Process Water and Effluent Treatment – Chemical Compatibility is Critical

The use of chemicals is key in many aspects of water and wastewater treatment. The chemicals used all have specific properties which may react differently to certain materials found in water treatment equipment, such as chemical metering pumps, and throughout the plant.

If chemical being dosed is a mismatch with the material used in construction of the dosing equipment it can lead to increased maintenance plus expense due to equipment damage or failure, and infrastructure damage. For well-established chemicals and materials, it may already be known which are compatible with which. But for infrequently used or proprietary products, it may not be so clear.

This article discusses simple steps to avoid compatibility issues.

Why Compatibility Matters

As mentioned, when chemicals are not compatible with materials they come into direct contact with, it can cause a range of chemical reactions that may result in increased costs. This includes:

Corrosion. Caustic chemicals, such as chlorine, chloramine byproducts, ozone, and acids used in pH adjustment can corrode certain metals. This can cause contaminants to leech into the water, disrupting downstream processes. Over time it can also cause pipes to leak prematurely and valves to fail.

Degradation. Rubber, plastic, and other synthetic material can degrade and lose structural integrity when exposed to certain chemicals. This can cause leaks from pipes, gaskets, connectors, and more. In pumps, degradation of diaphragms and other components can reduce performance, require more frequent and costly maintenance, and necessitate premature part replacement (Figure 2).

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Equipment damage. Poor chemical and material combinations can result in damage to a range of equipment, including mixers, meters, pumps, and more. Filter media may also be vulnerable to specific chemical types. Again, this will result in additional costs associated with maintenance, replacement, and downtime.

Health/safety risks. Because many of the chemicals in question are caustic, volatile, or otherwise highly reactive, there is a range of health and safety risks associated with their use. If equipment or piping begins to leak, or if machinery requires emergency maintenance, it can increase those risks by exposing personnel to these chemicals or to byproducts of their interaction.

How To Determine Compatibility

For commonly used chemicals, operators may already know what materials are compatible and which are not. For example, liquid chlorine is safe to use with PVC, Viton, PVDF, and Hastelloy, and other materials, but will corrode types of galvanized steel, copper and copper alloys, rubbers and elastomers, and certain plastics. When considering use of any chemical the operator is unfamiliar with, it pays to investigate.

In some cases, manufacturers or suppliers may offer compatibility charts. These typically list the types of materials used to construct the equipment and it’s components, as well as compatibility of those materials with certain chemicals. However, at other times this information may not be so readily available. When that is the case, it may be possible to at least get a list of the component materials. Once this is known, some research can be done to determine if the equipment will work with the chemical(s) in question.

On the other hand, sometimes the unknown is the chemical itself. Proprietary chemicals, for example, may not have published compositions. The safety data sheet (SDS) could potentially offer answers, but not always. When all else fails, operators or project engineers can try to obtain samples of the material and chemical and perform their own in-house testing. If time does not allow for that, it may be worth considering an alternate combination.

Consider The Application

When discussing chemical compatibility it’s important to understand that the application in question matters. For example, typically PVC can be used with sulfuric acid at low concentrations (ideally around 10% to 20%) and moderate to low temperatures. However, higher temperatures can soften PVC and make it more susceptible to acids and other caustic substances, even at typically low concentrations. Operators and project engineers need to consider these factors, as well as other chemicals that may come in contact with the primary chemical in question.

At the end of the day, it is important to balance all of these issues before choosing chemicals, equipment, and ancillary materials.

Whenever possible, it is worth partnering with equipment manufacturers who understand the importance of chemical compatibility and are willing to work together to find the right solution at the lowest possible cost. For example, Blue-White® Industries, located in Huntington Beach, California, has been manufacturing chemical feed pumps for 68 years. During that time they’ve seen many instances of the damage that can occur when chemicals and materials are not compatible.

For this reason, the company began publishing compatibility charts for its chemical metering pump components, as well as for their line of flow measurement equipment.

Blue-White also offers a variety of material options for pump components, as well as material test kits and a team of highly trained individuals to assist. All of these steps are designed to help ensure chemical compatibility within the system.