Project: Evaluation of manganese adsorption onto GAC using
isotherms and RapStech® service
Client: Severn Trent Water Ltd.
Jan’06 to Mar’07
in some surface waters can be adsorbed onto Granular Activated Carbon (GAC) filters at Water Treatment Works (WTWs) which can assist with meeting the final drinking water PCV of 50µg/l. A WTW was planning to introduce
changes to the coagulation process upstream of the GAC filters by the alteration
of pH and needed to determine if this would impact on
manganese adsorption within the GAC.
Laboratory scale investigations were conducted using field spent, recently regenerated and virgin GAC from the WTWs
with site water in batch isotherm tests at different pHs and Rapid Small
Scale Column Testing (RSSCT) using the RapStech® service.
Comparison of the isotherm and the RSSCT data has
highlighted the strengths and weakness of the two methods. Manganese
adsorption is greater under isotherm conditions (batch tests utilising long contact times) and RSSCT indicates the
adsorption of manganese which is likely to occur onsite with continuous flow
system and specific velocity. Isotherm analysis using site water and
also laboratory water, provided evidence for competitive adsorption, as adsorption of manganese was greater for the isotherms using just laboratory water spiked with manganese.