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

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.