Stanford Advisors

All Publications

  • Long-Term Robustness and Failure Mechanisms of Electrochemical Stripping for Wastewater Ammonia Recovery. ACS environmental Au Kogler, A., Sharma, N., Tiburcio, D., Gong, M., Miller, D. M., Williams, K. S., Chen, X., Tarpeh, W. A. 2024; 4 (2): 89-105


    Nitrogen in wastewater has negative environmental, human health, and economic impacts but can be recovered to reduce the costs and environmental impacts of wastewater treatment and chemical production. To recover ammonia/ammonium (total ammonia nitrogen, TAN) from urine, we operated electrochemical stripping (ECS) for over a month, achieving 83.4 ± 1.5% TAN removal and 73.0 ± 2.9% TAN recovery. With two reactors, we recovered sixteen 500-mL batches (8 L total) of ammonium sulfate (20.9 g/L TAN) approaching commercial fertilizer concentrations (28.4 g/L TAN) and often having >95% purity. While evaluating the operation and maintenance needs, we identified pH, full-cell voltage, product volume, and water flux into the product as informative process monitoring parameters that can be inexpensively and rapidly measured. Characterization of fouled cation exchange and omniphobic membranes informs cleaning and reactor modifications to reduce fouling with organics and calcium/magnesium salts. To evaluate the impact of urine collection and storage on ECS, we conducted experiments with urine at different levels of dilution with flush water, extents of divalent cation precipitation, and degrees of hydrolysis. ECS effectively treated urine under all conditions, but minimizing flush water and ensuring storage until complete hydrolysis would enable energy-efficient TAN recovery. Our experimental results and cost analysis motivate a multifaceted approach to improving ECS's technical and economic viability by extending component lifetimes, decreasing component costs, and reducing energy consumption through material, reactor, and process engineering. In summary, we demonstrated urine treatment as a foothold for electrochemical nutrient recovery from wastewater while supporting the applicability of ECS to seven other wastewaters with widely varying characteristics. Our findings will facilitate the scale-up and deployment of electrochemical nutrient recovery technologies, enabling a circular nitrogen economy that fosters sanitation provision, efficient chemical production, and water resource protection.

    View details for DOI 10.1021/acsenvironau.3c00058

    View details for PubMedID 38525023

    View details for PubMedCentralID PMC10958661

  • Ligand Exchange Adsorbents for Selective Phosphate and Total Ammonia Nitrogen Recovery from Wastewaters ACCOUNTS OF MATERIALS RESEARCH Clark, B., Sharma, N., Apraku, E., Dong, H., Tarpeh, W. A. 2024
  • Long-Term Robustness and Failure Mechanisms of Electrochemical Stripping for Wastewater Ammonia Recovery ACS ENVIRONMENTAL AU Kogler, A., Sharma, N., Tiburcio, D., Gong, M., Miller, D. M., Williams, K. S., Chen, X., Tarpeh, W. A. 2024
  • Exchange between Dissolved U(VI) and Adsorbed and Precipitated Forms of Solid-Associated U ACS EARTH AND SPACE CHEMISTRY Satpathy, A., Sharma, N., Pan, W., Catalano, J. G., Giammar, D. E. 2023
  • Solid-Water Partitioning and Speciation of Trace Metal Micronutrients in Wetland Soils and Stream Sediments ACS EARTH AND SPACE CHEMISTRY Sharma, N., Yan, J., Flynn, E. D., Catalano, J. G., Giammar, D. E. 2023
  • Copper availability governs nitrous oxide accumulation in wetland soils and stream sediments GEOCHIMICA ET COSMOCHIMICA ACTA Sharma, N., Flynn, E. D., Catalano, J. G., Giammar, D. E. 2022; 327: 96-115
  • Dynamic Responses of Trace Metal Bioaccessibility to Fluctuating Redox Conditions in Wetland Soils and Stream Sediments ACS EARTH AND SPACE CHEMISTRY Sharma, N., Wang, Z., Catalano, J. G., Giammar, D. E. 2022; 6 (5): 1331-1344
  • Impact of dissolved oxygen and pH on the removal of selenium from water by iron electrocoagulation WATER RESEARCH Bae, Y., Crompton, N. M., Sharma, N., Yuan, Y., Catalano, J. G., Giammar, D. E. 2022; 213: 118159


    Removing dissolved selenium (i.e., selenate and selenite) from wastewater is a challenging issue for a range of industries. Iron electrocoagulation can produce Fe(II)-containing solids that can adsorb and chemically reduce dissolved Se. In a series of bench-scale experiments we investigated the effects of dissolved oxygen (fully oxic, partially oxic, and strictly anoxic) and pH (6 and 8) on the rate and extent of dissolved selenate and selenite removal by iron electrocoagulation. These studies combined measurements of the aqueous phase with the direct characterization of the resulting solids. Among the conditions studied the rate and extent of dissolved selenium (Se) removal were highest at pH 8 and strictly anoxic conditions. X-ray absorption spectroscopy demonstrated that in the absence of oxygen, Se was primarily transformed to elemental selenium (Se0) and selenide. Green rust that formed in the suspension during electrocoagulation played a key role as a reductant and sorbent of Se. At pH 6 dissolved oxygen did not affect the rates and extents of dissolved Se removal. Under all the conditions studied, dissolved Se removal was more effective with iron electrocoagulation than with the direct addition of pre-synthesized green rust or ferrous hydroxide. The most rapid and substantial dissolved Se removal was achieved by freshly-formed green rust and ferrous hydroxide, which are both Fe(II)-bearing solids. With an improved understanding of the products and mechanisms of the process, iron electrocoagulation can be optimized for removal of Se from wastewater.

