Experimental investigation of system performance for combined desalination processes with membrane capacitive deionisation (MCDI)
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Cañas Kurz, Edgardo E.
Critelli, Salvatore
Gabriele, Bartolo
Figoli, Alberto
Hoinkis, Jan
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Dottorato di Ricerca in
Scienze e Ingegneria dell’Ambiente, delle contruzioni e dell’energia – SIACE.
Ciclo XXXIII; The water supply in many coastal regions worldwide is affected by progressive salinization. Here,
the use of desalination technologies is a viable solution for obtaining freshwater. In this thesis,
two modular concepts for brackish water (BW) desalination by the use of membrane capacitive
deionization (MCDI) and low-pressure reverse osmosis (LPRO) were developed and tested at
laboratory and pilot-scales with two pilot plants installed in Vietnam. The two concepts were
developed by using computer-based calculations (software: WAVE) and evaluated in a
socioeconomic and environmental multi-criteria analysis.
The first plant consisting of subsurface arsenic removal (SAR) as pre-treatment and MCDI for
desalination was installed in Tra Vinh, in the Mekong Delta for the treatment of arseniccontaminated
groundwater with a concentration of total dissolved solids (TDS) of 1.65 g/L.
Results showed the feasibility of the modular concept for producing drinking water
(TDS<0.45 g/L) with a specific energy consumption (SEC) of <3 kWh/m³. The relationship
between feed salinity and specific ion removal of the MCDI was evaluated in real environment and
compared with laboratory experiments. The use of renewable energies such as solar and wind for
autonomous supply was proven feasible for these technologies.
The second pilot plant was installed in a riverine estuary in the region of Cần Giờ, where no access
to freshwater is available due to the progressive salinization of river water and groundwater.
Here, river water showed TDS concentrations of up to 25 g/L. The combined system consisted of
UF pre-treatment, LPRO and MCDI to produce drinking water and product water with TDS of
<0.45 g/L and <1.5 g/L, respectively with a total SEC of 5.8 kWh/m³. Additionally, the
performance of the LPRO was compared to seawater-RO (SWRO) in pilot trials, which showed a
SEC of 5.5 kWh/m³. Although the SEC of single-stage SWRO was lower, the separate production of
drinking and product water by LPRO+MCDI showed different advantages including a reduced SEC
of 5.2 kWh/m³ for product water and additional 0.6 kWh/m³ for drinking water. Finally, an
optimization of the LPRO+MCDI can be possible by increasing the desalination efficiency of the
MCDI, increasing the efficiency of LPRO-pump and the MCDI power supply, and by aiming at feed
water qualities with lower salinity.; Department of Chemistry and Chemical Technologies, University of Calabria (UNICAL), Rende, Italy.
Center of Applied Research, Karlsruhe University of Applied Sciences (HKA), Karlsruhe, Germany.
National Research Council, Institute on Membrane Technology (CNR-ITM), Rende, Italy.Soggetto
Desalination; Energy demand; MCDI; Reverse osmosis; Arsenic
Relazione
CHIM/06;