Anaerobic BMP and ATA Tests

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Anaerobic BMP and ATA Tests

Biochemical Methane Potential (BMP) tests involve addition of test chemicals or wastewater samples of concern to an anaerobic culture that is contained within a sealed vessel. Methane or total gas production are measured over periods ranging from 1 to 60 days without addition of new chemical or wastewater sample. Modern BMP tests usually involve multiple additions of substrate or wastewater to anaerobic reactors over 3 to 60 days to assess the ability for sustained biodegradation. Example BMP test data are shown in Figure A for three wastewater streams as compared to an ethanol control when using a Challenge AER-200 aerobic/anaerobic respirometer system. In this case, substrate injections were made on three consecutive days and the methane production was expressed as mL/g COD added. These data show that only about 75% of the COD in Stream 1 and 50% of the COD in Stream 2 was converted to methane. The mixture showed COD conversion between 50 and 75%. The fact that the initial rate of methane production was the same as that for the control indicates that the wastewater streams contained no toxic substances. ATA tests involve addition of test chemical or wastewater plus a biodegradable organic substrate – ethanol, acetate, benzoate, etc. – to anaerobic cultures contained within sealed vessels. Concentrations of test materials range from 0 (Control) to 2 to 4 times anticipated field concentrations, in effect, a dilution series. Example ATA test results are shown in Figure B when testing the effect of a sanitizing agent on anaerobic the activity of an anaerobic culture. These tests indicated that mild inhibition occurred at a chemical dose as low as 12 mg/L. Inhibition increased with increasing dose of test chemical. A concentration of 120 mg/L produced a 50% decrease in methane production rate. The benefit of using respirometers to measure methane production at short time intervals is illustrated well in this case. Measuring cumulative methane production after 24 hours would have shown no toxic impacts.

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