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#8. Athens
Greece
Circular solutions for Water Materials Energy
Lead partner:
Relevant sectors
Horticulture
Water
treatment
Relevant data
9000 m³ water reused/ year 5000 kg compost production/ year 8700 kWh thermal energy recovery/ year
Energy
Other partners:
Dr. Klio Monokrousou
National Technical University of Athens

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1. Objectives of the NextGen solutions
Main principle of technology:
Wastewater is extracted from sewers, treated directly on site and
reused at the point of demand.
The treatment residuals are collected, treated locally in the site
and are transformed to an eco-friendly fertilizer (compost), when
merged with green waste from pruning.

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2. NextGen Athens pilot system

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2. New NextGen solutions: Sewer Mining unit
Sewer Mining unit: MBR technology consists of a hybrid unit UF and a biological unit. All
construction works have been completed and the unit has been installed in the Nursery. In
addition, the UV disinfection unit has been installed. Finally, tests have been performed
with clean water.

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2. New NextGen solutions:
Sewage tank & pumping station
Sewage tank: The sewage collection tank has been
installed for treatment after the necessary excavation
activities.
Pumping station: The pumping station has been
constructed and installed on site after excavation works. In
addition, all the necessary operation tests of the pumping
station have been carried out.

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2. New NextGen solutions:
First tests of the configuration operation with clean water

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Material recovery & fertilizer production
system:
The construction of the Rapid Composting
Bioreactor system has been completed.
The process is carried out by mixing
thickened sludge and treated pruning.
The installation and connection of the system
with the rest of the pilot device is pending.
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Procedure
Wastewater sludge Thickened
Wastewater sludge
Gardenwaste Sredded waste
Mixedwaste Compost
Raw waste Conditioning Mixing Composting End product
Feed 100l/d, DS = 50-60% Output 30-40 l/day, DS=25-30%
2. New NextGen solutions: Rapid Composting Bioreactor

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2. New NextGen solutions: heat recovery unit
Energy recovery system: The technical parameters of the wastewater heat recovery
system using heat exchangers and heat pumps have been finalized; the construction
and installation of the system is ongoing.
Completion of heat
recovery unit study
and P&ID

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3. Results: status of the construction
Installation of industrial concrete base: The horizontal industrial
concrete base is constructed to host the pilot configuration i.e. sewer
mining unit, composting bioreactor, associated additional parts.
Power supply: The power needs of the site have been defined and
power supply has been installed in the site.
Sewer Mining unit: The MBR technology has been constructed,
installed on the site and tested with clean water.
Pumping station: Excavation works and set up of the equipment has
finished. Testing of these elements has been performed.
Buffer tank: Excavation works have finished and the tank is set to be
connected with the pumping station & the SM unit.
Material recovery system: The construction of the Rapid Composting
Bioreactor system has been completed and the unit is transferred in the
site. The connection of the system with the rest of the pilot device is
pending.
Energy recovery system: The technical parameters of the heat
recovery system have been finalised in a technical description document
and the construction of the unit is in progress.

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4. Lessons learned so far
From the testing of the unit before the start-up several lessons were learned
Such a scheme in the context of a sewer mining application is expected to be a viable solution
for water reuse in combination with fresh water saving in highly urbanized, space-limited
environments.
Organic carbon and pathogenic content can be eliminated.
For the fertilizer production, the sludge by the MBR unit needs to be thickened; for this purpose
filter bags have been used to achieve the optimum thickening.

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5. Next steps
1 Connect the subsystems to commission the water reuse configuration
part for the irrigation of plants
2 Test system performance
3 Monitor the reduction of carbon, nitrogen and phosphorus, the pathogens
content of the wastewater as well as the TSS and turbidity of the treated
wastewater.
4 Install the sludge thicker filter bags
5 Connect the unit of the RCB for the production of compost
6 Construct and install the unit for recovery of thermal energy from the
MBR effluent

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Thank you!
xtGen - Community of Practice