Search Results (9)

Electrochemical methods show promise for wastewater treatment by removing pollutants, recovering nutrients, and generating hydrogen. To scale this technology, durable and affordable electrode materials are needed. This study evaluates aluminum 6061-T6, titanium grade II, ductile iron, and magnesium to understand their performance in promoting precipitation, gas production, and treating wastewater under several conditions. Electrodes were tested with ammonia-, magnesium-, and phosphate-spiked wastewater samples with induced precipitation at concentrations of 0.033 mol/L and 0.0033 mol/L; the liquid, gas, and precipitation phases were characterized. The results showed up to 35% reduction in ammonia, total phosphate recovery, and up to 70% reduction in magnesium. The cell generates hydrogen with purity levels of 95.6%, 96.1%, 87.9%, and 93.5% when utilizing iron, aluminum, titanium, and magnesium electrodes, respectively. The analyses of precipitants showed formation of vivianite crystals from iron, struvite precipitation from magnesium, and berlinite from aluminum. Overall, these results hold substantial promise for hydrogen generation from wastewater and potential for nutrient recovery and treatment. Full article

This study evaluates the feasibility of nitrogen recovery from wastewater via electrochemical methods as an alternative nutrient source for agricultural applications. Ammonium nitrogen (NH₄⁺-N) and phosphate (PO₄³⁻-P) contamination poses significant environmental risks and challenges water resource management globally. The electrochemical precipitation of struvite (MgNH₄PO₄·6H₂O) offers a promising solution for nutrient recovery, with potential applications as a slow-release fertilizer. Experimental results demonstrate that increased current density (from 2.5 to 7.5 mA/cm²) and reduced electrode distance (1 cm) significantly enhance NH₄⁺ and PO₄³⁻ consumption and struvite precipitation. Increasing the amperage from 2.5 to 7.5 mA·cm⁻² at a 1 cm electrode distance raised the ammoniacal nitrogen incorporation from 1.59 to 5.34 g/100 g, signifying greater struvite production. The Mg and P concentrations were 15.44 and 12.60 g/100 g, respectively, for this higher amperage, although lower than the concentrations seen with 2.5 mA·cm⁻² (22.16 and 14.52 g/100 g). The majority of Mg (60%) and P (93.6%) were, however, incorporated within struvite. Additionally, this study reveals that Mg is primarily incorporated as struvite when using higher current densities, while lower current densities yield greater Mg incorporation in non-struvite forms, such as magnesium carbonate. Findings suggest that optimizing current density and electrode distance can improve nitrogen and phosphorus recovery efficiencies, making electrochemical struvite production a viable, sustainable approach for nutrient recycling. This method not only reduces dependence on synthetic fertilizers but also supports sustainable agricultural practices by transforming wastewater contaminants into valuable resources. Full article

Research into alternative phosphorus (P) fertilizer sources that may be able to supplement P resources is necessary. Struvite (MgNH₄PO₄ · 6H₂O) can be made by removing excess nutrients from waste sources and may reduce greenhouse gas (GHG) emissions from cropping systems. This study sought to quantify GHG [i.e., methane (CH₄), nitrous oxide (N₂O), and carbon dioxide (CO₂)] fluxes, season-long emissions, and net GHG emissions from chemically precipitated struvite (CPST) and synthetic and real-wastewater-derived electrochemically precipitated struvite (ECST) compared to monoammonium phosphate (MAP) and an unamended control (UC) from flood-irrigated rice (Oryza sativa) grown in P-deficient, silt loam soil in a greenhouse. Gas samples were collected weekly over a 140-day period in 2022. Methane and CO₂ emissions differed (p < 0.05) among P fertilizer sources, while N₂O emissions were similar among all treatments. Methane, CO₂, and N₂O emissions from MAP-fertilized rice were the greatest (98.7, 20,960, and 0.44 kg ha⁻¹ season⁻¹, respectively), but they were similar to those of CH₄ and CO₂ for CPST and those of N₂O for all other P fertilizer sources. Season-long CH₄, CO₂, and N₂O emissions and net GHG emissions did not differ between ECST materials. This study’s results emphasized the potential that wastewater-recovered struvite has to reduce GHG emissions in rice production systems. Full article

