During the planning of sanitation measures for any community, safe disposal of excreta is of great importance for health and welfare of the concerned population. Sanitation is the highest priority for the local governments over the years now to ensure basic health of the communities.
There is a direct relation between better provision of sanitation facilities, safe drinking water supply and health care at the local level. Thus, improved sanitation and safe drinking water supply should be the highest priority areas to achieve the target of improved health in the urban and rural areas of the country. Keeping all these factors in mind sanitation must be given the highest importance by according it the status of basic human need like food, housing, health etc.
The urban areas are increasing at a very fast rate. These urban centers attract a large chunk of poor population from countryside. Majority of these people do not have adequate resources to take care the housing needs. Thus, majority of this type of population give rise to slums and squatter or unauthorized settlements at the periphery of towns and cities.
In all such localities, health risks are at peak. Higher density levels of population give rise to airborne respiratory infection and diseases due to unhygienic conditions. Malnutrition with in the community makes it highly susceptible for water borne diseases.
Since proper water supply is insufficient in most of the cases, the water borne diseases can spread widely within the community. Thus, adequate sanitation is of prime importance for the well being of the communities in general and in the aftermath of disaster in particulars.
Means and Methods of Adequate Sanitation
A large number of sanitation technologies are available. The selection of most suitable option must be done after careful analysis of all factors including cost, acceptability, operation and maintenance and locally available resources. Various factors can affect the selection of the most suitable option as discussed in the following paragraphs:
i) Water Supply Levels
The amount of water supply available to an individual holds the key in proper selection of sanitation option.
Options like the Ventilated Improved Pit (VIP) Latrines are available where no water is required except for toilet hygiene. This type of options must be utilized when water supply is insufficient. (Say 20-25 liters per capita/daily)
If the water supply is up to 50 liters per capita daily, the options like pour flush and vault toilets are the better options. Similarly, if there are no constraints on water supply, cistern flush toilets with conventional sewerage or septic tank options are more suitable.
ii) Soil Conditions
Local soil conditions play a very important role in determining the sanitation option except for those options, which are completely contained over the ground like vault toilets and bucket latrines. Soil stability and permeability are the two soil characteristics, which determine the technology selection.
The impermeable soil conditions are least appropriate for a majority of the options available. In case of unstable soil, the bases of pits must be lined as in case of Ventilated Improved Pit and Pour Flush toilet options. Rocky soils are the most unwanted soil type for any type of sanction option. In case the ground water table is within 1 meter below the ground surface, various toilet options, which require pits, are not possible at all.
iii) Population Density
The population density is also a very important factor in determining the sanitation options. In high dense areas, VIP latrines are not possible and pour flush toilets and septic tanks with soakways are feasible only under favorable conditions. Conventional sewerage pourflush system and vault toilets are feasible for these areas.
iv) Other factors
Various factors including costs, reuse potential, environmental factors and institutional constraints must be given must be given due consideration prior to finalizing the sanitation option for a particular locality.
i) Open Defecation:
Open defecation is a very common sight in the rural areas of the country. People generally defecate over the places like rubbish heaps, manure heaps, and in the fields. This encourages flies, which may spread various diseases. Other type of infections also develops due to this practice. This is the most undesirable means and must be avoided in the vicinity of human habitation.
ii) Shallow Pits:
This method comprises the digging of a shallow hole and covering the faeces with soil. Pits dug once can be utilized for longer durations also. The excavated soil is heaped beside the pit and some portion of it is put over the faeces after each use. Decomposition of faeces is quite rapid. The method costs nothing and is a good source of fertilizer to the farmers.
However, this method creates a lot of fly nuisance and leads to spread of hookworm larvae over the ground, if the pit is not dug unto one-meter depth.
iii) Simple Pit Latrines:
This type of latrine consists of a slab over a pit, which may be 2m or more in depth. The lavatory has a squatting hole or a seat so that excreta fall down in the pit directly. The slab is firmly supported on all sides and raised over the ground to prevent the water entry into the pit. This is a low cost technique, which requires no water. This type of latrine gives a bad smell and may create fly and mosquito nuisance, if the tight fitting cover over the squatting hole is not provided. When the pit is full up to half, a new pit has to be dug.
