Latest Research: Toilet Technology
INNOVATIONS IN SANITATION: TOILET TECH
Picture a toilet. Is it made of porcelain, perhaps? Does it have a water-filled bowl to collect the waste? Is the waste then flushed into a sewer system?
Does the toilet you imagined have a tank, fed by indoor plumbing? Does the tank hold clean water that is used to refill the toilet bowl?
If you pictured something like this,
chances are that you live in a part of the world where water is relatively plentiful. It’s a fair bet that you have indoor plumbing. And probably all of your neighbours do, too.
Flush toilets are a familiar part of everyday life for many. However, some areas of the world lack the resources to support flush toilets.
India’s water crisis makes flush toilets an impractical solution for the country’s sanitation needs. While flush toilets need no electricity to operate, their water requirements would be impossible to meet.
In addition, less than 15% of sewage in India is currently being treated. Adding yet more sewage to the overburdened waterways would hardly improve the state of sanitation in India.
Although many of us consider the flush toilet a given, there are over two billion people in the world today who do not have any sort of toilet. They don’t have a flush toilet, a pit latrine, or any sort of fixture with waste collection.
Instead, their toilet facilities are open areas. In fields. Near rivers.
India leads the world in open defecation. Untreated human waste contaminates waterways, spreading disease. This practice leads to stunted growth in 39% of India’s children. It has a detrimental effect on maternal and new-born health. It means lower life expectancy.
Some recent toilet innovations have focused on the separation of liquid and solid waste, which can each be reclaimed for different purposes.
Using treated, dried faecal matter for fuel is nothing new. But in the past few years, research has shown that urine can be processed and reused for various purposes, including generating low levels of electricity. In addition, the potassium, phosphate, and nitrogen content of human urine can be recycled into fertiliser.
Shrinking global phosphate reserves drive the need to find a sustainable source of phosphate and other plant-nourishing minerals. Urine certainly fits the bill as a sustainable, renewable resource.
Like urine, reclaimed solid waste can be used as fertilizer. Once treated and dried, it can also become fuel. This fuel can be used to produce electricity.
Recycling human waste for fuel solves several issues. Human waste can provide a renewable, eco-friendly power source, which decreases reliance on dirty fossil fuels or risky nuclear power.
In addition, treating and then recycling the waste means keeping it from contaminating India’s waterways. Since human waste is the single largest source of waterborne disease, recycling the waste will reduce disease.
Stopping the Spread of Disease…by Design
Disease prevention is critical in toilet design. Pit toilets, which take advantage of gravity and require the use of little or no water, often spread diseases because they leave human waste open to insects. These insects spread bacteria and pathogens from human waste into food and water supplies.
Pit toilets with a concrete slab, while more stable than a simple hole in the ground, can still be highly unsanitary. Without a means of sealing off sewage, disease will continue to spread as widely as it has with open defecation.
SaTo—the Safe Toilet
American Standard’s Sanitary Toilet Pan (SaTo) was designed to fit into existing concrete-slab pit toilets. This eliminates the need to rebuild the entire latrine.
SaTo uses a simple but effective mechanism to isolate waste: When a small amount of water is poured into the pan after use, the water pressure causes the trapdoor in the pan drain to open. This allows the urine or faecal matter to slip down into the pit. The trapdoor immediately rises up and seals again, preventing insects such as flies and mosquitos from accessing the waste material in the pit.
This simple innovation—a fairly low-tech mechanical trapdoor—greatly lowers the chances that insects will spread disease from human waste in the pit latrines.
Reinventing the Toilet
Some inventions, like American Standard’s SaTo, are add-ons to existing toilet designs. Generally, they make an improvement to the older concept.
Such add-ons can be integrated with existing units with less effort and cost than complete replacements. However, they often hearken back to older technologies, and ingrained ways of thinking.
Imagine what can be achieved when designers are challenged to reinvent the toilet completely from scratch.
The annual “Reinvent the Toilet Challenge”, sponsored by the Bill and Melinda Gates Foundation, has given rise to ideas from around the world.
The Cranfield Nanomembrane Toilet, recently highlighted on LEAF Society’s Facebook page, holds the promise of bringing household sanitation to areas without electricity, running water, or a sewer infrastructure. The Nano Membrane Toilet provides its own on-board waste processing plant. Like similar systems (such as this one developed at Research Triangle Park), it recycles urine into purified water. The purified water is usable for watering plants or washing. The Nanomembrane Toilet also dries solid waste in preparation for its use as a biofuel.
