Resource Recovery Technologies Research Articles

Non-targeted facilitation of primary sludge anaerobic fermentation by micro-aeration and the simultaneous nutrients transformations

Anaerobic fermentation is a widely used technology for resource recovery from municipal sludge (e.g., primary sludge). Micro-aeration is an emerging strategy which can be incorporated into this technology. However, the effect of micro-aeration on the anaerobic fermentation performance and the nutrients transformations are not well known. This study investigated the impact of micro-aeration on the production of volatile fatty acids (VFAs) from primary sludge as well as the simultaneous nitrogen (N) and phosphorus (P) transformations in the system. The obtained results indicated that application of micro-aeration improved the microbial activities and facilitated all the hydrolysis, acetogenesis and methanogenesis processes. Hydrogenotrophic methanogen was enriched by micro-aeration while the acetoclastic methanogenesis was still the dominant CH4 production pathway at gene level. The concentration of VFAs was lower with micro-aeration than in the control system, which could be attributed to the enhanced consumption of VFAs. The simultaneous transformations of N and P were observed with different patterns. Micro-aeration led to removal of up to 131.6 mg/L of N, with occurrence of nitrification and denitrification found to be responsible for the N removal. In contrast, the total P content remained unchanged in the reactor. However, micro-aeration was found to inhibit both extracellular organic-P mineralization and intracellular poly-P degradation, resulting in lower soluble PO43−-P and more P distributed in the organic-P fraction in solid phase. This study provides novel insights into the microscopic mechanisms of the micro-aeration on anaerobic fermentation and the simultaneous regulation of N and P release.

A data-driven framework to inform sustainable management of animal manure in rural agricultural regions using emerging resource recovery technologies

Thermochemical conversion technologies are emerging as preferred resource recovery practices for managing animal manure in agricultural regions. Although the implementation of such technologies has been previously studied, difficulties exist in maintaining balance between high rate of resource recovery and low environmental, economic, and social impacts, particularly in rural regions with limited resources. We developed a data-driven framework by integrating machine learning with life cycle thinking that can be used as an open-source tool to help overcome these barriers. The framework was applied to compare two emerging technologies: pyrolysis versus hydrothermal carbonization for managing the excess poultry litter in a rural agricultural region. Among different machine learning models, random forest regression was the most successful to predict resource recovery of both technologies. Next, sustainability analysis indicated that the environmental (global warming), economic (annual worth), and social (system intrusiveness) impacts of pyrolysis was lower than hydrothermal carbonization. Finally, the framework revealed that implementation of pyrolysis at 600 °C for 1 h with the heating rate of 20 °C/min would result in the highest rate of resource recovery that corresponded to the lowest impacts. These results can be helpful in providing operational conditions for implementing emerging resource recovery technologies in rural agricultural regions.

Performance of feeding black soldier fly (Hermetia illucens) larvae on shrimp carcasses: A green technology for aquaculture waste management and circular economy

Over 944 thousand tonnes of shrimp carcasses are produced worldwide during the shrimp production cycle, and black soldier fly larvae (BSFL) are a potential solution for this shrimp carcass accumulation. In this study, we evaluated the performance of BSFL feeding on shrimp carcasses. Six combinations of wheat bran and shrimp carcass powder (with replacement increments of 20 %) and one whole shrimp carcasses treatment were tested. The bioconversion rate (27.15 ± 3.66 %; p = 0.001), crude protein (55.34 ± 1.27 %; p < 0.001), and crude lipid (14.37 ± 1.86 %; p = 0.007) values of BSFL reared on whole shrimp carcasses were significantly higher than those of BSFL reared on wheat bran. Increasing the shrimp carcass amount in the feeding media resulted in significant increases in BSFL docosahexaenoic acid (with the highest value occurring for BSFL reared on whole shrimp carcasses; 1.46 ± 0.09 %; p < 0.001). Conversely, BSFL docosahexaenoic acid was not detected for BSFL reared on wheat bran. The detected heavy metal concentrations in BSFL were below the limits of the published international guidelines for animal feed. In the obtained BSFL, Salmonella was not detected, and the mould count was <10 CFU/g. The total bacterial count (Lg transformation) of obtained BSFL ranged from 7.88 to 8.07 CFU/g, and no significant differences among all treatments (p = 0.424). Overall, this study demonstrates that BSFL-based bioconversion presents a resource recovery technology for converting shrimp carcasses into high-value nutritional biomass.

