Term Paper on "Phosphogypsum Stack Reclamation"

Term Paper 18 pages (4983 words) Sources: 1+

[EXCERPT] . . . .

Phosphogypsum Stack Reclamation

Data-gathering Method

Database of the Study

An Analysis of Phosphogypsum Stack Reclamation

The types of contaminants that emanate from anthropogenic sources are extremely varied and range from simple inorganic ions such as the nitrate from septic tanks, feedlot wastes, and the use of fertilizer, chloride from highway deicing salts, saltwater intrusion, and certain industrial processes, heavy metal ions from many different industrial processes such as plating works, to complex synthetic organic compounds resulting from industrial and manufacturing processes and from the use of pesticides and household cleaning fluids, e.g., trichloroethylene. Some compounds of low solubility may yield solutions that are toxic or offensive. The chemical composition of wastes deposited in landfills or surface impoundments is frequently known; nevertheless, when the constituents of such wastes interact, new compounds may be created. A number of industrial waste-disposal practices now include the stabilization of wastes, thereby making them less active chemically; however, it is still possible that leachate production may transform some of the constituents (Patrick, Patrick & Pye, 1987). One such industrial waste is phosphogypsum, which is primarily composed of calcium sulfate and is a by-product of the reaction between sulfuric acid and phosphate rock in the manufacture of phosphoric acid (How Does Phosphogypsum Storage Affect Groundwaters?, 2002).

Problem Statement major focus is on phosphogypsum because the issue is of high priority from both technical and environmental standpoints. While one question is what could be done with the material, another question is what are the consequences of doing nothing with it and simply leaving it stockpiled on the ground? Today, a major concern about phosphogypsum storage is the potential for contamination of groundwater under and near the stacks. The growing body of evidence from past research has demonstrated that there is some influence on the aquifers from the presence of the gypsum stack in terms of several chemical parameters, but evidence for radionuclide contamination remains much less clear (How Does Phosphogypsum Storage Affect Groundwaters?, 2002). The closure of a phosphogypsum stack with a plastic liner and soil cover on top is also very expensive (Patel, Ericson & Kelley, 2002). Therefore, identifying the best approach to remediating phosphogypsum stacks for reclamation purposes has assumed an increasing level of importance today. The graphic at Appendix a illustrates the enormity of a typical phosphogypsum stack today.

Purpose of Study

In the United States, federal standards for new, existing or expanding municipal solid waste landfills (40 CFR Part 258) are generally followed by the states including technical design requirements for membrane liners with compacted soil or clay and/or double liners, leachate collection systems, leak detection and groundwater monitoring systems, final cap and cover provisions (Smith, 1998). Similarly, Canada has in place regulations that address phosphogypsum stack management, but there has been no firm consensus developed as to the most appropriate methods to be used depending on the unique factors associated with every phosphogypsum stack. The purpose of this study is therefore to identify the extent to which such reclamation techniques are effective in preventing contamination of groundwater sources, including liner applications and other stack closure techniques in use throughout the states and around the world, to arrive at recommendations for a best practices model to be followed in phosphogypsum stack reclamation efforts.

Importance of Study

The wet process manufacture of phosphoric acid practiced in the U.S. And a number of other regions of the world requires an enormous volume of water, which is commonly referred to as process water. Process water is used as a water source for the phosphoric acid, for gas scrubbing, to slurry the phosphogypsum produced and transport it to storage, to operate barometric condensers, and for a wide variety of other uses in the chemical complex. A major portion of the heat released in the process ends up in the process water and is lost to the atmosphere by evaporative cooling in ponds.

Process water is stored both in ponds maintained on top of the phosphogypsum stack and in a below ground level pond (cooling pond). These ponds provide the large surface area needed for evaporation and cooling of the water. When the average yearly rainfall and the evaporation rate are approximately equal, it is possible by strict control of the water inputs to the ponds to operate the chemical complex with a negative water balance; however, during years when rainfall is significantly above average due to multiple tropical storms, El Nino weather effects, etc. It may become necessary to treat the surplus water and release it to the surface waters in order to avoid an uncontrolled discharge of the untreated process water.

Furthermore, if one of the operating plants is shut down and it is necessary to close the phosphogypsum stack and pond water system, the water in inventory must be treated before it can be discharged. The volume of water that would need to be treated nay be as much as 2 to 3 billion gallons. The process water has a low pH of about 1 to 2 and contains a dilute mixture of phosphoric, sulfuric, and fluosilicic acids. It is saturated with calcium sulfate and contains numerous other ions found in the phosphate rock used as a raw material as well as ammonia from the solid fertilizer manufacturing process (Bencherifa & Swearingen, 1996). The current treatment practice is to lime to a pH of approximately 4.5, remove the solids formed, lime the water to a pH of approximately 11, remove the solids formed, air strip the water to remove ammonia, and add acid to reduce the pH to approximately 6.5 and any treatment procedure proposed should eliminate the dissolved solids problem (Bencherifa & Swearingen, 1996).

