SYKE Policy Brief: Enhanced utilization of wastewater nutrients

“More efficient recovery of nutrients from wastewater is a topical issue in today’s uncertain world situation, where the availability of nutrients can become increasingly difficult”, says Senior Research Scientist Suvi Lehtoranta from Finnish Environment Institute (SYKE), and continues: 

“Wastewater nutrients can replace artificial fertilizers used in agriculture and nutrients used by industry. This would improve security of supply. It would also reduce dependence on fossil fuels and imports while conserving natural resources.” 

According to Lehtoranta new technologies should be introduced in wastewater treatment plants and in sewage sludge processing, especially for the recovery of nitrogen, which is a critical nutrient in food production and industrial processes. 

“New technologies for recovering nutrients have already been developed in Finland and abroad, and more are being developed constantly”, Lehtoranta says. 

Highly processed nutrient products are most likely to end up in industrial use. “From the point of view of the security of food production, it would also be important to steer enough nutrients to agricultural use, if necessary”, Lehtoranta says. 

Source separation would lead to more efficient recovery of nutrients 

In the long term, bigger changes to wastewater systems are needed. 

In new residential areas, and when renewing old sewage networks, source separation of wastewater should be introduced whenever possible. Source separation can be implemented with double drainage, where nutrient-rich wastewater, such as blackwater, is treated separately from other wastewaters. This prevents nutrient-rich wastewater from being diluted by nutrient-poor wastewaters with a high volume of water, from which nutrient recovery is more difficult. 

Forty percent of Finland's sewer network will need renovation by 2040. “In connection with renovations, it would be important to find out whether it would be appropriate to introduce source separation of wastewater”, Suvi Lehtoranta observes. 

Such solutions have been introduced in new urban residential areas in Sweden and the Netherlands, for example. “The experiences have been good, and the costs have been reasonable, and bigger systems are being planned” Lehtoranta says.  

EU is revising its wastewater directive 

The European Union is currently revising its directive on the treatment of municipal wastewater. According to the proposal, minimum requirements should be set for the recovery of nutrients in sewage sludge treatment.  

“The directive should set clear and ambitious requirements for nutrient recovery. It should consider nutrients from sewage sludge processing and those recovered directly from wastewater”, says Senior Specialist Vuokko Laukka at SYKE. 

According to Laukka, the introduction of new technologies at wastewater treatment plants and sewage sludge processing plants should be expedited by setting criteria for the procurements of services for sludge treatment. Criteria can be set for the advancement of nutrient recycling, utilisation of end products, energy efficiency, and the reduction of greenhouse gases.  

Good experiences have been gained from circular economy criteria, for example, in the tenders for Porvoo’s water procurement, and for the sludge treatment service of Turku Region Wastewater Treatment Plant. New circular economy technologies have already been introduced at the sludge incinerator in Rovaniemi. 

Better control of harmful substances 

Municipal wastewater treatment plants receive wastewater from various sources, and the wastewater contains a wide range of harmful substances. Current wastewater and sludge treatment processes have not been designed to remove compounds that are harmful to the environment. These compounds can end up to the soil environment via the use of these sludge-based fertilizers.  

New nutrient recovery techniques and source separation of wastewater can decrease the discharge of harmful substances into the environment along with nutrients.  

“If we are to increase the use of wastewater-based nutrients, their safety must be guaranteed. It is important to set more comprehensive criteria for the occurrence of harmful substances contained in recycled nutrients which take their intended use into account”, says Researcher Lauri Äystö from SYKE. 

• SYKE Policy Brief: Utilization of wastewater nutrients (Issuu) 
• Link to video (YouTube)
• All SYKE Policy Brief publications in Finnish and English (Issuu) 

SYKE Policy Brief publications are statements directed at decision-makers and experts, presenting the views of SYKE, and making recommendations on a contemporary topic.