The Earth at 360 Degrees.

Sunday, April 19, 2009 12:18 AM

Alternative water supplies for Singapore..

Sources of water supply

Thirty years after the foundation of Singapore in 1819 the population of Singapore had grown from 150 to 50,000 inhabitants, spurred by its role as the port of call for the peninsula. By 1920, when its population touched 400,000, supply from existing hill reservoirs on the island was stretched to the limits. Attempts were initiated to seek sources from Johor on the southern tip of the Malay Peninsula across the Straits of Johor. The Gunung Pulai Scheme was selected and developed and water was supplied to the island through an agreement signed in 1924 between Singapore, a Straits settlement, and the Johor State, both under British colonial rule. In subsequent years new schemes were developed and the Tebrau River Scheme nearer Johor Bahru town was completed in 1953. Water was conveyed to the island via a 1,600 mm pipeline along the causeway from Johor Bahru. A decade later, the Skudai River Scheme and the Johor River Scheme were added; they became operational in 1964 and 1967, respectively, but they were preceded by agreements signed in 1961 and 1962. Some of these schemes were expanded in the 1980s while a new project on the Linggui River in the same state was developed and completed in 1993. In the same year a new agreement was signed between the sovereign republic of Singapore (1) and the Johor state. Johor currently accounts for half of Singapore's daily water needs of 1,299 million [m.sup.3]/day (286 mgd).

Given that a significant amount of water comes from outside its borders, and since water supply is a vital element of its national security, Singapore has been looking towards diversifying its external sources of supply. Indonesia was a logical choice, specifically from the larger islands closer to its borders. In the economic recovery following the mid-1980s recession, the Riau Province of Sumatra was identified not only as a potential economic growth area for Indonesia where Singapore could play a part but also as a potential supplier of water. Water could be conveyed from the Riau islands to Singapore via sub-marine pipelines. An agreement between the two countries, signed in 1991, provided for 4,545 million [m.sup.3] (1,000 million gallons) of water per day from the Riau Province to Singapore. Sungei Kampar on Sumatra was identified as another potential supplementary source of water for the Riau islands, which could be developed with Singapore's participation. Moves were initiated to develop the water supply on Bintan for the neighbouring islands in Riau and for Singapore. In fact, two agreements were signed between the two countries on 29 January 1993: one was a memorandum of understanding to develop water resources in the Sungei Kampar Basin in Sumatra for sale to Singapore (which would also benefit the rest of Riau Province) and the other was an agreement to jointly develop an industrial estate in Bintan (Straits Times 1993). Unfortunately, the economic downturn of 1997/98 and the subsequent political uncertainty in Indonesia put paid to these well-intentioned plans, and Singapore's reliance on Malaysia for its water remains. But this reliance is undesirable in light of the recent deterioration in bilateral ties between the two countries.

Domestic sources

Impoundments and reservoirs

Singapore has several impounding reservoirs inland including Seletar, Peirce and MacRitchie, which occupy 12.3 square miles (about 30 [km.sup.2]) and 12 square miles of protected catchment and unprotected catchment areas, respectively, and which belong to eight streams flowing into the partial pumped-storage Seletar scheme. To increase storage capacity, seven estuarine reservoirs have been developed by damming the river mouths. In the early 1970s Singapore recognised that as a matter of national priority all available water resources on the island should be harnessed, through short-term and long-term schemes (Sung 1972). Given that only 11% of the island's area had been utilised for water collection, the potential for harvesting domestically available water was still significant. It was in that context that a plan to maximise collection of surface resources by extending the present 24.3 square miles (about 75 [km.sup.2]) of collection grounds to 156 square miles (or about 484 [km.sup.2]; 75% of the island's total area) was proposed. Given that geological conditions limited the availability of groundwater (Chou 1972), the plan focused instead on retrieval of stormwater and water recycling.

