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11 pages, 1711 KiB

Open AccessArticle

Characterization of Sludge Resulting from Chemical Coagulation and Electrocoagulation of Pumping Water from Fishmeal Factories

by Edwar Aguilar-Ascón, Armando Solari-Godiño, Miguel Cueva-Martínez, Walter Neyra-Ascón and Miguel Albrecht-Ruíz

Processes 2023, 11(2), 567; https://0-doi-org.brum.beds.ac.uk/10.3390/pr11020567 - 13 Feb 2023

Cited by 2 | Viewed by 1506

Abstract

In the fishmeal industry, seawater is used to transport fish to the factories. Due to this, “pumping water” with high concentrations of organic matter is generated that is treated via chemical coagulation before letting it into the sea. The objective of this study [...] Read more.

In the fishmeal industry, seawater is used to transport fish to the factories. Due to this, “pumping water” with high concentrations of organic matter is generated that is treated via chemical coagulation before letting it into the sea. The objective of this study is to characterize and compare the sludge obtained from conventional chemical coagulation and the sludge from the electrocoagulation process. A pilot electrocoagulation plant was built next to a chemical coagulation plant. The sludge obtained from both methodologies was analyzed for its proximal composition, its iron and aluminum content, and the fatty acid profile in its contained fat. Electrocoagulation was found to produce sludge with a higher concentration of lipids and ash, which indirectly confirmed that it removes more organic pollutants and salts than chemical coagulation. The contents of aluminum and iron in the sludge obtained by electrocoagulation were 4.2% and 0.025%, respectively, while those in the sludge obtained from chemical coagulation were 0.01% and 4.8%, respectively. Aluminum comes from the sacrificial electrode of the electrocoagulation tank, while iron comes from the salts used in chemical coagulation. The sum of w-3 fatty acid values (EPA + DHA) was 12.5% and 18.8% for sludges from the electrocoagulation and chemical coagulation processes, respectively, so we can assume that electrocoagulation is a more oxidizing process than chemical coagulation. Due to their high organic load, both sludges must be assessed as an alternative feed ingredient. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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16 pages, 7000 KiB

Open AccessArticle

Increase by Substitution of Galvanized Steel for Aluminum Mirrors in the UV Solar Radiation in Canal with Fins and Side Panels That Disinfect Wastewater

by Pedro Cisterna-Osorio, María Galvez-Gonzalez, Miguel Moraga-Chaura and Sergio Quijada-Vera

Processes 2023, 11(1), 84; https://0-doi-org.brum.beds.ac.uk/10.3390/pr11010084 - 28 Dec 2022

Viewed by 1283

Abstract

The need arises to seek new depuration technological responses aimed at the reuse of wastewater, which requires the development and promotion of economically and environmentally sustainable technologies. In this paper, it studies an improvement to a disinfection system sustainable, low-cost, patented in 2019, [...] Read more.

The need arises to seek new depuration technological responses aimed at the reuse of wastewater, which requires the development and promotion of economically and environmentally sustainable technologies. In this paper, it studies an improvement to a disinfection system sustainable, low-cost, patented in 2019, and based on solar energy. The water passes through a canal of reflective material in the continuous regime, and in the batch regime, the water remains in the canal. The panels are located parallel to the lateral faces of the canal. The fraction of the radiation reflected outside the canal reaches the reflective side panels that return the radiation to the canal. These panels concentrate the radiation in the canal through reflection. The disinfectant canal with fins and side panels uses ultraviolet radiation to eliminate the bacterial load carried by treated wastewater. For this reason, the present work analyzes the incidence in the area of influence of the disinfectant canal. When reflective aluminum mirrors were installed on the sloping walls of the canal, global radiation increased by 4%, when they were used on the side panels, it increased 3%, and when the aluminum mirrors were used on the canal walls and side panels, it increased 8%. The important thing about this work is that it opens windows for improving the system through materiality so the new challenge is the search for the optimal material considering the impact on global radiation and consequently on the bacteriological elimination. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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15 pages, 1676 KiB

Open AccessArticle

Development of a Continuous Hydrothermal Treatment Process for Efficient Dewatering of Industrial Wastewater Sludge

by Douwe S. Zijlstra, Esther Cobussen-Pool, Dennis J. Slort, Mark Visser, Pavlina Nanou, Jan R. Pels and Heather E. Wray

Processes 2022, 10(12), 2702; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10122702 - 14 Dec 2022

Cited by 3 | Viewed by 1629

Abstract

Sludges from the papermaking industry represent a challenging residue stream that is difficult to dewater using conventional processes. The successful development and scale-up of innovative processes from lab- to pilot- to industrial-scale are required to tackle challenges for waste treatment, including paper sludges. [...] Read more.

Sludges from the papermaking industry represent a challenging residue stream that is difficult to dewater using conventional processes. The successful development and scale-up of innovative processes from lab- to pilot- to industrial-scale are required to tackle challenges for waste treatment, including paper sludges. Biological paper sludge was treated via a mild hydrothermal carbonization process (TORWASH^®) to improve dewaterability of the sludge, including long-duration, continuous testing. Initial lab-scale experiments indicated the optimal treatment temperature for sludge dewatering was 190 °C. Dewaterability improved with increasing temperature, but the obtained solid yield decreased. Scaling-up to a continuous flow pilot plant required a temperature of 200 °C to achieve optimum dewatering. Pilot-scale hydrothermal treatment and dewatering resulted in solid cakes with an average dry matter content of 38% and a solid yield of 39%. This study demonstrates the benefits of hydrothermal carbonization for the dewatering of biological paper sludge without the use of dewatering aids such as fiber sludge or polyelectrolytes. The results also demonstrate the successful adaptation of a lab-scale batch process to a pilot-scale continuous flow process for hydrothermal carbonization of industrial wastewater sludge. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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14 pages, 4565 KiB

Open AccessArticle

Optimization of the Biotreatment of GTL Process Water Using Pseudomonas aeruginosa Immobilized in PVA Hydrogel

by Somaya A. Ahmed, Riham Surkatti, Muneer M. Ba-Abbad and Muftah H. El-Naas

Processes 2022, 10(12), 2568; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10122568 - 02 Dec 2022

Viewed by 1347

Abstract

The COD reduction in gas to liquid (GTL) process water was optimized using response surface methodology (RSM). The biodegradation process was carried out in a spouted bed bioreactor (SBBR) using Pseudomonas aeruginosa immobilized in polyvinyl alcohol (PVA) gel. Different factors affecting the biological [...] Read more.

The COD reduction in gas to liquid (GTL) process water was optimized using response surface methodology (RSM). The biodegradation process was carried out in a spouted bed bioreactor (SBBR) using Pseudomonas aeruginosa immobilized in polyvinyl alcohol (PVA) gel. Different factors affecting the biological treatment of GTL process water (PW) were investigated. Three variables including PVA volume fraction, initial COD, and pH were investigated in the batch experiments. The biodegradation experiments were carried out by varying the initial COD values from 1000 to 3000 mg/L, pH from 5 to 8, and PVA v% from 20 to 30%. The maximum COD reduction was estimated to occur at an initial COD of 2595 mg/L, PVA v% of 27%, and pH of 7.3. At optimum conditions, the bioreactor system was able to achieve a maximum COD reduction of 89%, which is quite close to the RSM prediction value of 90%. The optimum operating conditions were used to carry out continuous biodegradation, and the results indicated that the COD reduction increased from 60% to 62% with an increase in the air flow rate from 2 to 3.3 L_a/L_r.min. However, by increasing the liquid flow rate from 2.1 to 4.2 mL/min and back to 2.1 mL/min, the COD reduction decreased from 66% to 39%. The system responded quickly to the change in liquid flow rate and returned to the initial COD level. This indicates that the system is highly stable and can easily recover. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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16 pages, 2630 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Occurrence of Selected Emerging Contaminants in Southern Europe WWTPs: Comparison of Simulations and Real Data

by Daniel Sol, Andrea Menéndez-Manjón, Paula Arias-García, Amanda Laca, Adriana Laca, Amador Rancaño and Mario Díaz

Processes 2022, 10(12), 2491; https://doi.org/10.3390/pr10122491 - 23 Nov 2022

Cited by 3 | Viewed by 1360

Abstract

Emerging contaminants (ECs) include a diverse group of compounds not commonly monitored in wastewaters, which have become a global concern due to their potential harmful effects on aquatic ecosystems and human health. In the present work, six ECs (ibuprofen, diclofenac, erythromycin, triclosan, imidacloprid [...] Read more.

