Urban Water Cycle

Water is essential for life. It is constantly renewed by the natural water cycle through processes such as evaporation, condensation and infiltration. These processes recycle water on a global scale and maintain the condition of soils and water bodies. Urbanisation, however, disrupts this natural cycle; impervious surfaces such as roads, roofs and walkways are unable to support infiltration, a process that replenishes the ground with water, thus requiring a localised water management system. The urban water cycle relates to the collection, treatment, distribution and recycling of water to meet the specialised needs of an urban community.

SCELSE’s Urban Water Cycle integrated programme investigates microbial processes associated with two major components of the urban water cycle - used water treatment and engineered waterways (concrete open storm water canals) – in partnership with Singapore’s water utility body, PUB. Using comprehensive meta-‘omics surveys, systems biology analysis and an ecological framework, this integrated programme is systematically assessing the microbial community composition, function, and resilience as well as the role of microbes in the removal of excess organic carbon/nutrients and pollutants in used water treatment and engineered waterways, to ensure a safe supply of water to the city. The research outcomes will further the translation of fundamental biological insights into water management and practices. Emerging work that builds on these concepts and methods includes incorporating biofilm biology and drinking water distribution systems into the integrated program, as another component of the urban water cycle.

Biofilms and used water treatment

SCELSE’s studies of the used water reclamation involve a range of tools, from laboratory scale bioreactors to full-scale water treatment plants. The availability of data on physico-chemical characteristics and process parameters for these systems, generated by PUB and SCELSE, facilitates a systems biology and ecological approach.

Biofilms in used water treatment systems most commonly occur as highly diverse activated sludge communities that range from loosely structured flocs to highly organised granules, with the formation of the latter significantly reducing energy expended, space used and cost incurred in treating used water, as well as enhancing nutrient removal.

To better understand the bioflm processes occurring in activated sludge, SCELSE is focusing on:

  • The nature and dynamics of the bacterial community;
  • The role of communal metabolism in these highly diverse systems;
  • The underlying mechanisms behind phosphorus removal under a tropical temperature regime;
  • Insights to be gained from comparing microbes from different sludge digesters to improve anaerobic digestion of sludge.

Biofilms and engineered waterways

Under PUB’s Active Beautiful Clean (ABC) Waters national campaign, SCELSE will help to develop technical innovations to address some of Singapore’s water challenges. For the waterways study, SCELSE with its expertise on microbial communities and bioprocesses joined an existing large scale environmental engineering program, within ABC Waters framework. PUB plans to integrate engineered waterways with the surrounding environment (via bioremediation, phytoremediation and adsorption) to create a holistic living space of picturesque streams, lakes and rivers. Understanding the transitional changes of biofilms as they are transported through these waterways and impacted by environmental conditions, such as the presence of pollutants and nutrients, will be invaluable in establishing self-purification waterways in Singapore.

Extensive field and flume-based experiments on the waterways are addressing:

  • Community composition and function of sediment microbial biofilms in different catchment areas, and their resilience to perturbations
  • How chemicals in the waterways contribute to shifts in sediment microbiome community composition and function
  • Whether sediment biofilms act as a possible source or sink for pollutants, toxic elements and pathogens
  • The role of the rhizosphere microbial community in phytoremediation of water contaminants.