NAMS 2002 Workshop - ICOM 2008

Drinking and Wastewater Applications V – 1 – Keynote
Friday July 18, 2:15 PM-3:00 PM, Maui
The Development of a Household Ultrafiltration System for Developing
Countries
M. Peter-Varbanets (Speaker), Eawag - Swiss Federal Inst. of Aquatic Science and Technology,
Duebendorf, Switzerland - maryna.peter@eawag.ch
M. Vital, Eawag - Swiss Federal Inst. of Aquatic Science and Technology, Duebendorf,
Switzerland
F. Hammes, Eawag - Swiss Federal Inst. of Aquatic Science and Technology, Duebendorf,
Switzerland
W. Pronk, Eawag - Swiss Federal Inst. of Aquatic Science and Technology, Duebendorf,
Switzerland
Global assessments by the WHO and UNICEF showed that one-sixth of the
world's population did not have access to safe water for drinking at the beginning
of 2000. A huge effort is required in order to reach the drinking water objectives
set out in the Millennium Development Goal: to half the proportion of population
without sustainable access to safe drinking water and sanitation by 2015 as
compared to 1990. A part of the solution is the application of decentralized Pointof-use
(POU) treatment systems. This solution is already practiced in some
areas, but available systems are often cost-intensive and require time consuming
maintenance. In principle, membrane technology is also attractive for such
applications because it provides absolute barriers for controlling hygiene hazards
and its modular construction allows implementation on all possible scales.
Furthermore, the costs of the membrane itself have decreased significantly in the
last decades. However, the application of UF technology in DC and TC is limited
by other factors. The basic principle of operation of traditional large scale UF
water treatment plant is to assure high flux avoiding large membrane surfaces.
Therefore, frequent chemical cleaning are usually applied and transmembrane
pressures are in the order of 0.5 - 1.0 bar. For application in households in
developing and transition countries, the application of pumps and chemicals, as
well as complex operation schemes should be avoided. Therefore, we focused
on developing a low-pressure, gravity-driven membrane system without the use
of cleaning chemicals. The system was operated at pressures between 40 and
110 mbar. This corresponds to a water column of 0.40 - 1.10 m, and such a
gravity- driven system can be easily implemented in households. A flat sheet
membrane module with a membrane surface of 0.0016 m 2 was operated in deadend
mode without any cross flow or backflushing.
For the experiments we used natural water from the Chriesbach river
(Dübendorf, Switzerland) with the following composition: Turbidity 0.2-1 NTU with
peak values of 30 NTU, and TOC 2-4 ppm. The membrane module was operated
at a transmembrane pressure of 110 mbar. The flux decreased within the first 2