All posts by Prithvi Simha

PhD Defence of Prithvi Simha on Alkaline Urine Dehydration, 2nd of June

The public defence of the doctoral thesis for Prithvi Simha, entitled “Alkaline Urine Dehydration. How to dry source-separated human urine and recover nutrients?” is scheduled –

When? 2nd of June at 13:00 Where? Room Framtiden at MVM-hus at SLU in Uppsala and via Zoom Click this URL to join via Zoom: with Passcode: 732271

External reviewer: Professor Nancy Love, Department of Civil and Environmental Engineering, The University of Michigan, Ann Arbor, USA.

Examining committee: Professor Annelie Hedström, Luleå University of Technology, Luleå, Sweden; Docent Sebastian Schwede, Mälardalen University, Västerås, Sweden; and PhD Surendra Pradhan, University of Eastern Finland, Kuopia, Finland

The thesis is openly available at:

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Prithvi Simha’s pre-dissertation PhD seminar

On 5th of March, Prithvi had his pre-dissertation seminar: Alklaine Urine Dehydration – how to dry urine and recover nutrients. David Gustavsson from VA SYD/Sweden Water Research was Prithvi’s opponent at the seminar and he quizzed Prithvi on his published papers as well as his preliminary thesis (or kappa). Overall, it was very interesting and long discussion ranging on topics like reactive nitrogen and ammonia capture, the use of different alkaline substrates, the use of IoT in sanitation and global sanitation outlook. With this successful seminar, Prithvi will now proceed further and have his PhD defence which is scheduled to be held on the 2nd of June in Uppsala and via zoom online. We thank David again for his thorough and insightful discussion on the topic!

Using MgO for Alkaline Dehydration of Human Urine Collected in Source-Separated Sanitation Systems

We recently published a new paper on the use of Magnesium Oxide as an alkaline substrate for dehydrating urine in the journal Frontiers in Environmental Science.

Abstract: Fresh human urine, after it is alkalized to prevent the enzymatic hydrolysis of urea, can be dehydrated to reduce its volume and to produce a solid fertilizer. In this study, we investigated the suitability of MgO to alkalize and dehydrate urine. We selected MgO due to its low solubility (<2 gL−1) and relatively high saturation pH (9.9 ± 0.2) in urine. Using a laboratory-scale setup, we dehydrated urine added to pure MgO and MgO mixed with co-substrates (biochar, wheat bran, or calcium hydroxide) at a temperature of 50°C. We found that, dehydrating urine added to a mixture of MgO (25% w/w), biochar, and wheat bran resulted in a mass reduction of >90% and N recovery of 80%, and yielded products with high concentrations of macronutrients (7.8% N, 0.7% P and 3.9% K). By modeling the chemical speciation in urine, we also showed that ammonia stripping rather than urea hydrolysis limited the N recovery, since the urine used in our study was partially hydrolyzed. To maximize the recovery of N during alkaline urine dehydration using MgO, we recommend treating fresh/un-hydrolysed urine a temperature <40°C, tailoring the drying substrate to capture NH+4 as struvite, and using co-substrates to limit the molecular diffusion of ammonia. Treating fresh urine by alkaline dehydration requires only 3.6 kg MgO cap−1y−1 and a cost of US$ 1.1 cap−1y−1. Therefore, the use of sparingly soluble alkaline compounds like MgO in urine-diverting sanitation systems holds much promise.

Contact: Prithvi Simha

Global survey of food consumer attitudes towards urine recycling

The findings from our multinational study that surveyed the attitudes of about 3800 people from 16 different countries, are now published in Science of the Total Environment and available here:


– Cross-cultural & country-level factors explanatory of respondent attitudes identified
– Respondents had positive intention overall but were unwilling to pay price premiums
– Social norms and cognitive awareness of urine’s benefits & risks featured strongly
– Building consumer trust via context-specific messaging can improve acceptance

Our main findings are best summarised by this picture below, which shows the strengths of association for factors explaining attitude of food consumers towards human urine as fertiliser. Factors are grouped by demographics, social norms, benefit/risk perception, substances that respondents believed are normally excreted in urine, and environmental outlooks. Dots are proportional and indicate the strength of association (Cramér’s V values); dashes indicate categories that could not be analysed due to insufficient data.

Picture inserted shortly.