In response to the need for improvement in the utilization of ammonium-rich solutions after the electrochemical reduction of nitrate (NO₃⁻–RR), this study combined phosphorus-containing wastewater and adopted the electrochemical precipitation method for the preparation of struvite (MAP) to simultaneously recover nitrogen and phosphorus resources. At a current density of 5 mA·cm⁻² and an initial solution pH of 7.0, the recovery efficiencies for nitrogen and phosphorus can reach 47.15% and 88.66%, respectively. Under various experimental conditions, the generated struvite (MgNH₄PO₄·6H₂O) exhibits a typical long prismatic structure. In solutions containing nitrate and nitrite, the coexisting ions have no significant effect on the final product, struvite. Finally, the characterization of the precipitate product by X-ray diffraction (XRD) revealed that its main component is struvite, with a high purity reaching 93.24%. Overall, this system can effectively recover ammonium nitrogen from the NO₃⁻–RR solution system after nitrate reduction, with certain application prospects for the recovery of ammonium nitrogen and phosphate. Full article

Nutrient recovery in domestic wastewater treatment has increasingly become an important area of study as the supply of non-renewable phosphorus decreases. Recent bench-scale trials indicate that co-generation of struvite and hydrogen using electrochemical methods may offer an alternative to existing recovery options utilized by municipal wastewater treatment facilities. However, implementation has yet to be explored at plant-scale. In the development of novel nutrient recovery processes, both economic and environmental assessments are necessary to guide research and their design. The aim of this study was to conduct a prospective life cycle assessment and cost analysis of a new electrochemical struvite recovery technology that utilizes a sacrificial magnesium anode to precipitate struvite and generate hydrogen gas. This technology was modeled using process simulation software GPS-X and CapdetWorks assuming its integration in a full-scale existing wastewater treatment plant with and without anaerobic digestion. Struvite recoveries of 18–33% were achieved when anaerobic digestion was included, with a break-even price of $6.03/kg struvite and $15.58/kg of hydrogen required to offset increased costs for recovery. Struvite recovery reduced aquatic eutrophication impacts as well as terrestrial acidification impacts. Tradeoffs between benefits from struvite and burdens from electrode manufacturing were found for several impact categories. Full article

Phosphorus (P) recovery from wastewaters as struvite (MgNH₄PO₄·6H₂O) may be a viable alternative fertilizer-P source for agriculture. The objective of this study was to evaluate the economic and environmental implications of struvite as a fertilizer-P source for flood-irrigated rice (Oryza sativa) relative to other commonly used commercially available fertilizer-P sources. A field study was conducted in 2019 and 2020 to evaluate the effects of wastewater-recovered struvite (chemically precipitated struvite (CPST) and electrochemically precipitated struvite (ECST)) on rice yield response in a P-deficient, silt–loam soil in eastern Arkansas relative to triple superphosphate, monoammonium and diammonium phosphate, and rock phosphate. A life cycle assessment methodology was used to estimate the global warming potentials associated with rice produced with the various fertilizer-P sources. Life cycle inventory data were based on the field trials conducted with and without struvite application for both years. A partial budget analysis showed that, across both years, net revenues for ECST and CPST were 1.4 to 26.8% lower than those associated with the other fertilizer-P sources. The estimated greenhouse gas emissions varied between 0.58 and 0.70 kg CO₂ eq kg rice⁻¹ from CPST and between 0.56 and 0.81 kg CO₂ eq kg rice⁻¹ from ECST in 2019 and 2020, respectively, which were numerically similar to those for the other fertilizer-P sources in 2019 and 2020. The similar rice responses compared to commercially available fertilizer-P sources suggest that wastewater-recovered struvite materials might be an alternative fertilizer-P-source option for flood-irrigated rice production if struvite can become price-competitive to other fertilizer-P sources. Full article

