scholarly journals Influence of Post- and Pre-Acid Treatment during Hydrothermal Carbonization of Sewage Sludge on P-Transformation and the Characteristics of Hydrochar

Processes ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 151
Author(s):  
Vicky Shettigondahalli Ekanthalu ◽  
Satyanarayana Narra ◽  
Tommy Ender ◽  
Edward Antwi ◽  
Michael Nelles
Keyword(s):  
Liquid Phase ◽  
Sewage Sludge ◽  
Agricultural Land ◽  
Great Influence ◽  
Calorific Value ◽  
Hydrothermal Carbonization ◽  
Proximate Analysis ◽  
Process Conditions ◽  
P Recovery ◽  
P Leaching

Phosphorus (P) recovery from alternative P-rich residues is essential to meet the growing demands of food production globally. Despite sewage sludge being a potential source for P, its direct application on agricultural land is controversial because of the obvious concerns related to heavy metals and organic pollutants. Further, most of the available P recovery and sludge management technologies are cost-intensive as they require mandatory dewatering of sewage sludge. In this regard, hydrothermal carbonization (HTC) has gained great attention as a promising process to effectively treat the wet sewage sludge without it having to be dewatered, and it simultaneously enables the recovery of P. This study was conducted to analyse and compare the influence of acid (H2SO4) addition during and after HTC of sewage sludge on P leaching and the characteristics of hydrochar. The obtained results suggested that despite using the same amount of H2SO4, P leaching from solid to liquid phase was significantly higher when acid was used after the HTC of sewage sludge in comparison with acid utilization during the HTC process. After HTC, the reduction in acid-buffering capacity of sewage sludge and increase in solubility of phosphate precipitating metal ions had a greater influence on the mobilization of P from solid to liquid phase. In contrast, utilization of H2SO4 in different process conditions did not have a great influence on proximate analysis results and calorific value of consequently produced hydrochar.

scholarly journals Sewage Sludge Treatment by Hydrothermal Carbonization: Feasibility Study for Sustainable Nutrient Recovery and Fuel Production

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2697
Author(s):  
Gabriel Gerner ◽  
Luca Meyer ◽  
Rahel Wanner ◽  
Thomas Keller ◽  
Rolf Krebs
Keyword(s):  
Liquid Phase ◽  
Sewage Sludge ◽  
Hydrothermal Carbonization ◽  
Economic Feasibility ◽  
Phosphorus Recovery ◽  
High Yield ◽  
Nutrient Recovery ◽  
Waste Biomass ◽  
Sludge Treatment ◽  
Sewage Sludge Treatment

Phosphorus recovery from waste biomass is becoming increasingly important, given that phosphorus is an exhaustible non-renewable resource. For the recovery of plant nutrients and production of climate-neutral fuel from wet waste streams, hydrothermal carbonization (HTC) has been suggested as a promising technology. In this study, digested sewage sludge (DSS) was used as waste material for phosphorus and nitrogen recovery. HTC was conducted at 200 °C for 4 h, followed by phosphorus stripping (PS) or leaching (PL) at room temperature. The results showed that for PS and PL around 84% and 71% of phosphorus, as well as 53% and 54% of nitrogen, respectively, could be recovered in the liquid phase (process water and/or extract). Heavy metals were mainly transferred to the hydrochar and only <1 ppm of Cd and 21–43 ppm of Zn were found to be in the liquid phase of the acid treatments. According to the economic feasibility calculation, the HTC-treatment per dry ton DSS with an industrial-scale plant would cost around 608 USD. Between 349–406 kg of sulfuric acid are required per dry ton DSS to achieve a high yield in phosphorus recovery, which causes additional costs of 96–118 USD. Compared to current sewage sludge treatment costs in Switzerland, which range between 669 USD and 1173 USD, HTC can be an economically feasible process for DSS treatment and nutrient recovery.

scholarly journals Influence of Hydrothermal Carbonization on Composition, Formation and Elimination of Biphenyls, Dioxins and Furans in Sewage Sludge

Energies ◽  
2018 ◽  
Vol 11 (6) ◽  
pp. 1582 ◽  
Author(s):  
Heiner Brookman ◽  
Fabian Gievers ◽  
Volker Zelinski ◽  
Jan Ohlert ◽  
Achim Loewen
Keyword(s):  
Sewage Sludge ◽  
Organic Pollutants ◽  
Total Concentration ◽  
Hydrothermal Carbonization ◽  
Process Conditions ◽  
Limit Values ◽  
Composition Formation ◽  
Input Material ◽  
Dioxins And Furans ◽  
Toxicity Equivalent

