Blog from the Environmental Engineering Research Group at SLU
Decentralised sanitation systems based on source separation and urine recycling can contribute much to the existing wastewater regime. Prithvi Simha and Bjorn VinnerÄs show how innovative technologies such as urine drying can improve the circularity of sanitation systems. Read the full article here: https://www.thesourcemagazine.org/the-disruptive-opportunity-for-mainstreaming-urine-recycling/
Check out our latest article, a collaboration with the Zifu Li group at USTB Beijing that was published in the journal Resources, Conservation and Recycling:
Zhou, X., Simha, P., Perez-Mercado, L. F., Barton, M. A., Lyu, Y., Guo, S., … & Li, Z. (2022). China should focus beyond access to toilets to tap into the full potential of its Rural Toilet Revolution. Resources, Conservation and Recycling, 178, 106100.
Abstract: In China, over 47 million toilets in rural areas have been upgraded since the nationwide sanitation program, popularly referred to as the âtoilet revolutionâ, was launched in 2015. However, little is known about the perceptions of rural households regarding these new toilets or the fate of human excreta collected using them. To investigate the other side of the toilet revolution, we surveyed 980 rural households from 22 provinces across China in 2020. We found that most households used an on-site sanitation system (i.e. septic tanks and pit latrines), where urine and feces were mixed and collected (88%), stored in pits or tanks (79%), emptied by the households themselves (60%), applied on farmland as fertilizer (45%), or used for biogas production (5%). Despite the toilet revolution-driven infrastructure upgrade, only 25% of the households were satisfied with their sanitation system and pointed to health risks from issues in the toilet interface and the treatment and reuse of excreta as areas of concern. The majority preferred an âout of sight, out of mindâ approach, in which the local government handles excreta without involving the households and without asking them to pay for such management. Meanwhile, 80% supported the idea of local nutrient recycling and believed that human excreta should return to farmland as fertilizer or used for biogas production. Our findings suggest that decision makers in local governments across China must urgently explore ways to upgrade all parts of the sanitation service chain so that rural sanitation can be truly improved to positively influence the progress on other national sustainability goals.
Check out the article we wrote with SLU Global for World Toilet Day.
Today is World Toilet Day. According to WHO and UNICEF around four billion people in the world does not have access to a safely managed sanitation service. Untreated wastewater released to the environment can contaminate drinking-water sources, rivers, beaches and food crops, spreading deadly diseases among the wider population. This is rather unfortunate because source-separated wastewater fractions like human urine and faeces are renewable resources from which water, nutrients and energy can be recovered and safely recycled and used as a fertiliser. So SLU cares!
In the wastewater that comes out of a household, human urine makes up just 1% of total volume. However, in terms of nutrients, urine contains more than 80% of the nitrogen and over half of the potassium and the phosphorus. In fact, urine produced by people worldwide contains enough nutrients to fertilise three-quarters of the food we eat.
Earlier this year, Dr. Prithvi Simha from the Department of Energy and Technology at SLU, defended his thesis, which developed a novel on-site sanitation technology called âalkaline urine dehydrationâ to capture all the nutrients in urine without its water. Prithvi and his team at SLU are working to disrupt the way we manage wastewater and design sanitation systems. They believe that resources like urine should be separately collected, safely treated to produce fertilisers, and returned to farmland to close the nutrient loop in our food system. If implemented globally, such a system could reduce the transgression of the planetary boundary for nitrogen and phosphorus by 35% and 25%, respectively.
Today is all about toilets! Can you imagine how your life would be without one? They are a part of our lives so much, that we don’t even think about their existence.
Unfortunately, that is not the case for more than 3.6 billion people. They lack access to safe sanitation and their lives without a toilet are dirty, dangerous and undignified. Public health greatly depends on the toilets, as well as the improvements in gender equality, education, economics, and the environment. Our sustainable future cannot happen without them!
Each of us will spend around a year of their lives using a toilet, so if you have one, thank it and give it some love!
If you want to know more about how we can use toilets to create more sustainable future, please free to check out some of our research:
In our latest paper, published in the Chemical Engineering Journal, we show how all the nitrogen in fresh human urine can be captured in the form of solid urine-based fertilisers.
