A Feasibility Study - Aaltodoc - Aalto-yliopisto

impediments commencing out of imperfect pre-treatment are the sand grains (and other
hard particles, i.e. parts of sea shells) and microbiological growth.
The current research carried out by e.g. Matsumoto (2012) on the use of biofouling
agents to reduce microbiological growth may be a functioning solution. It would reduce
the loss of performance and lifetime of the membranes, but despite promising results, its
effectiveness has not yet been broadly verified and its applicability to AaltoRO process
remains uncertain
The major threat caused by the minimum pre-treatment is the appearance of sand and
other hard particles in the feed water. They pose a serious threat since they can cause
abrasion on the piston pump of the WEC and the APG, resulting in mechanical wearing
and at worst frequent replacement of devices. The particles are also harmful for the RO
membranes and can cause ruptures and thus losses in performance.
The effects of the minimum pre-treatment cannot be verified without a comprehensive
practical research program and thus estimating the losses in performance, the costs of
the frequent maintenance and replacement are difficult to estimate. They have been
incorporated in the operational expenses in the calculations, but whether the estimation
is correct, too large or small, is impossible to determine.
10.1.4 Cost information
The cost information used in determining the feasibility of the AaltoRO process has
great uncertainties on almost every field. The WEC WaveRoller is still at a development
phase and the cost when it is in serial production may differ significantly from the
values used in this thesis. Also uncertain is how increasing the nominal pump capacity
of the WaveRoller affects the price.
The APG is at the beginning of its development and its costs and efficiency are likely to
change considerably in the future. As with the WEC, it is uncertain how the price will
change when the nominal volume flow rates change. The medium pressure piping can
be constructed of various different materials, e.g. from numerous plastics and metals.
Each supplier has different options and choosing the best one requires optimizing the
price and durability of each option. The installation expenses of the medium pressure
pipeline are also highly uncertain; it was extremely difficult to find comprehensive
information about that topic.
Estimating the maintenance costs of the RO system has been challenging. Due to the
chosen minimal pre-treatment, the need of maintenance has been considered to be
higher than in standard systems and the membrane replacement schedule more frequent.
Without experimental knowledge derived from an actual prototype it is impossible to
accurately evaluate the maintenance costs of the RO.
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