Emerging contaminants (ECs) include a diverse group of compounds not commonly monitored in wastewaters, which have become a global concern due to their potential harmful effects on aquatic ecosystems and human health. In the present work, six ECs (ibuprofen, diclofenac, erythromycin, triclosan, imidacloprid and 17α-ethinylestradiol) were monitored for nine months in influents and effluents taken from four wastewater treatment plants (WWTPs). Except for the case of ibuprofen, which was in all cases in lower concentrations than those usually found in previous works, results found in this work were within the ranges normally reported. Global removal efficiencies were calculated, in each case being very variable, even when the same EC and facility were considered. In addition, the SimpleTreat model was tested by comparing simulated and real ibuprofen, diclofenac and erythromycin data. The best agreement was obtained for ibuprofen which was the EC with the highest removal efficiencies. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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8 pages, 2660 KiB

Open AccessCommunication

Bioremediation of Crude Oil by Haematococcus Pluvialis: A Preliminary Study

by Rosa Paola Radice, Maria Sansone, Gabriele D’Arienzo, Antonio Scopa and Giuseppe Martelli

Processes 2022, 10(12), 2472; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10122472 - 22 Nov 2022

Viewed by 1685

Abstract

Nowadays, oil pollution is one of the main environmental problems. The current methods for recovering spills mainly involve chemical agents, but scientific research has focused on more natural and less harmful techniques for the environment, including a consortium of bacteria and microalgae to [...] Read more.

Nowadays, oil pollution is one of the main environmental problems. The current methods for recovering spills mainly involve chemical agents, but scientific research has focused on more natural and less harmful techniques for the environment, including a consortium of bacteria and microalgae to clean up water contaminated by hydrocarbons. The purpose of this preliminary study was to evaluate the ability of a microalga belonging to Chlorophyceae to grow in the presence of crude oil and remove the principal contaminants. H. pluvialis, which is usually used for nutraceutical purposes, thanks to the production of astaxanthin, was able to grow in anaerobic conditions, varying its metabolism from autotrophic to heterotrophic, exploiting the carbon present in the solution deriving from the presence of 1% of crude oil. Furthermore, the results of bioremediation showed a relevant reduction in chemical pollutants such as nitrate, fluoride, sulfate, and phosphate. The most important aspect of the study was the reduction after 160 days in the hydrocarbon concentration inside not only the culture medium (−32%) but also the algal biomass (−80.25%), demonstrating an optimized degradation rather than a simple absorption inside the alga. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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11 pages, 682 KiB

Open AccessArticle

Fermentation Wastes from Chrypthecodinium cohnii Lipid Production for Energy Recovery by Anaerobic Digestion

by Ana Eusébio, Patrícia Moniz, Teresa Lopes da Silva and Isabel Paula Marques

Processes 2022, 10(11), 2463; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10112463 - 21 Nov 2022

Cited by 1 | Viewed by 1096

Abstract

Wastes generated during the cultivation of marine microalga Crypthecodinium cohnii and after the lipid extraction process, were energetically valorized into biogas production through anaerobic digestion (AD). The tested wastes were extracted microalgae (Ae) with hexane (AeH) using supercritical extraction methods (AeS) and the [...] Read more.

Wastes generated during the cultivation of marine microalga Crypthecodinium cohnii and after the lipid extraction process, were energetically valorized into biogas production through anaerobic digestion (AD). The tested wastes were extracted microalgae (Ae) with hexane (AeH) using supercritical extraction methods (AeS) and the supernatant obtained after culture medium centrifugation (M). The digestion of the algae biomass in the admixture with the supernatant medium (AeH+M+I and AeS+M+I) provided a higher methane content and a higher methane yield (582 and 440 L CH₄/kg VS) than the substrates Ae and M, individually digested (155 and 96 L CH₄/kg VS, respectively). Flow cytometry monitoring processes during AD indicated that the yield of the accumulated biogas was influenced by the operating conditions. The mixture of AeH+M+I was the only assay with a proportion of cells with less damaged membranes after AD, providing the highest methane yield and productivity (582 L CH₄/kg VS and 31 L CH₄/kg VS.d, respectively) and the highest energetic potential of 5.8 KWh/kg VS of all the substrates. From the results, AD integration to lipid production by C. cohnii to recover energy from the generated wastes enhanced the sustainability of the entire process and promoted the practice of zero waste. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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13 pages, 1840 KiB

Open AccessArticle

Simultaneous Anaerobic Ammonium Oxidation and Electricity Generation in Microbial Fuel Cell: Performance and Electrochemical Characteristics

by Jiqiang Zhang, Zaiwang Zhang, Kun Rong, Haiying Guo, Jing Cai, Yajuan Xing, Lili Ren, Jiayun Ren, Tao Wu, Jialiang Li and Ping Zheng

Processes 2022, 10(11), 2379; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10112379 - 12 Nov 2022

Cited by 1 | Viewed by 1693

Abstract

In this study, a microbial fuel cell (MFC) that can achieve simultaneous anode anaerobic ammonium oxidation (anammox) and electricity generation (anode anammox MFC) by high-effective anammox bacteria fed with purely inorganic nitrogen media was constructed. As the influent concentrations of ammonium (NH₄ [...] Read more.

In this study, a microbial fuel cell (MFC) that can achieve simultaneous anode anaerobic ammonium oxidation (anammox) and electricity generation (anode anammox MFC) by high-effective anammox bacteria fed with purely inorganic nitrogen media was constructed. As the influent concentrations of ammonium (NH₄⁺-N) and nitrite (NO₂⁻-N) gradually increased from 25 to 250 mg/L and 33–330 mg/L, the removal efficiencies of NH₄⁺-N, NO₂⁻-N and TN were over 90%, 90% and 80%, respectively, and the maximum volumetric nitrogen removal rate reached 3.01 ± 0.27 kgN/(m³·d). The maximum voltage and maximum power density were 225.48 ± 10.71 mV and 1308.23 ± 40.38 mW/m³, respectively. Substrate inhibition took place at high nitrogen concentrations (NH₄⁺-N = 300 mg/L, NO₂⁻-N = 396 mg/L). Electricity production performance significantly depended upon the nitrogen removal rate under different nitrogen concentrations. The reported low coulombic efficiency (CE, 4.09–5.99%) may be due to severe anodic polarization. The anode charge transfer resistance accounted for about 90% of the anode resistance. The anode process was the bottleneck for energy recovery and should be further optimized in anode anammox MFCs. The high nitrogen removal efficiency with certain electricity recovery potential in the MFCs suggested that anode anammox MFCs may be used in energy sustainable nitrogen-containing wastewater treatment. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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14 pages, 1114 KiB

Open AccessArticle

Degradation of Polyvinyl Chloride (PVC) Waste with Supercritical Water

by Maja Čolnik, Petra Kotnik, Željko Knez and Mojca Škerget

Processes 2022, 10(10), 1940; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10101940 - 26 Sep 2022

Cited by 9 | Viewed by 2427

Abstract

The chemical degradation of PVC waste in SCW between 400 and 425 °C and reaction times from 30 to 60 min was studied. The PVC waste in SCW decomposed into the gas, oil, water soluble, and solid phases. The highest yield of the [...] Read more.