Contact: Prithvi Simha

Guide to Sanitation Resource Recovery Products & Technologies published!

We are very pleased to share with you the 1st edition of the Guide to Sanitation Resource Recovery Products & Technologies. The Guide is a popular science publication that gives an overview of the possible resources that can be recovered and provides guidance on treatment processes to achieve safe products for reuse. The specific objectives of this document are:

  1. To expose the user to a broad range of recovered sanitation products and innovative treatment technologies.
  2. To help the user to design functional solutions for resource recovery by illustrating the linkages between sanitation inputs, treatment technology and the recoverable products.
  3. To provide an overview of basic information regarding design aspects, operational requirements, and health, safety and social considerations related to resource recovery technologies and products.
  4. Describe and fairly present technology-specific advantages and disadvantages.

The Guide to Sanitation Resource Recovery Products and Technologies is primarily a reference book. It is intended to be used by engineers, planners, end-users, researchers, technology developers, sanitation entrepreneurs, non-governmental organisation (NGO) staff and students who are interested in creating circular systems for resource use. It aims to support and enable decision making for increased resource recovery by providing information on key decision criteria for a range of recovered products and treatment technologies, thus highlighting the diversity of options available for resource recovery.

Links to download the guide:

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Chris Buckley talks to Radio SAfm about urine drying

Last week, following our joint article on urine recycling in The Conversation Africa, Prof. Christopher Buckley from the University of KwZulu-Natal was interviewed by SAfm, South Africa’s national public radio station. In his interview with Stephen Groote, Prof. Buckley talked about our group’s pioneering urine treatment technology, alkaline dehydration, and how the technology holds promise for implementation across Africa. In the coming year, along with Prof Buckley’s research group and local stakeholders, we are hoping to implement our urine drying technology in Durban, South Africa. Listen to the interview below –

Studiebesök med masterstudenter på Hållbara livsmedelssystem

I september månad tog kretsloppsgruppen emot ett studiebesök från masterstudenter på programmet Hållbara livsmedelssystem. I kursen Prospects and challanges for sustainable food systems, som hålls av Pernilla Tidåker, universitetslektor vid institutionen för energi och teknik, ingår ett par föreläsningar om källsorterande avloppssystem och återvinning av näringsämnen och i dessa föreläsningar bakades studiebesöket in.

Victoria Wiklicky, forskningsassistent, gav en introduktion till fluglarvskompostering, Caroline Karlsson, också forskningsassistent, pratade om källsorterande avloppssystem och urintorkning och Annika Nordin, forskare, visade och berättade om kretsloppsgruppens innovativa avloppslösningar.

Studiebesöket hölls utomhus i linje med covid-19-restriktionerna. Studenterna fick cirkulera mellan de tre stationerna, lyssna och diskutera de olika forskningsområdena. De fick även (med avstånd) följa med upp och titta på Energi och tekniks urinsorterande toalett och urintork.

Study visit from Sustainable Food Systems

In September, the environmental engineering group received a study visit from students in the Sustainable Food Systems master program. The course Prospects and challenges for sustainable food systems, held by Pernilla Tidåker who is a senior lecturer at the Department of Energy and Technology, includes a couple of lectures on source separation of waste water and the concept of nutrient recycling. Victoria Wiklicky, research assistant, gave an introduction to fly larvae composting; Caroline Karlsson, also research assistant, talked about source-separation of waste water and urine drying and Annika Nordin, researcher, showed and talked about the environmental engineering group’s innovative waste water treatment solutions. The study visit was held outdoors in accordance with the covid-19 restrictions, the students circulated between the three stations, listened to and discussed the different research topics. They also got to pay a visit (at safe distance) to the urine diverting toilet and drying system at the department of Energy and Technology.

We developed a simple process to recycle urine. Here’s how it’s done in 10 Steps

Every year on November 19, the United Nations celebrates one of public health’s greatest inventions – the toilet. Those who are fortunate enough to have access to one spend more than a year of their lives on it, yet millions of people worldwide cannot use one and many have never even seen one.

Invented back in 1775, the flush toilet has changed surprisingly little in design. In fact, a toilet is nothing more than a seat (or a pan) connected to a pipe with a bend. If this pipe is further connected to a system of sewers that carries away excreta to a centralised treatment plant, then wastewater can safely be discharged into the environment.

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