According to the Public Utilities Board (PUB), the national water agency of Singapore, the current per capita daily water consumption of 154 litres is 9.22 per cent more than the consumption of 141 litres in 2018. The country is facing severe water stress due to the lack of natural aquifers and increased demand for water. In the last few decades, PUB has actively implemented measures to ration water usage and focused on the reclamation of sewage/wastewater. It has been working on closing the water loop by pushing the NEWater approach of water treatment and adopting new digital and sustainable treatment techniques. There has been rapid deployment of internet of things (IoT), data analytics, autonomous systems, artificial intelligence (AI), digital twin, robotics and carbon removal strategies. A look at the key highlights of the advanced and promising sewage treatment initiatives…
Growth of NEWater
Singapore’s water demand is met by four different sources, namely, water from local catchment, imported water, desalinated water, and high-grade reclaimed wastewater known as NEWater. While imported water serves half the water requirement of the country, NEWater contributes a significant share of 40 per cent. This technique recovers water from sewage within the quality standards set by the World Health Organization and the United States Environmental Protection Agency. Currently, there are five operational NEWater plants in Singapore, two of which are located in Changi, and one each in Bedok, Ulu Pandan and Kranji, while a plant in Tuas is under construction. These plants generate roughly 285 million cubic metres of treated water yearly, of which the highest amount (60 per cent) is received from the Changi plant. The Changi plant has the capacity to treat up to 900 million litres of wastewater daily.
As a part of the NEWater approach, the wastewater is first collected at water reclamation plants (WRPs) and then treated at the NEWater plants in three stages, namely, microfiltration or ultrafiltration, reverse osmosis (RO), and ultraviolet disinfection. It is expected that 20 per cent of Singapore’s water demand will be met by the Changi and Tuas plants by 2026 through the deployment of more advanced filtration technologies. The upcoming plant in Tuas is using the MemPulse membrane bioreactor (MBR) system by DuPont and RO technology by FilmTec. These technologies will allow energy efficient functioning of the plant and are proven to be low cost and less carbon-intensive. The execution of this plant is a part of the Deep Tunnel Sewerage System Phase 2 project undertaken by PUB and is scheduled to start initial operations in 2026. It is expected to be the world’s largest MBRbased plant upon completion, with capacity to treat 0.65 million cubic metres of domestic wastewater daily.
Digital initiatives for quality monitoring
Apart from drinking water usage, efficient treatment of wastewater is used for non-potable purposes. In Singapore, of the total consumption of a household, 29 per cent is used for showers, followed by 17 per cent for toilet and 16 per cent for kitchen. Therefore, treated water can be classified and used based on its quality. This has been made possible with the use of various digital tools in Singapore, especially with the adoption of the SMART PUB roadmap. This roadmap is designed to enable the use of technology in different stages of a project from planning to operation and maintenance. It relies on the exploration of five technology components namely, IoT, data analytics, autonomous systems, AI, and digital twin. These digital tools have been used in various ongoing programmes related to wastewater treatment by the Government of Singapore. Some of these are the Smart Water Grid, Smart Drainage Grid, and Smart Water Meter programmes.
As of November 2022, an Itron’s industrial IoT network has been introduced by PUB to connect around 0.3 million residences with smart water meters. This would allow optimisation of water usage and wastewater collection. Similarly, the use of AI in the Smart Water Grid Programme has helped monitor water quality with real-time data. Micro-invertebrates in treated water are detected through an automated detector system with image analytics capabilities.This has also allowed annual savings of 550 manhours per treatment plant as compared to manual inspection. Online sensors are also being used for monitoring different parameters of water such as organic, inorganic, radiological and microbiological. Besides, the NEWater plants are being equipped with data-driven decision support with machine learning and autonomous systems to perform manual high-risk jobs and diagnostic troubleshooting.
In another development, a digital twin prepared by Jacobs Solutions for the Changi WRP has helped control operations in real time with the development of a simulation model. This initiative is the first of its kind in the country and has been integrated with supervisory control and data acquisition system. A combined platform has been created for hydraulics, control systems, and data analytics, which replicates plant operations while predicting its future performance.
Sustainable treatment techniques
While wastewater treatment initiatives are gaining traction in Singapore, the government has also become conscious of introducing sustainable alternatives. Recently, a memorandum of understanding was announced between Xylem Water Solutions Singapore and Gross-Wen Technologies Incorporated to undertake research and development of an environment-friendly wastewater treatment solution. Under the agreement, they will work on a project to use a revolving algal biofilm technology.This algae based technology helps in nutrient recovery of treated water. The utilisation of an anaerobic digestor in the project will capture the carbon dioxide in the atmosphere and reduce the emission of nitrous oxide.
New technologies related to carbon removal and carbon capture, utilisation and storage – CCUS – are also being explored by PUB. It has undertaken studies that can allow the integration of water treatment plants with such technologies and reduce 40 per cent of yearly carbon dioxide emissions. The third edition of its Global Innovation Challenge was launched by PUB in January 2023 for the purpose. It invites innovative proposals for reducing carbon dioxide in water treatment processes along with recovery of phosphorus from wastewater, autonomous drainage inspection, and water quality monitoring. It has also encouraged the development of smart solutions such as smart drain inspectors and sewer sampling robots.
The way forward
Singapore has targeted reducing its per capita water consumption to 130 litres per day by 2030. Water supply through the NEWater approach along with desalinated water is expected to serve 80 per cent of the water requirement by then. The contribution of NEWater alone will reach 55 per cent by 2060 along with a reduction of water imports. PUB plans further technology enrichment to ensure that these goals are met and high-grade reclaimed water reaches more households. It aims to maximise the operational performance of treatment plants with scalable deployment of robotics, network communications, system automation, virtual modelling, remote sensing and predictive analysis systems.