Sanitation the science and practice of effecting healthful and hygienic conditions. Sanitation involves the study and use of hygienic measures to ensure safe and reliable water supply, proper drainage of wastewater, proper disposal of human wastes, and prompt removal of all refuse. The word sanitation actually refers to all conditions that affect health, and according to the World Health Organisation may include such things as food sanitation, rainwater drainage, solid waste disposal and atmospheric pollution.

The principal objectives of providing sanitation facilities are to maintain and improve public health and to minimise environmental pollution. Sanitation can contribute greatly to preventing spread of infectious diseases through transmission of disease causing agents into the body of a healthy person by different media such as contaminated foods and water, contact with contaminated soil and insect vectors.

A sanitation system involves arrangements necessary to store, collect, process and deliver human wastes or other forms of wastes back to nature in a safe manner. Sanitation systems with respect to human management may be considered to have these functions: excretion and storage; collection and transportation; process/treatment; and disposal or recycle. Sanitation systems may have varying combinations of these functions depending on local conditions. A sanitation system can, however, be classified as on-site sanitation and off-site sanitation. Again, sanitation is classified as wet and dry systems.

In Bangladesh, the main problem is proper management of human wastes. In the country, only 16% of the 90 million rural people use sanitary latrines; another 22% use the so-called home-made pit latrines. People are now becoming conscious of using latrines and about 60% of the total population has access to some form of latrines. Of about 30 million urban dwellers, sanitation coverage is available to about 42%. Conventional sewerage systems are used only in parts of dhaka and by only 18% of the city's 9 million people. The sanitation condition of the urban slums is deplorable. Most of the slum dwellers have literally no latrines; only a few have pit or surface latrines.

The major sanitation problem facing the rural people is the dearth of environmentally safe designs for installation of durable and low-cost pit-lined latrines in high water table or flood prone areas. Many latrines installed over the last decade leak and spread pathogens into the environment, particularly during flood conditions. Consumers will need to become aware of the advantages to the environment of certain sanitary latrine designs over others if this type of problem is to be resolved. If designs can be made flood-proof or more effective, the environmental pollution, which currently emanates from sanitary drainage, will be considerably reduced.

Sewerage is another important factor of sanitation. Conventional sewerage systems in Bangladesh exist only in parts of Dhaka city. The only sewage treatment plant at Pagla employs waste stabilisation methods of sewage treatment and discharges treated waste into the river buriganga. Storm water in Dhaka is collected by a separate drainage system. The dhaka water and sewerage authority (DWASA) is responsible for the construction as well as operation and maintenance of the waterborne sewerage system in Dhaka city. Dhaka's sewerage system is characterised by unauthorised connections, particularly by industries, resulting in huge revenue loss and adding unanticipated volumes to collect and treat.

In the absence of expensive conventional sewerage systems, septic tanks and pour-flush sanitation systems are largely used in the urban centres, including the major cities. However, the septic tank effluent disposal has generally been very poor. It is not uncommon to see, particularly in the country townships, septic tank effluents being discharged into open ditches without being aware of the effluent quality and their detrimental effects on the living environment.

Security of supplying pure drinking water is a major part of environmental sanitation. The Dhaka Water Supply and Sewerage Authority is responsible for water supply and sanitation within Dhaka city. Chittagong has a similar organisation, CWASA (Chittagong Water and Sewerage Authority). The current water supply capacity of DWASA is about 900 million litres/day (Ml/d). About 96% of it is obtained from 270 DTWs with the balance coming from two surface water treatment plants. Responsibility for water supply and sanitation outside the two major cities lies with the Department of Public Health Engineering (DPHE), which has been implementing a long-term programme. A total of 61 district towns and about 20 thana headquarters have piped water supplies, which serve, on average, about 25% of their populations. A further 55% of their populations have access to hand tubewells. Most of the piped systems obtain their water from DTWs, although four towns use treated surface water. In general, the piped urban water supplies are not affected by the arsenic problem but some hand tubewells in urban areas are affected.

The government supports involvement of NGOs, market-oriented business organisations and private organisations in water and sanitation development, particularly in the development of different types of tubewells and latrines and in piped water supply where feasible. Finally, the National Water Plan supports provision of credit facilities for the poor to enable them to bear the cost of water and sanitation services independently. [Kazi Matinuddin Ahmed]