Flushing With No Water

By Derek Lam 14 June, 2017

2.4bn people lack clean sanitation but flushing toilets may not be the answer; Derek Lam expands on an alternative

Flushing toilets consume 1.5-2L of water per use; dry sanitation is an alternative in water-scarce countries
DEHTLET is a waterless, chemical-free toilet system: dry organic matter may be used for agri & urine for energy
The system was piloted in the UK in 2010 then later installed in Sichuan for post-earthquake relief & in HK

Clean water and sanitation is a human right. When people, in particular children, have access to clean water, sanitation and hygiene, they lead healthier and more successful lives. Water, sanitation and hygiene are interdependent and these three core issues are grouped together to represent a growing sector.
However, according to UNICEF, there are about 2.4 billion people worldwide without access to proper sanitation and about 946 million people who have to resort to open defecation. Ending open defecation is of utmost importance as contact with human waste can cause diseases such as cholera, typhoid, hepatitis and diarrhoea. Providing clean and safe toilets and changing the behaviour of entire communities towards sanitation are therefore key.

Flushing & dry toilet systems

When we talk about providing toilet facilities, the first thing that often comes to mind is flushing toilets. Common in cities and communities with sewage systems and water treatment plants, flushing toilets consume 1.5 to 2 litres of water per use and are not without its flaws.

A flushing toilet consumes 1.5 to 2 litres of water per use…

For example, during the SARS incident in 2003 in Hong Kong, a malfunction and blockage of the drainage system in Amoy Garden caused such poor ventilation that the aerosol disease back-flowed to the flushing toilets in the building. Therefore, flushing toilets are not necessarily safe if not taken care of properly.

…in countries where water supply is scarce, dry sanitation is an alternative

In countries where water supply is scarce, dry sanitation which can treat human waste without the use of water is an alternative to flushing toilets. There are many traditional dry sanitation facilities such as composting toilets, biological toilets and chemical toilets being used worldwide. However, most of these toilets use anaerobic digestive systems where human waste is kept and stored in an enclosed container for a period before disposal. The risk of flammable and explosive gas emissions and bad smells are the biggest challenges for such dry sanitation techniques.

DEHTLET (Dehydration Toilet): a waterless, chemical-free system

So how can dry sanitation be improved? After the SARS incident, we started to investigate an alternative to current dry sanitation methods and to develop a simple new way to treat human waste safely and without smell.

DEHTLET (Dehydration Toilet) is an aerobic, non-pipe & non-mechanical human waste digestive system that does not use water or chemicals

After several years of research and development, the DEHTLET system was created and was granted a patent in the UK in May 2009. DEHTLET is short for ‘Dehydration Toilet’ and it is an aerobic, non-pipe and non-mechanical human waste digestive system that does not make use of water and chemicals. The system makes use of gravity to filter solid waste from urine. Ventilation also dehydrates the solid waste and oxidizes the urine and most importantly drives odour away. The highlight of the whole system is a wavy separation board, which speeds up the dehydration process by natural wind.
Without any flammable and explosive gas emissions from aerobic digestion, the system is therefore safe and free of smells unlike current models. Eventually, dry organic matters may be collected for agricultural use or disposal if necessary; while urine may be collected as an energy source to produce electricity. Moreover, DEHTLET also has a significantly low carbon footprint as it minimises the unavoidable transportation needed in traditional flushing toilets for service and maintenance.

Advantages of DEHTLET

  • Large effluent releases into watercourses and oceans are avoided
  • Disruption to soils systems through pipeline installation is eliminated
  • Leakage of raw sewage into groundwater through pipe deterioration and breakage is eliminated
  • Nutrients (nitrogen and phosphorus) are kept in tight biological cycles without causing problems to receiving waters
  • It is more cost-effective to treat waste onsite than it is to build and maintain a central sewerage system to which waste needs to be transported
  • Water is not wasted as a transport medium to flush toilets


Wide range of application locations

The DEHTLET system can typically be used for seasonal homes and remote areas where flush toilets are inconvenient or unavailable. Moreover, it can be useful in drought-prone areas, conservation areas and areas with high water tables.
The pilot installation of the DEHTLET toilet system was launched in Sutton Community Farm in the UK in 2010. This installation complied with local authority requirements as no sewage was generated. In addition, as the UK is a windy country, the installed unit does not use electricity and the system is still in perfect conditions 7 years on.