Back to the Earth
Social business Toilets for People is on its own mission to reinvent the toilet. Declaring composting toilets the “only self-contained technology appropriate for flood-prone areas,” Toilets for People put its own innovative spin on composting with its invention, the Compact Rotating Aerobic Pollution-Prevention Excreta Reducer.
Also known by its acronym, the Crapper, this composting toilet was purpose-built for poor areas.
The process is simple: The user urinates and/or defecates into the horizontally-mounted compost drum. (The drum is contained within the device, accessed through a large hole positioned beneath a Western-style toilet seat). Afterward, the user covers the excrement with dry leaves or sawdust.
Once a week, the user must spin the compost drum inside of the Crapper. The smells from the waste are neutralized by natural aerobic decomposition—and the pathogens present in the excrement are gradually eliminated by the same process.
Toilets for People’s waterless composting process reduces the waste volume by 80%, so the average user only needs to empty the drum about once every eight weeks. The waste can either be buried three decimetres deep in the ground (using wood ash as a disinfectant), or it can be used as fertilizer.
Thinking outside the Bowl
Traditional toilet technology is being revolutionised by a single-use plastic bag.
“Peepoo” is a double-layer bag, made of biodegradable plastic. Rather than being a permanent, multi-use (and multi-user) toilet, Peepoo is intended for one use only—by one single user.
Peepoo unfolds from the top, opening up into a wide funnel. The user can either hold Peepoo in one hand during use, or set it inside a bucket for hands-free operation.
Peepoople provides a supporting product, called the Kiti. The hexagonal Kiti is multi-functional: It simultaneously holds Peepoo open, stands it up inside a bucket-like structure (giving it room to be filled up), and acts as a toilet seat for the user.
Sealing up Peepoo after use is a straightforward process:
- Gather up the inner bag from underneath the funnel-like opening. (This protects the user’s hands from contamination.)
- Fold over the inner bag.
- Slip the folded inner bag back into the outer layer.
- Pull the outer bag over the inner bag completely.
- Tie off the outer bag tightly over the inner layer.
Source : www.leafsociety.com, updated on December 5th, 2016
Latest Innovation in Toilet Technology
Five years ago the Bill and Melinda Gates Foundation challenged researchers around the world to ‘Reinvent the Toilet’. The guidelines were simple, the toilet had to provide a safe sustainable solution to open defecation and cost less than $o.o5 per user per day.
As you all know poor sanitation and lack of hygienic toiletry facilities is one of the biggest killers in the developing world. Around 700,000 children die each year from diarrhoea, often contracted from food or water tainted with faecal matter and women and girls are left vulnerable to attack and rape when leaving their homes to use communal lavatories. One of the main problems in these areas is that many people do not have access to running water, electricity or functioning sewage systems; meaning it is not feasible to have a toilet in the house.
This challenge, which is part of the foundation’s Global Development Programme, was designed to combat these exact problems. Co-Founder Bill Gates released a statement saying, “Innovative solutions change people’s lives for the better. If we apply creative thinking to everyday challenges, such as dealing with human waste, we can fix some of the world’s toughest problems.”
We at SanEco could not agree more. A number of great projects emerged out of this challenge and one of them is set to be trialled in Ghana later this year. Researchers from Cranfield University received an $800,000 grant from the foundation in 2012 and created a self-sustaining nano-membrane toilet which changes solid waste into fuel or fertiliser. This in itself is not a new concept, in fact SanEco toilets are built around the same idea. Our public toilets, being used in schools around Kenya, also separate urine and faeces and through a process of fermentation turn the waste into fertiliser.
What makes Cranfield’s toilets so inventive is that the waste is not only being transformed into useful commodities. The device, which uses Nano-technology, also separates the water from waste and through a process called ‘pervaporation’ converts it into pure clean water that can be used for farming, household washing and even drinking. According to a recent Guardian article, Alison Parker, a water and sanitation expert at Cranfield University, has said that there should even be enough surplus power to charge a mobile phone. This odour free toilet is designed to be used in homes, providing families with a safe eco-friendly sanitary way to dispose of their waste as well as creating local jobs.
Here is a video released by Cranfield Water Science Institute explaining the mechanics of the toilet and the impact it’s having on local communities.
