Toilet Technologies
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.
Comment:
- 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.
Comment:
- 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)
Comment:
- 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.
Comment:
- 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.
5) GOUPRI
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)
Comment:
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)
Comment:
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.
Comment:
- 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.
Comment:
- 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.
Comment:
- 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.
Comment:
- 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.
Comment:
- 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.
Comment:
- 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)
Comment:
- 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.