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Sludge: A Renewable Source for Energy and Resources Recovery

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A special issue of Sustainability (ISSN 2071-1050). This special issue belongs to the section "Resources and Sustainable Utilization".

Deadline for manuscript submissions: closed (1 August 2022) | Viewed by 15314

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Special Issue Editor

Prof. Dr. Mohamed Hasnain Isa

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Guest Editor

Civil Engineering Programme, Universiti Teknologi Brunei, Tungku Highway, Gadong BE1410, Brunei
Interests: water and wastewater treatment; sludge treatment; waste management

Special Issue Information

Dear Colleagues,

The importance of sludge treatment and management in relation to a wastewater treatment plant cannot be overemphasized, as it typically accounts for around 50% of the operation cost of the plant. Sludges are generally characterized by high organic and solids contents. Increasingly stringent environmental laws and discharge/disposal standards have forced sludge generators and wastewater treatment plant operators to adopt suitable sludge treatment and management strategies. Advances in sludge treatment techniques have made it possible to view sludge as a resource rather than a waste.

This Special Issue aims to address the application of various technologies for the treatment and management of sludge with a focus on resource recovery to enhance environmental sustainability. Nutrients (nitrogen and phosphorus) and energy (carbon) are two components of sludge that can be economically recycled. Anaerobic digestion, gasification, incineration, pyrolysis, wet air oxidation, and supercritical oxidation are some examples of available technologies for resource recovery from sludge. Sludge can be used beneficially for the recovery of energy in terms of biofuels (solid, liquid and gas), recovery of nutrients (nitrogen and phosphorus) and production of fertilizers, adsorbents, and construction material.

Contributions to the Special Issue will give readers an insight into the above and other sludge treatment and management strategies that will promote the use of sludge as a resource. Original research papers and critical reviews will be welcomed.

Prof. Dr. Mohamed Hasnain Isa
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sustainability is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

sludge treatment
resources recovery
energy
nutrients
renewable
sustainability

Published Papers (7 papers)

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Research

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14 pages, 4949 KiB

Open AccessArticle

Microstructural Analysis and Compressive Strength of Fly Ash and Petroleum Sludge Ash Geopolymer Mortar under High Temperatures

by Mubarak Usman Kankia, Lavania Baloo, Nasiru Danlami, Noor Amila Zawawi, Abosede Bello and Sadiq Ibrahim Muhammad

Sustainability 2023, 15(12), 9846; https://doi.org/10.3390/su15129846 - 20 Jun 2023

Cited by 1 | Viewed by 1197

Abstract

The development of sustainable building materials and construction to decrease environmental pollution in both production and operational stages of the materials’ life cycle is appealing to great interest in the construction industries worldwide. This study evaluated the negative effect of temperature up to 1000 °C on the compressive strength and microstructure of fly ash and petroleum sludge ash (PSA) geopolymer mortar. A sodium silicate and sodium hydroxide mixture is used as an activator. The synthesized mortar was investigated using X-ray Diffraction (XRD), Fourier Transformation Infrared Spectroscopy (FTIR), Mercury Intrusion Porosimetry (MIP), and Field Emission Scanning Electron Microscopy (FESEM). As the temperature increased, the compressive strength of the geopolymer mortar decreased. The strength degradation is due to the damage to microstructure because of the temperature-induced dehydroxylation, dehydration thermal incompatibility between geopolymer aggregate and paste of geopolymer mortar at high temperatures. With an increase in temperature, the cumulative pore volume increased. The FESEM image showed the decomposition of the geopolymer matrix started at a temperature of 600 °C. Incorporating PSA in geopolymer mortar could result in an eco-friendly and sustainable environment that may reduce the problems associated with sludge disposal. Full article

(This article belongs to the Special Issue Sludge: A Renewable Source for Energy and Resources Recovery)

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19 pages, 4486 KiB

Open AccessArticle

Pretreatment of Slaughterhouse Effluent Treatment Plant Sludge Using Electro-Fenton Process for Anaerobic Digestion

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

Sustainability 2023, 15(4), 3159; https://doi.org/10.3390/su15043159 - 9 Feb 2023

Cited by 1 | Viewed by 1411

Abstract

Sludge management is an integral process of an effluent treatment plant (ETP). This study aimed at using the electro-Fenton (EF) process for pretreatment of a cattle-based slaughterhouse ETP sludge to enhance biogas production from anaerobic digestion. EF-oxidation experiments were conducted in 0.5 L beakers with mild-steel electrodes, to study the effect of factors, viz., H₂O₂ concentration, current density and reaction time on soluble chemical oxygen demand (sCOD) concentration, soluble extracellular polymeric substances (sEPS) concentration and volatile suspended solids (VSS) removal efficiency. This was followed by the quantification of biogas production from the raw and pretreated sludge in anaerobic digestion (AD). Experimental conditions for the EF process were optimized using response surface methodology (RSM). At optimized experimental conditions, EF pretreatment resulted in an increase in sCOD and sEPS concentrations, from 0.91 g/L to 6.1 g/L and 0.18 g/L to 1.4 g/L, respectively. VSS removal efficiency was 68.1%. Batch anaerobic digestion studies demonstrated an enhancement in the specific biogas yield, from 110 NmL/g-VS to 460 NmL/g-VS. Full article