Stormwater run-off

Harnessing stormwater at minimum cost requires proper land-use planning and pollution control to ensure that stormwater run-off can be efficiently collected and that pollution levels are low. Pollution control policies and enforcement acts were drawn up and promulgated, and, by the 1980s, Singapore was seeing the benefits of these measures. Stormwater harvesting from urban land was consistent with the overall policy of land use in this land-scarce republic, in which land was seen as too valuable for its use to be restricted to a single purpose such as for housing. In the words of the Minister for National Development: If we designate more land for water catchment, there will be less land for housing and other developments. The reverse is also true. Optimising and maximising the use of land and water helped the country to overcome constraints to a certain extent (Straits Times 1996a). Water supply schemes had to be planned to co-exist with other land users and innovative approaches to land use had to be thought out. Given this resolve, Singapore was the first country in South-East Asia to develop viable stormwater run-off schemes. Among the various schemes, the Bedok and Lower Seletar Schemes are the largest. Surface water for these schemes comes mainly from the housing estates and new towns of Ang Mo Kio, Bedok, Tampines and Yishun and the area near Changi International Airport. Water is conveyed to the storage reservoirs of Bedok and Lower Seletar. One important feature of this scheme is the emphasis on close co-ordination between several agencies, such as the Housing Board Development (HDB), the Ministry of the Environment (ENV) and the Planning Department, in order to ensure that water collected from urban surfaces is low in pollutants. Such co-operation and co-ordination between agencies sharing land use in catchment areas ensured that pollution did not result from their development projects (Sung 1972). Thus industries and other potential polluters were excluded from the catchments, construction and erosion curbed, and the drainage system designed in such a way that it channels water through concrete channels to suitable collection ponds situated at topographic low points. An automatic monitoring system ensures that only discharges produced by heavy storms resulting in run-off above a certain volume are collected. The 'first flush', which washes off all accumulated pollutants within the catchment, bypasses the stormwater collection facility and flows directly into the sea (Public Utilities Board Digest 1987). Over the years a number of such schemes have been implemented, and rainwater from as much as half of the island, including new towns, has been harnessed. One example of the innovative approach to stormwater collection is making use of the empty space under the interchange of the Seletar and Bukit Timah expressways for a water collection pond. The space is the size of two football fields with a depth of four Housing Development Board (HDB) storeys (Straits Times 1996b). One obvious concern in collecting water in this way is its quality. Analysis of the water collected showed that, for all parameters measured, the quality is comparable to that produced from natural upland catchments, and Table L adapted from Lee and Nazarudeen (1996), gives an indication of the high quality of stormwater collected in reservoirs. The low-lying nature of the Bedok area accounts for the higher conductivity values, and the coastal soils account for the higher sulphate content. For all other parameters including heavy metals and bacteriological counts the stormwater collected at the Bedok reservoir is of good quality.

Recycling and water reclamation

Recycling of water used in homes and industries is an attempt to augment water supplies locally, treating and using it as a resource rather than letting it flow as waste to the sea. Recycling efforts in Singapore started in 1966 when the Jurong Industrial Water Treatment Plant was commissioned to supply industrial water to the Jurong Industrial Estate. This water comes from treated sewerage effluent and is meant for industrial use in the Jurong area as well as by several oil refineries. In general, the Singapore government encourages industry and private enterprises to recycle water, and liberal tax rebates have been provided for factories that install water-saving plants under the Economic Expansion Incentives Act. An example of a successful programme is that implemented by the semiconductor company, STMicroelectronics, which has invested s$3.9 million (2) since 1995 into three water recycling systems in its wafer fabrication plant and to date has saved almost s$11 million. This translates into a recycling rate of 44% of its water usage, or 4.1 million [m.sup.3] of water saved in the past 3 years (Straits Times 2003c). Under pressure to reduce dependence on supplies from Malaysia, Singapore has aggressively embarked on increasing treatment of waste-water effluent, allowing development of a new product, 'Newater', to standards higher than industrial water. A four-stage process brings waste-water to a quality that is better than that produced by the Public Utilities Board, (3) and exceeds the United States Environmental Protection Agency (US EPA) and World Health Organisation (WHO) standards on all parameters. Treatment begins with the conventional waste-water treatment process, followed by microfiltration to remove suspended solids, colloidal particles, bacteria, some viruses and protozoan cysts, through reverse osmosis to filter all bacteria, viruses, heavy metals and other harmful substances, and finally to ultraviolet disinfection to guarantee complete purity of water, free of any organisms. (4)This water meets the requirements of industries such as the wafer fabrication plants and some commercial buildings, but the intention is to mix with reservoir water to supplement domestic supply. A pilot plant built in 2000 was able to demonstrate the feasibility of reclaiming high-grade water from treated used water using the processes described above. As of 21 February 2003, 2 million gallons (about 9,000 [m.sup.3]) a day, or 1% of consumption, will be blended with raw water in the Bedok, Kranji and Upper Seletar reservoirs (Straits Times 2003a). This amount will increase to some 10 million gallons (about 45,000 [m.sup.3]) a day in 2011, or 2.5% of consumption.

Reduction of water loss in the system

Water supplied from metered sources must be accounted for; the lower this unaccounted-for loss, the more efficient the water supply system. Losses during conveyance can be due to several factors: leakage, pipe breakages, delayed response and repair work, and water theft In many developing counties unaccounted-for water (UFW) may be as high as 30-60% of metered water supply. While technical problems can be solved by replacing old pipes and attending to repairs promptly when reported, water theft must be tackled through legal means. High wastage is a drain on the system: huge revenues are lost and the UFW could easily meet the needs of a significant proportion.

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