Sustainability effects of water reuse and infiltration and inflow on a wastewater treatment plant - a Multi Criteria Decision Analysis
Typ
Examensarbete på grundnivå
Program
Publicerad
2022
Författare
Ceder, Jakob
Backeström, Emmy
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
To lower the environmental impact of wastewater treatment in the Gothenburg area, Rya
wastewater treatment plant (WWTP) is constantly working towards a more environmentally
friendly and efficient wastewater treatment process. The function of the WWTP is
dependent on the inflow of wastewater. In this study, the sustainability effects of increased
and decreased infiltration and inflow (I/I), which is water that reaches the sewer system
that is not sewage water, are analyzed. Since the WWTP is connected to the entire sewer
system of the connected municipalities, the wastewater inflow can increase significantly
because of the excess water from I/I in the system. The sustainability effects of two types
of water reuse, upstream reuse and downstream reuse, were also analyzed. Upstream water
reuse refers to water that is reused before it reaches the WWTP and downstream refers
to treated wastewater that is used in some type of industry. To assess the sustainability
effects, six scenarios that represented increased or decreased fast and slow runoff I/I, as
well as upstream and downstream water reuse were constructed and compared to a base
case scenario using Multi Criteria Decision Analysis (MCDA). The criteria analyzed in
the MCDA were Effluent quality, Heavy metal content in sludge, Climate impact, Water
use, Energy use, Sphere of action/Political support, Local environment quality & amenity,
Working environment, Safety/Risks, Operating costs, Vulnerability and Flexibility. Data
and information for each criterion were gathered from measurements done at Rya WWTP,
literature study and interviews with Gryaab employees and analyzed for wastewater inflow
series constructed for each of the scenarios. The data and information were then presented
to an expert panel that graded and weighed each criterion. The results showed that an increase
in I/I has a negative effect on overall sustainability at the WWTP, while decreased
I/I has a positive effect. Fast runoff I/I was deemed to be the most preferred to lower
since it had the largest effect on sustainability and was mostly due to increased combined
sewer overflows caused by the selective increase of wastewater inflow. Upstream reuse is
preferable to downstream since it lowers drinking water use and reduces wastewater inflow
to the WWTP which has positive sustainability effects at the WWTP.
Beskrivning
Ämne/nyckelord
Wastewater , Wastewater treatment , Wastewater treatment plant (WWTP) , Sustainability , Infiltration and inflow (I/I) , Greywater reuse , Water reuse , Multi Criteria Decision Analysis (MCDA)