Source : www.saneco.org.uk, Updated on December 5th, 2016
Indestructible and smart: public toilet innovation in India
As a child, Mayank Midha remembers how his mother and sister suffered during long distance journeys in India. They had to “hold themselves up” because there were hardly any decent public toilets on the way.
There is still a shortage of well-maintained public toilets in India, says Mayank. This affects women and girls most. Men can more easily urinate or defecate in the open.
On 7 September 2016, Mayank Midha won the Sanitation Innovation Accelerator 2016, a search for an inclusive and sustainable solution for rural sanitation in India. The judges praised Mayank for developing an indestructible smart toilet, which is much cheaper than comparable models without comprising on quality.
Mayank has been in the manufacturing business for the past seven years. As an engineer with a post-graduate degree in rural management, he is interested in technical solutions for the poorest people at the “Base of the Pyramid” (BoP). After completing a project to manufacture telecom enclosure panels, he saw three spare panels lying in the factory. Their structure made Mayank think, why not change some specifications and use them to construct Portable Smart Toilets?
After a year a prototype was ready in 2015 and in 2016 the stainless steel insulated GARV Toilet was born. Solar panels power LED lights and exhaust fans inside the toilet. Using stainless steel for the superstructure, toilet pans, and washbasins has multiple advantages: the units are vandal-proof, easy to clean and they don’t rust. This means a higher shelf-life with lower operating costs.
Some friends helped Mayank incorporate smart technologies such as sensors and radio-frequency identification (RFID) tags. LED lights and exhaust fans switch on automatically when users open the toilet door. When users exit, the same technology can automatically activate floor washing and toilet pan washing systems.
Mayank’s friends also helped design a prototype dashboard to track data on numbers of users and how many times they flushed and used the soap dispensers. This kind of data, he says, can help implementing agencies monitor their hygiene behaviour change plans.
After a first pilot in Faridabad, Haryana, a Delhi based government contractor contacted Mayank’s business to install these toilets at the base of all footover or pedestrian bridges across the city. While this initial order was for portable toilets without incorporated smart technology, Mayank has now been asked to deliver 348 toilets with solar panels, LED lights and exhaust fans.
GARV Toilets are available in six models. One in particular has caught the attention of government agencies: “Toilets for her”. This model includes a sanitary pad vending machine with sanitary pad incinerators. Another model, suited for areas without sewerage connections, is equipped with biodigesters, which process the faecal matter through bacterial action. The only output is an odourless, colourless liquid that can be used as a pesticide spray.
Source: Sanitation Updates, Updated on December 5th, 2016
This new high-tech toilet could produce clean drinking water and charge your phone
In the future of toilet technology, your loo could be self-powered, recycle waste into water and even charge your mobile phone.
The “nano membrane toilet” is being developed with funding from the Bill and Melinda Gates Foundation, and aims to help bring sanitation into the homes of 2.5 billion people still living without it in developing countries – without needing water supplies or sewage pipes.
However, the team at Cranfield University say it could also be used in the developed world too in a huge range of situations – from luxury yachts to an odour-free alternative to stinky music festival portaloos.
PhD student Jake Larsson, one of the team working on the project, said: “The nano membrane toilet is a project that looks to serve the needs of people in developing countries to stop a major spread of disease, which is inadequate sanitation.
“It is a household scale toilet that produces clean water and manageable, pathogen-free, disposable waste, it’s self-standing, it’s small enough to fit in someone’s home and there’s even a little bit of energy left over to charge a mobile phone.
“It is very diverse. Not only is it for developing countries, but it’s also useful for developed countries, maybe for the military, they’re always in desolate places, or for the construction industry or even for yachts.
“The applications are endless and the need is also there.”
The high-tech toilet gets rid of any unfortunate odours by passing the waste into a separate holding tank. In the tank a “nano membrane” filters water from solid waste and pathogens which are too large to pass through.
The clever loo produces water which is clean enough for washing, cleaning and could be made pure enough to drink. Solid waste is transported to a gasifier, where it’s burned, creating enough energy to power the unit. There’s a little bit of left over energy too which could, in theory, charge your phone.
The Cranfield University team aims to start field testing the toilet in 2016, with a business model that will see communities renting the toilet for less than 5 US cents per user per day from a local franchisee who will be responsible for maintaining the units.
