Water, Sewage & Effluent September October 2018 | Page 10

Nature-based
wastewater treatment
The theme of this year’s World Water Forum in Stockholm was “Nature-based
Solutions”. As part of this, Mike Muller was invited to debate the thesis
that ‘natural infrastructure’ could replace the need for
built water infrastructure.
T
he idea that we can use
natural systems instead of built
infrastructure to meet our water
needs is obviously attractive. If we
used natural lakes to store water, we
could also go fishing. Wetlands to
purify water would be nature reserves
in the city. A reduction in soil erosion
from hillslopes would mean less
sediment to remove when we treat the
water for use.
Unfortunately, throughout most of
the world, simple, natural solutions
are not possible. There are just not
8
enough wetlands and not enough
lakes. And, while sedimentation can
be reduced, water will still have to be
treated to make it safe for use.
The world’s population is growing,
getting richer, and concentrated
in cities that are ever larger. All of
these people need water and, when
they have finished using it, need to
dispose of it. Quite often, they do
that by dumping the used water and
assorted human and other waste, into
the nearest water course. Cleaning
up polluted wastewater is today as
Water Sewage & Effluent September/October 2018
much of a challenge as providing
clean water for use in the first place.
Stockholm itself provides a good
illustration of the opportunities —
but also the challenges. A river runs
close to the conference hall where
the forum was held, and onwards into
the lovely Stockholm archipelago,
a prime summer holiday area for
Swedes and foreign tourists alike.
Even though it flows through the city,
the river is clean enough to swim in.
It was not always like this. Some
150 years ago, there was a toxic