Anaerobically treated swine wastewater contains large amounts of orthophosphate phosphorus, ammonium nitrogen and organic substances with potential nutrients recovery via struvite electrochemical precipitation post-treatment. Lab-scale batch experiments were systematically conducted in this study to investigate the effects of initial pH, current density, organic substances upon nutrients removal, and precipitates quality (characterized by X-ray diffraction, scanning electron microscopy and element analysis via acid dissolution method) during the struvite electrochemical precipitation process. The optimal conditions for the initial pH of 7.0 and current density of 4 mA/cm² favoured nutrients removal and precipitates quality (struvite purity of up to 94.2%) in the absence of organic substances. By contrast, a more adverse effect on nutrients removal, morphology and purity of precipitates was found by humic acid than by sodium alginate and bovine albumin in the individual presence of organic substances. Low concentration combination of bovine albumin, sodium alginate, and humic acid showed antagonistic inhibition effects, whereas a high concentration combination showed the accelerating inhibition effects. Initial pH adjustment from 7 to 8 could effectively mitigate the adverse effects on struvite electrochemical precipitation under high concentration combined with organic substances (500 mg/L bovine albumin, 500 mg/L sodium alginate, and 1500 mg/L humic acid); this may help improve struvite electrochemical precipitation technology in practical application for nutrients recovery from anaerobically treated swine wastewater. Full article

Phosphorus (P) is essential for life and has a fundamental role in industry and the world food production system. The present work describes different technologies adopted for what is called the second-generation P recovery framework, that encompass the P obtained from residues and wastes. The second-generation P has a high potential to substitute the first-generation P comprising that originally mined from rock phosphates for agricultural production. Several physical, chemical, and biological processes are available for use in second-generation P recovery. They include both concentrating and recovery technologies: (1) chemical extraction using magnesium and calcium precipitating compounds yielding struvite, newberyite and calcium phosphates; (2) thermal treatments like combustion, hydrothermal carbonization, and pyrolysis; (3) nanofiltration and ion exchange methods; (4) electrochemical processes; and (5) biological processes such as composting, algae uptake, and phosphate accumulating microorganisms (PAOs). However, the best technology to use depends on the characteristic of the waste, the purpose of the process, the cost, and the availability of land. The exhaustion of deposits (economic problem) and the accumulation of P (environmental problem) are the main drivers to incentivize the P’s recovery from various wastes. Besides promoting the resource’s safety, the recovery of P introduces the residues as raw materials, closing the productive systems loop and reducing their environmental damage. Full article

Batch electrocoagulation (BEC), continuous electrocoagulation (CEC), and chemical precipitation (CP) were compared in struvite (MgNH₄PO₄·6H₂O) precipitation from synthetic and authentic water. In synthetic water treatment (SWT), struvite yield was in BEC 1.72, CEC 0.61, and CP 1.54 kg/m³. Corresponding values in authentic water treatment (AWT) were 2.55, 3.04, and 2.47 kg/m³. In SWT, 1 kg struvite costs in BEC, CEC, and CP were 0.55, 0.55, and 0.11 €, respectively, for AWT 0.35, 0.22 and 0.07 €. Phosphate removal in SWT was 93.6, 74.5, and 71.6% in BEC, CEC, and CP, respectively, the corresponding rates in AWT were 89.7, 77.8, and 74.4%. Ammonium removal for SWT in BEC, CEC, and CP were 79.4, 51.5, and 62.5%, respectively, rates in AWT 56.1, 64.1, and 60.9%. Efficiency in CEC and BEC are equal in nutrient recovery in SWT, although energy efficiency was better in CEC. CP is cheaper than BEC and CEC. Full article