Grantee Research Project Results
Final Report: Economic recovery and reuse of nutrients from wastewater
EPA Contract Number: EPD18007Title: Economic recovery and reuse of nutrients from wastewater
Investigators: Kadossov, Evgueni
Small Business: XploSafe, LLC
EPA Contact: Richards, April
Phase: II
Project Period: February 1, 2018 through January 31, 2020
Project Amount: $300,000
RFA: Small Business Innovation Research (SBIR) - Phase II (2017) Recipients Lists
Research Category: Small Business Innovation Research (SBIR) , SBIR - Water
Description:
Nutrient pollution caused by excess nitrogen and phosphorus in the water is one of the United States’ most extensive, costly and challenging environmental problems. Nitrogen and phosphorus support the growth of algae and aquatic plants that provide food and habitat for fish, shellfish and other organisms that live in water. However, when too much nitrogen and phosphorus are introduced into water by human activities, nutrient pollution occurs in a process known as eutrophication. This leads to algae growing faster than ecosystems can handle it. As a result, the water quality, food resources and habitats deteriorate. In particular, such algal blooms can severely reduce or even eliminate dissolved oxygen in the water, leading to illnesses and even death of large numbers of fish. Algal blooms are harmful to humans because they produce elevated toxins and bacterial growth that can make people deadly ill if they come into contact with polluted water, consume tainted fish or shellfish, or drink contaminated water. Nutrient treatment and recovery technologies are being implemented but they suffer from difficulties in deployment, high-energy requirements, and high overall costs. The proposed solution to this problem is the capture of ammonium, urea, nitrate and phosphate on low-cost biodegradable sorbent pellets that upon saturation, with the nutrients could be employed directly as slow-release fertilizer that would add both minerals and key nutrients to the soil.
XploSafe successfully demonstrated the operational feasibility of two classes of highly economical and scalable sorbent-fertilizers for in-situ recovery of excess nutrients (nitrate, phosphate ions) from wastewaters. The first was a bio-degradable (metal oxide nanocomposite) sorbent media for the recovery and reuse of nitrogen and phosphorous from municipal (primary and secondary) wastewaters; and the second were inorganic (mixed metal double layered hydroxides) sorbent medias for the recovery of phosphate and nitrate ions from biologically active waters such as commercial and household aquaria, watering ponds, swimming pools etc. The sorbent media were independently evaluated in operational field tests. The bio-degradable sorbents were evaluated for the recovery of phosphorus and nitrogen from secondary wastewater in a pilot study at a municipal wastewater treatment plant. While the inorganic sorbent medias were evaluated independently for the removal of phosphorous and nitrogen from aquatic exhibit holding tanks at a commercial aquarium. Both the tested sorbent medias were subsequently applied as a slow-release fertilizer to effectively grow plants (radishes, marigolds) thus demonstrating the recovery and reuse of essential plant nutrients.
Summary/Accomplishments (Outputs/Outcomes):
Over the course of SBIR projects the XploSafe research team successfully demonstrated the technical feasibility of synthesizing two classes of highly economical sorbents (biodegradable) for the in-situ (selective) recovery of target nutrients (nitrate, phosphate ions) from wastewaters. Mixed metal oxide nanocomposites (in a biodegradable gelatinized matrix) and mixed metal double layered hydroxide were preapred and optimized to enhance their absoprtion of the target plan nutrients. Over 70 iterations of the sorben medias were developed and evaluated.
The organic metal oxide sorbent originally proposed were optimized for scale-up. The researchers developed a semi-automated extrusion process to generate highly consistent, spherical sorbent beads (Figure 1A). The spherical beads (3-5 mm in diameter), were easily packable in columns and exhibited relatively no signs of puncture, even when several kilograms were packed in columns. Although fantastic for the removal of nutrients (phosphate and nitrate ions) they disintegrated in a test run at the commercial aquarium. The high salinity and high biological activity of the saltwater aquarium resulted in degradation of the beads over time. Thus, the need for an alternative sorbent material resistant to high biological activity was realized.
