Sludge management modeling to enhance P-recovery as struvite in wastewater treatment plants. (1st July 2017)

• Record Type: Journal Article
• Authors: Martí, N.; Barat, R.; Seco, A.; Pastor, L.; Bouzas, A.
• Is Part Of: Journal of environmental management. Volume 196(2017)
• Page Start: 340
• Page End: 346
• Publication Date: 2017-07-01
• Subjects: Nutrient recovery -- Sludge treatment -- Crystallization -- Uncontrolled precipitation -- Urban WWTP; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2016.12.074
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: Interest in phosphorus (P) recovery and reuse has increased in recent years as supplies of P are declining. After use, most of the P remains in wastewater, making Wastewater Treatment Plants (WWTPs) a vital part of P recycling. In this work, a new sludge management operation was studied by modeling in order to recover P in the form of struvite and minimize operating problems due to uncontrolled P precipitation in WWTPs. During the study, intensive analytical campaigns were carried out on the water and sludge lines. The results identified the anaerobic digester as a "hot spot" of uncontrolled P precipitation (9.5 gP/kg sludge) and highlighted possible operating problems due to the accumulation of precipitates. A new sludge line management strategy was simulated therefore using DESASS © software, consisting of the elutriation of the mixed sludge in the mixing chamber, to reduce uncontrolled P precipitation and to obtain a P-rich stream (primary thickener supernatant) to be used in a crystallization process. The key operating parameters were found to be: the elutriation flow from the mixing chamber to the primary thickener, the digestion flow and the sludge blanket height of the primary thickener, with optimized values between 70 and 80 m 3 /d, 90–100 m 3 /d and 1.4–1.5 m, respectively. Under these operating conditions, the preliminary results showed that P concentration in the primary thickener overflow significantly increased (from 38 to 100 mg PO4 -P/L), which shows that this stream is suitable for use in a subsequent crystallization reactor to recover P in the form of struvite. Highlights: The anaerobic digester was a "hot spot" of uncontrolled phosphorus (P) precipitation. Only 9% of the P entering the WWTP was available for its further recovery. The simulated sludge management operation reduces uncontrolled P precipitation. P in the primary thickener overflow increased from 38 to 100 mg PO4-P/L. The thickener overflow is a P-rich stream for the crystallization process.