The construction of a microalgal-bacterial biofilm reactor for enhanced swine wastewater treatment

Traditional biological wastewater treatment methods face challenges in treating swine wastewater with a low carbon-to‑nitrogen ratio. Microalgae show great potential in low-cost swine wastewater treatment for nutrient recovery. This study investigated the effects of altering the carbon/nitrogen/phosphorus (C:N:P) ratio in swine wastewater and immobilizing microalgae for enhancing treatment using Desmodesmus sp. A C:N:P proportion of 106:16:1 was determined to be optimal for treatment. The implementation of an inclined plate bioreactor facilitated microalgal adherence, forming a biofilm that improved treatment efficiency. The biofilm exhibited removal rates of 92 % for ammonia nitrogen (NH4+-N), 98 % for total phosphorus (TP), and 99 % for chemical oxygen demand (COD). The harvested biomass from the biofilm was 7.6 times higher than that from the suspended system with a high content (63 %) of fatty acids (C16:0, C18:0, C18:1n9c and C18:2n6c) suitable for biodiesel production. Proteobacteria were dominant in the biofilm, while Firmicutes and Bacteroidetes contributed to effective organic matter and nitrogen removal. These findings present a promising technology for cost-effective swine wastewater treatment and resource recovery.

Enhanced the simultaneous removal and recovery of phosphorus in induced crystallization coupled biological phosphorus removal process

Remove and recovery of phosphorus from wastewater is expected to be a promising strategy to solve the shortage of phosphorus resources and control the water environment pollution. In this study, induced crystallization coupled biological phosphorus removal (IC-BPR) process was established to achieve simultaneous removal and recovery of phosphorus in wastewater. The effects of side stream ratio (SSR) on the removal and recovery efficiency of phosphorus and the microbial community structure were explored. The results indicated that the SSR of 40% was optimal to phosphorus removal and recovery in the IC-BPR. The total phosphorus removal efficiency was 94.23% under the SSR of 40%, of which the phosphorus removal efficiency by IC accounted for 74.87%. And the total phosphorus recovery efficiency was 67.29%. The particle size and crystal structure analysis of the crystallized products indicated that the increase of SSR was conductive to heterogeneous crystallization. Furthermore, typical polyphosphate accumulation organisms (PAOs), including Rhodocyclaceae, Acinetobacter, and Dechloromonasin, were enriched under the side stream ratio of 40%. And functional genes related to amino acid transport and metabolism, energy production and conversion were activated. The above results indicated that the IC could significantly enhance the removal and recovery of phosphorus under a suitable SSR condition. It will provide important reference for wastewater treatment coupled phosphorus resource recovery technology.

High-performance antibacterial tight ultrafiltration membrane constructed by co-deposition of dopamine and tobramycin for sustainable high-salinity textile wastewater management

High-salinity textile wastewater is a pressing environmental concern, urgently requiring the appropriate treatment. Sustainable management of high-salinity textile wastewater via fractionation of the existing dyes and inorganic salts (NaCl) using selective separation membranes is a key approach to address this detrimental concern. Herein, tight composite ultrafiltration membranes with impressive antibacterial function were constructed using one-step co-deposition of dopamine and tobramycin on the porous substrate to fractionate the dyes and NaCl. Triggered by ammonia persulfate, the polydopamine/tobramycin coating layer imparts the fabricated composite ultrafiltration membranes with tight surface structure and narrow pore size distribution, enabling effective dyes/salts fractionation. Specifically, the tight composite ultrafiltration membrane with a molecular weight cutoff of 3692 Da experienced a > 98.0 % rejection against various reactive dyes (molecular weight: <1000 Da) with nearly complete salt transmission (<0.8 % NaCl rejection), demonstrating an effective fractionation of dyes and salts. Additionally, the incorporated tobramycin as a broad-spectrum antibiotic endowed the tight composite ultrafiltration membrane with a sufficient inhibition efficiency (i.e., 100 %) against E. coli bacteria in a short-time contact (i.e., 3 min). Thereby, the tight composite ultrafiltration membrane constructed by fast co-deposition of dopamine and tobramycin established an unparalleled platform technology for sustainable resource recovery (dyes or salts) from high-salinity textile wastewater.