    View details for DOI 10.1016/j.watres.2022.118159

    View details for Web of Science ID 000758958500003

    View details for PubMedID 35172259

  • Metal-Catalyzed Hydrolysis of RNA in Aqueous Environments ENVIRONMENTAL SCIENCE & TECHNOLOGY Chatterjee, A., Zhang, K., Rao, Y., Sharma, N., Giammar, D. E., Parker, K. M. 2022; 56 (6): 3564-3574


    The stability of RNA in aqueous systems is critical for multiple environmental applications including evaluating the environmental fate of RNA interference pesticides and interpreting viral genetic marker abundance for wastewater-based epidemiology. In addition to biological processes, abiotic reactions may also contribute to RNA loss. In particular, some metals are known to dramatically accelerate rates of RNA hydrolysis under certain conditions (i.e., 37 °C or higher temperatures, 0.15-100 mM metal concentrations). In this study, we investigated the extent to which metals catalyze RNA hydrolysis under environmentally relevant conditions. At ambient temperature, neutral pH, and ∼10 μM metal concentrations, we determined that metals that are stronger Lewis acids (i.e., lead, copper) catalyzed single-stranded (ss)RNA, whereas metals that are weaker Lewis acids (i.e., zinc, nickel) did not. In contrast, double-stranded (ds)RNA resisted hydrolysis by all metals. While lead and copper catalyzed ssRNA hydrolysis at ambient temperature and neutral pH values, other factors such as lowering the solution pH and including inorganic and organic ligands reduced the rates of these reactions. Considering these factors along with sub-micromolar metal concentrations typical of environmental systems, we determined that both ssRNA and dsRNA are unlikely to undergo significant metal-catalyzed hydrolysis in most environmental aqueous systems.

    View details for DOI 10.1021/acs.est.1c08468

    View details for Web of Science ID 000776207100026

    View details for PubMedID 35226478

  • Consistent controls on trace metal micronutrient speciation in wetland soils and stream sediments GEOCHIMICA ET COSMOCHIMICA ACTA Yan, J., Sharma, N., Flynn, E. D., Giammar, D. E., Schwartz, G. E., Brooks, S. C., Weisenhorn, P., Kemner, K. M., O'Loughlin, E. J., Kaplan, D., Catalano, J. G. 2022; 317: 234-254
  • Role of precursors in the formation of trihalomethanes during chlorination of drinking water and wastewater effluents from a metropolitan region in western India JOURNAL OF WATER PROCESS ENGINEERING Sharma, N., Mohapatra, S., Padhye, L. P., Mukherji, S. 2021; 40
  • Seasonal variation in fluorescence characteristics of dissolved organic matter in wastewater and identification of proteins through HRLC-MS/MS JOURNAL OF HAZARDOUS MATERIALS Mohapatra, S., Sharma, N., Mohapatra, G., Padhye, L. P., Mukherji, S. 2021; 413: 125453


    In the present study, wastewater samples acquired from five wastewater treatment plants (WWTPs), located in western India were characterized using fluorescence spectroscopy, and resin-based fractionation was conducted to fractionate DOM into hydrophobic and hydrophilic base, acid, and neutral fractions. Among several fractions, the hydrophilic acid (HIA) and hydrophilic neutral (HIN) fractions were present in higher abundance (more than 50% of DOC) compared to the hydrophilic base (HIB) fraction in both influent and effluent wastewater stream obtained from WWTPs. Tryptophan-like and tyrosine-like substances were also abundant in the influent and effluent stream of WWTPs. Further, LC-MS/MS analysis could identify 235 and 288 DOM proteins in the influent and effluent stream of WWTP-1, respectively. These proteins revealed varying percentage of tryptophan and tyrosine residues. The tryptophan residues primarily contributed to protein-like fluorescence in wastewater. The proteins were further classified based on their role in biological processes, location in the cell, and molecular function. Among several proteins, Alzheimer's and Huntington disease biomarkers were identified at WWTP-1. Their presence in the surface water can serve as an early warning system for wastewater-based epidemiology.

    View details for DOI 10.1016/j.jhazmat.2021.125453

    View details for Web of Science ID 000647597600008

    View details for PubMedID 33930968

  • Modeling performance of rhamnolipid-coated engineered magnetite nanoparticles for U(vi) sorption and separation ENVIRONMENTAL SCIENCE-NANO Sharma, N., Ghosh, A., Fortner, J. D., Giammar, D. E. 2020; 7 (7): 2010-2020

    View details for DOI 10.1039/d0en00416b

    View details for Web of Science ID 000549099000008