The role of pH on the biological struvite production in digested sludge dewatering liquors

Abstract

Struvite production mediated by bacteria has opened up a new route for phosphorus recovery from wastewater streams but its application to digested sludge dewatering liquors is not yet well understood. This study investigates the growth and biological struvite production of selected bacteria in wastewater liquors with pHs between 5.7 to 9.1. The bacterial growth was assessed through flow cytometry. Bacillus pumilus, Halobacterium salinarum and Brevibacterium antiquum remained viable at pHs between 5.7 to 9.1 but B. antiquum was able to grow at pHs between 7.3 to 7.8. Further analysis allowed the identification of crystals as struvite in tests between pH 7.3 to 8.3. All strains were capable of producing struvite at a range of pHs, but the highest production of 135–198 mg/L was observed for pHs between 7.3 to 8.3. At pHs > 8.3, precipitation of struvite and calcium compounds was observed in inoculated and non-inoculated tests. This study demonstrates that biological struvite production can occur at a wide range of pHs, hence significantly different from chemical struvite precipitation that occurs at pH > 8.3, making it a potentially viable process for phosphorus recovery as struvite from wastewater streams and sludge liquors without strict pH control.

Effect of Varying Nitrate Concentrations on Denitrifying Phosphorus Uptake by DPAOs With a Molecular Insight Into Pho Regulon Gene Expression

“…Increase of pH over 96 h was observed in the media combinations with nitrate because of denitrification, with starting pH at 7 and the maximally increased pH at 7.6 (Supplementary Table S4). Any P-removal caused by chemical precipitation of phosphates at this increased pH can be easily ruled out as this observed pH is not at all favorable for chemical precipitation of insoluble phosphates (Kofina and Koutsoukos, 2005; Daneshgar et al, 2018; Simoes et al, 2018).…”

Nitrogen and Phosphorus Recovery From Anaerobically Pretreated Agro-Food Wastes: A Review

“…This fact is due to the high buffer capacity of the anaerobic digester effluent caused by NH 3 /NH + 4 and H 2 CO 3 /HCO − 3 /CO 2− 3 equilibria. In this sense, the use of biological processes, which involve reactions with HCO − 3 and/or ammonium consumption or pH changes, could be considered an attractive pretreatment to reduce the consumption of reagents during phosphorus recovery (Mañas et al, 2011;Johansson et al, 2017;Simoes et al, 2018). For example, the previous application of nitrification Equation 3or partial nitrification-anammox processes (Equation 4) would decrease the amount of NaOH required up to 50 and 89%, respectively, and, in the last case, struvite recovery would be economically profitable (Campos et al, 2017).…”

In Situ Sonification of Anaerobic Digestion: Extended Evaluation of Performance in a Temperate Climate

“…The pH of these tanks averaged 8.35 ± 0.083 and 8.39 ± 0.082 for the control and sound-treated systems, respectively, while carbonate (CO 3 2− ) alkalinity averaged 0.25 ± 0.037 and 0.28 ± 0.038 µmol L −1 (data not shown). Simoes et al found that bacterial precipitation of struvite was optimal at a pH range of 7.3 to 8.3 [30]. Struvite accumulation in anaerobic digesters and wastewater treatment systems forms scales which can block pipes and reduce the efficiency of pumps.…”