Assessment of Effluent Wastewater Quality and the Application of an Integrated Wastewater Resource Recovery Model: The Burgersfort Wastewater Resource Recovery Case Study

Rivers in Africa have experienced dire pollution as a result of the poor management of wastewater effluent emanating from water resource recovery facilities (WRRFs). An integrated wastewater resource recovery model was developed and applied to identify ideal wastewater resource recovery technologies that can be used to recover valuable resources from a mixture of wastewater effluents in a case study in the Burgersfort WRRF in the Limpopo province, South Africa. This novel model incorporates the process of biological nutrient removal (BNR) with an extension of conventional methods of resource recovery applicable to wastewater. The assessment of results of effluent quality from 2016 to 2022 revealed that ammonia, chemical oxygen demand, total coliform, fecal coliform, and Escherichia coli levels were critically non-compliant with the permissible effluent guidelines, indicating a stable upward trend in terms of concentrations, and scored a very bad wastewater quality index rating. All variables assessed showed a significant loading, except for orthophosphates, and significant correlations were observed among the variables. The results of the integrated wastewater resource recovery model revealed a high probability of reclaiming recoverable resources such as nutrients, sludge, bioplastics, biofuel, metals, and water from wastewater, which have economic, environmental, and social benefits, thereby improving the effluent quality of a WRRF.

Development of Risk-Based Approaches to Determining the Damageability and Useful Life of Railway Transportation Assets

Modern problems of railway transport in Russia, such as the general technical condition of transportation assets, and relevant issues of their safe operation, substitution of imported equipment and its components, implementation of the programs of technological development give rise to the need to create new equipment and technologies, constructing schemes for long-term development of transport based on new safety requirements and strategic planning. Current level of developments does not allow to completely eliminate damage, failures and accidents regarding railway transportation assets manufactured in accordance with the current regulatory framework. Solving these problems is possible by identifying the actual state of an object regarding cyclic, corrosion, wear and other damage accumulated during operation, which determines the onset of limit states of the basic elements of an asset, taking into account resource recovery technologies at various stages of the life cycle, both in standard (design) operating conditions and beyond them.The article refers to the problems associated with ensuring safe operation of railway transport, with the aim of substantiating based on existing regulatory and technical documents of new approaches to the analysis of damageability, vulnerability of objects and assessment of the risks of accidents and disasters. The development of interaction through a system of new problem statements and regulatory and technical documents, as well as more active involvement in the use and development of the fundamental laws of physics, chemistry, and mechanics of real-life processes in the environment, make it possible to implement new concepts, strategies, and developments of advanced research for technical objects with the use of digital and intelligent technologies.

Enhanced removal of copper ions from wastewater using small spherical Fe-N-C material via selective electro-sorption: Experiment and calculation

In the current research, the resource recovery technology for Cu-containing wastewater from electroplating is still a difficult problem. Capacitive deionization technology (CDI) has received widespread attention for its strengths of convenient operation, low cost, and environmentally friendly. In this paper, Fe-N-C was prepared as the electrode material for the treatment of Cu-containing wastewater by capacitive deionization technology through one-pot thermal method. The optimum treatment conditions of Fe-N-C for Cu-containing wastewater were voltage equal to 1 V, pH = 5, and the inlet flow rate was 5 mL/min. The electro-adsorption capacity of a single Cu-containing solution of 400 mg/L could reach 389.4 mg/g. Meanwhile, by carrying out ion competition experiments on five cations, namely Zn2+, Na+, Mg2+, K+, and Cu2+, which demonstrated Fe-N-C had a significant selectivity for the electro-adsorption removal of Cu2+. Theoretical calculations revealed that Fe3N and Fe4N were more dominant for Cu2+ adsorption energy and more binding for competing ions in the monovalent state, but had less practical effect on Cu2+ adsorption. The morphology of the Fe-N-C was analyzed in more depth by X-ray photoelectron spectroscopy (XPS) and other characterization methods. Combined with density functional calculations, Cu would not only displace with Fe in FeXN to form a more stable CuXN structure, but also combine with FeXN to form a Cu-FeXN structure. This is conducive to accelerating the application of CDI to recover Cu2+ from heavy metal wastewater.

