Research

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17 pages, 3370 KiB

Open AccessArticle

Cross-Linked Cationic Starch Microgranules for Removal of Diclofenac from Aqueous Systems

by Vesta Navikaite-Snipaitiene, Paulina Andriunaite, Deimante Rosliuk and Ramune Rutkaite

Water 2023, 15(24), 4237; https://doi.org/10.3390/w15244237 - 09 Dec 2023

Viewed by 912

The occurrence of pharmaceuticals, such as anti-inflammatories, antibiotics, antidepressants, antihistamines, and others in the effluents, is a very urgent problem and a big challenge for municipal wastewater treatment companies. Without special treatment, these microcontaminants are retained in discharged water and sewage sludge and [...] Read more.

The occurrence of pharmaceuticals, such as anti-inflammatories, antibiotics, antidepressants, antihistamines, and others in the effluents, is a very urgent problem and a big challenge for municipal wastewater treatment companies. Without special treatment, these microcontaminants are retained in discharged water and sewage sludge and this is a high threat to the environment. Cross-linked cationic starch (CLCS) adsorbents with various degrees of substitution (DS) of cationic groups were employed for the removal of diclofenac from aqueous systems. The equilibrium adsorption studies revealed that the driving force of adsorption was the electrostatic interaction between carboxylate groups of diclofenac and quaternary ammonium groups of CLCS. The sorption capacities of CLCS with DS of 0.21 (CLCS-0.21) and DS of 0.33 (CLCS-0.33) varied from 329 to 370 mg/g and from 597 to 684 mg/g, respectively. The release studies revealed that adsorbed diclofenac can be efficiently released into 0.25 mol/L NaCl solution. Adsorbent regeneration studies showed that after four regeneration cycles, the ability of CLCS-0.21 and CLCS-0.33 to remove diclofenac from the aqueous medium decreased by 6% and 3%, respectively. To conclude, CLCS-0.33 exhibited high absorption capacity and sustainability due to good recoverability properties and can be regarded as a promising microcontaminant adsorbent to be used in wastewater treatment processes. Full article

(This article belongs to the Special Issue Sewage Sludge: Treatment and Recovery)

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10 pages, 2351 KiB

Open AccessArticle

High-Performance Catalytic Wet Oxidation of Excess Activated Sludge Derived from Pharmaceutical Wastewater Treatment Process over a Cu/γ-Al₂O₃ Catalyst

by Shangye Chu, Xu Zeng, Hai Lin and Yuting Zhu

Water 2023, 15(19), 3494; https://doi.org/10.3390/w15193494 - 06 Oct 2023

Viewed by 806

Abstract

The performance of catalytic wet oxidation of excess activated sludge derived from pharmaceutical wastewater treatment over a Cu/γ-Al₂O₃ catalyst was investigated. The experiments were performed with a stainless steel autoclave reactor by using the prepared Cu/γ-Al₂O₃ catalyst. [...] Read more.

The performance of catalytic wet oxidation of excess activated sludge derived from pharmaceutical wastewater treatment over a Cu/γ-Al₂O₃ catalyst was investigated. The experiments were performed with a stainless steel autoclave reactor by using the prepared Cu/γ-Al₂O₃ catalyst. The effects of reaction conditions were examined, including additional catalyst amount, reaction temperature, time, and initial oxygen pressure. Results demonstrated that the catalyst, fabricated via co-precipitating method, has excellent catalytic performance. Through the study on condition optimization, the highest removal rates of volatile suspended solids (VSS, 93.6%) and total chemical oxygen demand (TCOD, 76.5%) were acquired with the reaction temperature 260 °C, time 60 min, initial oxygen pressure 1.0 MPa, and the prepared catalyst 5.0 g/L. The volatile fatty acids (VFAs) produced from the wet oxidation of sludge included acetic (mainly), propanoic, isobutyric, and isovaleric acids, which have great potential for the utilization as organic carbon sources in biological wastewater treatment plant. These results demonstrated that the proposed method, catalytic wet oxidation over Cu/γ-Al₂O₃ catalyst, is effective for treating excess activated sludge and resource utilization of organic carbon in the sludge. Full article