(This article belongs to the Special Issue Sludge: A Renewable Source for Energy and Resources Recovery)

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15 pages, 3045 KiB

Open AccessArticle

Struvite Production from Dairy Processing Waste

by Shane McIntosh, Louise Hunt, Emma Thompson Brewster, Andrew Rose, Aaron Thornton and Dirk Erler

Sustainability 2022, 14(23), 15807; https://doi.org/10.3390/su142315807 - 28 Nov 2022

Viewed by 1212

Abstract

Food security depends on sustainable phosphorus (P) fertilisers, which at present are mostly supplied from a finite rock phosphate source. Phosphate (PO₄³⁻) and ammonium (NH₄⁺) in dairy processing wastewater can be recovered as struvite (Mg + NH₄⁺ + PO₄³⁻ 6H₂0), a nutrient rich mineral for fertiliser application. The objectives of this study were to (1) quantify the effects of, pH, temperature and Mg: PO₄³⁻ dosing rates on nutrient (PO₄³⁻ and NH₄⁺) removal and struvite precipitation from post anaerobic digested dairy processing wastewater, and (2) co-blend different dairy processing wastewaters to improve the reactant stoichiometry of NH₄⁺ and PO₄³⁻ for optimal struvite recovery and NH₄⁺ removal. Phosphate removal (>90%) and struvite production (>60%) was achieved across a range of synthesis conditions, and was significantly impacted by pH as determined by response surface modelling. A combination of disproportionate molar ratios of PO₄³⁻ and NH₄⁺, presence of calcium and the apparent mineralisation of organic N, resulted in co-precipitation of hydroxyapatite and elevated levels of residual aqueous NH₄⁺. In the second phase of this study, struvite was successfully precipitated and NH₄⁺ removal was improved (~17%) however, higher concentrations of calcium in the wastewater blends resulted in greater hydroxyapatite co-precipitation (up to 30%). While struvite was the desired product in this study the formation of multiple heterogenous P-rich products (struvite and hydroxyapatite) has the potential to improve P recovery from dairy processing wastewaters and produce a fertiliser blend with amenity and value in agricultural systems. Full article

(This article belongs to the Special Issue Sludge: A Renewable Source for Energy and Resources Recovery)

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15 pages, 823 KiB

Open AccessArticle

Primary Treatment of Domestic Wastewater with the Use of Unmodified and Chemically Modified Drinking Water Treatment Sludge

by Camilo C. Castro-Jiménez, Julio C. Saldarriaga-Molina, Edwin F. García and Mauricio A. Correa-Ochoa

Sustainability 2022, 14(16), 9827; https://doi.org/10.3390/su14169827 - 9 Aug 2022

Cited by 3 | Viewed by 2557

Abstract

Improved wastewater (WW) treatment contributes to preserving human life and aquatic ecosystems and acting on climate change. The use of drinking water treatment sludges (WTS) as coagulants in the primary treatment of WW contributes, in this regard, and simultaneously enables the sustainable management of this waste. In this work, the improvement of the primary treatment of real domestic WW using unmodified WTS and chemically modified WTS with sulphuric and hydrochloric acids (reactive sludges—RSs) as coagulants was evaluated. The evaluated WTS contains a higher fraction of inorganic solids and is mainly an amorphous material. The wet WTS (W-WTS) showed a better performance in enhancing WW clarification (up to 76%), as measured by turbidity in comparison with the dry WTS (D-WTS). All RSs improved this performance considerably (up to 98%), and of these, the sulphuric reactive sludge generated from the W-WTS (SRS-W) showed the lowest costs associated with acid consumption for activation. The best treatments with W-WTS and SRS-W significantly improved the removal of solids (total suspended solids > 90% and volatile suspended solids > 80%), organic matter (total biochemical oxygen demand > 50% and total chemical oxygen demand > 55%), and total phosphorus (>75%) compared to natural sedimentation, with slight differences in favour of SRS-W, especially in the removal of phosphorus species. The reuse of WTSs in primary WW treatment becomes a valuable circular economy proposal in the water sector, which simultaneously valorises waste from the drinking water process and contributes to the fulfilment of Sustainable Development Goal 6 (Clean Water and Sanitation) Full article