Abstract: Recycling urine can reduce the flux of reactive nitrogen in the environment. This paper presents a novel approach to recover all N (Ntot) from urine, including ammonia (TAN; about 5% of Ntot), which is usually volatilised when alkalised urine is dehydrated. As analytical methods for measuring N have a standard deviation of at least 5%, real fresh urine was fortified with ammonia (urineN) or ammonia and phosphate (urineNP) so that TAN comprised 10% of Ntot. The urine was then added to different magnesium-based alkaline substrates (MgO, Mg(OH)2, MgCl2 + Mg(OH)2) and dried at 38 ËC. Chemical speciation modelling suggested that, irrespective of the substrate, >98% of Ntot in urineNP was recovered and 86% of TAN was precipitated as struvite. Experimental results showed that < 90% of Ntot was recovered when urineNP was dried in MgO and Mg(OH)2, suggesting that no TAN was captured. However, all phosphorus and potassium and 93% (±5%) of Ntot and 30% of TAN were recovered when urineNP was dried in MgCl2 + Mg(OH)2, as the [Mg]:[NH4]:[PO4] molar ratio of 1.69:1.14:1.0 in urine favoured formation of struvite. Overall, this study demonstrated that all ammonia excreted in real fresh urine (unfortified, TAN < 5% Ntot) can be captured if urine is dried in substrates containing 3.7 g MgCl2·6H2O Lâ1 or 2.2 g MgSO4 Lâ1, but no calcium. Ammonia can also be captured if fresh urine is saturated with MgO or Mg(OH)2 with high reactivity (<60 s citric acid test). If the drying substrate has pH > 10 throughout the treatment, urease enzyme-catalysed degradation of urea to ammonia is prevented, resulting in complete recovery of all nutrients. The end-product is a solid fertiliser containing 10â11% nitrogen, 1â2% phosphorus and 2â3% potassium.
Check out our new publication following up on China’s nationwide sanitation campaign, “the toilet revolution” in the journal, Science of the Total Environment.
Abstract: The ongoing Toilet Revolution in China offers an opportunity to improve sanitation in rural areas by introducing new approaches, such as urine source separation, that can contribute to achieving SDG6. However, few studies have systematically assessed the social acceptability of managing human excreta collected in new sanitation systems. Therefore, in this study we performed face-to-face interviews with 414 local residents from 13 villages across three provinces in western China, to analyze the current situation and attitudes to possible changes in the rural sanitation service chain. We found that the sanitation chain was predominantly pit latrine-based, with 86.2% of households surveyed collecting their excreta in a simple pit, 82% manually emptying their pits, and 80.2% reusing excreta in agriculture without adequate pre-treatment. A majority (72%) of the households had a generally positive attitude to production of human excreta-derived fertilizer, but only 24% agreed that urine and feces should be collected separately. Multivariate logistic regression indicated that three factors (level of education, number of permanent household residents, perceived social acceptability) significantly influenced respondents’ attitudes to reuse of excreta, although only perceived social acceptability had a high strength of association. Overall, our survey revealed that rural households often misuse toilet systems, fail to comply with government-specified sanitation guidelines, have low awareness of alternative solutions, and are over-reliant on the government to fix problems in the service chain. Thus while new sanitation technologies should be developed and implemented, information campaigns that encourage rural households to manage their excreta safely are also important.
Docent Jennifer McConville, at the Department of Energy and Technology, is one of the five researchers who has been awarded 3 million SEK as a career grant from the Vice-Chancellor of SLU.
SLUâs Career Grant is launched every second year to award researchers at the early stage of their careers. They receive a grant of 3 million SEK each. Jennifer McConville’s research uses systematic and applied sustainability analysis as decision support in planning and decision-making regarding sanitation and wastewater management. The aim is to improve resource recovery from these systems by adapting technical infrastructure and institutional arrangements. She performs her research in Sweden as well as low- and middle-income countries. She uses life cycle thinking, participation and socio-technical analysis to better understand and shape planning processes so that they can transition towards sustainability.
Jennifer McConville plans to use the career grant together with her research group to:
The results of Jennifer McConville’s research will help authorities responsible for sanitation and wastewater management to increase resource recovery and choose more sustainable systems.