(This article belongs to the Special Issue Sewage Sludge: Treatment and Recovery)

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16 pages, 3195 KiB

Open AccessArticle

Heavy Metals in Fly Ash as a Factor Limiting Its Use in Fertilizing Composts

by Maciej Malarski, Piotr Wichowski and Justyna Czajkowska

Water 2023, 15(12), 2247; https://doi.org/10.3390/w15122247 - 15 Jun 2023

Cited by 1 | Viewed by 1516

Abstract

Composting enables the recycling of significant amounts of biodegradable waste, while ensuring its disposal. The addition of fly ash increases the concentration of fertilizing substances in the compost. Compost is a source of many nutrients for plants. The addition of fly ash might [...] Read more.

Composting enables the recycling of significant amounts of biodegradable waste, while ensuring its disposal. The addition of fly ash increases the concentration of fertilizing substances in the compost. Compost is a source of many nutrients for plants. The addition of fly ash might also cause a slower release of these nutrients into an aqueous solution, meeting the fertilization needs of plants over a longer period of time. Tests were carried out using sewage sludge (WWTP Piaseczno, 163,500 P.E.), straw as a structure-forming material and fly ash (WWTP Krakow, 780,000 P.E.). The compost obtained in the research was analyzed in terms of environmental conditions specified in legal regulations. The most favorable compost mass density (520 kg/L) and the amount of air supplied to the process (5.0 L/(h∙kg d.m.)) were determined. The addition of fly ash to the compost mass did not significantly affect the temperature distribution obtained in the process. The increase in fly ash content increased the pH of the compost mass and was associated with higher nitrogen losses. It was found that the factor which may limit the possibility of using fly ash as a compost substrate is the presence of higher concentrations of heavy metals, especially chromium. It was determined that the maximum addition of fly ash to the compost mass was 154 kg d.m._ash/(ton d.m._straw+sludge). Full article

(This article belongs to the Special Issue Sewage Sludge: Treatment and Recovery)

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13 pages, 5269 KiB

Open AccessArticle

Promotion of Sugar Extraction from Sewage Sludge by Microwave Combined with Thermal-Alkaline Pretreatment

by Peng Cheng, Lei Yang, Yu Liu, Jiaxin Liu and Yujie Fan

Water 2023, 15(7), 1291; https://doi.org/10.3390/w15071291 - 24 Mar 2023

Cited by 2 | Viewed by 1693

Abstract

A large amount of sludge is produced in the process of municipal sewage treatment. The recovery and utilization of large amounts of sugar, protein, lipids and other organic matter from sewage sludge (SS) is of great significance for reducing environmental pressure and producing [...] Read more.

A large amount of sludge is produced in the process of municipal sewage treatment. The recovery and utilization of large amounts of sugar, protein, lipids and other organic matter from sewage sludge (SS) is of great significance for reducing environmental pressure and producing clean energy. In this study, microwave combined with thermal-alkaline pretreatment was used to accelerate the dissolution of primary sedimentation sludge and the release of intracellular substances, and to promote the extraction of sugar from SS. The results showed that the yield of crude sugar and the extraction efficiency of pure sugar increased with the increase in NaOH dosage. The extraction of crude sugar reached the equilibrium at about 30 min. During the response surface analysis, the optimal pretreatment conditions were determined as follows: the dosage of NaOH was 9.93 mL, and the leaching time and the microwave time were 27.65 min and 33.2 s, respectively. The crude sugar yield and extraction efficiency obtained under this condition were 39.80 ± 3.57% and 89.74 ± 3.61%, respectively. The pretreated sludge and crude sugar were characterized with scanning electron microscopy and Fourier transform infrared spectroscopy. The results showed that the combined use of thermal-alkaline and microwave effectively destroyed the structure of the sludge and increased the yield of crude sugar. Full article

(This article belongs to the Special Issue Sewage Sludge: Treatment and Recovery)

