Patent Application
20170211191
This invention relates to potable water delivery systems, and more specifically, systems and methods for preventing lead and iron contamination of potable water by the lead and iron delivery system. The method controls the internal corrosion by controlling the chemical redox reaction between the protective concentration of disinfection chemicals and the iron and lead metal pipes. The internal corrosion is prevented by maintaining the redox reaction in cathodic mode by impressing a cathodic potential on the system equivalent to, or higher than the cathodic potential of the redox reaction. External corrosion is prevented by the cathodic corrosion protection method, employing a sacrificial anode. Depending on conditions, this sacrificial anode may provide a high enough potential to control the internal redox reaction in cathodic mode. In such case, the anode is referred to as a sacrificial/potential anode.
During the late 19th century and early part of the 20th century, building codes required that cast iron pipe be used for mains, and lead pipe be used from the mains to the point of delivery of potable water. Many of these systems remain in use today, but over time, some pipe components have failed. By mid-century, failed components had been replaced with plastic components, which resulted in unintended and undesirable consequences, including contamination of the potable water with iron and lead.
The potable water is delivered to the distribution system (which includes the mains and the other piping components from the mains to the point of delivery) essentially lead and iron free. A small excess of disinfectants (chlorine, bleach, ozone, and/or other oxidants) referred to as a protective concentration, is left in the purified water to assure its purity at point of use, should the water become contaminated during delivery. This 1-4 ppm of chlorine or other oxidants can react with the interior of the iron mains and the lead piping, causing corrosion.by a redox reaction between the excess disinfectants and the lead and iron. However, the amount of iron corroded from the iron pipes is not enough to exceed permissible concentrations of iron in potable water, nor is it great enough to reduce its service life by an unacceptable amount.
Regarding lead, so long as the lead and iron pipes remain in electrical contact the lead does not corrode because it is at the reduction potential of iron, which is considerably higher than the reduction potential of lead. Additionally, should lead be present in the water, some would be plated on the iron.
However, the ageing iron and lead potable water distribution systems can no longer reliably deliver potable water that meets the current regulatory standard for lead content. Corroded iron mains are being repaired with plastic, thus breaking the electrical conductivity of the distribution system, which in turn negates the cathodic potential protection of the lead pipes. Consequently, the protective concentration of purification chemicals left in the potable water is corroding the interior of the lead pipes in a redox reaction, thus adding unacceptable amounts of lead to the water. This redox chemical reaction is generally not recognized by the potable water suppliers, or consumers as a source of lead contamination. Consequently, the lead contamination is ascribed to different sources. As a result, inappropriate, ineffective, and costly actions are taken in an attempt to correct the lead contamination.
Lead poisoning is a serious health concern, and even small amounts of lead can cause serious health problems. Infants and children under the age of 6 are especially vulnerable to lead poisoning, which can severely affect mental and physical development. At very high levels, lead poisoning can be fatal. As a result of the corrosion of the lead pipes, children may be physically and/or mentally damaged before the lead contamination is discovered and corrective action taken. The intelligence deficit and the tendency toward violent behavior is carried into adult life resulting in undesirable consequences, such as poverty and crime.
Corrosion inhibiting reagents are being used to mitigate this problem of iron and lead corrosion to a limited success. In some cases, to solve the problem, the lead pipe is being removed and replaced with copper or plastic piping. This is costly, and although this may solve the lead problem, it introduces a similar problem of copper corrosion and leaves the failing iron mains to be dealt with at a future date.
Other corrective actions can be very costly and may range from a few million dollars to supply bottled water for an extended period of time, or to complete replacement of the potable water distribution system at a cost of perhaps several billion dollars and the bankruptcy of a community.
There is, therefore, a need for potable water systems and methods that preemptively prevent or reduce the corrosion of iron and lead pipes in potable water systems.
It is an object of this invention to limit the lifelong loss of intellectual capacity and tendency to violent behavior due to lead poisoning, particularly of infants, young children, and to a lesser extent, of adults.
It is a further object of this invention to reduce the level of violence and criminal activity in older sections of our cities that requires additional policing to maintain order by reducing lead poisoning by potable water of children and adults.
It is also a further object of this invention to provide a relatively inexpensive way to control the lead content of potable water to regulatory standards, and to extend the useful life of the existing potable water distribution systems.
