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4.5        Accelerating the transition

Sewage treatment is an essential service which can provide clean water, nutrients and renewable energy. However, in its current operation it uses significant amounts of energy, leads to significant emissions of greenhouse gases and produces sewage sludge in large quantities which may represent disposal problem for utilities. The shift from “waste water management” to “resource hubs” is already happening in some forward-thinking towns and utilities (text boxes).

 Text box: Case study – Net zero emissions - Scottish Water, UK

Scottish Water have a target to reach net zero GHG emissions by 2040. Some actions are directly in their control, such as improving energy efficiency and hosting renewable energy. But others require efforts to influence customers and supply chains, such as the amount of water people use, removing surface water from sewers, and reducing emissions in the cement they buy (Scottish Water, 2021). They have identified areas for innovation, such as low energy treatment methods; ammonia and methane recovery; the need for digital and analytical tools; low/zero emissions materials for investment and operations.

Text box: Case study – Energy efficiency and recovery - Marselisborg UWWTP, Denmark

In 2005, Aarhus City Council decided to upgrade and consolidate its municipal waste water treatment system, which at that time comprised of 17 smaller facilities. The Danish water sector aims to be climate and energy neutral by 2030.

Marselisborg UWWTP has increased plant efficiency and reduced energy consumption by optimising its processes. It now produces 50 % more electricity than it needs for UWWT and 2.9 GW of heat for the district heating system. Energy-saving technologies include an advanced control system, a new turbo compressor, sludge liquor treatment and optimisation of the bubble aeration system. This has resulted in saving approximately 1 GWh/year (c.25 %) in power consumption. By implementing energy efficient solutions and producing biogas from the sludge, the utility is able to cover almost all the energy needed for the whole water cycle - from groundwater extraction, to pump stations, water distribution and waste water treatment.