Over the years regulations on how phosphogypsum is stacked have strengthened to protect groundwater seepage. There are also strict standards companies must meet before they can release any of the process water into the environment, but human error and natural occurrences such as heavy rains can cause the acidic water to spill. Even if there is never another spill, however, there remains a desperate need to timely process the billions of gallons of water that are stored in and around a phosphogypsum stack during rainy periods as well as when the stack is eventually closed. In addition, a number of harbors and other marine habitats around the world have experienced serious deterioration as a result of phosphogypsum discharges that are laden with heavy metals (Cd, Zn, Cu, Pb, and others). According to Bencherifa and Swearingen (1996), this type of pollution originates primarily from port activities, particularly those related to unloading and loading in the main harbors, many of which lack adequate devices to handle accidental pollution.

Scope of Study

While the study examines phosphogypsum stack management as it is practiced around the world, the focus will be on facilities in North America in general and Canada in particular.

Rationale of Study

Most authorities agree that "toxic waste disposal" is a misnomer; a better phrase would be "toxic waste storage" since these materials have a lengthy half-life and must be regarded as potentially hazardous for many years, in some cases for centuries or more. To the extent that a best practices approach to Definition of Terms

All terms used in this study follow the definitions provided by the State of Florida for phosphogypsum stack management.

Aquifer. This term means a geologic formation, group of formations, or part of a formation capable of yielding a significant amount of groundwater to wells, springs or surface water.

Closing. This term refers to the time at which a phosphogypsum stack system ceases to accept wastes, and includes those actions taken by the owner or operator of the facility to prepare the system for any necessary monitoring and maintenance after closing.

Closure. This term refers to the cessation of operation of a phosphogypsum stack system and the act of securing such a system so that it will pose no significant threat to human health or the environment. This term also includes closing, long-term monitoring, maintenance and financial responsibility.

Disposal. This term refers to the discharge, deposit, injection, dumping, spilling, leaking, or placing of any solid waste into or upon any land or water so that such solid waste or any constituent thereof may enter other lands or be emitted into the air or discharged into any waters, including groundwaters, or otherwise enter the environment.

Facility. This term refers to all contiguous land and structures, other appurtenances and improvements on the phosphate fertilizer manufacturing complex.

Final cover. This term refers to materials used to cover the top and sides of a phosphogypsum stack upon closure.

Geomembrane. This term refers to a low-permeability synthetic membrane used as an integral part of a system designed to limit the movement of liquid or gas in the system.

Lateral expansion. This term refers to the expansion, horizontally, of phosphogypsum or process wastewater storage capacity beyond the permitted capacity and design dimensions of the phosphogypsum stack, or cooling ponds, surge ponds, and perimeter drainage conveyances at an existing facility. For the purposes of… READ MORE

How to Reference "Phosphogypsum Stack Reclamation" Term Paper in a Bibliography

Related Term Papers:

Allocation of Assets Essay

Allocation for CVP

The process of allocation of costs proceeds from two distinct procedural approaches. First, a three-step process is adhered to. Subsequently, this three step process points to the… read more

Essay 3 pages (812 words) Sources: 1 Style: APA Topic: Government / Politics

---

Compare 2 Ethnographer Term Paper

Ethnography: A Comparative Study of Theory and Methodology

Many techniques have developed over the past several years that have helped to refine the study of people of different ethnic background.… read more

Term Paper 7 pages (1973 words) Sources: 1+ Topic: Family / Dating / Marriage

---

Carbon Tax and Mining Industry in Australia Essay

measure cause and effect of carbon tax on the mining industry in Australia and South Australia. The trick for Australian politicians will be to balance off saving the environment and… read more

Essay 3 pages (1020 words) Sources: 8 Style: Harvard Topic: Economics / Finance / Banking

---

Enterprise Architecture Term Paper

Enterprise Architecture

New text is in red, sorry for the delay

The Disruptive Innovation of Software-as-a-Service

on Enterprise Application Architectures

Re-aligning the economics of enterprise software, Software-as-a-Service (SaaS) is changing… read more

Term Paper 4 pages (1781 words) Sources: 6 Topic: Business / Corporations / E-commerce

---

Social Science Globalization Essay

Globalization is a complex phenomenon that is often misunderstood. Part of this trend deals with a movement toward more integrated economic and political systems. Much of the globalization trend has… read more

Essay 2 pages (555 words) Sources: 0 Topic: Economics / Finance / Banking

---

View 100+ more related papers  >>