Sustainability assessment of faecal sludge treatment technologies for resource recovery in Phnom Penh, Cambodia

Selection of appropriate sustainable treatment technologies involves satisfying user requirements, quality standards on treatment and products, and specific socio-technical constraints in the intended context. Using locally adapted multi-criteria assessment (MCA), this study investigated faecal sludge treatment technologies that enable resource recovery in Phnom Penh. A four-step structured approach was applied, involving i) identification of available options, ii) prerequisite screening, iii) MCA and iv) stakeholder discussions and ranking. Data were collected in a literature review, stakeholder interviews and an online survey. Lists of suitable primary (n = 7) and secondary (n = 13) treatment technologies were compiled based on the literature. Four secondary treatment technologies (solar drying, co-composting, vermicomposting, black soldier fly larvae (BSFL) composting) were retained after prerequisite screening and subjected to MCA. Co-composting was ranked highest in MCA, since it performed well in multiple aspects, especially for health criteria. However, when economic return on investment was prioritised and a lower treatment class was accepted, e.g. USEPA Class B biosolids, the highest ranking was achieved by vermicomposting or BSFL composting. If institutional criteria were included in the assessment, solar drying would likely be the highest-ranked option, since this simple technology requires less logistically complex stakeholder arrangements than co-composting. These results show that the ranking obtained for different sludge treatment options depends on criteria weighting and trade-offs. Considering secondary treatment options is crucial during early planning for faecal sludge management in a city of low-and-middle income countries, as the primary treatment must yield appropriate feedstock quality for the secondary treatment step.

A Critical Review of Data Science Applications in Resource Recovery and Carbon Capture from Organic Waste.

Municipal and agricultural organic waste can be treated to recover energy, nutrients, and carbon through resource recovery and carbon capture (RRCC) technologies such as anaerobic digestion, struvite precipitation, and pyrolysis. Data science could benefit such technologies by improving their efficiency through data-driven process modeling along with reducing environmental and economic burdens via life cycle assessment (LCA) and techno-economic analysis (TEA), respectively. We critically reviewed 616 peer-reviewed articles on the use of data science in RRCC published during 2002-2022. Although applications of machine learning (ML) methods have drastically increased over time for modeling RRCC technologies, the reviewed studies exhibited significant knowledge gaps at various model development stages. In terms of sustainability, an increasing number of studies included LCA with TEA to quantify both environmental and economic impacts of RRCC. Integration of ML methods with LCA and TEA has the potential to cost-effectively investigate the trade-off between efficiency and sustainability of RRCC, although the literature lacked such integration of techniques. Therefore, we propose an integrated data science framework to inform efficient and sustainable RRCC from organic waste based on the review. Overall, the findings from this review can inform practitioners about the effective utilization of various data science methods for real-world implementation of RRCC technologies.

Advances in the Application of Quorum Sensing to Regulate Electrode Biofilms in Bioelectrochemical Systems

Bioelectrochemical systems (BESs) are an emerging technology for wastewater treatment and resource recovery. These systems facilitate electron transfer between microorganisms and electrodes, enabling their application in various fields, such as electricity production, bioremediation, biosensors, and biocatalysis. However, electrode biofilms, which play a critical role in BESs, face several challenges (e.g., a long acclimation period, low attached biomass, high electron transfer resistance, and poor tolerance and stability) that limit the development of this technology. Quorum sensing (QS) is a communication method among microorganisms that can enhance the performance of BESs by regulating electrode biofilms. QS regulation can positively impact electrode biofilms by enhancing extracellular electron transfer (EET), biofilm formation, cellular activity, the secretion of extracellular polymeric substances (EPS), and the construction of microbial community. In this paper, the characteristics of anode electrogenic biofilms and cathode electrotrophic biofilms in BESs, EET mechanisms, and the main factors affecting biofilm formation were summarized. Additionally, QS regulation mechanisms for biofilm formation, strategies for enhancing and inhibiting QS, and the application of QS regulation for electrode biofilms in BESs were systematically reviewed and discussed. This paper provides valuable background information and insights for future research and development of BES platforms based on QS regulation of electrode biofilms.

