Corrosion Impacts of Title 22 Reclaimed Wastewater on Copper Pipe

Title 22 reclaimed wastewater, also known as recycled water, is increasingly being used for various non-potable applications, including irrigation, industrial processes, and toilet flushing. However, its chemical composition and potential corrosiveness pose challenges for materials exposed to it, including copper pipes commonly used in plumbing systems. In this article, we will delve into the corrosion mechanisms of copper pipes exposed to Title 22 reclaimed wastewater, examining the factors contributing to corrosion and potential mitigation strategies. Care must be taken before using the source of water in copper piping.

Introduction to Title 22 Reclaimed Wastewater:

Title 22 reclaimed wastewater refers to treated wastewater that meets specific quality standards outlined in Title 22 of the California Code of Regulations. These standards ensure that recycled water is safe for its intended use and minimize the risks associated with its application. While Title 22 reclaimed wastewater undergoes extensive treatment processes to remove contaminants, it still contains various dissolved ions and chemicals that can impact the corrosion behavior of materials in contact with it.

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Corrosion Mechanisms of Copper Pipes:

Copper is a widely used material in plumbing systems due to its excellent corrosion resistance and thermal conductivity. However, when exposed to aggressive environments such as reclaimed wastewater, copper can still corrode through various mechanisms, including:

·??????? General Corrosion: General corrosion occurs uniformly over the surface of the copper pipe due to chemical reactions with substances present in the wastewater. This type of corrosion typically occurs when the protective oxide layer on the copper surface is breached, exposing the underlying metal to corrosive agents.

·??????? Pitting Corrosion: Pitting corrosion involves the localized corrosion of copper, leading to the formation of small pits or craters on the pipe surface. Pitting corrosion is particularly problematic as it can lead to rapid pipe deterioration and eventual failure, even with low concentrations of corrosive species.

·??????? Microbiologically Influenced Corrosion (MIC): Microbiologically influenced corrosion occurs when microorganisms present in the wastewater interact with the metal surface, accelerating corrosion processes. MIC can result in localized corrosion patterns and is often challenging to control in plumbing systems.

Factors Contributing to Corrosion:

Several factors influence the corrosion behavior of copper pipes exposed to Title 22 reclaimed wastewater, including:

·??????? pH: The pH of reclaimed wastewater can vary depending on the treatment process and the source of the wastewater. Extremes in pH levels, particularly acidic or alkaline conditions, can accelerate corrosion rates and promote the breakdown of the protective oxide layer on the copper surface.

·??????? Dissolved Ions: Reclaimed wastewater contains various dissolved ions, including chlorides, sulfates, and carbonates, which can react with copper and promote corrosion. Chlorides are known to increase the susceptibility of copper to pitting corrosion.

·??????? Temperature: Elevated temperatures can enhance corrosion rates by accelerating chemical reactions between copper and corrosive species in the wastewater. Additionally, thermal cycling can induce stress corrosion cracking in copper pipes, further compromising their integrity.

·??????? Flow Velocity: Flow velocity within the plumbing system can influence corrosion rates by affecting the transport of corrosive species to the copper surface. High flow velocities can increase the erosion-corrosion of copper pipes, especially in areas of turbulence or localized flow restriction. Velocities more than 2 feet per second can cause erosion corrosion in hot water recirculating piping systems

·??????? Water Quality: The composition of reclaimed wastewater, including the presence of organic matter, dissolved solids, and trace contaminants, can impact corrosion rates and mechanisms. Water quality parameters should be carefully monitored to assess the potential risks to copper pipes and other materials in contact with the wastewater.

Mitigation Strategies:

To mitigate corrosion of copper pipes exposed to Title 22 reclaimed wastewater, engineers can implement various strategies, including:

·??????? Material Selection: Choosing corrosion-resistant materials, such as high-grade copper alloys or alternative materials like stainless steel or plastic, can minimize the risk of corrosion in aggressive environments.

·??????? Coatings and Linings: Applying protective coatings or linings to the interior surface of copper pipes can provide an additional barrier against corrosive agents and extend the service life of the plumbing system.

·??????? Water Treatment: Implementing water treatment processes, such as pH adjustment, filtration, or ion exchange, can help control the chemical composition of reclaimed wastewater and reduce its corrosivity towards copper pipes.

·??????? Monitoring and Maintenance: Regular inspection and monitoring of copper pipes, along with proactive maintenance practices such as cleaning and flushing, can help detect corrosion issues early and prevent catastrophic failures.

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Conclusion:

In conclusion, the corrosion of copper pipes exposed to Title 22 reclaimed wastewater is a complex phenomenon influenced by numerous factors, including water chemistry, temperature, flow velocity, and material properties. Engineers must carefully assess these factors and implement appropriate mitigation strategies to ensure the long-term reliability and integrity of plumbing systems conveying reclaimed wastewater. By understanding the corrosion mechanisms and adopting proactive measures, engineers can effectively address corrosion challenges and optimize the performance of copper pipes in recycled water applications.

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Jose L. Villalobos, P.E.

President

JLV Wolf Inc.

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