As a result of the regulations on DBPs, interest in NOM removal is
increasing and many water treatment plants in developed countries have
started to measure the concentration of TOC in their finished waters.
Promulgation of the rules will substantially increase these efforts in
other countries too. Since the cost of TOC (and DBPs) determination was
high, it was decided to study the traditional analysis of COD as a
surrogate measure to detect the organic constituents in raw water and
the extent to which optimized coagulation with ferric chloride can
increase COD removal. The two water samples studied belonged to Karaj
and Jajrood Rivers. For both samples the observed values of COD removal
by coagulation at lower pH (about 1-1.5 pH values less than the regular
pH) were about 85-95 percent without making water turbidity
unacceptable. In order to determine the effects of organic content on
coagulation, synthetic samples were also prepared with much higher COD
values. Again, considerable increases in COD removal have been observed
for most of these samples only by decreasing 0.5-2 pH value. The
results indicated that a modified coagulation process without need to
much increasing the amount of coagulant can be developed for these
water samples