Life-Cycle Assessment of Municipal Solid Waste Incineration Fly Ash Recycling as a Feedstock for Brick Manufacturing

The recovery of municipal solid waste incineration (MSWI) fly ash is currently considered to be the most viable solution for its management. However, in developing resource recovery technologies, it is crucial to consider the overall environmental impact. This study employed a life-cycle assessment (LCA) to compare environmentally friendly red bricks partially utilizing MSWI fly ash as a raw material with conventional red bricks. The results demonstrate that the use of phosphoric acid during the resource recovery process imposes the most significant environmental burden, followed by electricity consumption. To address this issue, in this study, we simulated the replacement of phosphoric acid with phosphoric acid monohydrate recovered from discarded fire extinguishers, resulting in the production of second-generation environmentally friendly red bricks. The analysis revealed that the environmentally friendly red bricks exhibited a mere 5.52% increase in total environmental impact compared with traditional red bricks. Moreover, by stabilizing heavy metals using recovered phosphoric acid monohydrate, the second-generation environmentally friendly red bricks achieved an 8.75% reduction in total environmental impact relative to traditional red bricks. These findings highlight the environmental benefits of fly ash reuse in red brick production, and the incorporation of other industrial waste or byproducts could further enhance its efficacy. The application of the LCA facilitated the identification of key areas for improvement and enabled precise evaluation of the environmental benefits associated with waste reuse.

Evaluation of artificial neural network models for predictive monitoring of biogas production from cassava wastewater: A training algorithms approach

Anaerobic digestion (AD) is an established technology for resource recovery and renewable energy production. However, its performance is dictated by diverse variables including operating parameters and system design. Then, the development of modelling and optimization strategies, such as the application of machine learning (ML), to predict/maintain its performance have received significant attention. In this study, ML integrated based models for predicting cumulative biogas from cassava wastewater AD were developed using artificial neural networks (ANN). Biogas generation was investigated for 21 days with and without the addition of calcium particles from milled calcined chicken waste as a low-cost substitute for buffering. Digestion time, pH, and calcium eggshell-based concentration were selected as input features for biogas prediction through the implementation of the ANN approach. Moreover, seven different training algorithms were used to train the model, and a genetic algorithm (GA) was also implemented to optimize the ANN architecture, resulting in faster learning and higher prediction performance. Given the data set, the Levenberg-Marquardt algorithm with a hyperbolic tangent as a transfer function to the hidden and output layers was the most efficient model in predicting the biogas produced with an R-value of 0.9999.

Thermal Decomposition of H2S at Low Temperature on Mo-Containing Catalysts Derived from MAlO (M = Mg, Co, and Ni) Layered Double Hydroxides

It is increasingly attractive to simultaneously recover the resources of hydrogen and sulfur by catalytic decomposition of hydrogen sulfide (H2S). Restricted by the low yield and high reaction temperature, searching for materials with excellent catalytic activity and stability on thermal decomposition of H2S is significant. A high dispersion and sulfidation degree of MoS2 phases with a promoter (Co or Ni) were prepared with the help of interaction between the layers of hydroxides (CoAl or NiAl) and Mo anions. The NiAlMo-s catalysts exhibited outstanding catalytic activity at 500 °C with H2 yield reaching 49.6%. Several characterizations verified that the excellent performance resulted from the Lewis acid on the surface. Accumulation of sulfides reduced stability, while generation of NiMoS contributed to good stability. Generally, these results will be beneficial to enrich the theory of designing H2S decomposition catalysts. Also, these findings will offer potential application of the resource recovery technology on H2S decomposition.

DMsan: A Multi-Criteria Decision Analysis Framework and Package to Characterize Contextualized Sustainability of Sanitation and Resource Recovery Technologies.

In resource-limited settings, conventional sanitation systems often fail to meet their goals-with system failures stemming from a mismatch among community needs, constraints, and deployed technologies. Although decision-making tools exist to help assess the appropriateness of conventional sanitation systems in a specific context, there is a lack of a holistic decision-making framework to guide sanitation research, development, and deployment (RD&D) of technologies. In this study, we introduce DMsan-an open-source multi-criteria decision analysis Python package that enables users to transparently compare sanitation and resource recovery alternatives and characterize the opportunity space for early-stage technologies. Informed by the methodological choices frequently used in literature, the core structure of DMsan includes five criteria (technical, resource recovery, economic, environmental, and social), 28 indicators, criteria weight scenarios, and indicator weight scenarios tailored to 250 countries/territories, all of which can be adapted by end-users. DMsan integrates with the open-source Python package QSDsan (quantitative sustainable design for sanitation and resource recovery systems) for system design and simulation to calculate quantitative economic (via techno-economic analysis), environmental (via life cycle assessment), and resource recovery indicators under uncertainty. Here, we illustrate the core capabilities of DMsan using an existing, conventional sanitation system and two proposed alternative systems for Bwaise, an informal settlement in Kampala, Uganda. The two example use cases are (i) use by implementation decision makers to enhance decision-making transparency and understand the robustness of sanitation choices given uncertain and/or varying stakeholder input and technology ability and (ii) use by technology developers seeking to identify and expand the opportunity space for their technologies. Through these examples, we demonstrate the utility of DMsan to evaluate sanitation and resource recovery systems tailored to individual contexts and increase transparency in technology evaluations, RD&D prioritization, and context-specific decision making.

