Modelling and techno-economic assessment of (bio)electrochemical nitrogen removal and recovery from reject water at full WWTP scale

Veera Koskue; Veli-Pekka Pyrhönen; Stefano Freguia; Pablo Ledezma; Marika Kokko

doi:10.1016/j.jenvman.2022.115747

Modelling and techno-economic assessment of (bio)electrochemical nitrogen removal and recovery from reject water at full WWTP scale

J Environ Manage. 2022 Oct 1:319:115747. doi: 10.1016/j.jenvman.2022.115747. Epub 2022 Jul 15.

Authors

Veera Koskue¹, Veli-Pekka Pyrhönen², Stefano Freguia³, Pablo Ledezma⁴, Marika Kokko²

Affiliations

¹ Faculty of Engineering and Natural Sciences, Tampere University, Korkeakoulunkatu 8, 33720 Tampere, Finland. Electronic address: veera.koskue@tuni.fi.
² Faculty of Engineering and Natural Sciences, Tampere University, Korkeakoulunkatu 8, 33720 Tampere, Finland.
³ Department of Chemical Engineering, The University of Melbourne, Grattan Street, Parkville, VIC 3010, Australia.
⁴ Australian Centre for Water and Environmental Biotechnology, University of Queensland, Gehrmann Laboratories Building (60), Brisbane, QLD 4072, Australia.

PMID: 35849924
DOI: 10.1016/j.jenvman.2022.115747

Abstract

At conventional wastewater treatment plants (WWTPs), reject waters originating from the dewatering of anaerobically digested sludge contain the highest nitrogen concentrations within the plant and thereby have potential for realising nitrogen recovery in a reusable form. At the same time, nitrogen removal from reject waters has potential to reduce the energetic and chemical demands of the WWTP due to a reduced nutrient load to the activated sludge process. In recent years, (bio)electrochemical methods have been extensively studied for nitrogen recovery from reject waters in laboratory-scale but not yet implemented in real WWTP environments, particularly due to concerns about the need for large capital investments. This study assessed the techno-economic feasibility of retrofitting a (bio)electrochemical nitrogen removal and recovery (NRR) unit into the reject water circulation line of a full-scale WWTP through modelling. Data from laboratory-scale (bio)electroconcentration ((B)EC) experiments was used to construct a simple, semi-empirical model block integrated into the Benchmark Simulation Model No. 2 (BSM2) simulating a generalised WWTP. The effects of nitrogen removal from the reject water on both the effluent quality and operational costs of the WWTP were assessed and compared to the BSM2 performance without an NRR unit. In all studied scenarios, the effluent quality index was improved by 4-11%, while both the aeration (7-19% decrease) and carbon (24-71%) requirements were reduced. The additional energy consumed by the NRR unit increased the total operational cost index by >18%, but the revenue assumed for the generated nutrient product (20 EUR kg_N^-1) was enough to make the BEC-NRR scenarios at realistically low current densities (1 and 5 A m^-2) economically attractive compared to the control. A sensitivity analysis revealed that electricity price and nutrient product value had the most notable effects on the feasibility of the NRR unit. The results suggest a key factor in making (bio)electrochemical NRR economically viable is to reduce its electricity consumption further, while the anticipated increases in nitrogen fertiliser prices can help accelerate the adoption of these methods in larger scale.

Keywords: BSM2; Bioelectrochemistry; Centrate; Electrochemistry; Nutrient recovery; Wastewater treatment.

MeSH terms

Denitrification
Nitrogen* / analysis
Sewage
Waste Disposal, Fluid / methods
Wastewater / analysis
Water / analysis
Water Purification* / methods

Substances

Sewage
Waste Water
Water
Nitrogen