The chemical degradation of PVC waste in SCW between 400 and 425 °C and reaction times from 30 to 60 min was studied. The PVC waste in SCW decomposed into the gas, oil, water soluble, and solid phases. The highest yield of the gas and oil phases was achieved at the temperature of 425 °C after 60 min. By increasing the reaction time at 400 °C, the yield of chloride ions in the aqueous phase increased and reached the maximum at 60 min. The gas and oil phases contained many valuable compounds similar to crude oil. Alkanes and chloroalkanes; alkenes, alicyclic, and aromatic hydrocarbons; as well as alcohols were the main groups of hydrocarbons in the oil phase, while the gas phase contained only light hydrocarbons (C₁–C₆), CO_2, and small amounts of H₂. This confirmed that the largest chlorine content remains in the aqueous phase and does not pass into the gas phase. It can be concluded that SCW presents effective decomposition media for plastic waste. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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15 pages, 5469 KiB

Open AccessArticle

Preparation and Phosphorus Removal Performance of Zr–La–Fe Ternary Composite Adsorbent Embedded with Sodium Alginate

by Xiuling Li, Hanyu Liang, Yanling Mo and Yansong Wei

Processes 2022, 10(9), 1761; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10091761 - 02 Sep 2022

Cited by 2 | Viewed by 1235

Abstract

Using single metal salts of zirconium, lanthanum, and iron as raw materials and sodium alginate as a cross-linking agent, a new composite adsorbent was prepared via the co-precipitation method and embedding immobilization technology, and its phosphorus adsorption performance in wastewater was evaluated. Scanning [...] Read more.

Using single metal salts of zirconium, lanthanum, and iron as raw materials and sodium alginate as a cross-linking agent, a new composite adsorbent was prepared via the co-precipitation method and embedding immobilization technology, and its phosphorus adsorption performance in wastewater was evaluated. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used for characterization, and a 0.5 mol·L⁻¹ sodium hydroxide solution was used to regenerate the adsorbent. The experimental results demonstrated that the adsorption rate reached 99.88% when the wastewater volume was 50 mL, the initial concentration of phosphorus-containing wastewater was 5 mg·L⁻¹, the pH was 5, the dosage of composite adsorbent was 0.2 g, and the adsorption time was 200 min. The prepared adsorbent could reduce the initial phosphorus concentration of 5 mg·L⁻¹ to 0.006 mg·L⁻¹ in simulated wastewater, and from 4.17 mg·L⁻¹ in urban sewage to undetected (<0.01 mg·L⁻¹), thus meeting the discharge requirements of the grade A standard of the Urban Sewage Treatment Plant Pollutant Discharge Standard (GB18918-2002). The adsorption process conformed to the Freundlich adsorption isothermal equation and quasi-second-order kinetic equation, and the adsorption reaction was exothermic and spontaneous. More importantly, after three lye regeneration tests, the removal rate of phosphorus in water remained above 68%, that is, the composite adsorbent could be reproducibly fabricated and recycled. The characterization results showed that the surface of the composite adsorbent was rough, with a complex pore structure. After phosphorus removal, the surface morphology of the composite adsorbent showed a similar honeycomb structure, with a P-H, P-O stretching vibration peak and a characteristic P2p peak. At the same time, the proportion of hydroxyl groups (M-OH) on the metal surface decreased after adsorption. Our findings thus demonstrate that the mechanism of phosphorus removal is mainly based on the coordination exchange reaction between phosphate and metal active sites and surface hydroxyl groups, resulting in the formation of granular phosphate deposits. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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11 pages, 1126 KiB

Open AccessArticle

Comparison between Regression Models, Support Vector Machine (SVM), and Artificial Neural Network (ANN) in River Water Quality Prediction

by Nur Najwa Mohd Rizal, Gasim Hayder, Mohammed Mnzool, Bushra M. E. Elnaim, Adil Omer Yousif Mohammed and Manal M. Khayyat

Processes 2022, 10(8), 1652; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10081652 - 20 Aug 2022

Cited by 19 | Viewed by 2887

Abstract

Both anthropogenic and natural sources of pollution are regionally significant. Therefore, in order to monitor and protect the quality of Langat River from deterioration, we use Artificial Intelligence (AI) to model the river water quality. This study has applied several machine learning models [...] Read more.

Both anthropogenic and natural sources of pollution are regionally significant. Therefore, in order to monitor and protect the quality of Langat River from deterioration, we use Artificial Intelligence (AI) to model the river water quality. This study has applied several machine learning models (two support vector machines (SVMs), six regression models, and artificial neural network (ANN)) to predict total suspended solids (TSS), total solids (TS), and dissolved solids (DS)) in Langat River, Malaysia. All of the models have been assessed using root mean square error (RMSE), mean square error (MSE) as well as the determination of coefficient (R²). Based on the model performance metrics, the ANN model outperformed all models, while the GPR and SVM models exhibited the characteristic of over-fitting. The remaining machine learning models exhibited fair to poor performances. Although there are a few researches conducted to predict TDS using ANN, however, there are less to no research conducted to predict TS and TSS in Langat River. Therefore, this is the first study to evaluate the water quality (TSS, TS, and DS) of Langat River using the aforementioned models (especially SVM and the six regression models). Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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11 pages, 862 KiB

Open AccessArticle

Extraction of Polyphenols from Unripened Coffee (Coffea Arabica) Residues and Use as a Natural Coagulant for Removing Turbidity

by Diana Marcela Cuesta-Parra, Felipe Correa-Mahecha, Juan Pablo Rodríguez-Miranda, Octavio José Salcedo-Parra and Edwin Rivas-Trujillo

Processes 2022, 10(6), 1105; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10061105 - 01 Jun 2022

Cited by 3 | Viewed by 2011

Abstract

The coffee agribusiness generates significant amounts of waste that becomes an environmental problem in producing countries. For example, synthetic coagulants have sustainability disadvantages. Immature coffee beans are collected together with mature beans, and their high polyphenol content makes them unsuitable for coffee production [...] Read more.

The coffee agribusiness generates significant amounts of waste that becomes an environmental problem in producing countries. For example, synthetic coagulants have sustainability disadvantages. Immature coffee beans are collected together with mature beans, and their high polyphenol content makes them unsuitable for coffee production and commercialization. This paper aims to test the coagulant activity of polyphenols extracted from Coffea arabica residues in synthetic water samples to use them as raw material for producing a natural coagulant based on bioeconomy. It would thus allow immature coffee beans to recover, avoiding their inadequate disposition. An extract was obtained from residual green coffee beans using the ultrasound-assisted separation technique with a mixture of ethanol and water in a 1:1 ratio. The Folin–Ciocalteu method was applied for the total polyphenols quantification, resulting in a concentration of 73.54 ± 0.05 mg GAE (Gallic Acid Equivalent) per gram on a dry coffee basis (GAE/gDB). The synthetic water for the study was prepared with kaolin, showing initial turbidity of 520.90 ± 0.1 NTU (Nephelometric Turbidity Units). First, the effect of pH was determined on the coagulant activity at a fixed dose of polyphenols 2.6 mg GAE/L. Second, the dose and pH results were evaluated using a multilevel factorial design with 5.20, 3.90, 2.60, and 1.30 mg GAE/L doses and pH at 2.5, 3.0, 3.5, and 4.0. Third, the turbidity removal achieved was 99.94% at a dose of 3.9 ± 0.05 mg GAE/L and a pH of 2.5. Fourth, the result was compared with the turbidity removal of the aluminum sulfate dosed at a concentration of 3 mg/L on the same water type, with a pH variation between 5.5 and 8, obtaining 98.69% of turbidity removed. Finally, the research demonstrated that the polyphenols extracted from the residues of the Coffea arabica species possess a high electrochemical affinity that would allow removing turbidity by coagulation in waters at specific pH levels with similar removals to those obtained with aluminum sulfate. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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30 pages, 1789 KiB

Open AccessArticle

Circular Economy Indicators for the Assessment of Waste and By-Products from the Palm Oil Sector

by Pedro-Antonio Cárdenas Bejarano, Juan-Pablo Rodriguez-Miranda, Rayma Ireri Maldonado-Astudillo, Yanik Ixchel Maldonado-Astudillo and Ricardo Salazar

Processes 2022, 10(5), 903; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10050903 - 03 May 2022

Cited by 7 | Viewed by 2682

Abstract

A circular economy (CE) promotes the reuse, reincorporation and valuation of waste and by-products under the framework of sustainable development through models and indicators that evaluate scenarios of second use and reduction in non-incorporated outputs to reduce negative externalities and pressures on the [...] Read more.

