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Electro-Membrane Technologies for Water Purification

#G-619


Development of Electro-Membrane Technological Process and Fabrication of the Full-Scale Electrodialysis Plant for Obtaining Drinking Water from Mineralized Waters

Tech Area / Field

  • MAN-MAT/Engineering Materials/Manufacturing Technology

Status
8 Project completed

Registration date
30.10.2000

Completion date
28.09.2005

Senior Project Manager
Ryzhova T B

Leading Institute
Georgian Academy of Sciences / P. Melikishvili Institute of Physical and Organic Chemistry, Georgia, Tbilisi

Supporting institutes

  • Scientific-Research Center "MEMBRANA" Ltd., Georgia, Tbilisi

Collaborators

  • Johns Hopkins University / Division of Infectious Diseases, USA, MD, Baltimore\nIONICS Inc., USA, MA, Watertown\nUniversity of Maryland / School of Medicine, USA, MD, Baltimore

Project summary

The main objective of the Project is to create highly effective plant for obtaining drinking water from mineralized water by a method of electrodialysis using ion-exchange membranes.

In desalinized water production membrane technology has demonstrated technical-economic advantages. Already by the 1980s about a quarter of the world’s desalinized water was produced by membrane technology.

The plant consists of the following units: preliminary processing of mineralized water (treatment for electrodialysis); demineralization by electrodialysis; and disinfection of demineralized water.

The composition of precursor water delivered to preliminary processing is as follows: total salinity is up to 15g/l, hardness - up to 20mg. equiv/l. The hardness of preliminary treated water delivered to demineralization does not exceed 5mg-equiv/l. The plant will produce drinking water with a total salinity of up to 1g/l. A super-cavitaion method will be applied in treating precursor water for the electrodialysis process.

The demineralization of pre-treated water is performed by the electrodialysis method using ion-selective membranes in electrodialysis plants of a filter-press type. The disinfection of demineralized water will be performed by a method of ozonizing or ultraviolet irradiation. The plant capacity will be 200l/h of drinking water.


The novelty of the proposed Project includes:
– utilization of the super-cavitation phenomenon in the preliminary processing of precursor water for eliminating sediment formation on membranes and electrodes;
– utilization of specially-designed components in the commercial electro-dyalizator to reduce leakage through concentrate collectors and the outer surface of membrane packaging;
– compatibility between structural and technological parameters of the super-cavitator and those of the electrodialysis apparatus, to obtain a highly effective softening (demineralization) of mineralized water;
– disinfection of demineralized water by ozonization with the use of an inexpensive (3–5 times cheaper than existing analogs), durable and compact ozonizing device or by ultra-violet irradiation.
Investigations, focused on solving scientific-technical and technological tasks, will be conducted on a special test bench, to study the following:
– dynamics of sediment formation on electrodes and membranes; measurement of ion concentration is performed by ion-selective electrodes and a conductometer;
– the hydrodynamics of flows in near-electrodes and inter-membranes spaces by probing and flow visualization methods;
– voltage-current characteristics of the desalination process;
– regimes of the membrane’s accelerated regeneration in the assembled electro-dialysator.

Super-cavitation processes will be investigated on the "USMAR" super-cavitator at different super-cavitation regimes and by using sediment formation activating agents.

Disinfection of demineralized water is performed by ozonization. The proposed ozone plant is distinguished by the fact that the common discharge tube, with the singular disposition of electrodes and a special regime of a high-voltage power supply, serves as an ozone-generating unit.

The following results of Project implementation are predicted:


Scientific results:
– development of the technological process of mineralized water treatment (before elctrodialysis) by a super-cavitation method, reducing sediment formation on membranes and electrodes and the partial annihilation of microorganisms;
– development and fabrication of components of a special design for the commercial electro-dyalizator to reduce leakage through concentrate collectors and the outer surface of the membrane packaging;
– development of a compatibility scheme between structural and technological parameters of the super-cavitator and those of the electrodialysis apparatus;
– development of the technological process for conditioning demineralized water and its disinfection for producing drinking water.

Economic results:


– realization of the preliminary super-cavitation treatment, leakage reduction in the electrodialysis demineralization process and bactericidal treatment of demineralized water by ultra-violet irradiation or by inexpensive ozonization source, all reduce the costs of obtaining 1m3 of demineralized water;
– delivery of demineralized water with a constant low value of hardness (after preliminary treatment) provides the durable uninterruptible operation of the electrodialysis plant, and this reduces the production cost of desalinated water.

Project realization will contribute to applied research and technology development in the utilization of natural resources and will promote, both nationally and internationally, the solution of technological problems, particularly those linked with the provision of drinking water.


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