Microbial and cod removal in a municipal wastewater treatment plant using coagulation flocculation process.
This study was designed to improve the removal efficiency of COD, SS, and microorganism at the S. Giovanni a Teduccio municipal wastewater treatment plant, Naples, Italy. The plant consists of screen, sand grinder, oil removal, coagulation, flocculation and sedimentation units, hypochlorite disinfection, mechanical dewatering, and thermal sludge conditioning. A series of Jar-test was conducted on twelve samples taken after screen using FeSO4 alone or together with Ca(OH)2 at 100 rpm rapid mixing for 1 min, 30 rpm for slow mixing for 20 min and 30 min for settling. 150 mg L(-1) and 450 mg/L doses of FeSO4 were used at a pH interval in between 6 and 9. The removals of COD, TSS, Escherichia coli and total coliforms were measured ranging from 40 to 70%, 70 to 90%, 96 to 99% and 97 to 99%, respectively when FeSO4 was used alone at 150 mg L(-1) and 450 mg L(-1) doses and at pH 6, 7 and 8. Wastewater discharge standards could be safely obtained at 150 mg L(-1) dose of FeSO4 with the use of 220 mg L(-1) Ca(OH)2 at pH 8 in terms of COD and E. coli removals resulted in 65% and 98%, respectively, with less sludge production to be disposed. Additionally, none of influent and supernatant samples tested in this study was found to be acute toxic on 24h-born Daphnia magna at 50% dilution.
D002126:Calcium Hydroxide / Q000737:chemistry; D004203:Disinfection / Q000379:methods*; D004926:Escherichia coli / Q000302:isolation & purification*; D005296:Ferrous Compounds / Q000737:chemistry; D005427:Flocculation; D014865:Waste Disposal, Fluid; D014871:Water Microbiology / Q000592:standards*; D014874:Water Pollutants, Chemical / Q000032:analysis; D018508:Water Purification / Q000379:methods*; D014881:Water Supply / Q000592:standards
D005296:Ferrous Compounds; D014874:Water Pollutants, Chemical; C020748:ferrous sulfate; D002126:Calcium Hydroxide