A circular economy (CE) promotes the reuse, reincorporation and valuation of waste and by-products under the framework of sustainable development through models and indicators that evaluate scenarios of second use and reduction in non-incorporated outputs to reduce negative externalities and pressures on the dimensions of development. A CE model applied to the transformation process of RFF in agro-industries is developed, which consists in the identification of the residue coefficients of EFB (22.48% ± 0.8), fiber (15.58% ± 0.49), husk (6.03% ± 0.66) and ash (0.55% ± 1.67). Subsequently, the valuation trends of potential second use were verified through a systematic review, which allowed the construction of the scenario of avoided costs of USD 678,721.5, a product of the total use of the outputs under bioenergy and nutrient source approaches. Finally, the RRSFM indicator was constructed, which can reach the level of 72% and a degree of improvement of 26% by 2026. In parallel, the HCRRS indicator revealed a reduction of 57.1%, 59.6% and 82.8% in emissions of t CO_2-eq product in the comparison of scenarios for the use of residues and by-products of palm oil from agro-industries in the Casanare Department. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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22 pages, 2767 KiB

Open AccessArticle

Using Periphyton Assemblage and Water Quality Variables to Assess the Ecological Recovery of an Ecologically Engineered Wetland Affected by Acid Mine Drainage after a Dry Spell

by Paul Johan Oberholster, Yolandi Schoeman, Johannes Christoff Truter and Anna-Maria Botha

Processes 2022, 10(5), 877; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10050877 - 29 Apr 2022

Cited by 4 | Viewed by 2085

Abstract

The Grootspruit valley bottom wetland in South Africa, due to the impact of acid mine drainage (AMD) from an abandoned coal mine, was severely degraded before ecologically engineered interventions, as a passive treatment process, in 2014. The surface water flow of the wetland [...] Read more.

The Grootspruit valley bottom wetland in South Africa, due to the impact of acid mine drainage (AMD) from an abandoned coal mine, was severely degraded before ecologically engineered interventions, as a passive treatment process, in 2014. The surface water flow of the wetland was redirected using concrete structures to enlarge the surface area of the wetland by 9.4 ha and to optimize passive treatment. Although the ecologically engineered interventions showed an improvement in water quality after the rewetting of the enlarged wetland areas, the 2016 drought had a devastating effect on the wetland’s water quality. Limited natural removal of metals and sulfate concentrations by the wetland occurred during the 2016 drought, when compared with the 2015 pre-drought conditions. This period showed higher concentrations of metals, sulfate (SO₄²⁻), and electrical conductivity (EC) associated with the acidic surface water. Of particular interest was an observation of a substantial shift in pollutant-tolerant algae species in the ecologically engineered wetland outflow between the years 2015 and 2016. During the dry spell period of 2016, the diatoms Gyrosigma rautenbachiae (Cholnoky), Craticula buderi (Brebisson), and Klebsormidium acidophilum (Noris) were observed at the outflow. The latter species were not observed during the wetland surveys of 2015, before the dry spell. From late 2017 onwards, after the drought, environmental conditions started improving. In 2018, periphyton indicator species and the surface water quality were comparable to the wetland’s recorded status pre-2016. The study revealed not only a regime shift, but also an ecological function loss during the drought period of 2016, followed by recovery after the dry spell. A distinct reduction in SO₄²⁻, sodium (Na), magnesium (Mg), EC, manganese (Mn), iron (Fe), silicon (Si), aluminum (Al), and pH, following the 2016 drought, highlights the utilization of water quality variables to not only assess the passive treatment responses of an ecologically engineered wetland, but also the progress relating to ecological recovery. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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23 pages, 55606 KiB

Open AccessArticle

Assessment of Natural Zeolite Clinoptilolite for Remediation of Mercury-Contaminated Environment

by Ivona Nuić, Mateja Gosar, Marin Ugrina and Marina Trgo

Processes 2022, 10(4), 639; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10040639 - 24 Mar 2022

Cited by 1 | Viewed by 1738

Abstract

The soil at ancient roasting sites in the surroundings of the Idrija mine (Slovenia) is highly contaminated with mercury. To assess the impact of mercury on groundwater by infiltration and find an eco-friendly remediation method, the leaching of mercury from the soil containing [...] Read more.

The soil at ancient roasting sites in the surroundings of the Idrija mine (Slovenia) is highly contaminated with mercury. To assess the impact of mercury on groundwater by infiltration and find an eco-friendly remediation method, the leaching of mercury from the soil containing 1347 mg Hg/kg, followed by sorption of the total leached mercury on cost-effective natural zeolite (NZ) clinoptilolite, was performed. The leaching of soil in ultrapure water of pH_o = 3.00–11.46 after 24 h resulted in the total leached mercury concentration in the range 0.33–17.43 µg/L. Much higher concentrations (136.9–488.0 µg/L) were determined after the first few hours of leaching and were high above the maximum permissible level in water for human consumption. The NZ showed very good sorption of the total leached mercury, with a maximum removal efficiency of 94.2%. The leaching of mercury in presence of the NZ resulted in a significant decrease of the total leached mercury (1.9–20.3 µg/L compared to 12.8–42.2 µg/L), with removal efficiencies up to 90.5%, indicating immobilization of mercury species. The NZ has a great potential for economically viable remediation of mercury-contaminated environment. However, efforts should be made in the further study of mercury leachability to reduce the mercury concentration in water to acceptable levels. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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12 pages, 16801 KiB

Open AccessFeature PaperArticle

Bioleaching and Selective Precipitation for Metal Recovery from Basic Oxygen Furnace Slag

by Klemens Kremser, Sophie Thallner, Sabine Spiess, Jiri Kucera, Tomas Vaculovic, Dalibor Všianský, Marianne Haberbauer and Georg M. Guebitz

Processes 2022, 10(3), 576; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10030576 - 15 Mar 2022

Cited by 7 | Viewed by 2728

Abstract

Decreasing ore grades and an increasing consumption of metals has led to a shortage of important primary raw materials. Therefore, the urban mining of different deposits and anthropogenic stocks is of increasing interest. Basic oxygen furnace (BOF) slag is produced in huge quantities [...] Read more.

Decreasing ore grades and an increasing consumption of metals has led to a shortage of important primary raw materials. Therefore, the urban mining of different deposits and anthropogenic stocks is of increasing interest. Basic oxygen furnace (BOF) slag is produced in huge quantities with the so-called Linz-Donawitz process and contains up to 5.2, 0.9, 0.1, and 0.07% of Mn, Al, Cr, and V, respectively. In the present study, sulfur-oxidizing Acidithiobacillus thiooxidans and iron- and sulfur-oxidizing Acidithiobacillus ferridurans were applied in batch and stirred tank experiments to investigate the biological extraction of metals from BOF slag. In the batch experiments, up to 96.6, 52.8, 41.6, and 29.3% of Cr, Al, Mn, and V, respectively, were recovered. The stirred tank experiments, with increasing slag concentrations from 10 to 75 g/L, resulted in higher extraction efficiencies for A. ferridurans and lower acid consumption. Selective metal precipitation was performed at pH values ranging between 2.5 and 5.0 to study the recovery of Mn, Al, Cr, and V from the biolixiviant. Selective precipitation of V and Cr was achieved at pH 4.0 from A. thiooxidans biolixiviant, while Fe and V could be selectively recovered from A. ferridurans biolixiviant at pH 3.0. This work revealed the potential of BOF slag as an artificial ore for urban mining and demonstrated that combining bioleaching and selective precipitation is an effective method for sustainable metal recovery. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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9 pages, 1273 KiB

Open AccessArticle

Titanium-Containing Coagulants in Wastewater Treatment Processes in the Alcohol Industry

by Evgenii Kuzin, Yulia Averina, Andrei Kurbatov, Natalia Kruchinina and Veniamin Boldyrev

Processes 2022, 10(3), 440; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10030440 - 22 Feb 2022

Cited by 6 | Viewed by 1681

Abstract

As part of the work, studies of the quality of wastewater from alcohol production were carried out; the main characteristics were determined, such as the charge of dispersed particles and the content of organic compounds and fats. A comparison is made of the [...] Read more.

