Grantee Research Project Results
Final Report: Management of CAFO Discharges Utilizing Controlled Eutrophication Process (CEP) Ponds for Liquid Waste Storage and Conversion to Bioproducts and Slow-Release Biofertilizers
EPA Contract Number: EPD05011Title: Management of CAFO Discharges Utilizing Controlled Eutrophication Process (CEP) Ponds for Liquid Waste Storage and Conversion to Bioproducts and Slow-Release Biofertilizers
Investigators: Massingill, Michael J.
Small Business: Kent SeaTech Corporation
EPA Contact: Richards, April
Phase: I
Project Period: March 1, 2005 through August 31, 2005
Project Amount: $69,831
RFA: Small Business Innovation Research (SBIR) - Phase I (2005) RFA Text | Recipients Lists
Research Category: Small Business Innovation Research (SBIR) , Watersheds , SBIR - Water and Wastewater
Description:
The United States is the world leader in efficient production of food. However, efficient and economical food production often requires the use of intensive farming practices, which, in some cases, have the potential to create negative environmental impacts (USEPA, 2003). Although the U.S. animal production industry has done a good job in controlling waste discharges, the extremely large size of the industry means that even a small percentage of inadequately treated discharges can result in measurable environmental impacts. In the Pacific Southwest, the excellent climate and water resources have allowed a large intensive animal production industry to develop, consisting primarily of beef cattle, dairy cattle, swine and poultry. California leads the nation in milk production, with approximately 2,400 dairies with 1.3 million cows producing more than 30 million tons of solid and liquid waste annually. California is also the nation’s largest source of eggs, with about 25 million birds housed in large concentrated poultry facilities. In California and Arizona, there are more than 3,000 concentrated animal farming operations (CAFOs) (USDA, 2000).
Most of the solid manure and liquid waste from CAFOs is applied to croplands as the final method of disposal. As a result, contamination of surface water and groundwater by CAFO discharges has become a significant problem in some areas. Nearly 2 million tons of manure are produced everyday in the United States (Honeycutt, 2003). This extremely large volume of waste, if deposited only in Rhode Island, would cover the entire state with more than 6 feet of manure each year. Fortunately, the loading is more widely distributed, but the problem still represents a serious waste management concern. Inadequately treated CAFO wastes impact surface water, groundwater and air quality in every state. More than 70 percent of the water quality problems in surveyed rivers and lakes are believed to result from agricultural nonpoint sources (Sharpley, 2003). Other studies indicate that cattle feedlot operations adversely impact 16 percent of all water bodies in the United States (USEPA, 1995). Surface waters can be affected in several ways, including: (1) storm water runoff from fields where solid or liquid waste have been applied, (2) direct runoff from feedlot facilities, and (3) failure of containment lagoons due to inadequate design.
Treatment Strategies
Although there are several significant environmental impacts that need to be addressed regarding CAFO nutrient discharges, the overall concept for disposal currently employed by the industry (land application) seems appropriate and cost-effective. It would be difficult to develop alternative treatment technologies that would be affordable by the low-profit, commodity-oriented food production industry, and if alternative methods of disposal were developed, field crop producers would need to find alternative sources of fertilizers, so little net reduction of nutrient inputs would be achieved. Instead, what is needed are advanced and cost-effective techniques to increase the effectiveness of the land-application methods currently in use, which are already perhaps 80 percent to 90 percent effective in dealing with the large amounts of waste produced. It would also be useful if reduced footprint processes for converting waste nutrients into animal feed or other higher value products could be implemented. The overall problem is one of balancing the nutrient loading more efficiently, so that it can be kept in greater synchrony with the ability of the land crops to uptake the nutrients and liquid waste stream. Researchers are attempting to address this problem in a variety of ways, including reducing the protein levels in animal feeds to limit nitrogen excretion, using chemical compounds to trap and settle a portion of the nutrients in CAFO feedyards and treatment lagoons, increasing the effectiveness of bacterial nitrification, and development of advanced treatment components that can remove, settle, bind or treat the high levels of nutrients more efficiently. Several of these methods are achieving success at the laboratory scale level, but the cost of the treatment modifications, if applied at full-scale, may be high. This Phase I research project involved a promising new method of nutrient reduction that may be applicable in treating CAFO waste.
The Controlled Eutrophication Process
Kent SeaTech Corp. and Clemson University have conducted preliminary research on a promising new concept for concentrating and removing nutrients from wastewater streams. The Controlled Eutrophication Process (CEP) is an innovative multistage water treatment process that uses dense populations of single-celled algae that are cultivated in high-rate algal ponds circulated by large, efficient paddlewheels. The algae are very efficient in capturing nutrients such as nitrogen and phosphorus, and are then removed (harvested) in several steps before the water flow exits the system. In previous applications, Kent SeaTech has seen that CEP technology can reduce the nutrient concentrations found in aquaculture wastewater effluent (7 to 15 mg/L nitrogen and 0.5 to 2.0 mg/L phosphorus) to essentially zero. Although the levels of nitrogen and phosphorus in CAFO discharges are higher than the levels present in aquaculture effluent, Kent SeaTech has developed several modifications of CEP technology that should allow it to remove significant amounts of nutrients in this application.
