Improving GAC performance by optimized coagulation

Abstract

Optimized coagulation results in benefits ranging from DBP reduction to improved GAC run times. The effect of optimized coagulation on granular activated carbon (GAC) performance for removal of natural organic matter and control of disinfection by‐products was investigated. Coagulation optimized for total organic carbon (TOC) removal increased GAC run times by a factor of 2–3 over run times observed for GAC receiving conventionally treated water. The improved performance was mainly a result of reductions in influent TOC and pH after optimized coagulation, as compared with conventional pretreatment. Conventional coagulation prior to GAC was more cost‐effective than optimized coagulation, because of increased costs associated with the high alum dosages used in this study.

Chlorination byproducts, their toxicodynamics and removal from drinking water

“…In this case THM formation reaction starts prior to addition of PAC and therefore the oxidation-reduction reaction between the chlorine and surface of activated carbon inhibited the adsorption capacity of the activated carbon for phenolic compounds [48]. Therefore the removal of THM precursor and THMs from drinking water by PAC is variable.…”

Ferric chloride plus GAC for removing TOC

“…Alum coagulation before GAC treatment increased the useful life of GAC used to remove TOC, 12 – 14 although many of these tests 12 , 13 were confounded by the concurrent reduction in pH caused by the coagulant dosage. At lower pH, NOM may be less soluble and more protonated, and it may adsorb more effectively than at higher pH.…”

“…Coagulation influences the molecular size distribution 13 , 28 , 29 and the humic and nonhumic fractionation of TOC. However, the adsorbability of a given molecular, humic, or nonhumic fraction was not altered by coagulation 13 …”

Economic Aspects of Application of Pretreatment Systems Before Granular Activated Carbon Filtration

“…Pretreatment can reduce CUR by decreasing NOM concentration in the GAC influent or by enhancing the adsorbability of NOM. Although pretreatment optimization usually cause the increase of treatment cost, a subsequent reduction in the CUR may lead to an overall savings [38]. However, in practice the application of preliminary treatment systems not always brings expected results.…”