On the Twin Leach Pit pour flush toilet -TPPFSeptember 28, 2013
Of all the countries grappling with a sanitation problem India tops the list. The number of households without access to a toilet and defecating in the open is nearly a staggering 50 % of the total households in India according to the census of 2011. Even where there is a toilet many simply discharge into the open drains and do not ensure safe disposal. An economic loss of 6.4 % of the GDP amounting to a staggering 53.8 billion US dollars annually was one estimate by the World Bank in 2006 for India. Another recent study establishes a distinct link between open defecation and stunting of growth in children having far reaching implications for a young population.
It is therefore time to revisit a technology more or less developed and fine tuned in India decades ago and which still continues to be extremely relevant for the sanitation sector. This is the Twin pit pour flush toilet – TPPF- to professionals in the sector.
The whole toilet users world is divided into sitters and squatters.
Then there are wipers and washers. The Indian populace is largely squatters and washers. Keeping this factor in mind the TPPF has been designed. It makes use of an Indian squatting pan with a steep slope that uses just 2-3 litres of water to flush and clean. It has a trap with a water seal, usually a minimum of 20 mm. This constant presence of water in the seal ensures that there is no foul smell that comes back into the toilet and that no insects or cockroaches come into the toilet. A 75 mm diameter to 90 mm diameter pipe then takes the washed material to an inspection chamber. Here a diversion trap is made wherein at a time one pipe is opened.
These pipes lead to twin pits which are generally honeycombed. A typical pit would be about 1 metre in diameter and about 1 .5 metre in depth with a solid cover on top. The washed material from the toilet ends up in one pit at a time. A pit takes about one year to fill. Once one pit is full at the diversion chamber the pipeline to this pit is blocked and the other pipe is opened to allow the second pit to fill. The distance between the pits is usually at least a minimum of the depth of one pit i.e. about 1.5 mt. This of course depends on the space available.
While it takes one year for the second pit to fill in the meantime through process of bacterial action the first pit is sanitized for most bacteria, virus and worms. This can then be emptied usually using mechanical evacuation methods such as that of the vacuum trucks called Honeysuckers. The emptied material especially in rural areas can be further composted and used as an excellent fertilizer by farmers.
The superstructure of the TPPF can be permanently done with brick or concrete blocks and a roof of sheet or RCC. In other places they can also be temporary with just privacy ensured for use. Typically a TPPF toilet should cost around Rs 10,000 in most places in India.
Water should be made available only in small buckets of 3 litres for ablutions as well as for pour flushing. This will ensure that excess water is not poured into the pit.
Pits can be designed in high water table areas with a concrete bed and with a 50 cm sand cushion all around. The pits should also be a minimum distance of 8 metres from a water source such as a well or a Borewell. Pits can also be lined with charcoal and limestone to further improve performance and remove pollutants.
Experience has shown that a well designed TPPF can provide safe sanitation and containment of excreta and over the life cycle it can also be much safer than toilets connected to underground sewage treatments with no treatment plants which end up contaminating and polluting water bodies such as rivers and lakes.
In urban areas for those without access to sanitation such as construction workers and in rural areas where open defecation is the norm the TPPF should be pursued and made mandatory for all to use, Skills in its construction also can be developed rather easily .
It is time we revisited this sanitation technology seriously and managed it in a safe manner so that all of India becomes open defecation free, safe sanitation is practiced and the health benefits accrue to all especially the young generation.
In safe sanitation lies water wisdom.