In accordance with the foregoing objectives and others, exemplary systems and methods are disclosed herein that can be used to prevent or reduce the corrosion of iron and lead pipes in potable water systems.
Each electrically isolated section of lead pipe is electrically connected to a grounded zinc or zinc alloy mass or other more cathodic metal or metal alloy, which serves as an electrode. This type of metal mass is commonly referred to as a sacrificial anode, and the process, as cathodic corrosion prevention. This method is commonly used to prevent the exterior corrosion of metals in contact with an electrolyte that is shared with the sacrificial anode. However, in this case, there are two purposes for the anode; firstly, to protect the iron pipe from exterior corrosion resulting from contact with soil or water electrolyte; secondly, to prevent the interior of the iron and lead pipes from corrosion by their redox reactions with the protective concentration of disinfectant chemicals, left in the potable water. This later objective is achieved by raising the internal potential of the pipes to, or beyond, the cathodic potential of their respective redox reaction potentials. It is recognized that so long as the lead is electrically connected to the iron, the lead is protected by the reduction potential of the iron. Alternatively, or in addition to, each electrically isolated section of iron or lead pipe is electrically connected to a grounded mass of zinc metal, zinc metal alloy, or a lesser noble metal such as aluminum or magnesium, or alloys thereof, or other source of appropriate electrical potential.
Alternately, the potential of the iron and lead pipes can be raised above their reduction potentials by connecting them to a source of DC power of appropriate potential above ground.
Because the sacrificial anode and the iron and lead pipes share a connection through the ground which acts as an electrolyte, the sacrificial anode and the external surfaces of the iron and lead pipes create an electrolytic cell which generates an electrical current that corrodes the anode and prevents corrosion of the exposed surfaces of the iron and lead cathodes. Because metallic iron has a higher reduction potential than lead, and because the iron and lead are electrically connected, and because the impressed DC voltage required to assure that the redox reaction between the iron and the protectant concentration of disinfectant chemicals is cathodic and at least equivalent to the reduction potential of iron, both the exterior and interior, the entire distribution system is protected from corrosion. By this method, all electrically connected metallic system components with reduction potentials more noble than the impressed cathodic voltage are protected from corrosion.
The details of one or more embodiments of the subject matter of this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.
Embodiments are illustrated by way of example and not limited to the figures of the accompanying drawings, in which like references indicate similar elements and in which:
The following detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show illustrations in accordance with example embodiments.
The systems and methods disclosed herein for preventing corrosion of lead and/or iron piping comprise electrically attaching a dedicated cathodic corrosion protection system to the lead and/or iron pipes. The passive cathodic protection system may comprise a sacrificial anode or multiple anodes made of, zinc metal, zinc alloy, or a lesser noble metal such as aluminum or magnesium, or alloys thereof. The sacrificial/potential anode is in contact with the ground and electrically connected to the lead and/or iron pipes. The sacrificial/potential anode maintains the lead and/or iron pipes at a voltage above the pipes' respective reduction potentials, thus preventing the external corrosion of the lead and/or iron pipes. If the sacrificial/potential anode creates a cathodic potential high enough to make the redox reaction between the protective concentration of disinfection chemicals cathodic, then the interior of the pipes will be protected from corrosion.
Alternatively, an active cathode corrosion protection system supplied by an independent electrical energy source may be used. The positive terminal of the active system is connected to ground by either a conducting non-sacrificial anode or a sacrificial anode. The negative terminal is connected to the lead and/or iron pipes. The voltage between the grounding anode and the lead and/or iron pipes is maintained at a level at, or above, the pipes' respective reduction potential, and the cathodic potential of the redox reaction between the pipe interior surface and the disinfectant chemicals. It must be understood that the necessary cathodic potential to make the redox reaction between the pipe interior and the disinfectant chemicals is dependent on the concentration of the chemicals and the temperature of the system.
