Summary
This thesis is part of the Sewer Mining project
aimed at developing a new technological concept
to extract water from wastewater by means of
forward osmosis (FO), a novel membrane
technology. In general, greater than 99.93 % of
municipal wastewater is composed of water. If the
water can be separated from the solids (suspended
and dissolved), it can be reused, alleviating the
global water stress that currently exists.
FO is driven by osmosis and therefore differs
from other membrane processes which depend on
hydraulic pressure. FO, in combination with a
reconcentration system, e.g. reverse osmosis (RO)
is used to recover high-quality water for use in
industrial processes. Furthermore, the subsequent
concentrated wastewater (containing an inherent
energy content) can be converted into a renewable
energy source, i.e. biogas, for further use in the
system.
FO, incorporated in sewer mining applications
shows great potential, as it could lead to a more
economical and sustainable treatment of
wastewater, but before it can reach full-scale
feasibility, several research questions need to be
addressed.
Efforts to address these pending questions
culminated into this thesis. The research approach
consisted of:
Inventory of existing knowledge on FO,
specifically relating to wastewater, via data
collection from scientific literature and other
sources;
Characterisation of wastewater (primary
effluent) from wastewater treatment plants, to
assess and analyse fouling properties on the FO
membrane;
Experimental investigations on lab-scale (Utube,
cross-flow) and pilot-scale;
Validation of experimental work via existing
and newly developed FO transport models,
coupled to a technical economic model.
The major topics in this thesis, which cover
limitations experienced by FO processes during
wastewater applications, are summarised below.