As part of the work, studies of the quality of wastewater from alcohol production were carried out; the main characteristics were determined, such as the charge of dispersed particles and the content of organic compounds and fats. A comparison is made of the effectiveness of titanium salts, traditional aluminum, and iron-containing coagulants. It has been established that titanium salts are much more effective than traditional reagents, but their high cost significantly limits the scope of their application. The possibility of increasing the efficiency of traditional coagulants by adding various titanium salts in an amount of up to 10% of the mass has been proved. It has been established that the addition of titanium compounds to aluminum or iron-containing coagulants makes it possible to increase the cleaning efficiency by an average of 10–20% while a significant reduction in the dose of reagents is possible, which will have a positive effect on the cost of the cleaning process. It was found that the addition of titanium salts to a coagulant based on aluminum sulfate allows not only an increase in the cleaning efficiency but also further intensifies the processes of sedimentation and filtration of coagulation sludge, which will significantly reduce the size of the treatment equipment and reduce capital costs. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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12 pages, 4045 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Comparative Metagenomics of Anaerobic Digester Communities Reveals Sulfidogenic and Methanogenic Microbial Subgroups in Conventional and Plug Flow Residential Septic Tank Systems

by James Naphtali, Alexander W. Y. Chan, Faizan Saleem, Enze Li, Jacob Devries and Herb E. Schellhorn

Processes 2022, 10(3), 436; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10030436 - 22 Feb 2022

Cited by 4 | Viewed by 2280

Abstract

On-site wastewater treatment systems (OWTS) are primarily monitored using physiochemical factors, including chemical oxygen demand (COD) and residual total suspended solids (TSS), which are indirect measures of the microbial action during the anaerobic digestion process. Changes in anaerobic digester microbial communities can alter [...] Read more.

On-site wastewater treatment systems (OWTS) are primarily monitored using physiochemical factors, including chemical oxygen demand (COD) and residual total suspended solids (TSS), which are indirect measures of the microbial action during the anaerobic digestion process. Changes in anaerobic digester microbial communities can alter the digester performance, but this information cannot be directly obtained from traditional physicochemical indicators. The potential of metagenomic DNA sequencing as a tool for taxonomic and functional profiling of microbial communities was examined in both common conventional and plug flow-type anaerobic digesters (single-pass and recirculating). Compared to conventional digesters, plug flow-type digesters had higher relative levels of sulfate-reducing bacteria (Desulfovibrio spp.) and hydrogenotrophic methanogens (Methanospirillum spp.). In contrast, recirculating anaerobic digesters were enriched with denitrifier bacteria and hydrogenotrophic methanogens, and both were significantly correlated with physicochemical factors such as COD and TSS. Stratification of microbial communities was observed along the digester treatment process according to hydrolytic, acidogenic, acetogenic, and methanogenic subgroups. These results indicate that the high-throughput DNA sequencing may be useful as a monitoring tool to characterize the changes in bacterial communities and the functional profile due to differences in digester design in on-site systems. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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12 pages, 2268 KiB

Open AccessFeature PaperArticle

Kinetics Study of Hydrothermal Degradation of PET Waste into Useful Products

by Maja Čolnik, Darja Pečar, Željko Knez, Andreja Goršek and Mojca Škerget

Processes 2022, 10(1), 24; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10010024 - 23 Dec 2021

Cited by 7 | Viewed by 3894

Abstract

Kinetics of hydrothermal degradation of colorless polyethylene terephthalate (PET) waste was studied at two temperatures (300 °C and 350 °C) and reaction times from 1 to 240 min. PET waste was decomposed in subcritical water (SubCW) by hydrolysis to terephthalic acid (TPA) and [...] Read more.

Kinetics of hydrothermal degradation of colorless polyethylene terephthalate (PET) waste was studied at two temperatures (300 °C and 350 °C) and reaction times from 1 to 240 min. PET waste was decomposed in subcritical water (SubCW) by hydrolysis to terephthalic acid (TPA) and ethylene glycol (EG) as the main products. This was followed by further degradation of TPA to benzoic acid by decarboxylation and degradation of EG to acetaldehyde by a dehydration reaction. Furthermore, by-products such as isophthalic acid (IPA) and 1,4-dioxane were also detected in the reaction mixture. Taking into account these most represented products, a simplified kinetic model describing the degradation of PET has been developed, considering irreversible consecutive reactions that take place as parallel in reaction mixture. The reaction rate constants (k₁–k₆) for the individual reactions were calculated and it was observed that all reactions follow first-order kinetics. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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10 pages, 2106 KiB

Open AccessArticle

Comparative Study on UV-AOPs for Efficient Continuous Flow Removal of 4-tert-Butylphenol

by Saule Mergenbayeva and Stavros G. Poulopoulos

Processes 2022, 10(1), 8; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10010008 - 22 Dec 2021

Cited by 9 | Viewed by 2226

Abstract

In the present study, UV-light-driven advanced oxidation processes (AOPs) have been employed for the degradation of 4-tert-Butylphenol (4-t-BP) in water under continuous flow conditions. The effects of varying space time (10, 20, 40, 60 and 120 min) and oxidant dosage (88.3 mg/L, 176.6 [...] Read more.

In the present study, UV-light-driven advanced oxidation processes (AOPs) have been employed for the degradation of 4-tert-Butylphenol (4-t-BP) in water under continuous flow conditions. The effects of varying space time (10, 20, 40, 60 and 120 min) and oxidant dosage (88.3 mg/L, 176.6 mg/L and 264 mg/L) were examined. 4-t-BP degradation efficiency in the UV-induced AOPs followed the order of UV/H₂O₂ (264.9 mg/L) ≈ UV/Fe²⁺/H₂O₂ > UV/Fe³⁺/H₂O₂ > UV/H₂O₂ (176.6 mg/L) > UV/H₂O₂ (88.3 mg/L) > UV/Fe-TiO₂ > UV/TiO₂ > UV, while UV/Fe³⁺/H₂O₂ was the most efficient process in terms of Total Organic Carbon (TOC) removal (at the space time of 60 min) among those tested. The combination of UV with 88.3 mg/L H₂O₂ enhanced pollutant removal from 51.29% to 93.34% after 10 min of irradiation. The presence of H₂O₂ contributed to the highest 4-t-BP and TOC removal values. Interestingly, the increase in space time from 20 to 60 min resulted in surpassing of the activity of the Fe-TiO₂ over commercial TiO₂, although it had an almost negligible positive impact on the performance of the UV/H₂O₂ system as well as H₂O₂ concentration. The results obtained showed that more than 80% of 4-t-BP could be successfully degraded by both heterogeneous and homogeneous AOPs after 60 min. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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13 pages, 3315 KiB

Open AccessArticle

Optimization, Kinetics, Thermodynamic and Arrhenius Model of the Removal of Ciprofloxacin by Internal Electrolysis with Fe-Cu and Fe-C Materials

by Tra Huong Do, Xuan Linh Ha, Thi Tu Anh Duong, Phuong Chi Nguyen, Ngoc Bich Hoang and Thi Kim Ngan Tran

Processes 2021, 9(12), 2110; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9122110 - 24 Nov 2021

Cited by 1 | Viewed by 1501

Abstract

The ciprofloxacin (CIP) removal ability of a Fe-Cu electrolytic material was examined with respect to pH (2–9), time (15–150 min), shaking speed (100–250 rpm), material mass (0.2–3 g/L), temperature (298, 308, 323) and initial CIP concentration (30–200 mg/L). The Fe-Cu electrolytic materials were [...] Read more.

