Concentrated Wastewater Treatment Using a Ferric Iron-dosed Anaerobic Upflow Sludge Blanket Reactor for Recovery of Phosphorus and Ammonium

Author

Carley E. ShingletonFollow

Semester

Spring

Date of Graduation

2023

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Lian-Shin Lin

Committee Member

Karen Buzby

Committee Member

Emily Garner

Committee Member

Kevin Orner

Abstract

This study evaluated the performance of a novel, ferric iron-dosed anaerobic bioreactor to recover two separate nutrient products from concentrated wastewaters -- phosphorus as vivianite (Fe₃(PO₄)₂×8H₂O) and an ammonium-containing effluent with low organics. A bench-scale upflow anaerobic sludge blanket (UASB) reactor fed with a synthetic wastewater (458.0 mg/L total organic carbon, 282.7 mg/L ammonium, and 84.4 mg/L phosphate) was dosed with a ferric chloride solution at an org. C/Fe³⁺ molar ratio ~17.5 to facilitate organic carbon oxidation coupled to iron reduction. The reactor design allowed natural settling of vivianite to its cone-shaped bottom for collection. The UASB reactor was operated under two hydraulic retention times (HRT, 7 and 10 hours) and the results showed that an increase in HRT from 7 hours to 10 hours resulted in a higher removal efficiency of TOC (54% to 58%) and a higher removal (loss) of ammonia (16% to 38%). The change in HRT did not affect phosphate removal (79%). The total suspended solids (TSS) were 0.3, 20.5, and 172.8 gTSS/L at three heights of the bioreactor from top to bottom. Nitrite was below detection limit (0.01 mg/L) in both the influent and the effluent. Average total iron concentration in the influent was 14.93 mg/L including 0.14 mg/L Fe²⁺ and 14.79 mg/L Fe³⁺. The effluent had an average total Fe concentration of 1.90 mg/L including 1.26 mg/L Fe²⁺ and 0.64 mg/L Fe³⁺. Analysis of the microbial composition within the reactor was performed using quantitative polymerase chain reaction (qPCR), and results indicated the presence of Feammox bacteria (Acidimicrobiaceae A6) and iron-reducing bacteria (Geobacter). Further characterization of the biomass was completed with x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy equipped with energy dispersive x-ray spectroscopy (SEM-EDS). These results revealed oxygen (O), iron (Fe), carbon (C), and phosphorus (P) as the major elements present in the sludge sample obtained from the bottom of the reactor. X-ray diffractometry (XRD) revealed vivianite formation in the bottom sludge material. The process outlined by this research has the potential of recovering nutrients from concentrated wastewaters as a standalone system or as an add-on to biogas producing systems. The separate products of vivianite and ammonium-containing effluent low in organics offer flexibility in applying these as fertilizers at ratios best suited for the applied soils.

Recommended Citation

Shingleton, Carley E., "Concentrated Wastewater Treatment Using a Ferric Iron-dosed Anaerobic Upflow Sludge Blanket Reactor for Recovery of Phosphorus and Ammonium" (2023). Graduate Theses, Dissertations, and Problem Reports. 11897.
https://researchrepository.wvu.edu/etd/11897