Source: http://www.irishexaminer.com/, 2015
REVIEW OF AVAILABLE TOILET TECHNOLOGIES
Water quality is deteriorating all over the world because of pollution by vast amounts of faecally contaminated material. Existing systems and available resources are often inadequate to deal with the associated social and behavioural factors, thus contributing to the escalation of ecological problems. Sanitation approaches based on flush toilets, sewers and central treatment plants cannot solve the sanitation problem, nor can the problem in high-density urban areas be solved by systems based on various kinds of pit toilets. Whatever technology is implemented, a cardinal principle should be kept in mind: it is better to protect the environment from faecal pollution than to undertake expensive measures to reduce pollution that has already taken place. Sanitation systems should neither pollute ecosystems, nor deplete scarce resources.
A significant change is needed in the manner in which sanitation systems are chosen, designed and implemented. The range of policy options in sanitation should be broadened to include ecological alternatives. The philosophy of ecological sanitation is based on the concept of human excreta as a valuable resource, not simply as a waste product to be disposed of. Key features of ecological sanitation are:
- Prevention of pollution and disease caused by human excreta;
- Treatment of human excreta as a resource rather than a waste product; and
- Recovery and recycling of the nutrients.
With crowded living space there comes the easy spread of disease. People are ignorant to the idea that filth and poor hygiene lead to the deteriorating of health and the spread of diseases. They throw their trash out of the window and allow human excretions to build up in the streets and in outhouses. Open drains, sewers made of poor construction, no running water, and outhouses that overflow lead to bacteria and disease that fill the air.
Toilets are taken for granted and don't get a lot of attention or respect. Historically toilets have improved living conditions and even reduced disease. Today, they are an integral part of virtually every building and home, and are a key component of water conservation. When they work properly, they go unnoticed. However, when the toilet malfunctions or problems occur, it can be very disruptive to day-to-day activities. It's important to recognize that toilets have changed dramatically and not just in appearance. Significant changes have been made over the years. The technological improvements use less fresh water supply than ever before. These enhancements include:
- Trapway diameters have increased, thereby enabling waste to evacuate more efficiently.
- The waterways from the tank to the bowl have been optimized to provide more efficient flow with reduction in velocity.
- The geometry of trapways have been developed to produce stronger siphonic action.
- Due to the latest advances, water surface areas (known as “water spots”) can now be made as large as the older, high water consumption models, resulting in a product that is easier to keep clean.
Considering the vastness of the country with its divergent culture, social customs and attitude together with variations in climate, geological and hydrological conditions and low income of people, design of latrine which could suit the needs of rural and urban population raises several complex problems.1930 onward a dynamic search for safe and economic alternative to sewerage and septic tank system for the disposal of night soil suited to our socio-culture and economic conditions started. Keeping this in mind we are reviewing the available toilet technologies that are functional today or have already become obsolete in the past. This search for alternatives would enable a sanitary environment engineer to design a better system for the future needs, by taking cue’s from the advantages and disadvantages of the technologies already available.
Various low cost sanitation methods developed and tried. They are described here:
1) TRENCH LATRINE
Trench latrine consists of a shallow pit 60 to 90 cm deep and 90 to 120 cm. Wide, either circular, rectangular and square, a wooden plank having a hole in the middle and covered from three sides without either by a tin or thatched. In a trench latrine the users have to put some earth and grass-leaves after defecation. The site of the trench latrine has to be changed after every six months when it is full.
- Trench latrine, although better than open defecation, does not serve the purpose.
- It is very difficult to change its place every six months.
- More over it does not eliminate fly breeding and odour.
- Sometimes bacteria produced in the night soil used to float on the surface of the latrine. Therefore, the people could not adopt this system in general.
2) BORE-HOLE LATRINE
Bore-latrine was developed under the joint collaboration of the All India Institute of Hygiene and Public Health, Calcutta, and the Rockefeller Foundation in pre independence days. It consists of a circular hole, usually 40 cms in diameter, bored vertically into the ground by means of an earth auger to a depth of 6-8 meters. The latrine floor and its super structure are also provided. This is used in the African, Western Pacific and South American countries.
- The greatest difficulty in a borehole latrine is the collapse or caving-in of the pit walls particularly in alluvial soils.
- It requires special equipments for its construction and the possibility of water pollution is also very high in this system.