The ciprofloxacin (CIP) removal ability of a Fe-Cu electrolytic material was examined with respect to pH (2–9), time (15–150 min), shaking speed (100–250 rpm), material mass (0.2–3 g/L), temperature (298, 308, 323) and initial CIP concentration (30–200 mg/L). The Fe-Cu electrolytic materials were fabricated by the chemical plating method, and Fe-C materials were mechanically mixed from iron powder and graphite. The results show that at a pH value of 3, shaking time 120 min, shaking speed 250 rpm, a mass of Fe-Cu, Fe-C material of 2 g/L and initial CIP concentration of 203.79 mg/L, the CIP removal efficiency of Fe-Cu material reached 90.25% and that of Fe-C material was 85.12%. The removal of CIP on Fe-Cu and Fe-C materials follows pseudo-first-order kinetics. The activation energy of CIP removal of Fe-Cu material is 14.93 KJ/mol and of Fe-C material is 16.87 KJ/mol. The positive ΔH proves that CIP removal is endothermic. A negative entropy of 0.239 kJ/mol and 0.235 kJ/mol (which is near zero and is also relatively positive) indicated the rapid removal of the CIP molecules into the removed products. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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10 pages, 550 KiB

Open AccessFeature PaperArticle

Characteristics of Hydrochar and Liquid Products Obtained by Hydrothermal Carbonization and Wet Torrefaction of Poultry Litter in Mixture with Wood Sawdust

by Rafail Isemin, Natalia Muratova, Sergey Kuzmin, Dmitry Klimov, Vadim Kokh-Tatarenko, Alexander Mikhalev, Oleg Milovanov, Antoine Dalibard, Olayinka Ahmed Ibitowa, Manuel Nowotny, Mathieu Brulé, Fouzi Tabet and Bernd Rogge

Processes 2021, 9(11), 2082; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9112082 - 20 Nov 2021

Cited by 6 | Viewed by 2331

Abstract

Poultry farms with floor-standing poultry generate large amounts of poultry litter waste. The direct application of this waste as an organic fertilizer does not ensure sustainable and cost-efficient utilization of all waste fractions, and can also be linked to environmental hazards. Therefore, the [...] Read more.

Poultry farms with floor-standing poultry generate large amounts of poultry litter waste. The direct application of this waste as an organic fertilizer does not ensure sustainable and cost-efficient utilization of all waste fractions, and can also be linked to environmental hazards. Therefore, the development of new technologies is required for processing poultry litter into a safe product with higher added value. In this work, the characteristics of activated carbon derived from hydrochar, along with the liquid products obtained from hydrothermal carbonization (HTC) and the wet torrefaction (WT) of poultry litter, were investigated. Poultry litter (PL) was applied in a mixture with sawdust (SD) in the following ratios: 1:0 (PL/SD 1:0), 1:1 (PL/SD 1:1), 1:2 (PL/SD 1:2), and 2:1 (PL/SD 2:1). WT processing took place in an innovative fluidized bed system in a superheated steam medium with low overpressure (less than 0.07 MPa) at 300 °C and 350 °C for 30–45 min. Conventional HTC processing was performed in a water medium at 220 °C for 1–4 h. The hydrochar produced in the experiments was activated with steam for 1 h at 450–750 °C. The porosity characteristics of activated hydrochar were measured, including pore size, pore volume, and specific surface area, in view of potential industrial applications as an adsorbent. Additionally, the contents of 5-hydroxymethylfurfural (HMF), as high-value product, were determined in the liquid products obtained from HTC processing, as well as in the condensate obtained after WT processing. Specific surface areas of the activated hydrochars may still be too low for application as adsorbent material. Hence, its use as a biofertilizer and soil improver should be preferred. Interestingly, the liquid fraction obtained from the innovative WT process displayed a significantly higher 5-HMF content compared to the conventional HTC process. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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14 pages, 1321 KiB

Open AccessArticle

Energy Flexibility Chances for the Wastewater Treatment Plant of the Benchmark Simulation Model 1

by George Skouteris, Mario Alejandro Parra Ramirez, Sebastian Felix Reinecke and Uwe Hampel

Processes 2021, 9(10), 1854; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9101854 - 19 Oct 2021

Cited by 1 | Viewed by 2009

Abstract

Future energy systems must mainly generate electricity from renewable resources. To deal with the fluctuating availability of wind and solar power, new versatile electricity markets and sustainable solutions concentrating on energy flexibility are needed. In this research, we investigated the potential of energy [...] Read more.

Future energy systems must mainly generate electricity from renewable resources. To deal with the fluctuating availability of wind and solar power, new versatile electricity markets and sustainable solutions concentrating on energy flexibility are needed. In this research, we investigated the potential of energy flexibility achieved through demand-side response for the wastewater treatment plant of the Benchmark Simulation Model 1. First, seven control strategies were simulated and assessed. Next, the flexibility calls were identified, two energy flexibility scenarios were defined and incorporated into the model, and the control strategies were evaluated anew. In this research, the effluent ammonia concentration needed to be maintained within the limits for as long as possible. Strategy 5, which controlled ammonia in Tank 5 at a low value and did not control any nitrate in Tank 2, of Scenario 1, which was characterized by an undetermined on/off aeration cycle, was then found to be the best. Although this control strategy led to high total energy consumption, the percentage of time during which aeration was nearly suspended was one of the highest. This work proposes a methodology that will be useful to plant operators who should soon reduce energy consumption during spikes in electricity prices. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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16 pages, 2306 KiB

Open AccessArticle

A Comparative Study of Improvement of Phycoremediation Using a Consortium of Microalgae in Municipal Wastewater Treatment Pond Systems as an Alternative Solution to Africa’s Sanitation Challenges

by Paul J. Oberholster, Maronel Steyn and Anna-Maria Botha

Processes 2021, 9(9), 1677; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9091677 - 18 Sep 2021

Cited by 6 | Viewed by 2284

Abstract

The reuse of wastewater has been observed as a viable option to cope with increasing water stress in Africa. The present case studies evaluated the optimization of the process of phycoremediation as an alternative low-cost green treatment technology in two municipality wastewater treatment [...] Read more.

The reuse of wastewater has been observed as a viable option to cope with increasing water stress in Africa. The present case studies evaluated the optimization of the process of phycoremediation as an alternative low-cost green treatment technology in two municipality wastewater treatment pond systems that make up the largest number of domestic sewage treatment systems on the African continent. A consortium of specific microalgae (Chlorella vulgaris and Chlorella protothecoides) was used to improve the treatment capacity of domestic wastewater at two operational municipality wastewater pond systems under different environmental conditions in South Africa. Pre- and post-phycoremediation optimization through mass inoculation of a consortium of microalgae, over a period of one year under different environmental conditions, were compared. It was evident that the higher reduction of total phosphates (74.4%) in the effluent, after treatment with a consortium of microalgae at the Motetema pond system, was possibly related to (1) the dominance of the algal taxa C. protothecoides (52%), and to a lesser extent C. vulgaris (36%), (2) more cloudless days, (3) higher air temperature, and (4) a higher domestic wastewater strength. In the case of the Brandwag pond treatment system, the higher reduction of total nitrogen can possibly be related to the dominance of C. vulgaris, different weather conditions, and lower domestic wastewater strength. The nutrient reduction data from the current study clearly presented compelling evidence in terms of the feasibility for use of this technology in developing countries to reduce nutrient loads from domestic wastewater effluent. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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16 pages, 5020 KiB

Open AccessArticle

Improving the Treatment Efficiency and Lowering the Operating Costs of Electrochemical Advanced Oxidation Processes

by Thorben Muddemann, Rieke Neuber, Dennis Haupt, Tobias Graßl, Mohammad Issa, Fabian Bienen, Marius Enstrup, Jonatan Möller, Thorsten Matthée, Michael Sievers and Ulrich Kunz

Processes 2021, 9(9), 1482; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9091482 - 24 Aug 2021

Cited by 13 | Viewed by 3182

Abstract

Electrochemical advanced oxidation processes (EAOP^®) are promising technologies for the decentralized treatment of water and will be important elements in achieving a circular economy. To overcome the drawback of the high operational expenses of EAOP^® systems, two novel reactors based [...] Read more.

