The meteorological phenomena of hurricanes and floods in South Florida, combined with the population explosion in Miami, Fort Lauderdale, Naples and Fort Myers, led the United States Congress to create flood control districts for South Florida in the 1940s. The U.S. Army Corps of Engineers would design and construct a vast network of canals, levees, man-made waterways, and other water control structures, which today would stretch 1,400 miles long if laid end-to-end. In 1972, the State of Florida Legislature divided the state into five regional districts for the purpose of managing the water needs of the state, including a greater emphasis on the quality of water and the protection of the fragile environment. Those flood control districts from the 1940s eventually turned into the South Florida Water Management District.
The district starts in central Florida, stretching from the Chain of Lakes (which start near the southern border of Orlando) to Lake Kissimmee. The 56-mile Kissimmee River connects Lake Kissimmee to Lake Okeechobee, 730 square miles of fresh water. From Lake Okeechobee, water stretches west to Fort Myers on the 67-mile Caloosahatchee River, east to St. Lucie on the St. Lucie River and St. Lucie Canal, and various canals and rivers head in a direction that is primarily southbound. The district is responsible for three water conservation areas, in the western portions of Palm Beach, Broward, and Dade counties, which encompass 1,337 square miles, which, with Everglades National Park, preserves approximately one-half of the original historic Everglades (which was before it was drained during the past century, so urban sprawl could spread across Dade, Broward and Palm Beach counties). Florida Bay and the Florida Keys combine to form the southern part of the district. The Big Cypress Basin, which is primarily undeveloped land, includes the Corkscrew Swamp and Sanctuary, the Big Cypress National Preserve, the Fakahatchee Strand, the Corkscrew Regional Ecosystem Watershed, and the Ten Thousand Islands. The Everglades Agricultural Area (EAA) is comprised of approximately 505,000 acres of agricultural production with over 80% of the crops consisting of sugar cane. The boundaries of the district cover a total of 17,930 square miles, to which over five million people call home.
To date, 215 primary water control structures are operated by the district. Almost two thousand smaller structures are in place to control the inflows from secondary sources (local government drainage and/or water control districts) into the district's primary system. Twenty-five major pumping stations can move hundreds of millions of gallons of water into (and out of) storage facilities, which provide water supply and protection from floods. This man-made system of water management is perpetually undergoing improvement and enlargement to ensure that it will be fully able to provide flood control and water supply protection, as well as preserve the quality of water and environments.
Some of the primary strategic goals of the district are: to determine the feasibility of changes to flood control projects to restore the South Florida ecosystem, to restore the Kissimmee River, to protect and enhance Lake Okeechobee , to restore the Everglades and Florida Bay, and to develop water supply plans. A primary detractor to those goals is the problem of excess phosphorus concentrations in the waters of the Everglades.
Phosphorus is a threat to the Everglades, although it is an essential nutrient for all life forms. It plays a role in deoxyribonucleic acid (DNA), ribonucleic acid (RNA), adenosine diphosphate (ADP), and adenosine triphosphate (ATP). Phosphorus is required for these necessary components of life to exist. So with all these good qualities, why is phosphorus such a problem in the Everglades? Well, the expression "too much of anything is not good" holds true in this case.
Phosphorus is an especially essential element for plants to grow. For this reason, fertilizers are loaded with phosphorus. In the Everglades Agricultural Area (EAA), fertilizers are used heavily for sugarcane and other crops. Unfortunately, this phosphorus-filled fertilizer does not stay exclusively where it is applied. Whenever heavy rains occur, which is quite frequently in South Florida, a runoff is created. This agricultural runoff water mixes with the interconnecting canals that run through agricultural areas. Since the Everglades is basically a huge wetland area that is all interconnected, this extra phosphorus coming from agricultural lands disturbs the natural processes throughout the area. The flow of water, either by natural flows or by pumping, disperses the phosphorus throughout the Everglades. Therefore, there is extra phosphorus contained throughout the system.
As previously stated, phosphorus is a life-essential element, but too much is not good for the complex ecosystems that are the Everglades. There are two major problems concerning this issue. The first, and perhaps most important, is that extra phosphorus in the water creates unnatural conditions. These conditions are far from ideal for the hundreds of ecosystems in the Everglades. Extra phosphorus content in the water induces giant algae blooms and other types of unusual plant growth that would not occur naturally. This may create aesthetically undesirable conditions. It could also affect the recreational uses of the Everglades area. But, more importantly, plants use oxygen and block light going to organisms beneath them from going under water. This can be very detrimental to many types of fish and other aquatic animals because of deprivation of oxygen and light. Eventually, eutrophication could occur and make the water practically useless for any other species which require oxygen and light to live there. The second problem is that the Everglades complex water systems are also used to supply the urban coastal areas of South Florida such as Miami, Fort Lauderdale, and West Palm Beach. High phosphorus levels are not suitable for common municipal uses such as drinking, bathing and washing.
