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Jothinathan H, Singh AP. Fecal sludge characterization, treatment, and resource recovery options: a state-of-the-art review on fecal sludge management. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023; 30:119549-119567. [PMID: 37945951 DOI: 10.1007/s11356-023-30539-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Accepted: 10/13/2023] [Indexed: 11/12/2023]
Abstract
A rise in population and urbanization demanded that a robust fecal sludge management (FSM) value chain be used to restructure the sanitation system throughout the world securely. A significant global need exists to adopt efficient and sustainable FSM. On-site sanitation systems (OSS) produce fecal sludge (FS). FS is produced when excreta and blackwater are combined and stored or treated, either alone or in combination with greywater. FS can be semisolid or slurry and raw or partially digested. Critical examination of FS characteristics, i.e., biochemical oxygen demand (BOD), chemical oxygen demand (COD), total solids (TS), and pathogen count, varies from 600-56,836 mg/l, 6656 to 201,200 mg/l, 830-123,000 mg/l, and 105 to 109 E. coli/l of FS respectively. Helminth eggs range from 2500-25,000/l of FS. Public health and the environment are negatively impacted by septic tank overflows and the careless discharge of FS into open spaces affecting groundwater quality, water bodies, irrigation fields, open drains, places outside villages, etc. Thus, deciding on a proper treatment technology for FS before discharging it into open land or reusing FS is essential to create a pollution-free environment. This paper highlights the practices adopted for FSM under its different processes, such as collecting, characterization, treating, and reusing of on-site FS and bibliometric analysis on documents on fecal sludge. A thorough analysis has been carried out by reviewing all important literature available globally.
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Affiliation(s)
- Harishvar Jothinathan
- Civil Engineering Department, Birla Institute of Technology and Science, Pilani, 333031, India
| | - Ajit Pratap Singh
- Civil Engineering Department, Birla Institute of Technology and Science, Pilani, 333031, India.
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Koulouri ME, Templeton MR, Fowler GD. Source separation of human excreta: Effect on resource recovery via pyrolysis. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2023; 338:117782. [PMID: 37015142 DOI: 10.1016/j.jenvman.2023.117782] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Revised: 03/13/2023] [Accepted: 03/19/2023] [Indexed: 06/19/2023]
Abstract
More people globally are now using on-site sanitation technologies than sewered connections. The management of faecal sludge generated by on-site facilities is still challenging and requires an understanding of all sanitation service chain components and their interactions; from source conditions to treatment and resource recovery. This study aimed to improve the current lack of knowledge regarding these interactions, by establishing a quantifiable relationship between human excreta source separation and resource recovery via pyrolysis. The effects of source separation of faeces and urine on biochar quality were investigated for different pyrolysis temperatures (450 °C, 550 °C, 650 °C) and this information was used to assess energy and nutrient recovery. Results quantify the benefits of urine diversion for nitrogen recovery (70% of total N losses during thermal treatment avoided) and show an increase in the liming potential of the produced faecal-based biochars. The quality of produced solid fuels is also improved when source-separated faeces (SSF) are used as a feedstock for pyrolysis, including a 50% increase in char calorific value. On the other hand, biochars from mixed urine and faeces (MUF) are more rich in phosphorus and potassium, and surface morphology investigation indicates higher porosity compared to SSF biochars. The high salinity of MUF biochars should be considered before agricultural applications. For both biochar types (SSF, MUF), the presence of phosphate compounds of high fertiliser value was confirmed by X-ray diffraction analysis, and temperatures around 500 °C are recommended to optimise nutrient and carbon behaviour when pyrolysing human excreta. These findings can be used for the design of circular faecal sludge management systems, linking resource recovery objectives to source conditions, and vice-versa. Ultimately, achieving consistent resource recovery from human excreta can act as an incentive for universal access to safe and sustainable sanitation.
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Affiliation(s)
- Maria E Koulouri
- Department of Civil and Environmental Engineering, Imperial College London, SW7 2AZ, UK.
| | - Michael R Templeton
- Department of Civil and Environmental Engineering, Imperial College London, SW7 2AZ, UK.
| | - Geoffrey D Fowler
- Department of Civil and Environmental Engineering, Imperial College London, SW7 2AZ, UK.
