title: Effectiveness of phosphate removal during anaerobic digestion of waste activated sludge by dosing iron(III).
abstract: Phosphate-Fe(II) precipitation induced by Fe(III) reduction during the anaerobic digestion of excess activated sludge was investigated for the removal of phosphorus and its possible recovery. The experiments were conducted with three Fe(III) sources at 35 °C and 55 °C. The results show that ferrihydrite-Fe(III) was effectively reduced during the anaerobic sludge digestion by 63% and 96% under mesophilic and thermophilic conditions, respectively. Whereas FeCl3-Fe(III) was only mesophilically reducible and the reduction of hematite-Fe(III) was unnoticeable at either temperature. Efficient precipitation of vivianite was not observed although high saturation index values, e.g., >14 (activity reduction not considered), had been reached. This reveals the complexity of vivianite precipitation in anaerobic digestion systems; for example, Fe(II) complexation and organic interference could not be ignored. With ferrihydrite amendments at a Fe/TP of 1.5, methane production from sludge digestion was reduced by 35.1% at 35 °C, and was unaffected when the digestion temperature went up to 55 °C. But, acidic FeCl3severely inhibited the methane production and consequently the sludge biomass degradation.
authors.affiliation: Beijing Key Laboratory for Source Control Technology of Water Pollution, Beijing Forestry University, Beijing 100083, China. Electronic address: xcheng@bjfu.edu.cn.
authors.forename: Xiang
authors.initials: X
authors.lastname: Cheng
authors.affiliation: Beijing Key Laboratory for Source Control Technology of Water Pollution, Beijing Forestry University, Beijing 100083, China.
authors.forename: Jue
authors.initials: J
authors.lastname: Wang
authors.affiliation: Beijing Key Laboratory for Source Control Technology of Water Pollution, Beijing Forestry University, Beijing 100083, China.
authors.forename: Bing
authors.initials: B
authors.lastname: Chen
authors.affiliation: Beijing China Sciences Guoyi Environment Protection Engineering Co., Ltd, No. 8 Caihefang Road, Beijing 100080, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Beijing Key Laboratory for Source Control Technology of Water Pollution, Beijing Forestry University, Beijing 100083, China.
authors.forename: Jiaqi
authors.initials: J
authors.lastname: Liu
authors.affiliation: California State University, Fresno, CA 93740, USA.
authors.forename: Lubo
authors.initials: L
authors.lastname: Liu
mesh_terms: D000693:Anaerobiosis; D019149:Bioreactors; D005290:Ferric Compounds; D007501:Iron; D008697:Methane / Q000096:biosynthesis; D010710:Phosphates; D012722:Sewage; D014865:Waste Disposal, Fluid
chemical_list: D005290:Ferric Compounds; D010710:Phosphates; D012722:Sewage; D007501:Iron; D008697:Methane
keywords: Anaerobic sludge digestion; Iron(III) reduction; Iron(III) sources; Phosphate removal; Vivianite