Author : Veronica Oliveira, Celia Dias-Ferreira, Isabel González-García, João Labrincha, Carmo Horta, María Cruz García-González

Address : (a. Research Centre for Natural Resources, Environment and Society (CERNAS), Portugal, b. Materials and Ceramic Engineering Department, CICECO, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal, c. Departamento de Ciências e Tecnologia (DCeT), Universidade Aberta, Lisboa, Portugal, d. Agricultural Technological Institute of Castilla y León (ITACyL) Ctra. Burgos, km. 19, 47071 Valladolid, Spain, e. College of Agriculture, Polytechnic Institute of Castelo Branco, Quinta da Senhora de Mércules, 6001-909 Castelo Branco, Portugal)

Abstract : A novel approach for nutrients recovery from municipal waste as biofertilizers by combining electrodialytic and gas permeable membrane technologies

Journal : Waste Management

Volume No. : Volume 125

Publish Year : 2021

Page No. : 293-302

Main Data : The recovery of valuable materials from waste fits the principle of circular economy and sustainable use of resources, but contaminants in the waste are still a major obstacle. This works proposes a novel approach to recover high-purity phosphorus (P) and nitrogen (N) from digestate of municipal solid waste based on the combination of two independent membrane processes: electrodialytic (ED) process to extract P, and gas permeable membranes (GPM) for N extraction. A laboratory ED cell was adapted to accommodate a GPM. The length of waste compartment (10 cm; 15 cm), current intensity (50 mA; 75 mA) and operation time (9 days; 12 days) were the variables tested. 81% of P in the waste was successfully extracted to the anolyte when an electric current of 75 mA was applied for 9 days, and 74% of NH4+ was extracted into an acid-trapping solution. The two purified nutrient solutions were subsequently used in the synthesis of a biofertilizer (secondary struvite) through precipitation, achieving an efficiency of 99.5%. The properties of the secondary struvite synthesized using N and P recovered from the waste were similar to secondary struvite formed using synthetic chemicals but the costs were higher due to the need to neutralize the acid-trapping solution, highlighting the need to further tune the process and make it economically more competitive. The high recycling rates of P and N achieved are encouraging and widen the possibility of replacing synthetic fertilizers, manufactured from finite sources, by secondary biofertilizers produced using nutrients extracted from wastes. Keywords: Phosphorus, Nitrogen, Struvite, Nutrient recycling, Waste valorization, Seawater