Electrochemical advanced oxidation processes (EAOP^®) are promising technologies for the decentralized treatment of water and will be important elements in achieving a circular economy. To overcome the drawback of the high operational expenses of EAOP^® systems, two novel reactors based on a next-generation boron-doped diamond (BDD) anode and a stainless steel cathode or a hydrogen-peroxide-generating gas diffusion electrode (GDE) are presented. This reactor design ensures the long-term stability of BDD anodes. The application potential of the novel reactors is evaluated with artificial wastewater containing phenol (COD of 2000 mg L⁻¹); the reactors are compared to each other and to ozone and peroxone systems. The investigations show that the BDD anode can be optimized for a service life of up to 18 years, reducing the costs for EAOP^® significantly. The process comparison shows a degradation efficiency for the BDD–GDE system of up to 135% in comparison to the BDD–stainless steel electrode combination, showing only 75%, 14%, and 8% of the energy consumption of the BDD–stainless steel, ozonation, and peroxonation systems, respectively. Treatment efficiencies of nearly 100% are achieved with both novel electrolysis reactors. Due to the current density adaptation and the GDE integration, which result in energy savings as well as the improvements that significantly extend the lifetime of the BDD electrode, less resources and raw materials are consumed for the power generation and electrode manufacturing processes. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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16 pages, 1476 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Dark Fermentation of Sweet Sorghum Stalks, Cheese Whey and Cow Manure Mixture: Effect of pH, Pretreatment and Organic Load

by Margarita Andreas Dareioti, Aikaterini Ioannis Vavouraki, Konstantina Tsigkou, Constantina Zafiri and Michael Kornaros

Processes 2021, 9(6), 1017; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9061017 - 09 Jun 2021

Cited by 16 | Viewed by 2629

Abstract

The aim of this study was to determine the optimal conditions for dark fermentation using agro-industrial liquid wastewaters mixed with sweet sorghum stalks (i.e., 55% sorghum, 40% cheese whey, and 5% liquid cow manure). Batch experiments were performed to investigate the effect of [...] Read more.

The aim of this study was to determine the optimal conditions for dark fermentation using agro-industrial liquid wastewaters mixed with sweet sorghum stalks (i.e., 55% sorghum, 40% cheese whey, and 5% liquid cow manure). Batch experiments were performed to investigate the effect of controlled pH (5.0, 5.5, 6.0, 6.5) on the production of bio-hydrogen and volatile fatty acids. According to the obtained results, the maximum hydrogen yield of 0.52 mol H₂/mol eq. glucose was measured at pH 5.5 accompanied by the highest volatile fatty acids production, whereas similar hydrogen productivity was also observed at pH 6.0 and 6.5. The use of heat-treated anaerobic sludge as inoculum had a positive impact on bio-hydrogen production, exhibiting an increased yield of 1.09 mol H₂/mol eq. glucose. On the other hand, the pretreated (ensiled) sorghum, instead of a fresh one, led to a lower hydrogen production, while the organic load decrease did not affect the process performance. In all experiments, the main fermentation end-products were volatile fatty acids (i.e., acetic, propionic, butyric), ethanol and lactic acid. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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Jump to: Research

20 pages, 1030 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Tertiary Wastewater Treatment Technologies: A Review of Technical, Economic, and Life Cycle Aspects

by Dimitris P. Zagklis and Georgios Bampos

Processes 2022, 10(11), 2304; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10112304 - 05 Nov 2022

Cited by 13 | Viewed by 5493

Abstract

The activated sludge process is the most widespread sewage treatment method. It typically consists of a pretreatment step, followed by a primary settling tank, an aerobic degradation process, and, finally, a secondary settling tank. The secondary effluent is then usually chlorinated and discharged [...] Read more.

The activated sludge process is the most widespread sewage treatment method. It typically consists of a pretreatment step, followed by a primary settling tank, an aerobic degradation process, and, finally, a secondary settling tank. The secondary effluent is then usually chlorinated and discharged to a water body. Tertiary treatment aims at improving the characteristics of the secondary effluent to facilitate its reuse. In this work, through a literature review of the most prominent tertiary treatment methods, a benchmarking of their technical efficiency, economic feasibility, and environmental impact was carried out. The photo-Fenton method proved to be the most technically efficient process, significantly reducing the microbial load and pharmaceutical content (by 4.9 log and 84%, respectively) of the secondary effluent. Chlorination and UV irradiation exhibited the lowest treatment costs (0.004 EUR/m⁻³) and the lowest global warming potential (0.04 and 0.09 kg CO₂eq. m⁻³, respectively). After all the data were aggregated, a decision-making tool was constructed in the form of a ternary diagram, which indicates the most appropriate tertiary treatment method according to the weight-per-process aspect (technical, economic, and environmental) selected by the user, with chlorination, UV irradiation, ozonation, microalgae cultivation, and constructed wetlands prevailing in the final results. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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14 pages, 324 KiB

Open AccessReview

Biotreatment Potential and Microbial Communities in Aerobic Bioreactor Systems Treating Agro-Industrial Wastewaters

by Nikolaos Remmas

Processes 2022, 10(10), 1913; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10101913 - 21 Sep 2022

Cited by 1 | Viewed by 1267

Abstract

The thriving agro-industry sector accounts for an essential part of the global gross domestic product, as the need for food and feed production is rising. However, the industrial processing of agricultural products requires the use of water at all stages, which consequently leads [...] Read more.

The thriving agro-industry sector accounts for an essential part of the global gross domestic product, as the need for food and feed production is rising. However, the industrial processing of agricultural products requires the use of water at all stages, which consequently leads to the production of vast amounts of effluents with diverse characteristics, which contain a significantly elevated organic content. This fact reinforces the need for action to control and minimize the environmental impact of the produced wastewater, and activated sludge systems constitute a highly reliable solution for its treatment. The current review offers novel insights on the efficiency of aerobic biosystems in the treatment of agro-industrial wastewaters and their ecology, with an additional focus on the biotechnological potential of the activated sludge of such wastewater treatment plants. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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23 pages, 1894 KiB

Open AccessReview

Emerging Pollutants in Wastewater, Advanced Oxidation Processes as an Alternative Treatment and Perspectives

by Alexis Rubén Bracamontes-Ruelas, Luis Alberto Ordaz-Díaz, Ana María Bailón-Salas, Julio César Ríos-Saucedo, Yolanda Reyes-Vidal and Liliana Reynoso-Cuevas

Processes 2022, 10(5), 1041; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10051041 - 23 May 2022

Cited by 16 | Viewed by 6526

Abstract

Emerging pollutants are present in wastewaters treated by conventional processes. Due to water cycle interactions, these contaminants have been reported in groundwater, surface water, and drinking waters. Since conventional processes cannot guarantee their removal or biotransformation, it is necessary to study processes that [...] Read more.

Emerging pollutants are present in wastewaters treated by conventional processes. Due to water cycle interactions, these contaminants have been reported in groundwater, surface water, and drinking waters. Since conventional processes cannot guarantee their removal or biotransformation, it is necessary to study processes that comply with complete elimination. The current literature review was conducted to describe and provide an overview of the available information about the most significant groups of emerging pollutants that could potentially be found in the wastewater and the environment. In addition, it describes the main entry and distribution pathways of emerging contaminants into the environment through the water and wastewater cycle, as well as some of the potential effects they may cause to flora, fauna, and humans. Relevant information on the SARS-CoV-2 virus and its potential spread through wastewater is included. Furthermore, it also outlines some of the Advanced Oxidation Processes (AOPs) used for the total or partial emerging pollutants removal, emphasizing the reaction mechanisms and process parameters that need to be considered. As well, some biological processes that, although slow, are effective for the biotransformation of some emerging contaminants and can be used in combination with advanced oxidation processes. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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20 pages, 2859 KiB

Open AccessReview

Oily Wastewater Treatment: Methods, Challenges, and Trends

by Alexandre D’Lamare Maia de Medeiros, Cláudio José Galdino da Silva Junior, Julia Didier Pedrosa de Amorim, Italo José Batista Durval, Andréa Fernanda de Santana Costa and Leonie Asfora Sarubbo

Processes 2022, 10(4), 743; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10040743 - 12 Apr 2022

Cited by 63 | Viewed by 15904

Abstract

The growing interest in innovations regarding the treatment of oily wastewater stems from the fact that the oil industry is the largest polluter of the environment. The harm caused by this industry is seen in all countries. Companies that produce such wastewater are [...] Read more.