iv) Ventilated Improved Pit Latrine:
The ventilated improved pit (VIP) latrines are the improved version of simple pit latrine, where the pit is provided with a vent pipe extending above the latrine roof. The inside of the super structure is kept dark. The vent pipe is provided with a netting to prevent flies and mosquitoes. This type of sanitation system is hygienic, low cost method, which requires no water. The system controls the fly and mosquito nuisance with minimal requirement of user care and involvement. The other advantage is the smell control. However, this type of latrine is highly unsuitable for high-density areas and may pollute ground water. Ventilated improved double pit latrine is another latrine of this type, but with two pits. One pit would be used until full and then sealed while second pit is in use. The first pit is emptied after filling up the second pit and used again.
v) Pour Flush Latrine:
Pour flush latrine have a trap providing water seal beneath the squatting plate. The water seal is cleared of faeces by pouring sufficient quantities of water to wash the solids into the pit. The water seal prevents the flies, mosquitoes and smell reaching the latrine from the pit. The pit is usually connected with the latrine through a short length pipe. It is convenient to have two pits instead of one pit. Both of these pits can be utilised alternatively. This type of latrine is low cost sanitation measure, which also controls the odour, fly and mosquitoes. This type of latrine can be upgraded by connecting it to sewer, when sewerage becomes available. The only drawback is that this system requires large quantity of water.
vi) Compositing Latrine:
In the composting latrines, excreta fall into a watertight tank to which inorganic materials like ash or vegetable waste is added. A careful control over moisture content and chemical balance decomposes the excreta into good manure, which can be utilised as fertilizer. The pathogens are killed during the decomposition process. The compositing latrines are two types. First is the continuous compositing while the second one is with containers used to do the compositing in batches. The method requires very small quantity of water and produces safe and stable humus. The technique is not for high population density areas and requires good quantities of inorganic biodegradable matter. For using this method and extremely high degree of user care and motivation is a must.
vii) Septic Tank Latrines:
A septic tank is a rectangular watertight settling chamber, located below the ground level. The septic tank receives both excreta and flush water from latrines and the raw sewerage from the other household activities. The retention time in the tank is usually 1-3 day, during which the solid particles settle down to the bottom, where they get digested and a thick layer of scum is formed over the surface. The effluent from the septic tanks is usually discharged to soakways of leaching fields. This system works very effectively in the permeable soil conditions and in the areas free from flooding and waterlogging. Now a day the septic tanks with two compartments are commonly used. The septic tanks are usually used for the individual household but can also be used at small community level. The septic tanks require large areas, higher costs and high level of user attention.
Aqua privy has a watertight tank immediately under the squatting hole. The excreta drop down into the tank through a pipe. The bottom of the pipe is submerged into the water in the tank thus preventing the smell, flies and mosquitoes entering the latrine. The tank functions like a septic tank. The effluent usually drains out through a soak pit. A vent pipe is also provided for ventilation. The water level must be maintained by adding sufficient quantities of water after every use to check the losses due to evaporation and leakage. The sludge so formed must be removed regularly. This system is less expensive than the septic tanks and there is no need for piped water supply. The technique is applicable in permeable soils to dispose of the effluent and dislodging requires careful handling by municipality staff. A significant amount of water is also needed.
ix) Overhung Latrine:
In this type of latrine, the excreta drops directly into a water body like river, sea etc. The strong current water takes away the excreta. The local communities must be aware about the higher level for health risks associated with this type of latrine and must take the preventive measures. This is a very cheap option of sanitation but leads to pollution of river/sea.
x) Bucket Latrines:
This type of latrine contains a bucket or other container located immediately below the squatting hole for collection of excreta. These buckets are periodically removed for treatment or disposal by a night soil laborer called scavenger. This system requires very low initial cost but has a very high health risk for those who collect the night soil. It is also against human dignity and has been given up in most places.
xi) Vault and Cartages System:
The vault latrines consist of a watertight tank to store the excreta until a vacuum tanker removes them. The vaults are emptied on regular intervals, when they are nearly full. The performance requires and efficient service along with an efficient infrastructure. Irregular collection can lead to tank overflow and may create unhygienic conditions. This is not a commonly used method.
The sewerage system is designed to transport a mixture of excreta and wastewater from households to the central treatment plant through a network of underground pipes. The system provides highest level of user convenience for all type of wastewater disposal, involving no health risks and a very minimal maintenance. The treated water can be utilized for irrigation purpose. The major hurdle is the very high initial cost, skilled laborer, large amount of water requirements making the system more urbanized and water intensive. If discharged into a water body it requires adequate pre-treatment.