CHAPTER ONE

INTRODUCTION

1.1     Background of the Study

The corrosion process is an oxidation/reduction reaction that returns refined or processed metal to their more stable ore state. With respect to the corrosion potential of water, the primary concerns include the potential presence of toxic metals, such as lead and copper; deterioration and damage to the household plumbing, and aesthetic problems such as: stained laundry, bitter taste, and greenish-blue stains around basins and drains.

The primary health concern is the potential for the presence of elevated levels of lead and copper in the water. The primary source of the lead includes the use of lead pipes, lead lined tanks, and use of 50/50 lead/tin solder. Because of the concern with lead, the EPA banned the use of high lead solders in 1986. The primary source of copper is the leaching of copper from the household piping used to convey the water throughout the home. In some cases, the water is so corrosive that the interior plumbing system needs to be changed and completely replaced with PVC piping, PEX, or other materials. Too bad, they did not test the water and install a neutralizing system before the piping corroded and caused leaks throughout the home.

Corrosion will occur anywhere a galvanic cell or field can be or has established. To establish the field all that is needed is two dissimilar metals that are connected directly or indirectly by an electrolyte, such as water. This is the same chemical reaction that occurs within a battery.

Nearly all metals will corrode to some degree. The rate and extent of the corrosion depend on the degree of dissimilarity of the metals and the physical and chemical characteristics of the media, metal, and environment. In water that is soft, corrosion occurs because of the lack of dissolved cations, such as calcium and magnesium in the water. In scale forming water, a precipitate or coating of calcium or magnesium carbonate forms on the inside of the piping. This coating can inhibit the corrosion of the pipe because it acts as a barrier, but it can also cause the pipe to clog. Water with high levels of sodium, chloride, or other ions will increase the conductivity of the water and promote corrosion. Corrosion can also be accelerated by:

1) low pH (acidic water) and high pH (alkaline water)- For high alkalinity water – it is possible that a chemical scale may form that would help to protect against corrosion, but if a bacteria becomes established the scale, such as SRB (sulfur reducing bacteria), you may experience a problem related to Microbiologically Induced Corrosion or;

2)High flow rate within the piping can cause physical corrosion; 3)High water temperature can increase biological rate of growth and chemical corrosion; 4) oxygen and dissolved CO2 or other gasses can induce corrosion; 5) high dissolved solids, such as salts and sulfates, can induce chemical or bio-chemical corrosion;

6) If the mass ratio (CMSR) of chloride to sulfate is > 0.2, but < 0.5 there is an elevated concern, but if the CMSR is > 0.5 and the alkalinity of the water is less than 50 mg CaCO3/L the concern should be significant; 7) corrosion related bacteria, high standard plate counts, and electrochemical corrosion can result in pinhole leaks and isolated corrosion and aesthetic water quality problems,  and

8) presence of suspended solids, such as sand, sediment, corrosion by-products, and rust can aid in physical corrosion and damage and facilitate chemical and biochemical corrosion.

If it is necessary to flush or run your cold water in the morning for a few minutes before you drink because the water has a bitter taste, your water is probably corrosive. If you see blue-green stains in your basins or some staining along the joints of your copper piping, your water is probably corrosive. As corrosive water stands or seats in pipes or tanks, it leaches metals from the piping, tanks, well casing, or other metal surfaces that water is in contact.  If you see pink standing on the waters edge – this may not be corrosion, but pink bacteria.

The cost of corrosion can be expensive. Corrosion can impact you and your families health, aesthetic quality of your water, waste money, and damage your household piping and fixtures. Corrosive water costs you in a number of ways: 1 ) decreases the efficiency of hot water heaters and may cause premature failure to the heater;

2 ) corrodes and causes premature failure of household plumbing and plumbing fixtures;

3 ) imparts a bitter taste to your water because of elevated levels of metals, which causes you to purchase bottled water;

4 ) results in the formation of red water or greenish-blue stains on drains; and

5 ) consumption of water with elevated levels of toxic metals, such as lead and copper, have been shown to cause both acute and chronic health problems.

