There is a concern about worker safety at a small European wastewater plant. The plant receives primarily residential wastewater at a flowrate of 0.95 MGD.
The first process unit is a 32,000 gallon flow equalization tank (nominal retention time - 48 minutes). From there it is pumped to coarse screening/grit removal.
Plant staff often work in the coarse screening and grit removal building where H2S levels of 40 to 100 ppm have been measured.
975 - UNITED CARUSOL® C is injected into the collected wastewater as it enters the equalization basin – initially at a 100 mg/L dosage.
The safety goal of <5 ppm was achieved.