Figure 1: A) Spherical mixed metal oxide nanocomposite beads (3-5 mm in diameter), B) Inorganic mixed metal sorbent media commercialized under the brand name PhosRoxTM
The researchers then explored the applicability of inorganic mixed metal oxides. The synthesized double layered hydroxides exhibited a much higher capacity for the uptake of phosphate and nitrate ions compared to the organic metal oxide beads. This material was also optimized over the course of the research project for structural rigidity and to facilitate quick adsorption of phosphate and nitrate ions. The developed inorganic media were inexpensive to produce and proved to be highly scalable in advancing from bench top (2 liters) to bucket size (5 gallons) to commercial scale (50 liter) batch synthesis.
The researchers conducted dozens of adsorption tests with stock solutions, various wastewaters, and several pilot-studies to gather real-time field data to investigate the sorbent uptake efficiency for the targeted nutrients. Table 1 summarizes the measured capacity for the recovery of phosphate and nitrate ions by the developed sorbents.
Sorbent Material | Phosphate Uptake Capacity (mg/g sorbent) | Nitrate Uptake Capacity (mg/g sorbent) |
Organic Metal Oxide Beads | 38.1 | 4.40 |
PhosRox™ | 69.5 | 24.1 |
Several of these adsorption tests took place as a part of successful pilot-studies at a municipal wastewater treatment plant; and at a large commercial aquarium.
The operational feasibility of recovering phosphorus and nitrogen from secondary wastewater was demonstrated in a pilot study at a municipal wastewater treatment plant. A pilot-scale (17-gallon) trough-like wastewater treatment module was designed and fabricated for on-site tests at the wastewater treatment plant. The trough included three removable steel holders that were filled with sorbent media and lowered into the trough. Water was diverted from the wastewater treatment facility into the trough, directing it through the three sorbent baskets (each containing 13 kg of organic metal oxide beads), before being discharged back into the influent waste stream. Samples of water were taken from the inlet, and just after the three sorbent baskets every 30 minutes. Testing of these samples showed a reduction in phosphate of 0.8 ppm from the inlet to the outlet of the trough consistently over the 15 hour testing period (split into two days, 7 hours and then 8 hours). The flowrate of 2.0 gpm allowed the wastewater to be retained within the trough system for approximately 7 minutes, before being pushed out of the discharge port. At the conclusion of the pilot-run, 1800 gallons of water had passed through the sorbent media, with a consistent reduction of 0.8 ppm of phosphate across the board. The sorbent material showed no signs of decay or bacterial interference, and it held up well to the adverse environmental ambient temperatures that dropped below freezing overnight.
In a second study independently conducted by the customer at a commercial aquarium the researchers successfully quantified the removal of phosphorous and nitrogen from large (400 gallon) aquatic exhibit holding tanks. These tests were conducted using the inorganic material (now commercialized as PhosRox™). The inorganic media was used initially to treat a 400-gallon quarantine saltwater tank for 12 weeks. Although free of animals, bacteria in the test system were still able to feed on the fish food which was added daily, thus continuously producing phosphate and nitrate throughout the duration of the study. Over the course of 3 months (12 weeks) of testing, the phosphate concentration steadily decreased from 1.65 ppm to 0.32 ppm, and continued to drop. It was determined that XploSafe media exhibited a substantially high capacity for the removal of phosphate ions in comparison to traditional aquarium phosphate removal medias. The XploSafe media also lasted significantly (over 2-3 times) longer, while not muddying or affecting water clarity as is the case with tradition ferric aquarium medias. It was also hypothesized that for most customers, the XploSafe PhosRox™ media would need to be changed as infrequently as every 6-12 months while still maintaining a clear, low phosphate environment. Next the aquarium staff evaluated the sorbent media with live animals, particularly feeder shrimp (raised for fish food on-site). After 5-weeks of successful testing, it was determined that phosphate numbers had been continuously falling, and the shrimp were healthy, growing, and transitioning from juveniles into adulthood. These tests demonstrated the technical feasibility of the PhosRox™ media to effectively control phosphorous and nitrogen concentration in large biologically active systems.