In many areas of application, the influence of hydrothermal carbonization (HTC) on the composition of organic pollutants is still unexplored. In this study, sewage sludge (SS) was carbonized and the input as well as the hydrochar were examined for the organic pollutants: polychlorinated biphenyls (PCB), polychlorinated dibenzo-dioxins (PCDDs), and polychlorinated dibenzo-furans (PCDFs). The process temperatures of carbonization were 200 °C, 220 °C, and 240 °C and the holding time was 5 h for all tests. The total concentration of PCBs was relatively stable for all temperatures, whereas the toxicity equivalent (WHO-TEQ) at 200 °C and 220 °C increases compared to the input material. The strongest impact on toxicity was observed for PCDDs where concentrations were reduced for higher temperatures, whereas the toxicity increases by more than 16 times for temperatures of 240 °C. The concentrations and toxicity of PCDFs were reduced for all carbonization temperatures. In hydrochar from HTC at 240 °C, the limit values for the application of SS in German agriculture have been exceeded. The results indicate that the process conditions for HTC should be controlled also for SS with average contamination if the hydrochar is to be used as material, especially in agriculture.

scholarly journals Hydrothermal Carbonization as a Strategy for Sewage Sludge Management: Influence of Process Withdrawal Point on Hydrochar Properties

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2890 ◽  
Author(s):  
Fabio Merzari ◽  
Jillian Goldfarb ◽  
Gianni Andreottola ◽  
Tanja Mimmo ◽  
Maurizio Volpe ◽  
...  
Keyword(s):  
Sewage Sludge ◽  
Oxygen Demand ◽  
Hydrothermal Carbonization ◽  
Volatile Matter ◽  
Ash Content ◽  
Process Conditions ◽  
Conventional Activated Sludge ◽  
Phosphorous Content ◽  
Sewage Sludge Management ◽  
Ph Decrease

Conventional activated sludge systems, still widely used to treat wastewater, produce large amounts of solid waste that is commonly landfilled or incinerated. This study addresses the potential use of Hydrothermal Carbonization (HTC) to valorize sewage sludge residues examining the properties of hydrochars depending on HTC process conditions and sewage sludge withdrawal point. With increasing HTC severity (process residence time and temperature), solid yield, total Chemical Oxygen Demand (COD) and solid pH decrease while ash content increases. Hydrochars produced from primary (thickened) and secondary (digested and dewatered) sludge show peculiar distinct properties. Hydrochars produced from thickened sludge show good fuel properties in terms of Higher Heating Value (HHV) and reduced ash content. However, relatively high volatile matter and O:C and H:C ratios result in thermal reactivity significantly higher than typical coals. Both series of carbonized secondary sludges show neutral pH, low COD, enhanced phosphorous content and low heavy metals concentration: as a whole, they show properties compatible with their use as soil amendments.

scholarly journals Hydrothermal carbonization of sewage sludge: Multi-response optimization of hydrochar production and CO2-assisted gasification performance

2021 ◽  
Author(s):  
Shuai Guo ◽  
DanDan Xu ◽  
Xin Guo ◽  
Xingcan Li ◽  
Chenchen Zhao
Keyword(s):  
Acetic Acid ◽  
Sewage Sludge ◽  
Activity Index ◽  
Calorific Value ◽  
Hydrothermal Carbonization ◽  
Carbonization Temperature ◽  
Waste To Energy ◽  
Response Optimization ◽  
C 30 ◽  
Processing Techniques

Abstract The harmful effects of improper sewage sludge (SS) treatment on the environment inspire the search for more benign sludge processing techniques such as hydrothermal carbonization (HTC); the abundant organic matter in SS is used for energy recovery. Herein, response surface methodology (RSM) was used to optimize the HTC-based preparation of SS hydrochar and its gasification performance. Specifically, the hydrochar yield, higher heating value (HHV), and gasification activity index were selected as optimization goals, while carbonization temperature (160–260°C), residence time (30–150 min), and acetic acid concentration (0–1.5 M) were selected as factors influencing the HTC process and CO2-assisted gasification performance. Carbonization temperature was the dominant parameter determining hydrochar yield, HHV, and gasification activity. The hydrochar yield (82.69%) and calorific value (7820.99 kJ kg−1) were maximized under comparatively mild conditions (160°C, 30 min, and 0.07 M acetic acid), whereas the gasification activity index (0.288 s−1) was maximized under harsher conditions (211.34°C, 88.16 min, and 1.58 M acetic acid). The obtained results help to guide the HTC of SS intended for gasification, thus promoting the development of this promising waste-to-energy technology, and may facilitate the design and further optimization of thermochemical SS conversion.