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Rowles LS, Morgan VL, Li Y, Zhang X, Watabe S, Stephen T, Lohman HAC, DeSouza D, Hallowell J, Cusick RD, Guest JS. Financial Viability and Environmental Sustainability of Fecal Sludge Treatment with Pyrolysis Omni Processors. ACS ENVIRONMENTAL AU 2022; 2:455-466. [PMID: 36164351 PMCID: PMC9502014 DOI: 10.1021/acsenvironau.2c00022] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Revised: 07/11/2022] [Accepted: 07/11/2022] [Indexed: 11/30/2022]
Abstract
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Omni Processors (OPs) are community-scale systems for
non-sewered
fecal sludge treatment. These systems have demonstrated their capacity
to treat excreta from tens of thousands of people using thermal treatment
processes (e.g., pyrolysis), but their relative sustainability is
unclear. In this study, QSDsan (an open-source Python package) was
used to characterize the financial viability and environmental implications
of fecal sludge treatment via pyrolysis-based OP technology treating
mixed and source-separated human excreta and to elucidate the key
drivers of system sustainability. Overall, the daily per capita cost
for the treatment of mixed excreta (pit latrines) via the OP was estimated
to be 0.05 [0.03–0.08] USD·cap–1·d–1, while the treatment of source-separated excreta
(from urine-diverting dry toilets) was estimated to have a per capita
cost of 0.09 [0.08–0.14] USD·cap–1·d–1. Operation and maintenance of the OP is a critical
driver of total per capita cost, whereas the contribution from capital
cost of the OP is much lower because it is distributed over a relatively
large number of users (i.e., 12,000 people) for the system lifetime
(i.e., 20 yr). The total emissions from the source-separated scenario
were estimated to be 11 [8.3–23] kg CO2 eq·cap–1·yr–1, compared to 49 [28–77]
kg CO2 eq·cap–1·yr–1 for mixed excreta. Both scenarios fall below the estimates of greenhouse
gas (GHG) emissions for anaerobic treatment of fecal sludge collected
from pit latrines. Source-separation also creates opportunities for
resource recovery to offset costs through nutrient recovery and carbon
sequestration with biochar production. For example, when carbon is
valued at 150 USD·Mg–1 of CO2, the
per capita cost of sanitation can be further reduced by 44 and 40%
for the source-separated and mixed excreta scenarios, respectively.
Overall, our results demonstrate that pyrolysis-based OP technology
can provide low-cost, low-GHG fecal sludge treatment while reducing
global sanitation gaps.
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Affiliation(s)
- Lewis Stetson Rowles
- Institute for Sustainability, Energy, and Environment, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Victoria L. Morgan
- Institute for Sustainability, Energy, and Environment, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Yalin Li
- Institute for Sustainability, Energy, and Environment, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Xinyi Zhang
- Department of Civil & Environmental Engineering, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Shion Watabe
- Department of Civil & Environmental Engineering, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Tyler Stephen
- Department of Civil & Environmental Engineering, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Hannah A. C. Lohman
- Department of Civil & Environmental Engineering, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Derek DeSouza
- Biomass Controls PBC, Woodstock, Connecticut 06281, United States
| | - Jeff Hallowell
- Biomass Controls PBC, Woodstock, Connecticut 06281, United States
| | - Roland D. Cusick
- Department of Civil & Environmental Engineering, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Jeremy S. Guest
- Institute for Sustainability, Energy, and Environment, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
- Department of Civil & Environmental Engineering, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
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Krueger BC, Fowler GD, Templeton MR, Septien S. Faecal sludge pyrolysis: Understanding the relationships between organic composition and thermal decomposition. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2021; 298:113456. [PMID: 34364246 DOI: 10.1016/j.jenvman.2021.113456] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 07/26/2021] [Accepted: 07/30/2021] [Indexed: 06/13/2023]
Abstract
Sludge treatment is an integral part of faecal sludge management in non-sewered sanitation settings. Development of pyrolysis as a suitable sludge treatment method requires thorough knowledge about the properties and thermal decomposition mechanisms of the feedstock. This study aimed to improve the current lack of understanding concerning relevant sludge properties and their influence on the thermal decomposition characteristics. Major organic compounds (hemicellulose, cellulose, lignin, protein, oil and grease, other carbohydrates) were quantified in 30 faecal sludge samples taken from different sanitation technologies, providing the most comprehensive organic faecal sludge data set to date. This information was used to predict the sludge properties crucial to pyrolysis (calorific value, fixed carbon, volatile matter, carbon, hydrogen). Samples were then subjected to thermogravimetric analysis to delineate the influence of organic composition on thermal decomposition. Septic tanks showed lower median fractions of lignin (9.4%dwb) but higher oil and grease (10.7%dwb), compared with ventilated improved pit latrines (17.4%dwb and 4.6%dwb respectively) and urine diverting dry toilets (17.9%dwb and 4.7%dwb respectively). High fixed carbon fractions in lignin (45.1%dwb) and protein (18.8%dwb) suggested their importance for char formation, while oil and grease fully volatilised. For the first time, this study provided mechanistic insights into faecal sludge pyrolysis as a function of temperature and feedstock composition. Classification into the following three phases was proposed: decomposition of hemicellulose, cellulose, other carbohydrates, proteins and, partially, lignin (200-380 °C), continued decomposition of lignin and thermal cracking of oil and grease (380-500 °C) and continued carbonisation (>500 °C). The findings will facilitate the development and optimisation of faecal sludge pyrolysis, emphasising the importance of considering the organic composition of the feedstock.
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Affiliation(s)
- Benedict C Krueger
- Department of Civil and Environmental Engineering, Imperial College London, SW7 2AZ, UK.
| | - Geoffrey D Fowler
- Department of Civil and Environmental Engineering, Imperial College London, SW7 2AZ, UK
| | - Michael R Templeton
- Department of Civil and Environmental Engineering, Imperial College London, SW7 2AZ, UK
| | - Santiago Septien
- Water, Sanitation & Hygiene Research & Development Centre, University of KwaZulu-Natal, Durban, 4041, South Africa
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