Chemical Engineering

Case Name: Acid Waste Neutralization System (AWN)

Problem Description: An elementary neutralization system for acidic wastewater was designed, installed, and operated for a semiconductor research facility. The original design was based upon known and projected R&D and maintenance waste streams operations from two buildings The AWN system had maximum design capacity of 200 gallons per minute in a three tank continuous stirred tank reactor (CSTR) system with a net residence time of 30 minutes. It was not designed to process high flow rates of concentrated acids (pH <1 and/or reactive acids). After the installation of the original system, both the R&D and maintenance streams were significantly increased in both hydraulic flow rates and chemical quantities requiring treatment. The result of the process stream increases was inefficient operation of the AWN system

Our Involvement: We performed a detailed Waste Demand Analysis of the requirements for neutralization of strongly acidic wastewater and concentrated acids. Based upon the information from the Demand Analysis, we provided a detailed conceptual design for modifications and improvements to the existing system to meet the new requirements. The Conceptual Design provided an appropriate, reliable, fail-safe system that would operate automatically.

The conceptual design was used as the client's new standard design basis for upgrades to several other AWN systems at other client facilities. The conceptual design included the installation of equalization and divert tanks, segregation of waste streams for separate treatment, improvements in the neutralization reactors for uniform mixing, effective use of Feed Forward/Feed Back pH control loops in the instrumentation, improvements in the process control sequences and instrumentation; detailed evaluations of materials-of-construction; and upgrades to caustic delivery systems. We also provided complete Permit-by-Rule and Industrial Wastewater Discharge Permits submittals to the agencies for the upgraded system and further assisted as a design consultant to the MEP contractors through startup and performance testing of the system.