DESALINATION Desalination 131 (2000)345-352
ELSEVIER
Production of demineralized water out of rainwater: environmentally saving, energy efficient and cost effective Hieke A. Oosterom a*, Dick M. Koenhen a, M. Bos b aS.Search b.v., P.O. Box 19, 7700 AA Dedemsvaart, Rollepaal 7b, 7701 BR Dedemsvaart, The Netherlands Tel. + 31 (523) 617-465; Fax + 31 (523) 617-466, e-mail:
[email protected],
[email protected] bSepeQ b.v., P.O. Box I9, 7700 AA Dedemsvaart, Rollepaal 7b, 7701 BR Dedemsvaart, The Netherlands Tel. +31 (523) 617-389; Fax +31 (523) 617-392; e-mail:
[email protected]
Received 5 July 2000; accepted 20 July 2000
Abstract Membrane based processes for conventional production of demineralized water often consist of ion exchange and/or reverse osmosis. An innovative alternative process is using rainwater followed by low-pressure micro-/ ultrafiltration offering potential benefits concerning the environment, energy consumption and costs. A project is carried out to determine the benefits of the alternative process for the production facility of S.Search b.v., a company that develops and produces membranes. The project is partially funded by Novem b.v., the Dutch organization for energy and environment. Data of rainfall is collected and attuned to water consumption using a inhouse developed spread sheet. It appears that at average annual rain fall of 850 mm there is no shortage of demineralized water at a water consumption of 1 m3/d discontinuous. Membrane performance on rainwater is currently tested, but is expected to show high flux together with low frequency of flushing and cleaning. Rainwater quality after treatment by micro-/ultrafiltration seems sufficient for S.Search b.v. Flexibility of the process using rain water in terms of water quality and quantity however is less compared to the conventional process. Therefore a cost calculation and comparison is carried out to determine when use of rainwater followed by micro-/ ultrafiltration is attractive compared to processes using reverse osmosis and ion exchange. Keywords: Micro-/ultrafiltration; Rainwater; Demineralized water; Cost comparison
I. Introduction General processes world wide for production o f boiler feed water or demineralized water *Corresponding author.
consist o f (multi stage flash) evaporation, ion exchange, reverse osmosis in combination with ion exchange or double pass reverse osmosis. With either of these processes dissolved solids are removed until required water quality guidelines are reached. Pretreatment is often necessary to
Presented at the Conference on Membranes in Drinking and Industrial Water Production, Paris, France, 3--6 October 2000 InternationalWaterAssociation,EuropeanDesalinationSociety,AmericanWaterWorksAssociation,Japan WaterWorksAssociation 0011-9164/00/$- See front matter © 2000 ElsevierScience B.V. All rights reserved PII: S0011-9164(00)00128-4
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prevent fouling of equipment or membranes by removal of suspended solids and colloids. In some applications, for example in the case of boiler feed water, very strict demineralized water quality requirements have to be reached as is shown in Table 1. Other applications might need less stringent water quality requirements as is the case in the membrane production facility of S.Search b.v., where demineralized water is used during membrane production as well as for rinsing and testing of membranes. S.Search b.v., located in Dedemsvaart, the Netherlands, is a young and innovative company that develops and produces membranes for various applications, mainly for water purification and (waste) water treatment. As usually hot water is used during the production processes of S.Search b.v., one of the major items concerning water here is that no scaling of calcium carbonate or other components occurs. From the point of view of product purity use o f demineralized water is also desirable. Finally because of implementation of wastewater reuse it is also necessary that the wastewater has low contents of dissolved solids. Estimated demineralized water quality guidelines for S.Search b.v. are also given in Table I. Table 1
Demineralized water quality requirements [1] Parameter
Boiler feed water (medium pressure) >30 6-9
