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Electrochemically Activated Water as a Sanitising Agentin the
Beverage Industry: A Critical Assessment
Master of Science Thesis
by
Ennie Muchelemba
SupervisorProf. Gary Amy (UNESCO-IHE)
MentorsDr. B. Petrusevski, Associate Prof. (UNESCO-IHE)Dr. K.
Ghebremichael (UNESCO-IHE)
Examination committeeProf. Gary Amy (UNESCO-IHE), Chairman
Dr. K. Ghebremichael (UNESCO-IHE)
Associate Prof. B. Petrusevski (UNESCO-IHE)Johannes A. Siepert
(BEVTECHNOLOGIE GmbH)
This research is done for the partial fulfilment of requirements
for the Master of Science degree at theUNESCO-IHE Institute for
Water Education, Delft, the Netherlands
DelftMay 2009
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Abstract
The main sanitizer, long recognised to have high disinfection
efficiency in the
beverage industry is chlorine normally as sodium hypochlorite
(NaOCl). When it
reacts with water, it forms hypochlorous acid, which is an
extremely potentbactericidal agent. Nonetheless, re-evaluation of
its use in the beverage industry has
been considered because it imparts taste and odour as well as
creates storage and
transportation problems due to the high concentrations required
for sanitization.Recently electrochemically activated (ECA) water
emerged as one of the
alternatives to chlorination in water treatment. The beverage
industry has also
considered its use implementing it through a process referred to
as Cleaning-in-Place. However consensus has not been reached on the
applicability of ECA as a
disinfectant to replace chlorine. On one hand, some researchers
claim this is by and
large a chlorine solution. On the other hand, other researchers
recognise its higher
disinfection efficiency attributing it to the presence of
reactive oxygen species suchas ozone and hydroxyl radicals. But
even within this group, some have limited the
contribution of these species to direct current because of their
short life and more so
because they are produced in minute quantities in relation to
the chlorine species.
The study employed an in depth literature review related to the
use of ECA as a
disinfectant or sanitizer. In parallel, experimental work was
carried out to compareNaOCl with ECA by means of disinfection
efficiency, THM formation and stability
tests. These tests were carried out under different process
conditions such as
varying pH values, disinfectant concentrations and dissolved
organic carbon (DOC)concentrations. The experiments were carried
out using de-ionised water or Milli-Q
water and Delft tap water.
Findings from this study indicated that ECA has higher
disinfection efficiency thanNaOCl in de-ionised water or Milli-Q
water at pH 5 and 7. This was further
enhanced with increase in concentration. The presence of organic
matter, on the
other hand diminished this observed superiority. With further
increase in DOC itsdisinfection efficiency, THM formation potential
and stability became comparable
to that of NaOCl. Also, a very small quantity of ozone in
comparison to chlorine
was measured in freshly generated ECA solutions. At low
temperatures, between 3-5C, for an observation period of thirty
days, 40 mg/l ECA decayed by 5percent
while NaOCl of the same concentration decayed by 37.5 percent.
This was in the
absence of DOC.
Keywords: Electrochemically activated water, disinfection, plant
sanitation,beverage industry, THM formation, stability of
disinfectants.
