S-1000
Regional Project
Animal Manure
and Waste Utilization, Treatment and Nuisance Avoidance for a Sustainable
Agriculture
2003 Station
Reports
Use of The Controlled
Eutrophication Process (CEP) to Reduce
Nitrogen and Phosphorus Concentrations Entering the Salton Sea
A. Reporting Scientists and Location;
David E. Brune, Dept of Agri and Biol Engr. Clemson, University, Clemson
SC 29634
B. Progress to Date by objective and task
Kent SeaTech Corporation conducts extensive research and development in water
treatment and aquatic biology. Dr. David E. Brune and his colleagues
in the Department of Agricultural and Biological Engineering at Clemson University
are recognized worldwide as outstanding biological engineers who have developed
successful solutions for a variety of difficult wastewater management problems
over the past 30 years. Dr. John Benemann is a recognized expert in
microalgae technologies. This partnership of leading private and academic
researchers conducted a pilot-scale demonstration of the application of high
rate algal pond water treatment technology to reduce the level of phosphorus
and nitrogen nutrients that flow into the Salton Sea through its tributaries
and cause serious eutrophication problems. This technology is termed
the Controlled Eutrophication Process (CEP) and was originally developed
as a cost-effective and environmentally sound technology for treating the
low to medium concentrations of waste nutrients present in aquaculture effluent.
Nutrient levels in the Salton Sea tributaries are similar to the levels found
in aquaculture effluent and the CEP technology appears to provide a more
cost-effective solution than either chemical treatment alone or the expensive
Biological Nutrient Reduction (BNR) processes used to treat high strength
municipal or industrial waste streams.
The project was conducted using existing pilot-scale CEP units that were
available at Kent SeaTech's facilities in Mecca, CA, adjacent to the Whitewater
River. All of the tanks, treatment system components, and data monitoring
recorders required for this assessment were already in place and therefore
the studies were conducted for a fraction of what the true cost would have
been. A centrifugal pump and piping was installed on the Whitewater
River to deliver river water to the test facility located just 100 meters
away. The overall approach of the CEP concept is to stimulate rapid
growth of algae in a well-mixed, high rate algal pond using a process design
that permits accurate control of pond mixing rates, algal cell age, and nutrient
concentrations. Nutrients are assimilated into the algal population
and then removed from the ponds using gravity settling and consumption by
managed populations of filter-feeding fish species such as tilapia.
Studies were conducted to determine the optimal water flow rates, recirculation
strategies, filter-feeder densities, and other critical operating parameters
so that the uptake and removal of phosphorus could be maximized. Related
pilot-scale studies to refine techniques for settling, concentrating, and
removing algal cells from the water column were conducted in existing systems
located at Clemson University.
The results of these studies were very encouraging. The CEP process
consists of two major treatment steps: 1) the assimilation of phosphorus
and nitrogen into algal biomass, and 2) the removal or harvest of the algal
biomass from the water column. In indoor, lab-scale tests, we were
able to achieve nearly 100% efficiency for both of these steps. In
the pilot-scale studies conducted in the 0.7 acre CEP units, we were able
to achieve assimilation efficiencies as high as 83%, and algal removal efficiencies
as high as 93%. The product of these two efficiencies, 77%, is the
maximum overall treatment efficiency achieved during these trials, which
were conducted in existing CEP units that were not originally designed for
this application. We anticipate that even higher treatment rates can
be achieved in CEP systems that are designed specifically for treating nutrients
present in the Salton Sea tributaries.
c. Usefulness of Findings and Impacts
The ultimate full-scale implementation of this concept will consist of a
series of high rate algal ponds utilizing the CEP technology to reduce phosphorus
and nitrogen in the Whitewater, New, and Alamo Rivers, which will significantly
reduce the nutrient input driving the eutrophic conditions in the Salton
Sea. Full-scale implementation of CEP technology for removing 80-90%
of the eutrophying nutrient input to the sea is projected to require approximately
4,000 acres of land. In addition to filter-feeder biomass, the system
would produce several valuable byproducts, including marketable fish, a concentrated
algal sludge that could be used as a feed additive and as agriculture fertilizer,
and energy from the on-site digestion of algae and production of methane.
d. Planned work for the next year
A techno-economic analysis is being developed to estimate the capital and
operating costs that would be required in a full-scale application of CEP
technology for nutrient bioremediation of the Salton Sea tributaries
The next step in developing this concept for application at the Salton Sea
would be to construct and operate several full-scale CEP units of 10-20 acres
in size, to obtain more accurate data on the operating costs and variability
in treatment rates that will occur seasonally. Kent SeaTech is preparing
several proposals to government agencies that would provide funding for these
demonstration-scale studies.
e. Publications (since last report; also, please list refereed articles)
Brune D.E., G. Schwartz, A.G. Eversole, J. A. Collier, and T. E. Schwedler,
Accepted for Publication 2002, "Intensification of Pond Aquaculture and High
Rate Photsynthetic Systems," Aquacultural Engineering: An International Journal.
Brune, D. E., “The Controlled Eutrophication Process”, 2003, Clemson
University Patent Application, U.S. Patent Office, Washington D.C.