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22 pages, 1212 KiB

Open AccessArticle

Opportunities of Integrating Slow Pyrolysis and Chemical Leaching for Extraction of Critical Raw Materials from Sewage Sludge

by Andrea Salimbeni, Marta Di Bianca, Giacomo Lombardi, Andrea Maria Rizzo and David Chiaramonti

Water 2023, 15(6), 1060; https://doi.org/10.3390/w15061060 - 10 Mar 2023

Cited by 3 | Viewed by 1960

Abstract

Slow pyrolysis is a promising technology to convert sewage sludge into char: a stable solid product with high carbon and phosphorus content. However, due to its heavy metals content, char use in agriculture is avoided in many European Union (EU) countries. This study [...] Read more.

Slow pyrolysis is a promising technology to convert sewage sludge into char: a stable solid product with high carbon and phosphorus content. However, due to its heavy metals content, char use in agriculture is avoided in many European Union (EU) countries. This study aimed to test a solution, based on integrating slow pyrolysis and chemical leaching, to separate phosphorus and other inorganics from char, obtaining an inorganic P-rich fertiliser and a C-rich solid usable for industrial purposes. The sludge was first characterized and then processed in a 3 kg/h slow pyrolysis reactor at 450 °C for 30 min. The resulting char was processed by chemical leaching with acid (HCl, HNO₃) and alkali (KOH) reagents to extract inorganic compounds. To optimize the inorganic extraction, three case studies have been considered. The char obtained from sewage sludge pyrolysis contained around 78% d.b. (dry basis) of inorganics, 14% d.b. of C, 14% d.b. of Al, and almost 5% d.b. of P. The leaching tests enabled to extract 100% of P, Mg, and Ca from the char. The remaining char contained mainly carbon (27%) and silica (42%), with a surface area of up to 70 m²/g, usable as adsorbent or precursor of sustainable materials. Full article

(This article belongs to the Special Issue Sewage Sludge: Treatment and Recovery)

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Review

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24 pages, 3375 KiB

Open AccessReview

Ascertaining and Optimizing the Water Footprint and Sludge Management Practice in Steel Industries

by Atun Roy Choudhury, Neha Singh, Arutchelvan Veeraraghavan, Ayushi Gupta, Sankar Ganesh Palani, Mohammad Mehdizadeh, Anahita Omidi and Duraid K. A. Al-Taey

Water 2023, 15(12), 2177; https://doi.org/10.3390/w15122177 - 09 Jun 2023

Cited by 2 | Viewed by 2514

Abstract

Steelmaking is a water-intensive process. The mean water intake against each ton of steel manufactured is ascertained as between 2 and 20 m³. Primarily, the stated requirement is in the form of make-up water to compensate for evaporation and mechanical losses [...] Read more.

Steelmaking is a water-intensive process. The mean water intake against each ton of steel manufactured is ascertained as between 2 and 20 m³. Primarily, the stated requirement is in the form of make-up water to compensate for evaporation and mechanical losses and does not contribute to wastewater generation. Conversely, unit operations, such as rolling, continuous casting, pickling, etc., generate highly complex wastewater rich in polycyclic aromatic hydrocarbons (PAH), cyanide, ammonia, non-consumed acids, benzene, toluene, xylene, oil, grease, etc. Further, the conjugative wastewater contains a high concentration of metallic oxides, toxic elements, oil, nitrogen, and heavy metals such as zinc, nickel, chromium, etc. These contaminants are generally treated and neutralized using physicochemical and membrane-based systems. This also yields hazardous sludge, which is landfilled, thereby incurring an ancillary financial burden. However, sludge can be a frugal source of extracting multi-dimensional benefits. The present review investigated and identified the most water-intensive and wastewater/sludge-contributing unit operations and proposed a preferential combination of treatments to balance efficacy and economy. Further, the various global practices for sludge recycling and management documented in the existing literature are summarized and ranked with the help of the analytic hierarchy process (AHP). The findings revealed concrete making and nutrient recovery as the most- and least-preferred recycling alternatives. Full article

