Waste Ochre for Control of Phosphates and Sulfides in Digesters at Wastewater Treatment Plants with Enhanced Biological Phosphorus Removal

Svetlana Öfverström, Åsa Davidsson, Salar Haghighatafshar, Hamse Kjerstadius and Jes la Cour Jansen
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Svetlana Öfverström: Department of Water Management, Vilnius Gediminas Technical University, Sauletekio av. 11, LT-10223 Vilnius, Lithuania
Åsa Davidsson: Water and Environmental Engineering, Department of Chemical Engineering, Lund University, Box 124, 22100 Lund, Sweden
Salar Haghighatafshar: Water and Environmental Engineering, Department of Chemical Engineering, Lund University, Box 124, 22100 Lund, Sweden
Hamse Kjerstadius: Nordvästra Skånes Vatten och Avlopp AB, Box 2022, 250 02 Helsingborg, Sweden
Jes la Cour Jansen: Water and Environmental Engineering, Department of Chemical Engineering, Lund University, Box 124, 22100 Lund, Sweden

Clean Technol., 2020, vol. 2, issue 1, 1-11

Abstract: Ochre, waste iron sludge from the treatment of iron rich groundwater for potable use, makes up a significant waste problem. Furthermore, wastewater treatment plants with enhanced biological phosphorus removal and the digestion of sludge are in lack of iron for the prevention of hydrogen sulfide production and the release of phosphorous during anaerobic digestion. Thus, the addition of ochre to anaerobic digestion is a potential beneficial reuse of ochre. Sludge from wastewater treatment plants with enhanced biological phosphorus removal was used for the experiments. Batch and continuous pilot-scale tests were performed for the mesophilic digestion of primary and waste-activated sludge with different doses of ochre. Two different doses of ochre corresponding to molar ratios of 1 and 2 moles Fe 3+ /mole P released in the batch test resulted in 29% and 57% reductions of phosphates respectively in the sludge liquor compared to the control sludge without inhibiting the digestion process. In the pilot experiment, the dosing of ochre at both a high and low dose (molar ratios of 1.6 and 0.8 Fe 3+ /S 2− , respectively) resulted in an immediate drop in the H 2 S concentration (from >2000 ppm down to 570 ppm), while the control reactor still produced biogas with a high hydrogen sulfide concentration. The inhibition of the digestion process was observed (accumulation of acetate) at the higher dose. In a second pilot scale experiment, lower doses of ochre were tested continuously (1.5 and 0.75 mole Fe 3+ /mole P released ) to avoid any inhibition, while evaluating the phosphate precipitation. A reduction of phosphates in sludge liquor (33% and 66% for the low and high doses respectively) was obtained.

Keywords: waste ochre; biogas; enhanced phosphorus removal; hydrogen sulfide; phosphates precipitation (search for similar items in EconPapers)
JEL-codes: Q2 Q3 Q4 Q5 (search for similar items in EconPapers)
Date: 2020
References: View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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