(This article belongs to the Special Issue Sludge: A Renewable Source for Energy and Resources Recovery)

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14 pages, 2076 KiB

Open AccessArticle

Sustainability of Egyptian Cities through Utilizing Sewage and Sludge in Softscaping and Biogas Production

by Usama Konbr, Walid Bayoumi, Mohamed N. Ali and Ahmed Salah Eldin Shiba

Sustainability 2022, 14(11), 6675; https://doi.org/10.3390/su14116675 - 30 May 2022

Cited by 11 | Viewed by 2623

Abstract

The National Egyptian Agenda 2030 recently adopted the concepts of sustainable cities, mitigating and adapting to climate change. This study responded to these concepts by treating sewage to reuse it in softscaping and recycling sludge to reduce energy consumption and support heating systems by producing biogas. Of the limitations of this study, it focuses on a compound to propose a model to increase the sustainability of Egyptian cities. This study used many technologies, such as biological treatment processes, activated sludge, trickling filters, and fixed bioreactors. However, Membrane bioreactors (MBRs) have seemed to be the most suitable technology because of their low cost and footprint. Additionally, a pilot laboratory was established to simulate the sewage treatment plant. It consisted of a primary sedimentation tank followed by an MBR tank and a chlorine disinfection tank, where the sludge was fed into a cylindrical anaerobic digester. The amount of sludge collected generated 41.5 mL/day of biogas. The application of this large-scale batch reactor will produce around 38 m3/day of biogas. Applying the findings of this study to the treatment and reuse of domestic sewage and sludge can provide up to 50% of the water needed for the green area of the compound. Full article

(This article belongs to the Special Issue Sludge: A Renewable Source for Energy and Resources Recovery)

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Review

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17 pages, 1620 KiB

Open AccessReview

Sewage Sludge Biorefinery for Circular Economy

by Daniele Cecconet and Andrea G. Capodaglio

Sustainability 2022, 14(22), 14841; https://doi.org/10.3390/su142214841 - 10 Nov 2022

Cited by 13 | Viewed by 2155

Abstract

Sewage sludge processing and disposal have a significant weight on the energy and economic balances of wastewater treatment operations and contribute substantially to greenhouse gas emissions related to wastewater processing. Despite this, sewage sludge contains substantial recoverable resources in the form of energy and useful molecules. The current challenge, other than reducing the environmental and economic impacts of its disposal, is to recover energy and materials from this waste stream, implementing a biosolid-centered circular economy with the greatest possible added value. A number of options along these lines exist, and others are being investigated, ranging from biological processes, thermochemical technologies, bioelectrochemical processing, biorefineries and others. Recoverable resources comprise biogas from sludge fermentation, liquid and solid end products (e.g., biodiesel and biochar) and valuable nutrients (N and P). This paper presents a state of the art of biorefinery, with emphasis on recent developments in non-conventional resource recovery from EBSS streams for sludge-based circular economy implementation. Expectations and limitations, including technological readiness, of these technologies are discussed. Full article

(This article belongs to the Special Issue Sludge: A Renewable Source for Energy and Resources Recovery)

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21 pages, 2704 KiB

Open AccessReview

The Influence of Municipal Wastewater Treatment Technologies on the Biological Stabilization of Sewage Sludge: A Systematic Review

by José Luis Cárdenas-Talero, Jorge Antonio Silva-Leal, Andrea Pérez-Vidal and Patricia Torres-Lozada

Sustainability 2022, 14(10), 5910; https://doi.org/10.3390/su14105910 - 13 May 2022

Cited by 11 | Viewed by 3244

Abstract

Various wastewater treatment technologies are available today and biological processes are predominantly used in these technologies. Increasing wastewater treatment systems produces large amounts of sewage sludge with variable quantities and qualities, which must be properly managed. Anaerobic and aerobic digestion and composting are major strategies to treat this sludge. The main indicators of biological stabilization are volatile fatty acids (VFAs), volatile solids (VS), the carbon/nitrogen (C/N) ratio, humic substances (HS), the total organic carbon (TOC), the carbon dioxide (CO₂) evolution rate, the specific oxygen uptake rate (SOUR), and the Dewar test; however, different criteria exist for the same indicators. Although there is no consensus for defining the stability of sewage sludge (biosolids) in the research and regulations reviewed, controlling the biological degradation, vector attraction, and odor determines the biological stabilization of sewage sludge. Because pollutants and pathogens are not completely removed in biological stabilization processes, further treatments to improve the quality of biosolids and to ensure their safe use should be explored. Full article

(This article belongs to the Special Issue Sludge: A Renewable Source for Energy and Resources Recovery)

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