Natural organic matter removal from Tigris River water in Baghdad, Iraq

Experimental measurements were conducted to determine the level of natural organic matter (NOM) and its disinfection by-products formation potential (DBPFP) for Tigris River water in Baghdad. The results showed that raw water total organic carbon (TOC) levels have a potential to produce concentrations of trihalomethanes (THM) exceeding the USEPA stage 1 guideline of 80 μg/l during 7 months of the year comprising spring, summer and early autumn (March-September). Treatment options were tested for their efficacy to reduce raw water NOM; namely granular activated carbon (GAC) adsorption, enhanced coagulation (EC), and combination of both. With a raw water TOC concentration of 2.2. mg/l, GAC adsorption was found to be capable of treating 3300 be volumes up to breakthrough at UV254 absorbance removal of 99%. EC treatment achieved TOC removal efficiencies of 18% and 23% with hydrated aluminum sulfate dose of 4 mg/l as Al and ferric chloride dose of 8 mg/l as Fe respectively. These TOC removal values increased to 22% and 24% respectively when raw water initial pH was reduced from 7.9 to 6.5 prior to coagulation. GAC-treated water volume was increased by 12% when a column was fed with either coagulated-only or acidified-only raw water. However, this volume-increase reached 59% when the GAC column was fed with acidified-coagulated raw water. Presently, EC without raw water acidification is capable of reducing NOM to an acceptable level according to USEPA requirements. Use of GAC (with/without pretreatment) is a future option dependent on the raw water trophic state.