Reverse osmosis concentrate secondary resource
Concentrated aqueous reject stream generated during reverse-osmosis water treatment, considered here as a secondary feed for constituent separation and recovery. Its salts, nutrients, contaminants and treatment additives depend on the source water and process. The curated experiment used concentrate produced in the laboratory from Arkansas River water, not natural geothermal brine or oil-and-gas produced water. This process-generated mixture is distinct from its dissolved elements, precipitated mineral phases and traded products. No criticality designation is inherited from a constituent.
Microbial & Biochemical Mechanisms (1)
Activated-sludge-associated precipitation during concentrate treatment
biomineralization
Microbial
Aerated concentrate amended with activated-sludge biomass and glycerin produced more suspended solids and lower filtered calcium and sulfate concentrations than the reported unamended controls over 18 hours. Soluble total phosphorus declined as a surrogate for the added phosphonate-containing antiscalant. Microbial antiscalant assimilation and carbon-phosphorus bond cleavage are proposed explanations, not demonstrated enzyme activity. SEM/EDS and modeling suggested gypsum and calcite in mixed solids, but did not independently establish crystalline phase identity or pure-product recovery. The supported outcome is a laboratory treatment association in one river-derived concentrate.
Experimental Context & Analytical Limits:
Arkansas River water collected near Garden City, Kansas on 27 March 2024 was ultrafiltered and processed by batch reverse osmosis at 85% water recovery on 22-23 April 2024, with 3.0 mg/L proprietary polymer- and phosphonate-based antiscalant dosed into the feed. Three-liter concentrate batches in 4-liter jars received particulate biomass retained from 100 mL of Boulder wastewater-treatment activated sludge on a 0.7-micrometer filter and resuspended in the concentrate, plus 325 mg/L glycerin. The mixed, aerated treatment ran for 18 hours in triplicate, with initial volatile suspended solids approximately 0.50 g/L. Table S3 reports treatment temperatures around 21-22 degrees C and pH changing from 8.07 to 8.23; these are observed batch conditions, not prescribed optima. The stagnant control had two replicates and the mixed/aerated control one; both lacked added sludge and glycerin. They were not demonstrated sterile controls, and no glycerin-only, killed-biomass or matched-pH control was reported. Analytical water samples were filtered through 0.45-micrometer nylon filters. Community sequencing does not identify which organism caused the change; no isolate or causal taxon identifier is assigned. Downstream cation exchange and modeled membrane steps are separate processes, not microbial lithium, magnesium or rubidium product recovery.
Arkansas River water collected near Garden City, Kansas on 27 March 2024 was ultrafiltered and processed by batch reverse osmosis at 85% water recovery on 22-23 April 2024, with 3.0 mg/L proprietary polymer- and phosphonate-based antiscalant dosed into the feed. Three-liter concentrate batches in 4-liter jars received particulate biomass retained from 100 mL of Boulder wastewater-treatment activated sludge on a 0.7-micrometer filter and resuspended in the concentrate, plus 325 mg/L glycerin. The mixed, aerated treatment ran for 18 hours in triplicate, with initial volatile suspended solids approximately 0.50 g/L. Table S3 reports treatment temperatures around 21-22 degrees C and pH changing from 8.07 to 8.23; these are observed batch conditions, not prescribed optima. The stagnant control had two replicates and the mixed/aerated control one; both lacked added sludge and glycerin. They were not demonstrated sterile controls, and no glycerin-only, killed-biomass or matched-pH control was reported. Analytical water samples were filtered through 0.45-micrometer nylon filters. Community sequencing does not identify which organism caused the change; no isolate or causal taxon identifier is assigned. Downstream cation exchange and modeled membrane steps are separate processes, not microbial lithium, magnesium or rubidium product recovery.
Curated Evidence Points:
Support
Source:
usbr20092
Appendix A Sections 2.1-2.4, Table 2 and Table S3 establish feed origin, living mixed-sludge preparation, glycerin addition, replication and conditions. Sections 3.2.1 and 3.2.4 and Figures 3-5 report total suspended solids of 1.05 g/L in the treatment, versus 0.0089 and 0.14 g/L in stagnant and aerated controls, respectively, and average filtered calcium/sulfate reductions of 41%/10% from initial concentrate. Controls also showed calcium reductions (12% and 5%) and sulfate reductions (4% each). These are source-reported solution comparisons and mixed-solids measurements, not phase-specific recovery yields.
Partial
Source:
usbr20092
Sections 3.2.1-3.2.3 and Figure 4 report an 88% decrease in soluble total phosphorus used as an antiscalant surrogate. Assimilation, carbon- phosphorus cleavage and organism-specific contributions were inferred; enzyme activity and gene necessity were not tested. Controls lack both inoculum and glycerin, so the design does not isolate their separate effects. Aeration-induced carbonic-acid stripping, pH variability, endogenous organisms and biomass-associated sorption can contribute. Section 3.2.1 also reports limited precipitation in another drainage concentrate with more orthophosphate, with data not shown; performance is not generalized to all concentrates.
Partial
Source:
usbr20092
Sections 3.2.4-3.2.6 explicitly request additional solids analysis to confirm SEM/EDS and modeled phase assignments. The reported 64% gypsum purity assumes CaSO4.2H2O; neither it nor modeled pH control establishes an isolated pure gypsum product. Proposed gypsum yield per million liters, subsequent water-recovery percentages and brucite purity are scale-normalized or modeled projections. Figure 1's million-liter basis does not change the 3-liter reactor scale in Table 2. Section 3.3 reports uranium was not precipitated; its 0.422 mg/L value differs from 0.444 mg/L in Table S4, so no uranium removal efficiency is curated. Section 2.7 assigns sequencing to batch 2 while Figure S2 labels batch 1; the discrepancy prevents an exact batch-specific community claim.
Context_only
Source:
usbr20092
Sections 2.5 and 3.3 and Figures 7-8 describe subsequent nonmicrobial cation-exchange loading and regeneration. The authors acknowledge co-elution and lack of high-purity constituent recovery. Table S4 labels later RO/NF results as modeled data and some ion-exchange values as assumed conserved; nondetects are not zero. These process proposals explain resource interest but do not demonstrate microbial recovery of individual critical elements or industrial deployment.
Sources & References
-
usbr20092: Scarim, Bernardino-McCloud and Arias-Paic. Biological and Ion Exchange Mining of Reverse Osmosis Concentrate: Enhancing Water and Mineral Extraction from a Salinity Impaired Surface Water. Bureau of Reclamation Final Report ST-2024-20092, December 2025 cover and signatures; documentation page dated 7 November 2025. Appendix A contains the accepted manuscript associated with DOI 10.1061/JOEEDU.EEENG-8371, Journal of Environmental Engineering 152(1), 04025092 (2026), and its supplements. Sections 2.1-2.8 and 3.2-3.3, Tables 1-3/S3-S4 and Figures 1-6/S2-S3; PDF pages 21-30 and 41-53.
https://data.usbr.gov/rise/content-rise-public/rise/catalog-item/binary/S%26T%20Final%20Report%2020092%20Signed.pdf (accessed 2026-10-11)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-11T10:50:18Z |
codex (GPT-6; codex) | CREATE | Created a process-defined secondary-resource record and scoped laboratory precipitation mechanism from the complete USBR report and supplements. Preserved controls, unproven antiscalant and phase assignments, source inconsistencies, and the distinction between measured treatment and projected downstream recovery. |
Record source: data/records/reverse-osmosis-concentrate.yaml