Copenhagen capital of Denmark

How this city gets the best tap water in the world

Hygge. It souns something like hoo-gha, and describes a feeling of cozy contentment by enjoying the simple things in life. It’s big here in Denmark, and I understand why. Simple things here are good; better than good even. Take the tap water as example. In Danish capital Copenhagen, the tap water is said to be the best in the world. I can vouch for it – it’s great. So, how do they do it?

The goodness that comes straight from the tap is especially curious seeing as the city has not escaped many of the problems that plague other urban areas today. Even more so, Copenhagen’s roots reach back all the way to the 10th century. Vikings used to roam these shores, after all. This place is old, and so is much of its infrastructure.

Copenhagen has the reputation as the city with the best drinking water in the world
Just another day in Copenhagen.

I think its part of the hygge, but the lessons from Copenhagen on how to provide excellent drinking water is actually quite simple. The lessons they share can be applied by many of us – whether on the receiving end of the tap, or on the side that has to ensure it keeps running. And, its relevant to places anywhere on the globe.

First, let’s look at where that tap water comes from. The source is key to keeping the water so very clean, and sweet.

That sweet Copenhagen water

Copenhagen sits on the eastern coast of the island of Zealand. Until 2009, locals also drank water from places above ground (like rivers) that was treated with chlorine but since, they have been tapping from under ground.

In fact, Trine Hybholt, project manager for HOFOR showroom, at Energy & Water – Greater Copenhagen Living Lab explains that the city relies only on groundwater. They pump this from well-fields as far as 55 kilometers away from the city centre. There are also aquifers under Copenhagen, but the usual mix of urban pollution has already caused it to be too dirty to drink. In comparison, water from the aquifers outside the city are of excellent quality. Due to the geology, the aquifers are also easy to access.

talking about Copenhagen and tap water quality
Trine Hybholt at the Copenhagen Living Lab

These well-fields are made up of Quaternary deposits overlying Tertiary layers such as sand, clay and lignite. The groundwater lies in a layer of limestone underneath. (In some cases groundwater is extracted from the mesozoic layers of limestone.) The aquifers are refilled by the rain. Once it hits the surface it will slowly make its way though the layers of the topsoil, clay and sand to reach the aquifer around 30 years later. These layers are like filters, that clean the water in the process. As a result, the water is very clean, and needs little treatment.

Copenhagen groundwater geology - where the best tap water in the world comes from
Trine explains the geology of the wellfields where the groundwater is abstracted from

A near-pristine water source

In fact, the water is only put through a process of oxidation (almost like airing it a little) to remove gasses. Then it is put through a simple sand filter system to remove minerals such as iron and manganese. Trine says they do not need to add any chlorine or other chemicals before people can drink it.

The water is then pumped from the treatment plants to a central height tank. From here, a gravity-fed system distributes it to people in town.

Trine explains the water provision system from the Greater Copenhagen Living Lab

In this way, HOFOR (the Greater Copenhagen Utility) extracts about 52 million m³ (0.052 km³) water each year for its 1.1 million customers in Copenhagen and the greater Copenhagen area. (Eight municipalities share ownership of the utility.)

Still, like cities elsewhere, water supply in Copenhagen is not without challenges.

Not all smooth sailing

For one, though relatively small, Copenhagen is growing fast; around 10 000 more people move in each year. This means that HOFOR also needs to supply 365 000 m³ more water to customers each year.  

Copenahgen is the city with the best tap water in the world.
Life here is good! No wonder more people move to Copenhagen every year

Second, water quality is a concern. Denmark has a rich farming history, with more than two thirds of the land changed to fields and farmlands. This results have have filtered underground. It’s common for groundwater to be polluted with pesticides and fertilizers, says Trine.

At the wellfields closer to the city centre, the mix of pollutants can also include pesticides and fertilizers, paint and oil used by private households. “Large-scale and long-term abstraction of groundwater also has an undeniable impact on the environment,” says Trine. “The truth is, what we did 50 and 100 years ago can still affect the water quality today and what we do today will affect the future.”  

So, what does Copenhagen’s problems and opportunities mean to you, especially if you’re not in Denmark? Well, its about that water source, and how they meet those mentioned challenges in Copenhagen. Once known as the Cinderella of water sources, groundwater is now often presented as the belle of the water-provision ball. If somebody is doing it right, we should take note.

