Shortly after the start up of a new RO brackish water desalination pla
nt equipped with polyamide membranes, a severe decline in permeate flo
w rate was recorded. An extensive water analyses program urgently carr
ied out indicated that the most likely cause for the flux decline was
fouling of the membranes by phthalate esters, mainly di-butylphthalate
. The origin of the phthalate esters contamination was traced to the n
ewly installed reinforced polyester pipe (16 '' diameter, 14 km long),
conveying brackish well water to the RO plant. Direct evidence was ob
tained in laboratory experiments, confirming that di-butylphthalate is
indeed a foulant capable of reducing significantly permeate flux. The
laboratory data also showed that di-butylphthalate was even capable o
f destroying the membrane at high concentrations, causing severe leaka
ge of raw water into the permeate stream. With the help of the above f
indings, the plant was quickly brought back to normal operation.