The conventional analytical procedures for monitoring concentrations of metals in water are both costly and time-consuming. The MetalyzerTM 5000 technology had previously been successfully validated for measurements of lead in drinking water. In this project, its applicability to other metals such as arsenic, chromium, copper and mercury was evaluated for regulatory compliance at two Navy Industrial Wastewater Treatment Plants (IWTPs).
The MetalyzerTM 5000 measures toxic metal concentrations in water using an electrochemical technique called Potentiometric Stripping Analysis (PSA). PSA can analyze multiple metals simultaneously and calculate subparts-per-billion concentrations in on-the-spot measurements of a waste stream. The device is computer-controlled and can be left alone to monitor waste streams for extended periods of time.
The technology worked as expected in terms of sensitivity and accuracy in the laboratory; however, when samples were spiked with metals other than the target metal, there was interference (i.e., reduced sensitivity). This interference would limit its applicability in certain waste streams. In the first demonstration at Naval Air Station (NAS) North Island IWTP, the technology exhibited an unacceptable reduction in sensitivity in the real-world waste stream. The PSA measurements were significantly lower than standard Environmental Protection Agency (EPA) methods conducted in the laboratory. The target metals were thought to have been bound to flocculants. The PSA method worked acceptably well in the second demonstration, monitoring an innovative molecular recognition technology process for copper breakthrough at Puget Sound IWTP. There was a linear response between 0 and 250 micrograms per milliliter although there was a slight 15 micrograms per liter offset compared to EPA standard tests.
The main strengths of the MetalyzerTM 5000 are rapid results, versatility, simplicity and lower analytical costs. The turnaround time for conventional methods is typically 2 to 4 weeks versus 15 minutes for the PSA method. The traditional laboratory analytical cost of a single metal measurement in water ranges from $20 to $75. In a cost comparison between Graphite Furnace Atomic Absorption (GF-AA) analysis and PSA analysis, the GF-AA cost per sample was $64.37 while the PSA cost per sample was $15.64. The estimated capital cost of the MetalyzerTM 5000 is $25,000 for over 20,000 samples (i.e., $1.25 per sample compared with the GF-AA cost of $50.00 per sample). The MetalyzerTM 5000 is commercially licensed and would pay for itself within 6 months based on the savings as compared to traditional off-site analysis in a certified laboratory.
Use of the MetalyzerTM 5000 would allow Department of Defense (DoD) facilities to quickly and inexpensively monitor wastewater streams for regulatory compliance. If the MetalyzerTM 5000 gains EPA acceptance for wastewater monitoring, DoD could benefit from greatly simplified compliance procedures. (Project Completed - 2003)