Why care about groundwater?

Let’s take South Africa as an example. We are no strangers to the use of groundwater. A lone windpomp (windmill) perched heroically on a parched-looking landscape is a familiar sight to most of us. Groundwater is indeed already crucial to towns like Beaufort West and Musina. Even our large cities like Pretoria and Johannesburg are partly dependent on it. Cape Town is including aquifers as part of the mix of water sources they want to bank on for a more water secure future (to stave off another potential Day Zero).

Still, the water below the ground remains an under-used resource in South Africa, and elsewhere. Our most recent National Water Resources Strategy (second edition published in 2013) reports that we can potentially use 7.5 km³ of it per year, though we only use 2 km³ at the moment (or, when the report was written). Even if we under-estimate numbers, about 3.5 km³ could be available per year further development. In a country that knows drought, this is a lot.

Regardless of this potential, many municipalities tend to turn to groundwater as a last resort; mostly when drought is already knocking on the door. There are signs that the tide is slowly turning. The City of Johannesburg, for one, recognizes groundwater as a possible source to supplement drinking water. The city is busy with a study to determine the areas with the biggest potential for groundwater use, and to identify what this water can be used for. The reasons for this are many.

The logic of groundwater

Groundwater might not be as sexy as desalination, as bold as building a dam or as flashy as towing in an iceberg, but it is a very logical bet with practical benefits. For one, the environmental impact of pumping groundwater can be much lower than for big desalination plants, or building large dams and reservoirs. Stored underground, less water evaporates. Also, tapping into groundwater is much faster than constructing the other options mentioned.

For all of these reasons, groundwater is enjoying a growing reputation as a sustainable resource that can increase the resilience of a city and settlement.

Saying that, Copenhagen is a very different cup of tea than Cape Town. The mix of factors involved to successfully use groundwater is vastly different from one country to another, and even one city to the next.

This is why the lessons from Copenhagen are such beauties. They are surprisingly simple and, the basics principles can be applied anywhere.

First, keep the environment safe

In Denmark, groundwater outside the city is regulated by the national Water and Nature Plans, which the Danish Environmental Protection Agency (EPA) implements. The EPA thus reviews and awards permits for HOFOR to extract water from the well-points. In other words, the environment comes first.

According to the permits, HOFOR can only take groundwater if they compensate the environment for the impact of doing that. For example, if the flow of a stream above the surface is affected by HOFOR taking water from underground, they have to put enough water back into the stream again. They do this by adding groundwater, surface water, wastewater or rainwater to the streams.

HOFOR also adheres to comprehensive groundwater protection plans.

Keep the water clean

There are strict specifications for land use in their catchment areas. HOFOR assesses all the sources of pollution they are aware of, and monitors vulnerable areas. Then, they act upon it.

One example in application, says Hybholt, is that farmers receive financial compensation to stop the use of pesticides and other potentially harmful substances close to drilling holes. In other instances, farmers receive payment to switch from planting agricultural crops to planting forests. This allows HOFOR better control of any potential sources of contamination in areas deemed important to water supply.

In certain areas, limits for the use of fertilizer and pesticides are set. HOFOR also runs regular campaigns to warn residents about the impact of private use of herbicides on their drinking water, especially in those areas close to well-points.

Still, they are always investigating new drilling areas and the impact of pumping more from their current fields. Trine says they do not have historic data on which pesticides and fertilizers were used where, though they investigate what the land was historically used for before they drill. Yet they never know when there might be contamination discovered that could potentially affect the water. Trine says they have drilled around 750 access points, but have had to shut down those where contamination was found.

As such, Copenhagen’s tap water is heavily controlled. The same safety regulations as those applied to food processing (the international ISO 22000 standards), also applied to the water.

The quality of every drop counts

HOFOR’s comprehensive control programme entails testing for bacterial contamination daily at several points along the water supply system. Water is tested from the waterworks, along the pipe network and at the final distribution point. Should contamination be found, a control system kicks in. The affected residents are notified and water supplied to them by trucks until the problem is fixed.

A large part of their work to keep the water resource safe, is also to use it as efficiently as possible. 

