Some removal of TOC is achieved through the conventional drinking water treatment processes, while carbon absorption may be used to further enhance the removal of TOC prior to chlorine disinfection.Activated carbon regeneration provision is must .

I think it is way cheaper to use enhanced coagulation rather than GAC to remove TOC. If the TOC concentrations are high the GAC amendments are going to get saturated very fast and loose their ability to remove both TOC and DBP. A good and well-constructed drinking water plant with DBP control before and after chlorination/ozonation is required in order to evaluate if GAC is needed to minimize the DBP.

Please refer : SJ Randtke,   Journal of American Water Works Association ,1988. Detailed study available on line with cross references.

Hope you find these links helpful. 

https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwiyqZKBmqnUAhVLQY8KHXVpBqoQFggnMAA&url=https%3A%2F%2Fwww.geinstruments.com%2FGetLibraryDoc.aspx%3Fid%3D18966442-2363-496a-a834-026f045c3f47&usg=AFQjCNGh3FAQfA9AxFG75cbsOIhaZ3ZkhQ&sig2=eXf1IZUus56isVg6WpCn1g

https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0ahUKEwiyqZKBmqnUAhVLQY8KHXVpBqoQFggzMAI&url=https%3A%2F%2Fwww.emdmillipore.com%2FUS%2Fen%2Fwater-purification%2Flearning-centers%2Fapplications%2Forganic-analysis%2Ftoc%2Fwater-impact%2FLiab.qB.wMcAAAFULn0SsxXF%2Cnav&usg=AFQjCNEBEURYhpX2maHyVR2MHhlW2Qab6A&sig2=8U76Hwr8oEHIB623ONI34Q

https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&cad=rja&uact=8&ved=0ahUKEwiyqZKBmqnUAhVLQY8KHXVpBqoQFgg4MAM&url=https%3A%2F%2Fwww.wateronline.com%2Fdoc%2Ftoc-reduction-bank-using-uv-treatment-0002&usg=AFQjCNF4WLFkPbIJuWfVCERrbR8FPy38qQ&sig2=TQkXPQ5tElEsfEA44mJsHw

https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&cad=rja&uact=8&ved=0ahUKEwiyqZKBmqnUAhVLQY8KHXVpBqoQFghKMAY&url=http%3A%2F%2Fwww.liquicel.com%2Fuploads%2Fdocuments%2FTOC%2520reduction.pdf&usg=AFQjCNFwxViZeySJI4ZAregW_kBw0pVbPQ&sig2=dxC0D9uO5OfEKr-qedEdrQ

https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=10&cad=rja&uact=8&ved=0ahUKEwiyqZKBmqnUAhVLQY8KHXVpBqoQFgheMAk&url=https%3A%2F%2Fwww.amtaorg.com%2Fsuccessful-treatment-of-high-toc-surface-water-with-low-pressure-membranes&usg=AFQjCNFCMxmMDzaXL31DgYreVmDAZIh5WA&sig2=25HCS1VVYjZwxnBdmvF1-A

in case of monitoring the efficiency of TOC removal, it is necessary to check the pore size distribution of GAC(macro-, meso-, micro-, and so on).

Reference: Performance of an activated carbon adsorber in a water reclamation system with an electrolysis reactor

Journal of Industrial and Engineering Chemistry, 15 /2, 2009