The levels of phosphorus have to be reduced in the Everglades; it must be removed somehow from the water in the Everglades until the overall phosphorus levels have been reduced to acceptable levels, which can be defined as the levels that would be present in an unmolested Everglades.
On 31 July 1996, the district reported that farmers in the EAA achieved a 68% across-the-board reduction in phosphorus levels in water discharged from farm fields in the EAA. This reduction greatly exceeds the 25% annual goal required for the entire EAA basin by the state's Everglades Forever Act.
During 1991 and 1992, the District began developing the EAA Regulatory Program. The twelve month period between May 1995 and April 1996 was to be the first full year in which farmers were to meet the mandated 25% goal. In addition to exceeding the goal for the first full reporting year, monitoring in the EAA basin has shown farmers to have achieved an average total phosphorus reduction of more than 30% over the past four years.
To determine phosphorus reduction, the District compares current year phosphorus amounts with a base period between the years 1979 through 1988. Water samples are collected by the District at points of discharge from the EAA to the Everglades. In the event that the 25% annual basin reductions are not met, the farms with the highest phosphorus would be targeted for additional on-farm BMPs. This would continue until the entire EAA basin again meets the annual 25% target.
Of the varying methods of reducing the concentration of phosphorus in water, one of the most cost-effective is that of secondary water treatment; the purpose of which is to reduce the concentration of phosphorus in water from 120 parts per billion (ppb) down to 10 ppb. The method by which the reduction occurs is by mechanical filtering, which is cost-effective and requires low maintenance: for starters, a pump station pumps water to the raw water reservoir, where coagulation occurs. Coagulation is the process by which coagulants break down the weak bonds that hold the phosphorus molecules together. Then the coagulants and other agents called "flocculators" force the phosphorus into bigger particles called "floc," which is a mass formed by the aggregation of a number of fine suspended particles. The floc settles to the bottom in a sedimentation basin, where filters trap the remaining particles. It is then removed from the system as sludge. Finally, for purposes of disinfection, chlorine is usually added to the treated water to kill any pathogenic organisms that might remain.
It is the purpose of this paper to analyze two different plants that utilize the methods of secondary water treatment, and compare and contrast the economics behind each. To begin, we will make two broad assumptions: that the water has an incoming concentration of 120 ppb of phosphorus (P), and that it must have an outgoing concentration of 10 ppb P.
Also, the following definitions, as defined by Dr. Donna Lee of the University of Florida Institute of Food and Agricultural Sciences, will also be utilized:
1 ppb = 0.001 mg/L
1 gal = 3.785 L
From these definitions, we can assume:
10 ppb = 0.010 mg/L = (0.010 mg/L)(1 L/0.2642 gal) = 0.03785 mg/gal
120 ppb = 0.120 mg/L = (0.120 mg/L)(1 L/0.2642 gal) = 0.45420 mg/gal
1 L = (1/3.785) gallons = 0.2642 gal
Furthermore, we will assume in the first part of these calculations that the average amount of water processed per day is one million gallons. Given this assumption, we can calculate the amount of phosphorus removed per year.
(0.45420 mg/gal incoming) - (0.03785 mg/gal outgoing) = 0.4164 mg/gal P removed
(0.41634 mg/gal)(1,000,000 gal/day) = 416,350 mg/day
(416,350 mg/day)(365.25 day/yr) = 152,071,837.5 mg/yr
(152,071,837.5 mg/yr)(1 kg/1,000,000 mg) = 152.0718 kg/yr
(152.0718 kg/yr)(1 lb/0.4536 kg) = 335.2554 lb/yr
(335.2554 lb/yr)(1 ton/2000 lb) = 0.1675 tons/yr
Therefore, 0.1675 tons of phosphorus is removed in one year's time in the process of reducing phosphorus concentrations from 120 ppb to 10 ppb in an average of one million pounds of water per day.
This report will analyze two different plants: one real plant in Pennsylvania (which processes 14,000,000 gallons of water per day), and one imaginary plant (which processes 1,000,000 gallons of water per day) with estimated figures from "Package Water Treatment Plants, Volume 2: A Cost Evaluation," a publication of the U.S. Environmental Protection Agency.