The present invention adds sacrificial anode 180, which is electrically connected to the lead piping by, e.g., electrical conductor 190 and clamps 200. While electrical conductor 190 and clamps 200 are provided as an example, any means of electrically connecting sacrificial/potential anode 180 to the lead piping may be used, and one of ordinary skill in the art will recognize other such connections. At least part of sacrificial/potential anode 180 is grounded, as indicated by the cross hatches in
The ground medium provides the electrical return leg of the electrolytic circuit. The required size of sacrificial anode 180 depends on the size and length of the distribution system. The required number and location of sacrificial anodes 180 is dependent on, whether, or not, the lead pipe is electrically connected to the iron main. The iron main acts as a sacrificial/potential anode for the lead pipe. If the lead pipe is not electrically connected to the iron main, a separate sacrificial/potential anode connected to the lead pipe is required to protect the lead pipe from both external and internal corrosion.
Multiple sacrificial/potential anodes and/or DC voltage sources may be connected to any part or parts of the electrically connected potable water distribution system so as to, maintain a desired uniform voltage throughout the entire potable water distribution system.
Fire hydrants, control valves, and flow meters are above ground components that can be utilized as connection points;
Similar systems may be used to limit or prevent corrosion of iron pipes. A passive corrosion prevention system for iron pipes includes the components described in
An active corrosion prevention system for iron pipes includes the components described in
The present invention prevents the excessive lead and/or iron contamination of the potable water, while extending the service life of the iron mains and lead laterals by using cathodic corrosion protection techniques for protecting the exterior surfaces of the lead and iron pipes and potential to control the reaction protect at great savings over the
Additional benefits of this invention include: 1) the cathodic potential will prevent pinhole corrosion of any copper tubing in the distribution system and in the final plumbing; 2) water loss will be reduced; 3) the cost to maintain the potable water distribution system will be reduced; and 4) the use and cost of water purification chemicals will be reduced by eliminating the need for corrosion inhibitors, and less disinfection agent.
Additional Notes:
The protection methods are implemented by electrically connecting to a fire hydrant or multiple hydrants, valves, or flow meters.
Bypass breaks and non-conducting repairs to the iron mains by installing electrical conductors between hydrants located on opposite ends of the break, thus restoring electrical continuity of the underground system without disturbing the ground surface.
Bypass electrical continuity breaks in lead laterals by installing metallic jumpers between a fire hydrant and a water meter on the lateral.
Detect the local level of cathodic corrosion protection by measuring the electrical potential between a hydrant and the ground
Connect the protective power source to a hydrant to boost a decayed protective voltage to protection levels.
Reduce maintenance and capital costs and extend the useful life of the potable water system by implementing these claims that also reduces the iron and lead contamination in the delivered potable water to regulatory levels. (we are assuming that the water purification plant is delivering water with lead content that meets regulatory specifications.)
The corrosion protection system prevents the potable water from being contaminated with lead and iron by the existing water distribution system when this process is implemented. The system maintenance and capital costs are reduced by using surface components such as fire hydrants to electrically detect and correct existing underground electrical faults. Further, fire hydrants are conveniently available throughout the system and can be used to monitor the system's protective voltage, and to provide a local connection to the distribution system to boost any decayed protective voltage. Once preexisting conditions are corrected, my method will deliver potable water without adding lead or iron for a very long time. My methods rejuvenate existing systems and protect new and future systems from decay due to corrosion.
Although the invention has been described in terms of particular embodiments, one of ordinary skill in the art, in light of the teachings herein, will be able to generate additional embodiments and modifications without departing from the spirit of, or exceeding the scope of, the claimed invention. This invention is not limited to using the particular elements, materials, or components described herein, and other elements, materials, or components will be equivalent for the purposes of this invention. Accordingly, it is understood that the drawings and the descriptions herein are proffered only to facilitate comprehension of the invention and should not be construed to limit the scope thereof.
This Application claims to priority to U.S. Provisional Utility Application Ser. No. 62/388,798 filed Feb. 8, 2016, the contents of which are incorporated herein by this reference. This Application is also a Continuation-in-Part of application Ser. No. 15/177,770, filed Jun. 9, 2016, and a Continuation-in-Part of application Ser. No. 14/811,629, filed Jul. 28, 2015 the contents of both applications are incorporated herein by this reference.
| Number | Date | Country | |
|---|---|---|---|
| 62388798 | Feb 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15177770 | Jun 2016 | US |
| Child | 15428102 | US | |
| Parent | 14811629 | Jul 2015 | US |
| Child | 15177770 | US |
