Best Practices for Chemical Facility Design in Water Treatment

Authors:

  • Sara Gibson, Michael Wang, Alana Loughlin

The intent of this paper is to review considerations and identify best practices for chemical design at water treatment plants. Chemical storage and feed systems are an essential component of drinking water treatment plants. From pre-oxidants to distribution system corrosion inhibitors, chemicals are prevalent throughout the whole treatment train. If designed properly and maintained effectively, chemical systems provide safety for plant staff and stability to the treatment process and distribution system. However, an inadequate chemical system and insufficient maintenance could result in a chemical spill, operator injury, improper dosing, treatment process upset, or poor distribution system water quality.

Chemical system design includes consideration of many factors. Chemical state (gas, liquid, solid/dry) and form (for example, ammonium hydroxide versus ammonium sulfate) greatly influences the type of chemical system. Plant operation should be assessed including maximum and minimum flows and number of operational hours per day. Considerations for equipment selection should include redundancy, storage methods, feed equipment type and turndown capabilities, and chemical compatibility with selection of materials of construction. The application means and location ensure effective use of the chemical. Safety in the design includes containment, personal protective equipment, eyewash and showers, and proper ventilation. Instrumentation and control for optimal chemical system operation varies based on plant preference and monitoring/control needs. This could include critical safety features, alarms, sensors, automation, and measuring devices such as weigh scales and flow meters. Many other aspects will require consideration depending on the specific chemical.

A great chemical design does not end after construction, start-up, and troubleshooting. Maintenance becomes key to retaining a fully optimized system. Upgrades to existing chemical systems by consultants or internally by plant staff should reference updated codes and manuals to ensure that the most recent design practices are incorporated.

For more information, please contact the author at sgibson@hazenandsawyer.com.

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