The ChemWatch^tm Feed Rate Controller is an operator-mediated optimization program that economizes chemical use while minimizing odor excursions and documenting performance.  It provides up to 24 discrete hourly feed rates matched to diurnal H₂S levels.  For most operations, this translates into chemical savings of 10-20% over conventional two-pump systems.  Labor is also minimized by a cell phone communications package that allows the process to the managed from anywhere using a Windows-based PC.

The ChemWatch^tm Feed Rate Controller is housed in an integrated NEMA-4X enclosure with an LED tank level display (in gallons) on the faceplate; and an 8-bit computer, power supply, cell phone modem, and support software in the box.   The unit can also perform extensive pump diagnostics for scheduled maintenance and troubleshooting.  The output signal to the chemical metering pump(s) is 0-20 mV.  The controller can accommodate up to 24 discrete hourly feed rates that can be input using either a local keypad or a remote Windows-based PC. 

Step-1:    Datalog and graph H₂S values from a suitable instrument (e.g., AppTek OdaLog or Industrial Scientifics STX-70 – SewerGuard).

Step-2:    Determine the hourly feed rates needed to equalize the H₂S levels to a constant control level.

Step-3:    Connect to the ChemWatch^tm pump controller and input the adjusted feed rate values.

Most odors from municipal wastewater systems (from e.g., collection systems, headworks, holding tanks, and scrubbers) exhibit a high degree of periodicity – that is, H2S levels may change enormously from hour to hour, but the basic profile tends to remain the same – a “diurnal” profile of H2S levels on Tuesday will resemble one on Thursday.  The figure below shows such a typical profile and how one might alter the chemical feed rates:  first by using a conventional two-pump metering unit, and then by using the ChemWatch^tm Feed Rate Controller.

The graph shows the dilemma inherent in two-pump systems – how much red can you tolerate (non-compliance = odor complaints) while minimizing the green (overdosing = wasted money)?  In this example, the two-pump system will use about 15% more chemical than is actually needed to control the odors, while failing to meet compliance about 3% of the time.  On the other hand, with the ChemWatch^tm Feed Rate Controller, excess chemical use is 2.4% while non-compliance is < 1.5%.  In this case, the savings is 12%.

A similar exercise for seasonal (month-to-month) variations would show how monthly use of the ChemWatch^tm Feed Rate Controller can save another 5-10% in chemical use.

The ChemWatch^tm Feed Rate Controller is currently available through chemical service programs provided by US Peroxide, Inc.  Other related ChemWatch^tm products (also available exclusively through US Peroxide) include tank level management (use-rate reporting and delivery scheduling) and site stewardship (limit controls and alarm notification).