For safe tap water, save water

Residents are by far the largest water user group in Denmark. To reduce pressure on the groundwater, reducing the amount of water that people use in their homes is thus key. And, in Copenhagen, residents take their water use seriously.

The average water consumption in households in Copenhagen peaked in the 1960s at approximately 235 litres per citizen per day. Since, the figures have been dropping steadily. HOFOR still set an optimistic target of 100 litres per person per day by 2020. Surprisingly, people achieved this ahead of schedule, in 2017.

People in Copenhagen have lowered their water use to a thrifty 100 litres each, per day

Trine says the installation of private water meters at households resulted in some of the largest water cuts – as much as 25%. Now, under Danish legislation, all properties connected to common waterworks must have water meters installed. Old buildings with several flats are only required to install one water meter at property level, but new buildings must have one for each flat.

To help people save water, households were motivated to switch to water efficient appliances such as toilets, washing machines and showers.

Trine says that there are more factors at play. Though nothing in comparison to buying bottled water, people perceive tap water in Copenhagen to be expensive. People are more inclined to use it sparingly.

Still, they are not done. “Now that we’ve reached our target of 100 liters per person, we’ve set ourselves a new one, and am aiming for 90 liters of water per person by 2025”, she says.

Copenhagen harbour , a place of the best drinking water in the world
Copenhagen harbors are kept clean, and have become popular spots to hang out

Trine says this missions is helped along by a growing awareness of the importance of sustainable living by the Danes, reinforced by constant education campaigns. Large-scale success stories such the rehabilitation of the Copenhagen harbor have also contributed. The harbor is now so clean, it’s a popular place for people to swim. “This has created a lot of understanding of the concept of sustainable water use,” says Trine.

Yet, Hofor understands that responsible water use is not only the job of its customers.

Don’t lose water

They are also setting the trend in curbing water loss in the distribution system (the pipes). In comparison to a world-wide average of 36.2% (and an average of 36.8% in South Africa, according to research published by the WRC in 2013), water losses for HOFOR amounts to a neat 7%. They achieve this by controlling the pressure in the supply system, replacing old pipes and running a systematized leakage detection pro­gram.

They also runs ongoing campaigns and education programs on various public platforms and at schools to motivate people to use even less.

Trine says the process is an ongoing one, and they are constantly trying new approaches to sustainable and more efficient water use. For example, they are now able to reuse up to 85% of the water that the sand filters are flushed with in the water works – water that used to go to waste.

Though the city has won international recognition for the quality of their tap water, the core lessons they can share with other urban areas that aim to supply residents with clean and safe groundwater are simple.

Lessons from Copenhagen

One key to success, says Trine, is that the resource must be used sustainably. For groundwater, this includes not over-extracting from the aquifer.

Second, the utility must ensure that the water quality is not compromised.

Then, the environment (basin) that the aquifer is located in must be kept healthy. “It is inevitable that you will have an impact on the environment, but your impact must be sustainable,” she says.  

Copenhagen has the best tap water in the world
Water is an intimate and clear part of the city of Copenhagen, and the people that live there.

To achieve this, Trine says that we must see water as a limited resource. Water must be understood as something that we have to reuse over and again in order to survive, and thrive. “It must be understood as part of the water circle.”

“Copenhagen residents are immensely proud of the fact that we are a city that drinks such clean water from the tap,” she says. While some countries still see groundwater as a backup plan, the opposite is the norm in Copenhagen. See that long coastline, all 8000 + kms of it? Desalination is not even mentioned as an option here.

Hygge on tap

So, that is how they get some of the best tap water in the world in Copenhagen. Really, they mostly keep it clean, and they use it wisely. Then, they respect the environment that it’s from. This is done by everybody involved, including the government that wrote and enforces the necessary laws and the utility that has to practice it. Then, the people that use it, do so very sparingly. They too have to help keep it clean.

The feeling of hygge is apparently like a cup of hot chocolate on a winter’s day, snuggling on the couch with a book on a Sunday afternoon, or a comforting hug from a loved one. The descriptions are many. For one, “to give courage, comfort, joy.” For me, a cup of Copenhagen’s tap water might just do the trick.

*A version of this article first appeared in the Water Wheel, published by the Water Research Commission

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