W
astewater treatment plants
don’t just have to deal with
household and industrial
wastewater. Rainwater also
enters the cleaning process via the sewer
system. Because wastewater treatment
plants are designed to cope with a certain
load, just like manufacturing plants,
above-average rainfall tends to push them
to their limits. Stormwater retention
tanks are the solution. They collect the
excess water from the sewer system
and thus relieve pressure on wastewater
treatment plants and the natural body
of water. There is, however, one problem –
stormwater retention tanks are often
located in remote areas where there is
no regular power supply. These facilities
therefore cannot be automated and
employees must actuate gate valves
manually, which takes up valuable time.
Sophisticated monitoring
The management of stormwater retention
tanks is a constant challenge for the local
municiple authority, Abwasserverband.
Wastewater from 22 municipalities enters
the central wastewater treatment plant at
Heidelsheim. Every time it rains, all 39
local stormwater retention tanks should,
strictly speaking, be checked. This is a
difficult task, particularly during prolonged
spells of wet weather. Furthermore, during
the cold months of the year there can
sometimes be complications with the
electrically actuated exhaust flow control
valves that control the flow of wastewater
into the sewer system. The electric
spindle drive soon reaches its
performance limits when the butterfly
valves are frozen. Both of these problems
were discussed when a Festo field sales
representative came to visit, and this
paved the way for a forward-looking
project.
An energy self-sufficient solution
Back in Esslingen, the discussion with
the field sales representative led to
the drafting of a research paper, which
examined the available options and
their feasibility. A practical concept was
created as part of an undergraduate thesis
and this resulted in a forward looking
complete solution for the energy self
sufficient automated and remote
controlled handling of gate valve
actuators. Shortly afterwards, an initial
pilot project was set up with the
Abwasserverband Weißach und Oberes
Saalbachtal. Solar energy harvested
using photovoltaics is used to power the
control unit and operate the pneumatic
actuators type DLP. If there is an
extended power failure, an integrated
emergency operation function allows
the process valves to be actuated several
times. The plant can continue to operate
for around a week even in bad weather.
A GSM modem forwards all the relevant
data to the wastewater treatment plant’s
control centre simultaneously. From
here, the gate valves can be closed and
opened centrally. As an extra safeguard
and to ensure shorter response times
High rainfall levels are overloading many wastewater treatment plants.
Stormwater
retention tanks can prevent this from happening. An energy self-sufficient, automated
control system with pneumatic actuators from Festo ensures greater reliability and
lower costs. It has proven to be a major success in a pilot project.
Rain under
control
Energy self-sufficient automation of wastewater technology
Photo: © saiva/shutterstock