Optimization of nutrient recovery treatment trains using a new nutrient recovery model (NRM) library
Vaneeckhaute, C.1,4, Belia, E.2, Meers, E.3, Tack, F.M.G.3, Vanrolleghem, P.A.4
1BioEngine, Chemical Engineering Department, Université Laval, Canada, 2Primodal Inc., Canada,
3EcoChem, Ghent University, Belgium, 4modelEAU, Université Laval, Canada
(free)
Abstract
In order to hasten the implementation of optimal, cost-effective, and sustainable treatment trains for resource recovery, a nutrient recovery model (NRM) library has been developed and validated at steady-state. Dynamic physicochemical three-phase process models were proposed for precipitation/crystallization (NRM-Prec), stripping (NRM-Strip), and acidic air scrubbing (NRM-Scrub) as key units. In addition, a compatible biological-physicochemical anaerobic digester model (NRM-AD) was built. The latter includes sulfurgenesis, biological nitrogen, phosphorus, potassium, and sulfur release/uptake, interactions with organics, among other relevant processes, such as precipitation, ion-pairing, and liquid-gas transfer. In order to facilitate numerical solution, a generic methodology to allow for both accurate chemical speciation and reaction kinetics at minimal computational effort is proposed. The use of the NRM library to establish the operational settings of a sustainable and cost-effective treatment scenario with maximal resource recovery and minimal energy and chemical requirements is demonstrated. Under the optimized conditions and assumptions made, potential financial benefits for a large-scale anaerobic digestion and nutrient recovery project are estimated at ± € 75 tonne-1 solids in average based on net variable cost calculations or an average of € 35 ton-1 total solids y-1, over 20 years when also taking into account capital costs.
Keywords
Circular Economy; Global Sensitivity Analyses; Green Process Engineering; Mathematical Modelling; Renewable Materials; Treatment Train Optimization; Waste Valorisation; Water Resource Recovery Facility.
Introduction
Driven by economic, ecological, and community considerations, waste(water) treatment plants (WWTPs) are increasingly transformed into water resource recovery facilities (WRRFs). Next to the long recognized and successfully recovered resources, water itself and energy, attention is growing to extract other valuable products from waste(waters), in particular nutrients. Although to date several processes for the recovery of nutrients from waste(water) have been proposed and applied at pilot and/or full scale (Vaneeckhaute et al. 2016a), challenges remain in improving their operational performance, decreasing the economic costs, and recovering the nutrients as pure marketable products with added value for the chemical or agricultural sector. Finding the appropriate combination and sequence of technologies to treat a particular waste flow and the optimal operating conditions for the overall treatment train are key concerns (Mo and Zhang 2013; Vaneeckhaute et al. 2016a).