Next the researchers demonstrated the reuse of the recovered nutrients (phosphorus and nitrogen) by the spent sorbent media as a slow-release fertilizer post sorption of nutrients from wastewaters. The researchers conducted two main growth studies using the spent sorbent medias post capture of nutrients in order to test their suitability for land-application after use. First, a cherry radish growth study, was successfully conducted to determine the effects of nutrient loaded organic metal oxide beads on the growth of radish in comparison to a control (no fertilizer) and a commercial fertilizer (NPK of 9/13/22). Although the commercial fertilizer resulted in the most rapid and healthiest growth of the radishes, the XploSafe plants showed more foliage growth and a stronger root system than the control group. Furthermore, it was shown that the XploSafe sorbent fertilizer comprised of dried metal-oxide sorbent beads was capable of sustaining plant growth, while simultaneously not causing any withering or sickness in the plants.
The second growth study demonstrated the growth of Marigold flowers to compare XploSafe sorbent/fertilizer medias in comparison to a control group without any fertilizer exposure. 1 g each of the three different XploSafe sorbent fertilizer types were added to 5 plants each (1 g dry weight or 7 g wet weight for the organic metal oxide beads) on the day following initial sprouting and 8 days after planting the 20 plants. There were no observed adverse effects on the growth of the plants at the 21-day mark, with none exhibiting any nutrient burn or stunted growth. In fact, the 5 plants with organic metal oxide beads grew slightly faster than the other plants, averaging 6.8 leaves per sprout compared to the 6.0 leaves per sprout for the control plants, suggesting that the proteins and nutrients of the sorbent media may have promoted better growth.
Conclusions:
The XploSafe researchers developed, optimized, and commercialized an inorganic sorbent media which demonstrated a very high capacity for the recovery of phosphates and nitrates from various wastewater sources. The developed medias exhibited robustness while exposed to high salinity, bacterial growth, pH and microorganisms in operational field tests. The treated sorbents when subsequently applied as a fertilizer showed no negative effects while assisting in plant growth. The developed medias exhibited relatively higher (up to 2 times more) capacity for the removal of phosphate ions when compared to industry standard ferric oxide based medias. They also exhibited a remarkable capacity for the removal of nitrates from the waste streams. The developed medias exhibited a longer service-life while also leading to healthier, more clear water in commercial aquairum. Thus, a highly economical, scalable and net cost reducing solution was developed for several wastewater treatment applications.
Hydra Water Technologies LLC was spun-off as a portfolio company dedicated to the commercial scale manufacturing and commercialization of the developed water treatment technology. It is commercializing two scalable, high value proposition solutions for the in-situ recovery (selective capture) and reuse of the excess nutrients (phosphorus and nitrogen) from wastewaters. First product was launched under the brand name PhosRoxTMwhich is an inorganic sorbent media for phosphate and nitrate removal; targeting customers and end-users of commercial and household aquaria, watering ponds, swimming pools, water features etc.A second product is underdevelopment which is a turn-key, off-grid (potentially solar powered) system for the recovery of nutrients from rural and agricultural watering ponds, and lagoons at livestock farming operations.
Over the course of the Phase II project the company expanded by acquiring a 11,500 sq. ft. research and production facility in Stillwater, OK. This new facility will serve as the company headquarters and facilitate the go-to market commercial scale production of the developed sorbent materials. Several commercial scale equipment including industrial scale jacketed reactors, chillers, integrated heater, filter press and sieve were also acquired. Hydra Water Technologies invested over $75k in equipment and resources that shall provide adequate capacity to support the forecasted demand for the developed sorbents over the next 2 years.
Journal Articles:
No journal articles submitted with this report: View all 2 publications for this projectSBIR Phase I:
Economic recovery and reuse of nutrients from wastewater | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.