Multi-objective application of granular activated carbon (GAC) in the production of carbonated beverage process water and bottled water

Coca-Cola's water quality criteria for carbonated beverage process water include an absence ofchlorine residual and total trihalomethanes (TTHMs) below the local drinking water standard or, inthe absence of a local standard, the WHO standard is used. The TTHM requirement of Coca-Colatreated water is less than 100ìg/L.Granular Activated Carbon (GAC) is used by Coca-Cola Plant in Antwerp primarily for dechlorinationof municipal chlorinated water and/or process water subjected to in-plant chlorination atchlorine doses of several mg/L. Secondary objective of GAC is the removal of trihalomethanes(THMs) pre-formed in municipal water and/or formed upon in-plant chlorination. GAC mediabackwashing and steam regeneration are done on weekly bases to inhibit microbial activity as well asto regenerate THM adsorption capacity as THM species are volatilized.There are a number of issues in Coca-Cola's mode of GAC operation. First, what truly controlsregeneration, chlorine or THM breakthrough, given that the former is a reduction reaction and thelatter is an adsorption reaction? Second, how effective is steam/high temperature regeneration forTHM adsorption compared to thermal regeneration and what should be the frequency of GACregeneration for THM removal? Third, how the competitive adsorption of different THM behave ondifferent type of GAC?In this research two types of GAC namely, Calgon F200 and Norit GCN1240 were used. To study dechlorinationdeionized (DOC-free) water spiked with 2mg/L chlorine (HOCl) was used. To studyTHM's removal model water was prepared from deionized water by spiking two THM species(chloroform, bromoform or mixture of both components) at TTHM concentration of approximately80ìg/L and 5000ìg/L for Rapid Small Scale Column Test (RSSCT) and for batch adsorptionexperiment respectively. Batch isotherm adsorption experiments were carried out with powderedgranular activated carbon (PGAC) to examine the effectiveness and adsorption capacity of GACs,from two suppliers. In addition multi-component adsorption isotherms were established to examinethe competition of one adsorbate in the presence of another. In a second set of experiments, GACbreakthrough curves were established with the help of the rapid small-scale column test (RSSCT)protocol, for all spiked THM components to predict frequency of full scale steam regeneration forTHM breakthrough.The results obtained demonstrated that adsorption of chloroform and bromoform on GAC can be wellexpressed by the Freundlich adsorption model. Results obtained for multi-component adsorptionfitted well the Freundlich adsorption model. Adsorption of Calgon F200 and Norit GCN 1240 GACtypes was higher for bromoform than chloroform. Reduction of chloroform concentration increasesthe GAC media time of regeneration than reduction of bromoform concentration.GAC regeneration is controlled by THMs removal. Extrapolation of results from RSSCT suggeststhat at the Coca-Cola Antwerp Treatment Plant (THMs concentration in feed water of approximately80ìg/L) Calgon F200 GAC (EBCT=7.12 min) could treat up to 12000 BV before breakthrough of 10ìg/L is achieved and this would correspond to 2 month operation. Steam/high temperature waterregeneration is less effective than thermal regeneration of GAC