Report No DWI0286
SURVEY OF THE EFFECTIVENESS OF GRANULAR ACTIVATED CARBON IN REDUCING THE CONCENTRATION OF PESTICIDES IN DRINKING WATER (WTT 9891 SLG)
Final Report to Department of the Environment
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.
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.
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 0.1µg/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.
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 10Ml/d of water containing 5µg/l of pesticide, the increased cost of water resulting from GAC treatment ranged from about 1.9p/m3 for simazine to about 8.lp/m3 for malathion.
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 areas particularly for the listed pesticides encountered in drinking water at concentrations above the EC Directive standard.
V RESUME OF CONTENTS
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.
Copies of this report may be available as an Acrobat pdf download under the 'Pre 2000 Reports' heading on the DWI website.