(439d) Statistical and Energy Consumption Analyses of Multi-Factor Effect on Nutrient Removal and Recovery Via Electrochemical Animal Waste Remediation

In modern agriculture, the primary source of phosphate fertilizer rocks. The gradual depletion of phosphate rock supplies has created a need for phosphate recovery from other sources to assure long-term food production. Therefore, a growing number of studies have turned their attention to wastewater phosphorus recovery. In addition, excess nutrient runoff (predominantly composed of nitrogen and phosphorus) from agricultural land, inadequately managed farming activities, and point sources such as wastewater treatment plants are all causes of anthropogenic nutrient pollution. Harmful algal blooms (HABs), and eutrophication are only a few of the nutrient pollution effects. More effective nutrient source management would help to reduce nutrient pollution and its consequences on watersheds and waterbodies, which pose quality-of-life issues, ecological impairments, and economic costs.

Phosphorus can be recovered and used as a slow-release fertilizer called struvite, which makes use of existing scale deposits, decreases phosphorus release into receiving ecosystems, and provides a phosphorus source to maintain present agricultural process¹. This recovery as struvite can occur with a minimum molar ratio of Mg:N:P of 1. On the other hand, alternative phosphorus recovery products are calcium phosphates. These calcium phosphates have additional value including improvement of the cost/benefit of phosphorus recovery processes, utilization in the food and beverage sector and as animal feed^2,3. The recovery of these products provides sustainable solutions to the problems caused by pollution and depletion of phosphate rocks.

At Ohio University, a green technology is being developed with an electrochemical technique for nutrient removal from wastewater. Simple and easy-to-operate equipment, short operating time, no or little chemicals, and reduced sludge are all characteristics of the electrochemical technology. Furthermore, the operation of the technology does not involve carbon emissions if operated using renewable energy. Previously, the performance of the electrochemical approach was evaluated by examining the effect of one variable at a time on quantifying the phosphorus recovery⁴. In addition, a theoretical simulation was created to better understand the equilibrium conditions that maximize nutrient recovery and the effect of temperature on the thermodynamics of predicting phosphorus-based species from wastewater^4,5.

Therefore, the focus of this new study was the statistical analysis and simultaneous experimental investigation of multiple parameters (Mg:Ca and N:P, temperature, cell voltage, and flow conditions) that influence nutrient recovery in the form of struvite and calcium phosphates. The results indicate that Mg:Ca molar ratio is the only significant parameter affecting the phosphorus removal from animal wastewater with the removal efficiency of 51 ± 8% at Mg:Ca molar ratio of 2 and 22 ± 3% at Mg:Ca ratio of 1. More results from the bench-scale analyses will be presented at the conference.

(1) Le Corre, K. S.; Valsami-Jones, E.; Hobbs, P.; Parsons, S. A. Phosphorus Recovery from Wastewater by Struvite Crystallization: A Review. Critical Reviews in Environmental Science and Technology 2009, 39 (6), 433–477. https://doi.org/10.1080/10643380701640573.

(2) Request Sample - Calcium Phosphate Market Outlook - Industry Size, Share Report 2025 https://www.gminsights.com/request-sample/detail/1425 (accessed 2022 -04 -02).

(3) Dorozhkin, S. V. Calcium Orthophosphates: Occurrence, Properties, Biomineralization, Pathological Calcification and Biomimetic Applications. Biomatter 2011, 1 (2), 121–164. https://doi.org/10.4161/biom.18790.

(4) Belarbi, Z.; Daramola, D. A.; Trembly, J. P. Bench-Scale Demonstration and Thermodynamic Simulations of Electrochemical Nutrient Reduction in Wastewater via Recovery as Struvite. J. Electrochem. Soc. 2020, 167 (15), 155524. https://doi.org/10.1149/1945-7111/abc58f.

(5) Pindine, G. P.; Trembly, J. P.; Daramola, D. A. Equilibrium-Based Temperature-Dependent Economic Analysis of the Recovery of Phosphorus from Different Wastewater Streams via Chemical Precipitation. ACS ES&T Water 2021. https://doi.org/10.1021/acsestwater.1c00166.