scholarly journals Acid-Induced Phosphorus Release from Hydrothermally Carbonized Sewage Sludge

2021 ◽  
Author(s):  
Carla Pérez ◽  
Jean-François Boily ◽  
Stina Jansson ◽  
Tomas Gustafsson ◽  
Jerker Fick
Keyword(s):  
Sewage Sludge ◽  
Treatment Plant ◽  
Acid Leaching ◽  
Direct Consequence ◽  
Hydrothermal Carbonization ◽  
Phosphorus Release ◽  
Treatment Temperature ◽  
Recovery Treatment ◽  
P Recovery ◽  
Total P

AbstractPhosphorus (P) recovery from P-rich residues is crucial to sustain food and industrial demands globally, as phosphate rock reserves are being depleted. The aim of this study is to investigate the speciation and recovery of P from hydrochars (HC) of a metal-bearing sewage sludge (SS) produced by hydrothermal carbonization (HTC). We here focus on extractions by acid leaching as P cannot be directly recovered by HTC due to insoluble metal-P compounds. Acid leaching of SS and HCs was investigated using H2SO4 and HCl over a range of leaching times, and explained in terms of how composition affects P and metal release efficiency. HTC at 180, 215 and 250 °C showed that P remained immobilized (> 75% of total P) in the HCs. More than 95% was present as inorganic P, and was the direct consequence of the double addition of iron salts in the wastewater treatment plant. Leaching experiments in 2.5 M acid solutions showed that a near complete release of P could be achieved in HCs, while it was only incomplete in SS (up to 85%). Lower acid concentrations were ineffective for total P recovery. Treatment temperature exceeding 180 °C however decreased P release rates, such that total removal took at least 2 h of reaction time instead of a few minutes. On the other hand, acid leaching transferred more than 70% of iron, manganese, copper and zinc into the leachate, necessitating a post-treatment purification process. This work therefore reveals that HC produced at low HTC temperatures could offer promising avenues for time- and energy-efficient P recovery from SS. Graphic Abstract

scholarly journals Sewage Sludge Valorization via Hydrothermal Carbonization: Optimizing Dewaterability and Phosphorus Release

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4417
Author(s):  
Taina Lühmann ◽  
Benjamin Wirth
Keyword(s):  
Sewage Sludge ◽  
Scale Up ◽  
Reaction Times ◽  
Hydrothermal Carbonization ◽  
Phosphorus Release ◽  
Process Conditions ◽  
The European Union ◽  
Relevant Effect ◽  
Input Material ◽  
Initial Ph

As the use of sewage sludge as a fertilizer in agriculture is increasingly restricted in the European Union, other ways to utilize this waste stream need to be developed. Sewage sludge is an ideal input material for the process of hydrothermal carbonization, as it can convert wet biomass into a solid energy carrier with increased mechanical dewaterability. Digested sewage sludge was hydrothermally carbonized at 160–200 °C for 30–60 min with initial pH levels of 1.93–8.08 to determine optimal reaction conditions for enhanced dewaterability and phosphorus release into the liquid phase. Design of experiments was used to develop response surface models, which can be applied to optimize the process conditions. For optimal dewaterability and phosphorus release, low initial pH values (pH 1.93) and mild temperatures around 170 °C are favorable. Because holding time had no statistically relevant effect, a dependency of reaction time was investigated. Though it did not yield substantially different results, it could be included in investigations of short reaction times prospectively. Low reaction temperatures and short holding times are desirable considering economic reasons for scale-up, while the high acid consumption necessary to achieve these results is unfavorable.

scholarly journals Studies on the Gasification Performance of Sludge Cake Pre-Treated by Hydrothermal Carbonization

Energies ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1442 ◽  
Author(s):  
Sang Yeop Lee ◽  
Se Won Park ◽  
Md Tanvir Alam ◽  
Yean Ouk Jeong ◽  
Yong-Chil Seo ◽  
...  
Keyword(s):  
Sewage Sludge ◽  
Moisture Content ◽  
Energy Recovery ◽  
Calorific Value ◽  
Hydrothermal Carbonization ◽  
Treatment Technique ◽  
Gasification Process ◽  
Cold Gas Efficiency ◽  
Sludge Cake ◽  
Gas Efficiency