The pilot installation of the DEHTLET toilet system was launched in Sutton Community Farm in the UK in 2010…
…the installed unit is still in perfect conditions 7 years on

Dehtlet UK installation (1)
DEHTLET was also involved in the post-disaster reconstruction of Pengzhou City after the Sichuan Earthquake in 2011. Two portable units were installed to allow easy access to sanitation facilities in more rural areas and a permanent unit was built to serve the village after the disaster.

DEHTLET was also involved in the post-disaster reconstruction of Pengzhou City after the Sichuan Earthquake in 2011

Later, DEHTLET was put to use in Hong Kong. The first 2 units were installed at the TungWah Group of Hospitals Ma Tso Lung Composite in 2013 and in November 2014, 4 more units were set up. A DEHTLET unit was also installed as part of a community project led by the University Of Hong Kong in 2015 in Kam Tin.

HKU project

DEHTLET provides a safe, affordable & hygienic method to treat human waste without polluting the environment

In sum, by making use of natural means, DEHTLET provides a safe, affordable and hygienic method to treat human waste in any location without polluting the environment. With the DEHTLET patent now covering 29 countries (including 19 African countries), this invention can help alleviate sanitation and water pollution challenges around the world.

Further Reading

  • No Safe Haven For Polluters – As affluent eastern Chinese provinces are cleaning-up, companies are relocating to inland provinces with more lenient regulations. China Water Risk’s Hubert Thieriot explores this pollution haven effect & why it can be a short-sighted strategy
  • Integrated Wastewater Treatment In PRD – Guangdong needs RMB39.8bn for wastewater treatment in the 13FYP. Hear from CT Environmental Group’s Liang Xiangjing & Zeng Sasha on how a key wastewater plant can help pollution control in the region as well as benefit its various stakeholders
  • 2016 State of Environment Report Review – The signs are positive for China’s environment in 2016. Groundwater quality improved after 5 years of decline though there is mixed news for rivers & lakes. Is the tide turning in China’s ‘war on pollution’?
  • A New Model In Village Water Management – Water projects in China suffer from sustainability issues. Ivanna Tan from Lien Aid on how their Village Water Management programme overcomes these issues and has delivered clean & sustainable water to more than 72,000 rural villagers
  • Water: Habits & Actions – What are your water habits? Even giving up chocolate for one week can positively impact our waters as Patricia Dwyer, Founder & Director of The Purpose Business Group, tells us. See what other changes you can make
  • Water SMART Blue Buildings For Sustainable Urbanisation – Complete coverage of centralized water & sewage systems may never be possible in China, so what can one do? Ecosoftt’s Stanley Samuel & Marcus Lin share how their Water SMART Blue Buildings Standard can be a valid alternative
  • Changing Filters: Benefits of AFM vs Sand – Sand filters are the primary means of treatment but there are performance & stability issues. Dr Howard Dryden, inventor of the up-cycled AFM® filter tells us how his filter means lower costs & bacteria & longer life


Derek Lam
Author: Derek Lam
Derek was born in Hong Kong in 1960 and graduated from Hong Kong Polytechnic in 1984. He worked as a textile machinery sale engineer until 1991. Then he started a joint venture woollen spinning factory in Zhangjiagang city of Jiangsu Province and he successfully built up the brand Tian Yi worsted yarn in Hong Kong. Derek became an active member of the Hong Kong Institute of Marketing since 1993 and served the institute as Chairman in 1997. Derek worked with the Former Formula One and Motorcycle World champion John Surtees as a motorsport consultant for Chinese market in 2000-2009. In 2003, the outbreak of SARS in Hong Kong killed hundreds of people was caused by the malfunction of drainage system of the flushing toilet. Derek started to investigate an eco-toilet system without the use of water and chemicals. After years of R+D, he successfully launched his products and his new sanitation technology has won three international awards namely World Technology Award from US, Thomas Edison Grand Award from S. Korea and Gold Medal of Taipei Invention Show & Technomart of Taiwan and patents were granted from 29 regions including UK, China, Hong Kong, US and Japan.
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