The growing interest in innovations regarding the treatment of oily wastewater stems from the fact that the oil industry is the largest polluter of the environment. The harm caused by this industry is seen in all countries. Companies that produce such wastewater are responsible for its treatment prior to disposal or recycling into their production processes. As oil emulsions are difficult to manage and require different types of treatment or even combined methods, a range of environmental technologies have been proposed for oil-contaminated effluents, such as gravity separation, flotation, flocculation, biological treatment, advanced oxidation processes, and membranes. Natural materials, such as biopolymers, constitute a novel, sustainable solution with considerable potential for oily effluent separation. The present review offers an overview of the treatment of oily wastewater, describing current trends and the latest applications. This review also points to further research needs and major concerns, especially with regards to sustainability, and discusses potential biotechnological applications. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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10 pages, 926 KiB

Open AccessFeature PaperReview

Recovery of Phosphorus in Wastewater in the Form of Polyphosphates: A Review

by Weiran Chu, Yi Shi and Liang Zhang

Processes 2022, 10(1), 144; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10010144 - 11 Jan 2022

Cited by 3 | Viewed by 2780

Abstract

As non-renewable resource, the recovery and utilization of phosphorus from wastewater is an enduring topic. Stimulated by the advances in research on polyphosphates (polyP) as well as the development of Enhanced Biological Phosphorus Removal (EBPR) technology to achieve the efficient accumulation of polyP [...] Read more.

As non-renewable resource, the recovery and utilization of phosphorus from wastewater is an enduring topic. Stimulated by the advances in research on polyphosphates (polyP) as well as the development of Enhanced Biological Phosphorus Removal (EBPR) technology to achieve the efficient accumulation of polyP via polyphosphate accumulating organisms (PAOs), a novel phosphorus removal strategy is considered with promising potential for application in real wastewater treatment processes. This review mainly focuses on the mechanism of phosphorus aggregation in the form of polyP during the phosphate removal process. Further discussion about the reuse of polyP with different chain lengths is provided herein so as to suggest possible application pathways for this biosynthetic product. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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36 pages, 2812 KiB

Open AccessReview

Two-Dimensional Nanomaterials for the Removal of Pharmaceuticals from Wastewater: A Critical Review

by Sergio González-Poggini, Andreas Rosenkranz and Melanie Colet-Lagrille

Processes 2021, 9(12), 2160; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9122160 - 29 Nov 2021

Cited by 24 | Viewed by 2632

Abstract

The removal of pharmaceuticals from wastewater is critical due to their considerable risk on ecosystems and human health. Additionally, they are resistant to conventional chemical and biological remediation methods. Two-dimensional nanomaterials are a promising approach to face this challenge due to their combination [...] Read more.

The removal of pharmaceuticals from wastewater is critical due to their considerable risk on ecosystems and human health. Additionally, they are resistant to conventional chemical and biological remediation methods. Two-dimensional nanomaterials are a promising approach to face this challenge due to their combination of high surface areas, high electrical conductivities, and partially optical transparency. This review discusses the state-of-the-art concerning their use as adsorbents, oxidation catalysts or photocatalysts, and electrochemical catalysts for water treatment purposes. The bibliographic search bases upon academic databases including articles published until August 2021. Regarding adsorption, high removal capacities (>200 mg g⁻¹) and short equilibrium times (<30 min) are reported for molybdenum disulfide, metal-organic frameworks, MXenes, and graphene oxide/magnetite nanocomposites, attributed to a strong adsorbate-adsorbent chemical interaction. Concerning photocatalysis, MXenes and carbon nitride heterostructures show enhanced charge carriers separation, favoring the generation of reactive oxygen species to degrade most pharmaceuticals. Peroxymonosulfate activation via pure or photo-assisted catalytic oxidation is promising to completely degrade many compounds in less than 30 min. Future work should be focused on the exploration of greener synthesis methods, regeneration, and recycling at the end-of-life of two-dimensional materials towards their successful large-scale production and application. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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28 pages, 871 KiB

Open AccessFeature PaperReview

Biological Indicators for Fecal Pollution Detection and Source Tracking: A Review

by Enze Li, Faizan Saleem, Thomas A. Edge and Herb E. Schellhorn

Processes 2021, 9(11), 2058; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9112058 - 17 Nov 2021

Cited by 21 | Viewed by 11805

Abstract

Fecal pollution, commonly detected in untreated or less treated sewage, is associated with health risks (e.g., waterborne diseases and antibiotic resistance dissemination), ecological issues (e.g., release of harmful gases in fecal sludge composting, proliferative bacterial/algal growth due to high nutrient loads) and economy [...] Read more.

Fecal pollution, commonly detected in untreated or less treated sewage, is associated with health risks (e.g., waterborne diseases and antibiotic resistance dissemination), ecological issues (e.g., release of harmful gases in fecal sludge composting, proliferative bacterial/algal growth due to high nutrient loads) and economy losses (e.g., reduced aqua farm harvesting). Therefore, the discharge of untreated domestic sewage to the environment and its agricultural reuse are growing concerns. The goals of fecal pollution detection include fecal waste source tracking and identifying the presence of pathogens, therefore assessing potential health risks. This review summarizes available biological fecal indicators focusing on host specificity, degree of association with fecal pollution, environmental persistence, and quantification methods in fecal pollution assessment. The development of practical tools is a crucial requirement for the implementation of mitigation strategies that may help confine the types of host-specific pathogens and determine the source control point, such as sourcing fecal wastes from point sources and nonpoint sources. Emerging multidisciplinary bacterial enumeration platforms are also discussed, including individual working mechanisms, applications, advantages, and limitations. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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27 pages, 1297 KiB

Open AccessReview

Wastewater Treatment Using Constructed Wetland: Current Trends and Future Potential

by Ikrema Hassan, Saidur R. Chowdhury, Perdana K. Prihartato and Shaikh A Razzak

Processes 2021, 9(11), 1917; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9111917 - 27 Oct 2021

Cited by 40 | Viewed by 12089

Abstract

Constructed wetlands (CW) is an environmentally friendly technique for removing pollutants from wastewater and has been applied to municipal wastewater, petroleum refinery wastewater, agriculture drainage, acid mine drainage, etc. The past decade has seen a remarkable number of innovations in the exponentially growing [...] Read more.

Constructed wetlands (CW) is an environmentally friendly technique for removing pollutants from wastewater and has been applied to municipal wastewater, petroleum refinery wastewater, agriculture drainage, acid mine drainage, etc. The past decade has seen a remarkable number of innovations in the exponentially growing field of microbiology. This manuscript covers a critical review of key aspects of CW, such as various types of CW, the contaminants and their removal mechanisms, degradation pathways, challenges and opportunities, materials, applications, and theory with a focus on recent advances in the last three decades. In addition, an attempt has been taken to project future advances in the field of CW and facilitate these advances by framing key unsolved problems in CW. Guidelines are prepared for the fast-growing CW field through the standardization of key design aspects. This review covers the evaluation of the current state-of-the-art of CW technology and provides definitions and performance metric nomenclature in an effort to unify the fast-growing CW community. It also contains an outlook on the emerging trends in CW and proposes future research and development directions. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends)

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