7.5 and 12 mg/L in the effluent with the Fe:CN⁻ molar ratio of 0.8 for initial concentrations of 10, 50 and 100 mg CN⁻/L, respectively. A polishing treatment with H₂O₂ oxidation was employed to lower the residual CN⁻ concentration to meet the discharge limit of <1 mg CN⁻/L. Full article

One of the main problems of waste stabilization ponds (WSP) is that they cannot remove nutrients when treating wastewater. Polishing ponds (PP) can efficiently remove nitrogen and phosphorus from effluents after efficient anaerobic pretreatment. It shown that the feasibility of nutrient removal is directly related to the pH that is established in the ponds. WSP normally operate at near neutral pH, but the biological processes that develop in PP tend to cause an elevation of pH and this, in turn, triggers the mechanisms of nutrient removal in ponds. In PP oxygen production by photosynthesis predominates over the oxidation of organic material. The net oxygen production has an equivalent CO₂ consumption and this induces an increase in pH. The mechanism for nitrogen removal was identified as the desorption of ammonia from the liquid phase of the ponds. It was established that in ponds with a uniform concentration profile in the liquid phase the process developed in accordance with Fick’s law. The governing mechanism of phosphorus removal was precipitation with ions present in the wastewater, presumably calcium and magnesium. Polishing ponds can be operated with two different hydrodynamic regimes: flow-through (FTPP) and sequential batch (SBPP) ponds. The SBPP have the advantage that the pH elevation is more rapid, and that the final pH is higher. Full article

Photoelectrocatalysis (PEC), photolysis (PL), and photocatalysis (PC) were applied to increase the biodegradability of wastewaters effluents sampled from a plant collecting both municipal wastewaters and aqueous waste. In PEC, the catalyst was a porous TiO₂ photoanode obtained by plasma electrolytic oxidation and electrically polarized during operation. In PC a dispersion of TiO₂ powders was used. The same irradiation shielding, and similar catalyst surface areas were set for PC and PEC, allowing a straightforward evaluation of the catalytic effect of the electrical polarization of TiO₂ during operation. Results showed that the chemical oxygen demand (COD) and color removal rates follow the order: PEC > PL and PEC > PC. The specific biodegradability rate (SBR) increased following the same order, the PEC process allowing SBR values more than twice higher than PL and PC. The operating costs were calculated based on the electrical energy per order of COD, color, and SBR values, demonstrating that at the laboratory scale the energy demand of PEC is significantly lower than the other two tested processes. Full article

Wastewater treatment is one of the main end-of-life scenarios, as well as a possible reentry point into the environment, for anthropogenic nanoparticles (NP). These can be released from consumer products such as sunscreen or antibacterial clothing, from health-related applications or from manufacturing processes such as the use of polishing materials (nCeO₂) or paints (nTiO₂). The use of NP has dramatically increased over recent years and initial studies have examined the possibility of toxic or environmentally hazardous effects of these particles, as well as their behavior when released. This study focuses on the fate of nTiO₂ and nCeO₂ during the wastewater treatment process using lab scale wastewater treatment systems to simulate the NP mass flow in the wastewater treatment process. The feasibility of single particle mass spectroscopy (sp-ICP-MS) was tested to determine the NP load. The results show that nTiO₂ and nCeO₂ are adsorbed to at least 90 percent of the sludge. Furthermore, the results indicate that there are processes during the passage of the treatment system that lead to a modification of the NP shape in the effluent, as NP are observed to be partially smaller in effluent than in the added solution. This observation was made particularly for nCeO₂ and might be due to dissolution processes or sedimentation of larger particles during the passage of the treatment system. Full article