ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Investigation of hydrodynamics of inverse fluidized bed reactor (IFBR) for struvite (NH₄MgPO₄·6H₂O) recovery from urban wastewater

Kiruthika Sathiasivan, Samdavid Swaminathan, Jeyalakshmi Ramaswamy, and Mathur Rajesh

Department of Chemical Engineering, College of Engineering and Technology, Faculty of Engineering and Technology, SRM Institute of Science and Technology, Kattankulathur, India

E-mail: jeyalakr@srmuniv.ac.in

Received: 20 April 2021  Accepted: 4 September 2021

Abstract:

The removal of nitrogen and phosphorus from wastewater developed with established struvite (magnesium ammonium phosphate; MAP) production technology is the best alternative to newly produced or freshly degraded phosphate fertilizers. However, the production of struvite from domestic wastewater is not used extensively as initially expected in India because of the poor quality of production technology, competitive prices, and consumer acceptance as a fertilizer. Against this background, the present study aims to expand struvite production from phosphorus-rich wastewater, and bittern waste materials as a secondary source of magnesium in an inverse fluidized bed reactor by investigating their hydrodynamics characteristics. The study examined the influence of hydrodynamic parameters such as minimum fluidization velocity, bed expansion and pressure drop with polypropylene beads of different density under an optimized Mg/P ratio of 1.0. The O-phosphate recovery efficiency of over 95% was achieved by reaching the minimum fluidization velocity at a bed height of 45 cm, with a polypropylene bead with a diameter of 5 mm and a density of 836 kg/m³. The yield of struvite in a day for ten cycles for 30 days was estimated to be about 30–35 kg with 92% phase purity (XRD pattern of crystal). The cost economics suggested that the full-scale IFBR operation for struvite crystallization would be helpful for the community wastewater treatment plant.

Keywords: Hydrodynamics; Inverse fluidization; Recovery of nutrients; Struvite; Wastewater treatment

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-021-01863-w

Chemical Papers 76 (1) 361–372 (2022)