Solar thermal drying systems for faecal sludge

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  • SeptienS
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  • Post-doctorate from the Pollution Research Group, University of KwaZulu-Natal, Durban
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Re: Solar thermal drying systems for faecal sludge

Dear Debaspreep, 

Solar thermal drying is a cost-effective way to treat FS in countries with good solar radiation. It can combined with technologies as the Omni-Processor, as you indicated. Solar thermal drying systems would substantially increase the production of dried FS compared to conventional drying beds so that the OmniProcessor process will benefit from this performance gain. 
In our tests, we managed to dry around 10 kg of sludge for 1 m2 in a couple of days. We are currently conducting a techno-economic analysis of the process. 

We must continue the conversation by email. You can contact me at: This email address is being protected from spambots. You need JavaScript enabled to view it..

Kindly, 
Santiago
Dr. Santiago Septien Stringel
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  • SeptienS
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Re: Solar thermal drying systems for faecal sludge

Dear Proj Ajit,

Thanks for the comment. 

Yes, the dried sludge can be reused as fertilizer or construction material. It is rich in organic matter and nutrients, and pathogens have been normally deactivated. The dried sludge also exhibits a low thermal conductivity, which is positive for use as construction material (it will act as a thermal insulant agent). 

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Kindly, 
Santiago
Dr. Santiago Septien Stringel
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  • AjitSeshadri
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  • Marine Chief Engineer by profession (1971- present) and at present Faculty in Marine Engg. Deptt. Vels University, Chennai, India. Also proficient in giving Environmental solutions , Designation- Prof. Ajit Seshadri, Head- Environment, The Vigyan Vijay Foundation, NGO, New Delhi, INDIA , Consultant located at present at Chennai, India
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Re: Solar thermal drying systems for faecal sludge

Member Debasreep
FS well dried sanitised very fine.
If dried FSmatter if reused for monetary benefits,  then its more rewarding for communities 
Pl assess if usages possible :
1. As added as Night soil in Brick raw matter with clay at casting phase.
Under FS Bricks are suitable and have good insulation properties 
2. FS admixed with bio matter and evolved as compost soil.
Thank you for your comments 
Well wishes 
Prof Ajit Seshadri 
Prof. Ajit Seshadri, Faculty in Marine Engg. Deptt. Vels University, and
Head-Environment , VigyanVijay Foundation, Consultant (Water shed Mngmnt, WWT, WASH, others)Located at present at Chennai, India

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  • debasreep23
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  • Debasree is a Marie Skłodowska-Curie Actions postdoctoral fellow at Nord University (Norway). She has completed her doctoral study in Waste segregation and treatment using Black Soldier Fly Larvae (BSFL). Her research interest is waste management and faecal sludge management.
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Re: Solar thermal drying systems for faecal sludge

This is a very insightful study to understand the moisture content associated with FS in various forms. Primarily my take after roughly studying this report is that removal of 70% MC (upto capillary moisture) is energy efficiently possible with solar thermal drying with substantial cost savings. If I have understood this correctly (Santiago Please correct me if I haven't understand it correctly), than this can be a win-win situation for Pyrolysis Omni-Processor (POP) and Janicki  Omni-Processor (JOP) because this will substantially help in cutting down the energy cost in drying the FS. Perhaps than Solar supported POP and JOP can be explored further for its techno-commercially feasibility. My previous organization Atlas Sani-Tech has been recommending this and I can see that this scientific report is a testimony of how Solar can be a game changer in Sanitation industry.   
--
Heartful Regards,
Debasree Purkayastha
Marie Skłodowska-Curie Actions (MSCA) Postdoc
Faculty of Biosciences and Aquaculture,
Office no. P341, Nord University, Steinkjer (Norway)
| Google scholar | scholar.google.com/citations?user=CiD64xUAAAAJ&hl=en |
| LinkedIn | www.linkedin.com/in/debasreepenvirontmentalengg/ |
| Researchgate | www.researchgate.net/profile/Debasree_Purkayastha2 |
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  • SeptienS
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Solar thermal drying systems for faecal sludge

Dear Colleagues,
The final report for a project about the development of solar thermal drying systems for faecal sludge treatment is now available at the SuSana library  through the following link: www.susana.org/en/knowledge-hub/resource...library/details/5227.

The project was funded by the Water Research Commission.

Please don't hesitate to contact me in the case of any inquiry or question related to the report.

Kindly,
Santiago

ABSTRACT:
The present project (K5/2897) was about the development, testing and evaluation of two prototype solar thermal drying technologies for the treatment of faecal sludge, namely a greenhouse-type solar dryer and a screw conveyer, and it included a pre-feasibility study. The prototype testing showed that, temperatures between 35 and 45°C could be obtained with peaks up to 50°C, as well as relative humidities lower than 40%, leading to favourable conditions for drying. The prototypes were capable to handle material from viscoelastic consistency (paste-like aspect) to granular solids, but they were not adapted to a too watery feedstock. Under the most favourable weather and operating conditions, the feedstock could be dried in the prototypes at drying rates around 1-2 kg/h/m2, efficiencies up to 30-70% and a specific energy consumption of 100-400 kWh/ton, which is lower than the typical values found in conventional thermal driers (800 and 1000 kWh/ton). The drying rate drastically slowed down at the last phase of drying and the specific energy consumption increased to values superior than 800
kWh/ton, which was presumed to be due to remaining moisture being tightly bounded to the solid matrix. The screw conveyer solar drier shown a higher performance than the greenhouse, but it experienced serious stickiness issues that can compromise the long-term operation of the prototype. This stickiness issues were attempted to be mitigated by mixing the sludge with additives. So far, lime addition to the sludge was observed to diminish the stickiness problem but not yet in a significant way. Based on a techno-economic analysis, it was estimated that the cost to treat one tonne of sludge would be approximately ZAR600 and ZAR150 for the greenhouse and screw conveyor solar thermal drying prototypes, respectively. Some potential technical challenges and areas of improvement were identified after the testing of the prototypes. The operation of the prototypes can be further optimised, which will lead to a further decrease of specific energy consumption, as well as the design specification for the reduction of the construction costs. This study confirmed that solar thermal drying is an interesting cost-effect alternative for faecal sludge treatment. In the developed solar driers, the drying of faecal sludge is expected to occur at the optimal time and at low energy consumption when the weather conditions are favourable, and with the correct operating conditions. The process could be stopped at low moisture content before reaching a high level of moisture boundness where drying progresses very slowly and the process becomes inefficient.
Dr. Santiago Septien Stringel
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