Proper treatment and careful management of sewage sludge are essential because its disposal can lead to adverse environmental impacts such as public health hazards, as well as air, soil, and water pollution. Several efforts are being made currently not only to safely dispose of sewage sludge but also to utilize it as an energy source. Therefore, in this study, initiatives were taken to valorize sewage sludge cake by reducing the moisture content and increasing the calorific value by applying a hydrothermal treatment technique for efficient energy recovery. The sludge cake treated at 200 °C for 1 h was found to be the optimum condition for hydrothermal carbonization, as, in this condition, the caloric value of the treated sludge increased by 10% and the moisture content removed was 20 wt.%. To recover energy from the hydrothermally treated sludge, a gasification technology was applied at 900 °C. The results showed that the product gas from hydrothermally treated sludge cake had a higher lower heating value (0.98 MJ/Nm3) and higher cold gas efficiency (5.8%). Furthermore, compared with raw sludge cake, less tar was generated during the gasification of hydrothermally treated sludge cake. The removal efficiency was 28.2%. Overall results depict that hydrothermally treated sewage sludge cake could be a good source of energy recovery via the gasification process.

scholarly journals Oxy-steam co-gasification of sewage sludge and woody biomass for bio-methane production: an experimental and numerical approach

2021 ◽  
Vol 238 ◽  
pp. 01006
Author(s):  
Roberto Gabbrielli ◽  
Stefano Frigo ◽  
Luigi Bressan
Keyword(s):  
Sewage Sludge ◽  
Agricultural Land ◽  
Calorific Value ◽  
Woody Biomass ◽  
Chemical Conversion ◽  
Energy Conversion Efficiency ◽  
Numerical Approach ◽  
High Energy ◽  
Added Value ◽  
Sludge Management

Sewage sludge management is a current problem of extreme concern in Europe. Till now, the most frequent route for sludge management has been incineration or the reuse by shedding on agricultural land both directly or after composting. However, this last method is critically reconsidered lately owing to the increasing contamination of sewage sludge by chemicals, heavy metals, residual organic oils, etc.. In the present study, the performance of a steam-oxy gasification plant has been analyzed. The plant allows the thermo-chemical conversion of sewage sludge, together with woody biomass, into a gas mixture (syngas) composed by basic chemicals (synthetic hydrocarbons), suitable for subsequent industrial production of very high added-value products such as methane. In particular, a numerical model of methanation plant, composed by a downdraft gasifier, a syngas cleaning system and a Sabatier reactor, has been created within the commercial code Aspen-One and validated with the results obtained from a real scale air gasifier fed with sewage sludge and woody biomass. First results showed that the steam-oxy co-gasification process has a high energy conversion efficiency that reaches roughly 80% (i.e. produced syngas calorific value vs the dried feedstock calorific value) with an overall methane yield of about 20% (by mass) of the feedstock utilized.

scholarly journals Combustion behaviour of different types of solid wastes and their blends with lignite

2018 ◽  
Vol 22 (2) ◽  
pp. 1077-1088 ◽  
Author(s):  
Andreas Iordanidis ◽  
Argyro Asvesta ◽  
Agapi Vasileiadou
Keyword(s):  
Weight Loss ◽  
Sewage Sludge ◽  
Solid Waste ◽  
Energy Recovery ◽  
Calorific Value ◽  
Proximate Analysis ◽  
Northern Greece ◽  
Inorganic Matter ◽  
Different Types ◽  
Value Determination

The combustion characteristics of blends of lignite with various organic waste materials are evaluated in this study in order to assess their potential for energy recovery. Different types of municipal solid waste (i. e. paper, plastic, textile, organic), as well as sewage sludge and agri-residues (sunflower shells) samples were collected from the Western Macedonia region, northern Greece. Mixtures of each one of them with lignite in different proportions (30-50-70 wt.%) were prepared. Proximate analysis, calorific value determination, and thermogravimetry (TGA/ DTG) were performed. Thermal parameters such as ignition temperature, total weight loss, maximum rate of weight loss, peak and burnout temperatures and burnout time were determined from the TG/DTG profiles of the raw materials and their blends. The combined utilization of proximate analysis, calorific value determination and TG/DTG method proved to be an effective method for a preliminary assessment of the energetic potential of raw solid waste ?combustible? materials and their blends with lignite. The analytical results revealed that most of the blends are promising for energy recovery. Regarding the raw wastes, sunflower shells were the most reactive. A non-synergistic effect was found for the blends. Organic and sewage sludge blends revealed the lowest combustibility, which is attributed to the high content of inorganic matter and the heterogeneity of these two types of wastes.

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