(This article belongs to the Special Issue Sewage Sludge: Treatment and Recovery)

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25 pages, 3719 KiB

Open AccessReview

Recent Advancement in Commercial and Other Sustainable Techniques for Energy and Material Recovery from Sewage Sludge

by Mohd Imran Siddiqui, Hasan Rameez, Izharul Haq Farooqi and Farrukh Basheer

Water 2023, 15(5), 948; https://doi.org/10.3390/w15050948 - 01 Mar 2023

Cited by 8 | Viewed by 3033

Abstract

Rapid population growth and urbanization have resulted in a multi-fold increase in water consumption over the last few decades, resulting in the generation of large amounts of sewage and sewage sludge that impose severe environmental burdens if not handled properly. Sludge management itself [...] Read more.

Rapid population growth and urbanization have resulted in a multi-fold increase in water consumption over the last few decades, resulting in the generation of large amounts of sewage and sewage sludge that impose severe environmental burdens if not handled properly. Sludge management itself accounts for up to 50% of the total operating costs of wastewater treatment plants (WWTPs). Conventional sludge management practices such as incineration, landfilling, and ocean disposal have been deemed difficult in light of today’s stringent environmental legislation and compliance standards. As a result, progress has been made toward developing more sustainable approaches for sludge management. This study reviews recent advancements in sewage sludge management techniques that not only ensure the safe disposal of sewage sludge but also focus on utilizing the potential of sewage sludge as feedstock for energy and resource recovery. Energy could be recovered by subjecting the pre-treated sludge to controlled anaerobic digestion (AD) to produce biogas or by utilizing the lipid content of the sewage sludge through esterification or direct sludge pyrolysis to produce biodiesel/bio-oil. Heavy metals such as Ag, Au, Cu, Fe, Ga, Cr, and others, as well as nutrients such as N, P, K, Mg, S, and others, could also be recovered. If energy and resource recovery from sewage sludge is practiced on a global scale, it could significantly contribute to global greenhouse gas (GHG) emission reduction. This review discusses the commercially developed and still-under-research technologies for energy and other resource recovery of sewage sludge. Additionally, techniques, along with their limitations and potential measures to improve their yields, are also discussed. Full article

(This article belongs to the Special Issue Sewage Sludge: Treatment and Recovery)

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20 pages, 1327 KiB

Open AccessEditor’s ChoiceReview

Full-Scale Sewage Sludge Reduction Technologies: A Review with a Focus on Energy Consumption

by Roberta Ferrentino, Michela Langone, Luca Fiori and Gianni Andreottola

Water 2023, 15(4), 615; https://doi.org/10.3390/w15040615 - 04 Feb 2023

Cited by 21 | Viewed by 7621

Abstract

In recent years, increasing attention has been paid to the problem of sewage sludge management and the relevant energy consumption, which represent the main cost items in wastewater treatment plants. Therefore, implementation of technologies that can reduce sludge production and ensure a positive [...] Read more.

In recent years, increasing attention has been paid to the problem of sewage sludge management and the relevant energy consumption, which represent the main cost items in wastewater treatment plants. Therefore, implementation of technologies that can reduce sludge production and ensure a positive impact on the energy of the entire sewage treatment plant has gained considerable importance in the scientific and technical community. The objective of this study was thus to screen full-scale sludge reduction technologies integrated into both the water line and the sludge line of a municipal sewage treatment plant with a sustainable impact on the overall balance of the plant. The results showed that, within the water line, ultrasound in the recirculation line of the activated sludge allowed for greater reductions in sludge production than the Cannibal and UTN systems, despite the higher energy consumption. CAMBI^TM, BioThelys^TM, Exelys^TM and TurboTec^® enabled the greatest reductions in sludge production among the technologies integrated into the sludge line, and although they required a large amount of energy, this was partially offset by energy recovery in terms of additional biogas production. Full article

(This article belongs to the Special Issue Sewage Sludge: Treatment and Recovery)

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