- Fly breeding is another serious problem in this type of latrine
Due to these reasons the borehole latrine could not get acceptance on a mass scale. (Bhaskaran; 1966)
3) DUG-WELL LATRINE
It is about 75 cm in diameter and 3-6 metres deep in hard soil. The well is lined to prevent caving-in of the soil and is brimmed with concrete around its entry point. The squatting plate is placed over the pit for defecation with a suitable super structure for the privacy of the users. (Bhaskaran; 1966)
- The dug-will latrine is fairly expensive and
- It is difficult to construct it at places where the water table is high.
- The function of the dug-well is the same as that of borehole. If it penetrates ground water, it carries with it the risk of contamination.
Because of these limitations, the dug-well latrine cannot be used in most of the parts of India.
4) ULTA MATKA PRIVY
A large earthenware pot (matka) is buried upside down in a pit, at least 0.75 metre below the ground level, which acts a lining. The Matka is about 1.5 metre high. A hole is made to fix a pipe joining, the wc for discharging the waste. A layer of horse dung is laid at the bottom in the beginning to accelerate the process of decomposition. Salt water is also flushed once a week to help liquification of the faecal matter. The maximum leaching takes place from the open end at the bottom and a little from the porous side of the Matka.
- The gases produced in the pit are absorbed by the soil. When the Matka gets filled up; it is kept close for about two years and the digested material can be used as fertilizer. During this period an alternative Matka has to be provided
- Although Matka privy has been tried in rural areas, it has not gained popular acceptance and adoption on account of its very temporary nature.
Gopuri is a form of compost latrine provided with two tanks, which are constructed over the ground level, instead of being dug in the ground. A movable seat with pan is fixed on the tank in use. The filled up tank is covered with gray earth, ashes, leaves and domestic waste materials. Gopuri latrine has permeable bottom and, like other compost latrines, the night soil filling it up is transformed into compost after a certain period of time. It has a vent pipe, which keeps it reasonably odourless (Bhaskaran; 1966)
Although there is no handling of faeces or urine, fly breeding can be the problem with the Gopuri type. The main disadvantage, however, is the location of its receptacles above the ground level which makes it unsuitable for most of the households in India (Winblad; 1980)
6) SOPA SANDAS LATRINE
It is type of compost latrine, which was first introduced in the State of Maharashtra. It consists of
- RCC or stone slab with concrete or mosaic WC Pan.
- Steep sloping pipe with a tin flap at the upper end.
- Rectangular pit of 120 x 90 x 90 cm.divided into two parts with partial honey-comb brick lining.
- Y-pipe to connect both pits.
A vent pipe to carry away odours from the pit. It has been observed that the tin flap prevents bad odour from entering the toilet and also prevents the passing of flies, etc. The flap, however, wears out after use and has to replace from time to time. The pit is covered with a sheet of tin when full and eventually the human excreta is transformed into compost. It is shoveled from the pit in course of time and spread in the fields to augment the fertility of the soil.
7) HAGEBU LATRINE
This is also a modified form of pit latrine, which is dug upto 90 cms in the first instance with a diameter of 52.5 cm. The diameter is gradually increased to 1120 cm.at the base, while the depth is extended upto 480 to 510 cm. A latrine seat is placed over the pit and a suitable superstructure is also built (Bhaskaran; 1966)
Here also space is a problem, as once the pit is filled up, another fresh pit hole has to be dug nearby. The question of its popular acceptance, therefore, does not arise.
8) BARAPALLI TYPE OF LATRINE
For the environment of villages, Dr. Edwin Abbot developed a pit latrine in the Barapalli village of the State of Orrissa, India. This type of latrine is 90 to 150 cm.deep with a diameter of 75 cm. About 200 sq. ft. of land is needed for the installation of this latrine. A container of tin or an earthen vessel is provided to store water for flushing and also for washing after defecation. A broom is also provided for cleaning the pan. (Bhaskaran; 1966)
9) PRAI TYPE LATRINE
After a number of trials and intensive research spread over a long period, the Planning and Research Action Institute, Lucknow, India, has designed hand flush water-seal latrine with a pan and a trap. Two types were developed- a direct type in which the latrine is placed over the pit and the other type in which the latrine is away from the pit and connected with a pipe. Two or three litres of water are usually sufficient to make by its side, which is connected to the latrine. The contents of the first pit may be used as manure after it is left for a sufficient period.
- The one pit system is not very filled up. In most of the cases house owners dropped the idea of getting constructed the other one. Secondly, the cost of the second pit would go up with the passage of time.
