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Hygienic grey water container with reduced biofilm growth

Periodic Reporting for period 2 - HYGIEIA (Hygienic grey water container with reduced biofilm growth)

Reporting period: 2021-07-01 to 2022-06-30

The initial objective of the project was to design and manufacture a grey water container with reduced biofilm growth, based on appropriate surface coatings. HYGIEIA has evaluated two surface coating technology solutions which incorporate broad spectrum antimicrobial materials applied using wet and dry approaches: (1) paints, and (2) vacuum coatings by physical methods (PVD).
As a general conclusion, HYGIEIA has obtained two coatings (a PVD coating and a MNP loaded paint, that fulfil the initially established properties: high antimicrobial efficacy, low weight materials, high adhesion (compliance of RTCA Do160 Rev. G). The mentioned coatings were deposited on a series of containers designed and manufactured using the contemplated industrial approach which in principle could be installed directly in an aircraft environment.
The work performed during the first year of the project can be divided in two main blocks:

(1) Coupon and container design and manufacturing:
The design of the container was outlined in order to ensure the fulfilment of all the requirements described for the grey water re-use system components. In addition polymeric flat and curved coupons were designed and manufactured by mould injection, these samples were used to validate the properties of the PVD coatings and PAINTS.

(2) Development of the coatings:
(2a) PVD coatings: two approaches were considered: Metallic and ceramic layers. Several sets of PVD coatings were deposited and characterised, including: roughness, chemical composition (GD-OES), thickness, adhesion (cross-hatch test), contact angle and antibacterial efficacy (JIS Z 2801:2010). Remarkable antibacterial efficacy and mechanical properties were achieved.
(2b) MNP loaded paints: the paints to be developed in the project should combine two main features (1) superhydrophobic behaviour and (2) antimicrobial properties. For this purpose, HYGIEIA consortium selected two references of paints (polyurethane and epoxy) and synthesised a wide range of metal oxide and metallic MNPS with different functionalisation treatments.

During the second year of the project these two work lines were unified. Once the design of the container was finalised, a series of containers were manufactured by mould injection. Coatings that showed the best performance during the first characterisation stages (a PVD formulation and a paint) were applied on the inner surface of the containers. These coated components were tested to evaluate their mechanical behavior (Shock&Vibration test) and their performance was validated at a full-scale test rig in contact with synthetic grey water.
The results obtained in the project, are aligned with the initially stablished objectives, therefore, the main impacts envisaged by HYGIEIA are achievable:
- The technology developed for the biofilm-proof GWRS container will have a significant economic impact in the aircraft OEMs and on the value chain, including SMEs. The three value pillars of HYGIEIA (intelligent design, antimicrobial coatings and robust testing methods) have a notable market demand, inside and outside the aviation industry.
- There is a growing concern on creating clean and safe surfaces justified by the current COVID-19 pandemic but also by the increasing resistance of micro-organisms to traditional products (antibiotics, etc), which is leading to difficult to cure infections. Antibaterial/microbial coatings or additives rapidly penetrating markets such as US, KR, JP or China, where the Public health protection systems are less powerful, and the treatment costs are mainly paid by people’s private resources. Market forecast of antimicrobial coatings up to 2-5 b$/year, with annual growths bigger than the 10% according to different market survey sources.
- Environmental is the major side driver of HYGIEA. 30% weight savings in flight represent a significant fuel saving consumptions when extrapolating the numbers to the vast amount of aircrafts operated annually. The biofilm-proof system proposed by HYGIEIA will lead to water saving during the flight, which is one of the most remarkable aspects of the project regarding the environmental point of view. Since grey water is up to now expelled directly from the aircraft via the drain mast, this water is lost; whereas, if reused, it may make it possible to carry up to 30% less potable water in the main sump; a considerable weight saving.

The exploitation activities will be extended after the project conclusion upon TRL5 maturity attained.
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