According to Louis Soulcheck of the Greater Johnstown Water Authority in Johnstown, Pennsylvania, the cost of the Riverside Water Treatment Plant was $21,000,000, including the purchase of the land and all construction costs. Mr. Soulcheck assured the authors of this paper that the data available on the aforementioned web site reflects secondary water treatment in particular. Assuming r = 4% discount rate, T = 20 years, the annuity payment (A) on the initial cost of that cost is equal to:
21,000,000 = (A)(1-[1+r]-T)/(r)
21,000,000 = (A)(0.543613)/(0.04)
21,000,000 = (A)13.5905
$1,545,197 = (A)
Adding (A) to yearly operation and maintenance costs of $4,575,400 (which was obtained from the aforementioned web site) produces a total cost per year of $6,120,597.
Because this plant can take in fourteen times that of the example given above, we will use the following formula:
(0.1675 tons/year)(1 day/1,000,000 gal)(14,000,000 gal/day) = 2.345 tons per year
Dividing total cost per year ($6,120,597) by tons of phosphorus removed per year (2.345 tons) yields a final report of $2,610,063 per ton of phosphorus removed. This particular piece of information is not on an annual basis, because the years cancel in the formula described above.
Our imaginary plant, the Dewey, Cheatham & Howe Memorial Water Treatment Plant, cost $1,124,000 in 1980 dollars. To adjust for 1996, we will inflate by 4%:
(1,124,000)(1.0416) = $2,105,231
This cost includes the purchase of the land and all construction costs. Assuming the aforementioned r = 4% discount rate, T = 20 years, the annuity payment (A) on the initial cost of that cost is equal to:
2,105,231 = (A)(1-[1+r]-T)/(r)
2,105,231 = (A)(0.543613)/(0.04)
2,105,231 = (A)13.5905
$154,905 = (A)
The plant has a yearly operation and maintenance cost of $62,571 in 1980 dollars. To adjust for 1996, we will assume a 4% discount rate:
(62,571)(1.0416) = $117,195
Adding that amount to (A) produces a total cost per year of $272,100.
Dividing total cost per year ($272,100) by tons of phosphorus removed per year (0.1675 tons) yields a final report of $1,624,478 per ton of phosphorus removed. This particular piece of information is not on an annual basis, because the years cancel in the formula described above.
To reiterate, the Johnstown plant has a cost of $2,610,063 per ton of phosphorus removed. The Dewey, Cheatham & Howe Memorial Plant has a cost of $1,624,478 per ton of phosphorus removed. The real plant removes more phosphorus per day (or year) than the fake plant, but at a cost of almost one million dollars per ton more. Then again, the real plant processes fourteen times as much water as the fake plant, so it is only fitting that more phosphorus was removed. The cost of doing so, however, remains to be seen.
In general, usually it is fairly safe to assume that because of economies of scale, the bigger an operator is, the more efficient it should be. In this study, the smaller plant actually came across looking a lot more efficient than the larger plant. A main reason for this could be because the data for the smaller plant ion the initial cost was only construction costs, while the larger plant's initial cost number included land purchase and construction costs. If these two numbers were consistent for the two plants, the effectiveness numbers (cost per ton removed) may have been more accurate and consistent.
In summation, this paper accurately demonstrated the science and the economics of secondary water treatment, comparing a real-world example to a model. Finding data for this report was difficult, even with the vast resources available to college students, including the Marston Science Library at the University of Florida, the Internet, and the collective knowledge of the faculty of the University of Florida Department of Food & Resource Economics. Secondary water treatment plants are only recently coming into existence, and that might be a reason for the aforementioned lack of available resources. If more time, money, and resources were available to produce this project, we would take full advantage of the South Florida Water Management District, and get more information from the Water Reclamation Facility on the University of Florida campus.
Sources
Strategic Goals of the South Florida Water Management District
http://www.sfwmd.gov/stratgoal.html
Latest News Releases of the South Florida Water Management District
http://www.sfwmd.gov/newsrel.html
Who Drained the Everglades?
http://www.ussugar.com/drained.htm
Water Resource Characterization DSS - Phosphorus
http://h2osparc.wq.ncsu.edu/info/phos.html
Public Enemy No. 1? Phosphorus
http://www.blueworld.com/iol/isspress/back_issues/4.10.96/phosphorus.html
How a Conventional Treatment Plant Works
http://www.indirect.com/www/bver/ovrvue1.htm
James Lee, P.E., P.W.S., Ecologically Engineered Systems Research Division,
South Florida Water Management District
james.lee@sfwmd.gov
Dr. Thomas Kosier, South Florida Water Management District
thomas.kosier@sfwmd.gov
Louis Soulcheck, Greater Johnstown Water Authority
gjwa01@ctcnet.net