The basic concept of the CEP approach to treating nutrient pollutants is to divide a treatment pond into a series of zones and link them in a sequential pattern of water flow driven by low-energy paddlewheels. The design and operation of each zone can then be optimized for the type of treatment that it will provide. Physical separation of the algal removal components from the algal production and water purification zones allows separate optimization of the algal biomass production process from the algal removal processes, thus maximizing the performance of each component. In the application of CEP technology to treat CAFO discharges, wastewater containing high levels of nutrients enters a large algal treatment zone continuously, supporting a dense, stable bloom of microalgae that rapidly converts these nutrients into algal biomass. In a separate algal harvest zone, the algae are caused to settle onto a moving conveyor belt that exits the system, producing a dense algal paste. The CEP process can be optimized for treatment of various nutrient loadings through management of the paddlewheel mixing rates, pond depth, water velocity, system retention time, sedimentation velocities, harvest belt optimization and final effluent polishing.
Phase I Research Project
The overall goal of the Phase I research was to determine whether the CEP process could be interfaced with existing methods of CAFO waste management to reduce nutrient discharges to the environment. The studies were conducted using existing pilot-scale CEP units (0.7 acres) and four smaller (7.5 m2) CEP units receiving waste material from a cooperating CAFO facility (a dairy in Hemet, Calif.). The larger CEP systems were constructed at Kent SeaTech’s research facilities in the Coachella Valley, Calif., and were made available to the project at no cost. Managed populations of single-celled algae converted nitrogen and phosphorus nutrients to algal biomass, and a portion of the algal biomass was then consumed by managed populations of algivorous fish. Some aspects of the project also were carried out using existing research facilities at Clemson University in South Carolina.
Summary/Accomplishments (Outputs/Outcomes):
There were seven work Tasks addressed in Phase I. The first, construction and modification of the CEP pilot-scale and experimental systems, was completed during the first 30 days of the project and the systems were stocked with populations of microalgae. Tasks Two and Three involved studies of the CEP operational parameters needed to successfully introduce solid and liquid CAFO waste into the algal cultures. These studies demonstrated that when the proper concentrations of nutrients were introduced into the CEP units, large populations of single-celled microalgae could be cultured using the waste nitrogen and phosphorus provided by CAFO waste. Preliminary studies concerning the amount of CAFO waste that could be supplied to experimental CEP units in order to achieve maximum nutrient removal indicated that optimal results were obtained when the CAFO waste first went through an extended aeration process, in order to reduce the biological oxygen demand (BOD) to concentrations that did not hinder maximal photosynthesis and growth of the microalgae. Task Four studies concerning the ability of filter-feeding fish, such as tilapia, to consume a portion of the CAFO liquid waste directly indicated that although this was possible, it did not appear that a significant portion of the waste could be utilized in this direct manner.
In Task Five, Kent SeaTech conducted studies to determine methods for removing the microalgae from the CEP system, a critical step in the use of the CEP process to capture and convert CAFO waste nutrients into byproducts that could easily be transported away from CAFO facilities, in order to reduce the local groundwater pollution in the immediate areas. Kent SeaTech determined that the Algal Sedimentation Belt system being developed by the firm has considerable potential to assist in algal harvest. Kent SeaTech also determined that a promising new method of stimulating algal species to settle spontaneously might have considerable potential in CAFO applications.
Task Six involved studies on the use of a low-protein feed supplementation strategy to add carbon to the CEP units and thus provide enhanced growth of filter feeder biomass. The results of these studies suggested that optimum CEP algae removal rates (up to 90 percent) could be obtained by dividing the filter-feeding tilapia into several subgroups, with each group rotated through a dietary sequence of low-protein feed, high concentrations of algae and, finally, low concentrations of algae. In Task Seven, progress was made to determine the effects of biomass loading rate and algal concentration on anaerobic fermentation of algal biomass to methane gas for biofuel production. The data Kent SeaTech obtained suggested that anaerobic digesters loaded with mixtures of algae and dairy manure can produce as much as 1 liter of biogas for every liter of digester volume per day, which is considered an excellent energy return.
Conclusions:
This Phase I research project was very successful in demonstrating that the microalgae-based CEP treatment technology can be utilized to convert waste nutrients into algal biomass. Further, preliminary studies indicated that large-scale harvest and removal of the algal biomass produced may be economically achievable and that the concentrated algal paste produced may be utilized in anaerobic digesters. Successful demonstration of these basic concepts puts Kent SeaTech in an excellent position to begin Phase II studies, in which the ultimate objective will be to determine: how the CEP process can be scaled up to interface with large CAFO facilities; the effects of seasonal variations on treatment rate; the methods of operation that will be most cost-effective in providing year-round treatment; and the usefulness of byproducts that will be derived from the treatment process.
Supplemental Keywords:
concentrated animal farming operations, solid manure, liquid waste, pollution control, water quality, paddlewheel, bioremediation, nutrient reduction, Controlled Eutrophication Process, algae, biological oxygen demand, Algal Sedimentation Belt, tilapia, anaerobic digesters, EPA, small business, SBIR,, RFA, Scientific Discipline, INTERNATIONAL COOPERATION, Waste, Sustainable Industry/Business, Chemical Engineering, Sustainable Environment, Environmental Chemistry, cleaner production/pollution prevention, Technology for Sustainable Environment, Ecology and Ecosystems, Chemicals Management, Groundwater remediation, nutrient supply, concentratred animal feeding operations, phosphorus recovery, biofertilizer, chemcial synthesis, euthrophication, controlled eutrophication process ponds, algal pond water treatment, contaminated groundwater, groundwater contamination, pollution prevention, municipal sewage, application of agricultural chemicalsThe 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.