Skip to content

Perspective

Nature based solutions

Urban water management

Nature-based solutions and treatment of runoff

Improving the water cycle by ensuring an appropriate quality of rainwater runoff.

Local management of storm water runoff in Nature-based Solutions includes the runoff to be collected, delayed and/or stored and hereafter used as a recreational asset in channels or ponds in the city or discharged slowly to a receiving water body, such as a groundwater aquifer, the ocean, streams or wetlands. However, runoff can contain a variety of pollutants such as oil components, heavy metals, endocrine disrupters, pesticides, road salt and nutrients.

Therefore, runoff must often undergo treatment before being discharged to the receiving water body. In accordance with the European Water Framework Directive and the Danish Environmental Protection Law, Danish municipalities must determine whether treatment of the runoff is required for each case that utilises NbS. This requirement depends on the pollution level of the runoff as well as the sensitivity of the recipient.

Thus, when choosing a treatment solution,  it is important to ensure the water can betreated sufficiently to meet the quality requirements related to the particular recipient. If the water is infiltrated, it must not contaminate the groundwater. If the water is discharged to a lake or a stream, it must not deteriorate the biological and ecological state of the receiving body of water. And if it is used for recreational purposes, the rule of thumb is that rainwater can be stored  for a maximum of 24 hours due to concerns about pathogens.

If the treated runoff is to be sprayed or pumped for play, e.g. at laygrounds, UV disinfection is often necessary. Several solutions for treatment of runoff are available and they are often already an integrated part of the NbS. These include basic treatment mechanisms such as sedimentation, filtration, absorption, biological degradation and flocculation – often in combination.

Proper documentation of the treatment efficiency of the solutions is paramount to ensure that the receiving water bodies are protected. Establishing a sound, pragmatic and useful documentation procedure is still an ongoing process in Denmark, as well as in many other countries.

Nature based solutions

Download our publication on nature-based solutions today

This article is part of our publication ‘Nature-based solutions’.

Download now

You should consider reading

Nature based solutions
Urban water management

Perspective

Wind energy

+32

10 green news stories from Denmark in 2022

22 December 2022
With a significant focus on energy transition, 2022 has been buzzing with new climate pledges and cross-border initiatives. In this recap, we serve the ten most popular news stories published in 2022.

News

Living labs

+61

Danish companies obtain the most green patents

16 January 2023
Known to be among the globe's most sustainable, Danish companies are number one in obtaining green patents in both Europe and the US over the past ten years.

News

Job creation and transition

+101

Sound of Green, a podcast series with insights from Denmark’s green transition

27 January 2023
From managing cloudbursts to setting up climate partnerships, we examine how Denmark has turned acute climate challenges into new opportunities. In our podcast series Sound of Green, experts convey how Danish experiences can push the needle toward global green transition. Find it on Spotify, Apple Podcast and stateofgreen.com.

News

Green financing

+101

New Danish models assess the economic and fiscal impacts of climate policies

31 January 2023
Economists from the University of Copenhagen have developed green models to calculate environmental and climate effects on Denmark's entire economy. The models can have a major impact on how we view and measure economic growth and green transition worldwide.

News

Climate change adaptation

+34

Danes are European champions in applying for green patents

15 August 2023
Almost every fifth Danish patent application is green, which ensures Denmark a European top position in green innovation.