I
SUMMARY
OBJECT
II
III
The objective of this work was to perform a review of available
literature with the aim of determining the suitability of granular (GAC)
and powdered (PAC) activated carbon for treating water containing
pesticides.
REASONS
Water Authorities and companies have been proposing the use of GAC in
water treatment for the removal of one or more pesticides from drinking
water. The DOE have been concerned that the applications for capital
expenditure in this area are based on inadequate process design data for
some of the pesticides present in water. Therefore, they commissioned WRc
to perform a literature review to assess the potential of GAC to reduce
concentrations of any of the 19 pesticides (that have been detected in UK
drinking water supplies at concentrations above the EC Directive
standard) from water.
CONCLUSIONS
The overall conclusion from the study would be that there is very little
experience with the use of GAC to remove any of the pesticides on the DoE
list of 19 from water. Of the list of 19 pesticides, there is information
about only 7 pesticides that relate to the use of GAC for their removal.
These were atrazine, simazine, propazine, 2,4-D, linuron, malathion and
MCPA .
The type of information available on these 7 pesticides varied from
detailed pilot and full scale process performance to laboratory isotherm
tests. GAC was capable of removing or reducing to below O,lpg/l, all of
these compounds from water but the capacity of the GAC for these
compounds varied widely. Of these 7 pesticides all but malathion and MCPA
were apparently strongly adsorbed by GAC.
(i)
A WRc cost model for adsorption onto GAC was used to compare the costs of
removing these 7 pesticides from water. The costs were estimated for a
range of plant water throughputs and pesticide concentrations. However,
for a plant treating lOMUd of water containing 5ug/l of pesticide, the
increased cost of water resulting from GAC treatment ranged from about
1.9p/m3 for simazine to about 8.1p/m3 for malathion.
IV RECOMMENDATIONS
The lack of information about the removal of pesticides from water by GAC
indicates that there is a need for more work to be performed in this
area, particularly for the listed pesticides encountered in drinking
water at concentrations above the EC Directive standard.
V REsd OF CONTJSNTS
A review of literature related to the use of activated carbon for the
control or removal of the listed pesticides from water is presented. The
data, presented in the papers found, is reproduced as isotherms and/or
volumes of water treated per kg carbon in column tests. Where possible
operating conditions have been given.
The best isotherm and GAC capacity data have been used to develop costs
for treating water, contaminated by individual pesticides. It is hoped
that this allows a relative comparison between the effectiveness of GAC
to treat pesticide contaminated water to be made.
(ii)