Review and Opinions on the Research, Development and Application of Microalgae Culture Technologies for Resource Recovery from Wastewater

Wastewater is an abundant source of nutrients and energy. Under the circumstances of circular economy and carbon neutrality, resource recovery from wastewater has recently been motivated. The microalgal process is a promising alternative for resource recovery from wastewater, and it possesses potential for the cost reduction of wastewater treatment and fertilizer production, energy generation, and greenhouse gas emissions reduction. This paper reviews and discusses state-of-the-art microalgal process development, including microalgal species screening, configuration, biotic consortia construction, infection avoidance, nutrients balancing, operational parameter optimization, and biomass harvesting enhancement. Due to the lack of literature on practical applications, the microalgal process lacks economic and environmental feasibility assessments. Life cycle assessments from the perspective of circular economy and carbon neutrality on upscaled microalgal processes are required for various wastewater scenarios. To promote the upscaled application and successful implementation, efforts are also suggested to establish utilization guidelines, advanced recommendations, reliable standards, and proper safety evaluation criteria. This work could provide a reference and direct the follow-up research, development, and application of microalgae (MA)-based processes for resource recovery from wastewater.

Biostimulation of jarosite and iron oxide-bearing mine waste enhances subsequent metal recovery.

Novel resource recovery technologies are required for metals-bearing hazardous wastes in order to achieve circular economy outcomes and industrial symbiosis. Iron oxide and co-occurring hydroxysulphate-bearing wastes are globally abundant and often contain other elements of value. This work addresses the biostimulation of indigenous microbial communities within an iron oxide/ hydroxysulphate-bearing waste and its effect on the subsequent recoverability of metals by hydrochloric, sulphuric, citric acids, and EDTA. Laboratory-scale flow-through column reactors were used to examine the effect of using glycerol (10% w/w) to stimulate the in situ microbial community in an iron oxide/ hydroxysulphate-bearing mine waste. The effects on the evolution of leachate chemistry, changes in microbiological community, and subsequent hydrometallurgical extractability of metals were studied. Results demonstrated increased leachability and selectivity of Pb, Cu, and Zn relative to iron after biostimulation with a total of 0.027kg of glycerol per kg of waste. Biostimulation, which can be readily applied in situ, potentially opens new routes to metal recovery from globally abundant waste streams that contain jarosite and iron oxides.

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

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.

Integrated resource recovery from aerobic granular sludge plants

The study evaluated the combined phosphorus, nitrogen, methane, and extracellular polymeric substances (EPS) recovery from aerobic granular sludge (AGS) wastewater treatment plants. About 30% of sludge organics are recovered as EPS and 25–30% as methane (≈260 ml methane/g VS) by integrating alkaline anaerobic digestion (AD). It was shown that 20% of excess sludge total phosphorus (TP) ends in the EPS. Further, 20–30% ends in an acidic liquid waste stream (≈600 mg PO4-P/L), and 15% in the AD centrate (≈800 mg PO4-P/L) as ortho-phosphates in both streams and is recoverable via chemical precipitation. 30% of sludge total nitrogen (TN) is recovered as organic nitrogen in the EPS. Ammonium recovery from the alkaline high-temperature liquid stream is attractive, but it is not feasible for existing large-scale technologies because of low ammonium concentration. However, ammonium concentration in the AD centrate was calculated to be 2600 mg NH4-N/L and ≈20% of TN, making it feasible for recovery. The methodology used in this study consisted of three main steps. The first step was to develop a laboratory protocol mimicking demonstration-scale EPS extraction conditions. The second step was to establish mass balances over the EPS extraction process on laboratory and demonstration scales within a full-scale AGS WWTP. Finally, the feasibility of resource recovery was evaluated based on concentrations, loads, and integration of existing technologies for resource recovery.