Grantee Research Project Results
Final Report: The Application of Ferrate for Wastewater Reuse
EPA Contract Number: EPD07050Title: The Application of Ferrate for Wastewater Reuse
Investigators: Daly, Luke J. , Alig, Craig S.
Small Business: Ferrate Treatment Technologies, LLC
EPA Contact: Richards, April
Phase: I
Project Period: March 1, 2007 through August 31, 2007
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2007) RFA Text | Recipients Lists
Research Category: Small Business Innovation Research (SBIR) , SBIR - Water and Wastewater
Description:
Worldwide fresh water supplies are being depleted rapidly by drought, population growth, increased per capita consumption, and industrial pollution. The growing need for clean water now shapes development, communities, governments, national economies, and, most importantly human health. Because human toxins can be identified with much greater precision, it is now known that some commonly used disinfectants produce carcinogens, and hormone replacement therapies produce byproducts that end up in area water supplies. Worse yet, antibiotics in water supplies may help create “superbugs” that evade medical treatment. An increasingly concerned public as well as public health officials are demanding protection through more stringent treatment regulations, and alternatives to conventional treatment technologies are being sought to meet these threats.
Ferrate was explored in the 1970s as a replacement chemical for chlorine, but prior synthesis methods made its use cost prohibitive. With recent advances in new onsite production methods for ferrate, it has the potential to quickly become a preferred alternative to existing oxidation and disinfection processes. Additionally, there is scientific evidence that ferrate can effectively oxidize and remove endocrine disrupting chemicals (EDCs) and pharmaceuticals and personal care products (PPCPs) from water and wastewater. As a disinfectant, ferrate is effective in killing Eschericha coli (E. coli) and fecal coliform, and in reducing total coliform counts. In addition, chlorine-resistant bacteria can be treated easily with ferrate. Ferrate is introduced into a water or wastewater stream as a liquid and can therefore be pumped, metered, and retrofitted in an existing treatment plant. The byproduct of ferrate oxidation is the ferric ion (Fe+3), which is environmentally benign and is a micronutrient for plant life.
Summary/Accomplishments (Outputs/Outcomes):
The project goal was to optimize the onsite ferrate synthesis technology patented by Ferrate Treatment Technologies, LLC (FTT) to be cost effective when produced in scalable quantities for applications in water reuse. FTT defines optimization as the ability to maximize the strength of ferrate (FeO4-2) in solution from a Ferrator® while being able to predict and measure synthesis byproduct concentrations in disinfected wastewater after ferrate is added. FTT accomplished this by varying the quantities of the synthesis chemicals as well as reaction times and temperatures, developing analytical measurement techniques, and testing the effectiveness of new ferrate synthesis “recipes” in killing bacteria in wastewater from three treatment plants.
The cost of the ferrate is influenced heavily by the quantities of synthesis chemicals used. This research is instrumental to transitioning the synthesis of ferrate from the laboratory and FTT’s prototype manual Ferrator® to an optimized and fully automated system necessary for large-scale water reuse facilities. FTT developed a number of ferrate synthesis “recipes” that enabled control of the ferrate strength in solution, the synthesis byproducts, and the cost. FTT found that some customers demand chlorine residual (e.g., wastewater reuse on public lands) while other customers do not want chlorine residual (e.g., disinfected effluent discharged to surface waters and wetlands).
Another challenge was how to measure the residual byproducts. Both ferrate and chlorine are oxidants, and the standard DPD method used by most wastewater treatment plants to measure residual chlorine actually measures total oxidant. As an oxidant, ferrate interferes with this method, giving erroneous results. To demonstrate disinfection with little to no chlorine residual, an analytical method was developed that would differentiate between chlorine and ferrate that was present in a sample. This was accomplished by using electrochemical potentiometric methods of analysis. A protocol was developed to identify the presence of ferrate and hypochlorite when together in a solution and distinguish between the two oxidants without being adversely affected by the complex chemistry of either species. Methods include: cyclic voltammetry and amperometric techniques to quantify hypochlorite concentration and cyclic voltammetry, chronoamperometry, and the quartz crystal microbalance to quantify ferrate concentration. These methods are being refined to accurately measure the concentrations of ferrate and hypochlorite when together in solution.
Using the new formulas developed under this project, FTT tested ferrate disinfection on samples collected from three wastewater treatment plants. In Louisiana, influent from a wastewater treatment plant after primary settling had fecal coliform most probable number (MPN) per 100 mL at a 6.65 log concentration; a ferrate dose of 2 mg/L killed 3.5 log and 6 mg/L killed 5 log. In Pennsylvania, treatment plant secondary effluent had fecal coliform MPN per 100 mL at a 4 log concentration; the discharge limit of 14 MPN per 100 mL was achieved after 20 minutes at a dose of 2 mg/L and after 10 minutes at a dose of 3 mg/L. In Florida, a wastewater treatment plant was using 15 mg/L of chlorine for secondary effluent disinfection; ferrate doses in the 3 to 10 mg/L range under a variety of conditions killed total coliform up to 4 log and E. coli up to 5 log.
Conclusions:
Results of this research demonstrate that FTT successfully optimized ferrate synthesis in the laboratory. FTT was able to precondition the synthesis chemicals 33 percent faster with no negative effects on ferrate strength. This will allow a ferrate treatment system to be designed that will produce more ferrate per unit of time than previously achieved. Cost of the synthesis feedstocks was reduced 17 percent below the previous cost while achieving the same performance by adjusting the synthesis formula, accepting a slightly lower ferrate yield, and dosing a slightly higher volume of ferrate solution into a waste stream.
FTT developed a simple protocol that will allow water and wastewater treatment plant operators to use the DPD colorimetric method to quantify residual oxidant levels after ferrate is dosed in wastewater. It calls for the pH to be adjusted to a value of 6 to 7, then prescribes a “holding” time following pH adjustment to allow the ferrate to completely degrade before the DPD test is run.
Cyclic voltammetry shows great potential for development into an oxidant measurement tool. It could be used in a ferrate treatment control system as a feedback sensor to assure the appropriate quantity of ferrate is being added to a water or wastewater stream. FTT tailored the ferrate synthesis formula to control the concentrations of residual oxidants in treated effluents. By carefully synthesizing ferrate, predictable chlorine residuals were achieved in treated wastewater at levels that will meet customer requirements. FTT now can adjust the process to meet a customer’s need relative to the concentration of byproducts they require, if any, in their effluent. Ferrate synthesized using the new formulas developed under this project killed fecal coliform, total coliform, and E. coli at very low doses during field tests on wastewater from treatment plants in Louisiana, Pennsylvania, and Florida.
Supplemental Keywords:
small business, SBIR, EPA, ferrate, Ferrator®, disinfection, oxidation, water reuse, endocrine disrupting chemicals, EDCs, pharmaceutical personal care products, PPCPs, wastewater treatment, water treatment,, Scientific Discipline, Water, Wastewater, Environmental Chemistry, Environmental Engineering, ferrate production, wastewater reuse, treatment, wastewater dischargesThe 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.