- The PRAI type latrine was constructed mostly during the later part of the 40’s and in the early 50’s, but it remained confined mostly to rural areas.
10) VENTILATED IMPROVED (VIP)
This is based on an improved design of the pit latrine developed in Rhodesia. Aerobic action takes place in the through a cycle provided by air- suction through the toilet seat and up the vent pipe, which is warmed by the sun and thereby draws up the air. It is claimed that the odour emanating from the pit is expelled through the vent pipe.
- As flies cannot enter the pit through the flue pipe, chances of fly breeding in the pit is reduced.
- Other deficiencies, however, continue to exist. The latrine cannot be constructed at places where the groundwater table is high.
- When the pit gets filled up, a new latrine has to be constructed.
- However, the VIP latrine is a considerable improvement over the traditional pit latrine.
11) VENTILATED IMPROVED DOUBLE PIT LATRINE (VIDP)
VIDP latrines differ from the VIP in only respect, viz. that it has two alternating pits. When one is filled up, it should rest for atleast one year before it is emptied to ensure pathogen destruction. The operation and maintenance is the same as that of the VIP. Constructing a separate wall in the VIP pit provides two pits, or by once the pit is full, is precluded.
- As the VIP and VIDP are designed for use without water, they require good maintenance, which consists principally of keeping the squatting plate and superstructure clean. Otherwise, the risk of fly and mosquito breeding is increased.
- The ventilation system has also to be designed properly to minimize fly and other nuisance.
12) REID’S ODOURLESS EARTH CLOSET (ROEC)
An alternate design for the VIP latrine is the ROEC. In this latrine, the pit is completely offset and the excrement is introduced into the pit via a chute. A vent pipe is provided as in the VIP latrine.
- A serious disadvantage of the ROEC, however, is that the chute is easily fouled with the excrement and this may cause fly breeding. The chute is, therefore, to be cleaned regularly by brush.
13) RCA LATRINE
An appropriate design of latrine for rural areas has been designed under the RCA project. Particularly the Poonamallee Centre, near Madras, did considerable work in this direction. A composite design was prepared which embodied the salutary features of the earlier designs.
14) CHEMICAL TOILET
The chemical closet consists of a metal tank containing a solution of caustic soda. A seat with cover is placed over the tank, which is ventilated by a flue rising through the house roof. The excreta deposited in the tank is liquefied and sterilized by the chemical, which also destroys all the pathogens. After several months of operation, this spent chemical and liquefied matter are drained or removed.
- This system is quite satisfactory, safe and hygienic. But, the cost of construction and maintenance of chemical toilet is prohibitive, which is why this system could not become popular.
- This system cannot, therefore, be recommended for a large-scale use.
15) AQUA PRIVY
The aqua privy consists of a tank filled with water into which plunges a drop pipe hanging from the latrine floor. The excreta and the urine fall through the drop pipe into the tank where they under go anaerobic decomposition as in septic tank. The digested sludge, which reduced to about a quarter of the volume of the deposited excreta, accumulates in the tank and has to be removed at intervals.
- In aqua privy, there is no provision of soak pits for the discharge of the effluents. This is therefore, not hygienic.
- Secondly, whenever the water level falls below the drop-pipe, the smell comes out of the tank and the entire surrounding is filled with stink.
- This system could not, therefore, be adopted on a large scale.
16) VIETNAM COMPOST TOILET (THE DOUBLE VAULT LATRINES)
The double vault latrines consists of two receptacles, each with a volume of 300 litres. The receptacles are covered with a squatting slab, which has two holes, foot rests and a channel for urine. Faeces are deposited in one of the receptacles, which can be used for about three to six months by a household of 5-10 persons. Urine is drained away and collected in a jar behind the latrine. The input in the receptacles is, thus, only faeces, ashes and toilet paper. The contents are fairly dry and the decomposition process is the first container is two-thirds full; it is filled with dried and powered earth, ash or paper and then sealed. The other one is used in its place. When the second vault is nearly full, the first is open and emptied. The decomposed excrement, how odourless, provides a good fertilizer. Vietnamese health authorities claim that after 45 days in a sealed container, all bacteria and pathogens get killed (Winblad; 1980)
- From health point of view, this system should be acceptable but it cannot be recommended in India where water is used after ablutions.
- Moreover, it is built above the ground; the latrine cannot be constructed inside the house and has to be located.
17) Sulabh Toilet Technology - Described later