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Used Water

History of Used Water Management in Singapore

The management of used water has come a long way since Singapore’s first water-borne used water infrastructure was built in the 1910s.

At the time, it served only a small portion of the 300,000-strong population. Today, the population has grown to about 5.3 million, and a comprehensive used water infrastructure is in place to serve every household and business.

The First System

The first proposal on how to handle used water in Singapore was prepared in 1890 by Municipal Engineer James MacRitchie. He proposed the collection of nightsoil and disposal by dumping it in the sea. The reason for focusing on nightsoil was the widespread use of the nightsoil system and the unsatisfactory disposal of nightsoil on agricultural land, by burial or by overflows into the monsoon drains. However, MacRitchie’s proposal was not found to be feasible because of unfavourable sea currents and tidal conditions.

In 1893, MacRitchie prepared a further report proposing the municipal collection of nightsoil and its disposal at a plant. In addition, mains would be provided to pump the dry weather flow in the monsoon drains into the sea. The first part of the proposal was implemented and an experimental plant was set up in 1898. It used coal fire to boil off the liquid portion of the nightsoil and reduce the solid portion to a powder called poudrette. Poudrette could be used by farmers as manure in place of nightsoil. However, this plant was discontinued in 1904 as it was expensive to run, it smelled and the farmers did not like using the poudrette.

In 1911, R. Peirce, the then Municipal Engineer proposed dividing the city into 3 areas, each to be served by a trunk sewer that drained into a pumping station. The used water would be sent to a new Sewage Disposal Works at Alexandra Road. There, it would be treated by trickling filters and humus tanks before being discharged into the Singapore River. This scheme was accepted for implementation. Construction started in 1912 and was gradually implemented from 1915 to 1917.

Developing the Infrastructure

The Pre-War Years

The first used water system was completed in 1917 and it was gradually expanded with the addition of more sewers and pumping stations. By the 1930s, the population of Singapore had reached half a million people and a major expansion of the used water system was needed.

The then City Engineer, together with the consultant J. D. Watson, submitted a report to the Municipal Commissioners proposing that nightsoil be collected and pumped to a new activated sludge plant called Kim Chuan Sewage Treatment Works. The digested sludge would then be sent to another new facility, Serangoon Sludge Treatment Works for drying.

These two facilities would serve areas outside the city, in the eastern part of Singapore, that were not previously served by sewers. Some flows would also be diverted into them from the eastern part of the city area which was served by the Alexandra Sewage Disposal Works. The two facilities were completed in the late 1930's just before the Japanese Occupation. As a result, many of the units were not used until the end of the Second World War.


The Post-War Years

After the war, the population hit 1 million. The Alexandra Sewage Disposal Works was overloaded and housing developments were encroaching into its vicinity. In 1955, the City Council engaged the consultant, Messers JD & DM Watson, to prepare plans to remove the Alexandra Sewage Disposal Works. The consultant proposed new sewers and pumping stations to divert the flows into a new facility, Ulu Pandan Sewage Treatment Works which would be located away from the city. These facilities were completed in 1961 and the Alexandra Sewage Disposal Works was then decommissioned.

Concurrently, more sewers and pumping stations were constructed to serve developments in the northern and eastern part of the city. The Kim Chuan  Sewage Treatment Works was expanded in 1963 to serve these developments.


The Era of Independence

The 1960s heralded the development of new towns with multi-storey flats built by the Housing and Development Board. More of the households were served with sewers. The used water facilities required to serve the new towns had to handle the high population density. The first major new town was Queenstown and it was completed at about the time when the Ulu Pandan Sewage Treatment Works was put into use. Following this, the Kim Chuan Sewage Treatment Works was again expanded to serve Toa Payoh New Town. More new towns (e.g. Ang Mo Kio, Tampines, Bedok, Clementi, etc) were subsequently completed with some of them located away from the city. During this period, an industrialisation programme was also initiated and the Jurong area was rapidly developed. It became clear that more new sewage treatment works would be required to cope with these developments. Accordingly, the Bedok, Kranji, Seletar and Jurong Sewage Treatment Works were built between 1979 and 1985.

The Last Nightsoil Bucket

24 January 1987 was another milestone in the history of used water management. On this day, the nightsoil removal service was phased out and the last bucket latrine was replaced by alternative on-site sanitation system.


Separate Sewerage System

Singapore’s first sewerage scheme started in 1910. The system then consisted of only a network of sewers and 3 pumping stations and a trickling filter plant to serve the central area of Singapore.

An intensive sewerage development programme began in the 1960's to meet the demand of the rapid housing and industrialisation programme.

The current sewerage system is designed based on a 'separate system' whereby used water is collected separately in a network of underground sewers that lead to a treatment plant whereas stormwater and surface runoff are collected in open drains and channelled to rivers and reservoirs.

Today, 100% of our population is served by modern sanitation.

Renaming of Sewage Treatment Works to Water Reclamation Plants

On 1 April 2001, the six Sewage Treatment Works were renamed Bedok, Jurong, Kim Chuan, Kranji, Seletar and Ulu Pandan Water Reclamation Plants (WRPs) to emphasise their new role of not only treating used water for discharge into the sea, but also to reclaim used water for reuse. With the implementation of large-scale water recycling, treated used water has become a valuable resource for the production of NEWater which augments water supply.

The Kim Chuan WRP (previously known as Kim Chuan Sewage Treatment Works) along with the Serangoon Sludge Treatment Works were decommissioned in 2007. The Bedok and Seletar WRPs were also decommissioned in 2009 and 2011 respectively.

Today, Singapore’s used water network comprises four WRPS: Ulu Pandan, Jurong, Kranji and Changi.


The Deep Tunnel Sewerage System (DTSS) is an efficient and cost effective solution to meet Singapore's long-term needs for used water collection, treatment and disposal.

Unlike some other countries, Singapore has separate networks to collect used water and rainwater. This reduces the amount of pollution that gets into the waterways and helps ensure that the quality of the water harnessed from the catchments is of good quality.

The DTSS will enable Singaporeans to continue to enjoy a first-class used-water infrastructure for years to come.

Last updated on 11 Mar 2015