 

Besides the aesthetic concerns, the corrosion process can result in the presence of toxic metals in your drinking water. These metals include chromium, copper, lead, and zinc. The following are the recommended maximum contaminant levels for regulated public water supplies for the aforementioned metals: chromium (0.05 ppm), copper (1 ppm), lead (0.05 ppm), and zinc (5 ppm). To protect the public,  the EPA and PADEP requires public water supplies to be non-corrosive and the “Lead and Copper Rule” has set new action levels for lead and copper of 0.015 ppm and 1.3 ppm, respectively. Because of the toxicity of lead to children, the EPA has established a recommended maximum contaminant level of 0 ppm for lead. If a public water supply is corrosive, the state requires that the water be treated to make the water non-corrosive.

There are no regulations in many states that require private water wells or individual water wells or springs to be tested or treated for corrosivity water.  In many states, it is not necessary or even suggested to test private wells for toxic metal, pathogenic organisms, or organic chemicals.

The Langelier Saturation Index is a means of evaluating water quality data to determine if the water has a tendency to form a chemical scale. In order to use this index, the following laboratory analysis is needed: pH, conductivity, total dissolved solids, alkalinity, and total hardness.

The Saturation Index is typically either negative or positive and rarely 0. A Saturation Index of zero indicates that the water is “balanced” and is less likely not to cause scale formation. A negative SI suggests that the water is would be undersaturated with respect to carbonate equilibrium and the water may be more likely to have a greater corrosive potential.

A corrosive water can react with the household plumbing and metal fixtures resulting in the deterioration of the pipes and increased metal content of the water. This reaction could result in aesthetic problems, such as bitter water and stains around basins/sinks, and in many cases elevated levels of toxic metals. A positive SI suggests that water may be scale forming. The scale, typically a carbonate residue, could clog or reduce the flow in pipes, cause buildup on hot water heaters, impart an alkali taste to the water, reduce the efficiency of the water heaters, and cause other aesthetic problems.

This research work focused on the effect of corrosion on surface water quality.

1.2       Statement of the Problem

Water quality can be deteriorated through occurrence of corrosion. Portions of treatment of water costs can be attributed to corrosion, and corrosion specialists are often employed to implement corrosion control programs.

Capital costs also are incurred because of corrosion. The availability of good drinking water is reduced by corrosion.  For the end user or consumer, corrosion costs are incurred for purchases of corrosion prevention and control products, maintenance and premature replacement. The costs of corrosion control are straightforward, as are the technical support (engineering, research and development, and testing) costs associated with corrosion. Corrosion costs associated with design are not always as obvious and its effects on human health make it a problem for a researcher to work on.

1.3        Aims and Objectives of the Study

The aims and objective of this work are as follows:

• To identify the various factors that cause corrosion in water
• To highlight the process of corrosion occurring in water
• To identify the effects of corrosion on surface water quality
• To examine ways of controlling water corrosion in water

1.3     Significance of the Study

This project intends to act as reference, material to students of civil engineering who may have similar topic to carry out research work.

Water companies are not left out. The project will enable them to know the effect of  corrosion on water surface quality and appreciate the need to control it. It will also help the students, contractors, consultants and other readers of this work to understand the causes of corrosion, its effects and then guide against it.

1.5       Scope and Limitation of the Study

The scope of this research work is on the “effect of corrosion on surface water quality, it covers how corrosion occur, its effect on water surface quality, the effect the of the affected water on the users.

In this research work there were factors that affected the smooth process of the work, some of which are;

1. Inadequate information disclosed by personals
2. Time factor
3. Inadequate availability of material related to this work in a journals, textbook and Articles.
4. Financial factor.

1.6     Definition of Terms

`        The following terms are used in this study and are defined as follows:

• Corrosion: Corrosion is the breaking down or destruction of a material, especially a metal, through chemical reactions. The most common form of corrosion is rusting, which occurs when iron combines with oxygen and water.