Presentation on theme: "Rapid determination of Biochemical Oxygen Demand (BOD)"— Presentation transcript:
Rapid determination of Biochemical Oxygen Demand (BOD)
The Present Situation In heavily polluted water, BOD and COD tests are used for estimation of potentially bio-metabolized organic compounds in water. The BOD test measures the oxygen demand by a mixed microbial population due to biochemical oxidation of organic compounds during 5 days of incubation. The COD (chemical oxygen demand) test measures the chemically oxydizable organic matter in water. This test analyzes both biodegradable and non- biodegradable organic matter.
The Disadvantages of the BOD5 and the COD Tests The results of the standard BOD method are obtained only after 5 days. Organic consumption due to anaerobic respiration pathways is not recorded. The results of the COD test (although obtained in a few hours) are usually higher than the corresponding BOD test due to the fact that inert organic compounds give false positive results..
PCB-BOD Function & Application The non-assimilable organic compounds are first hydrolyzed by a mild HCl pre- treatment. This treatment breaks down polymers into assimilable oligomers and monomers. CheckLights specially formulated reagent is then exposed to the treated sample, and luminescence is recorded after 2-3 hours of incubation at ambient temperature. The level of luminescence is proportional to the concentration of utilizable organic carbon in the sample.
PCB-BOD Key Features Time saving - accurate and meaningful results of dozens of samples obtained within 3- 4 hours. No need for sample transportation to external labs. Easy to use - personnel do not require special laboratory skills to use kits. Sensitive - a vast range of organic compounds can be detected at a wide concentration range (5-1000ppb). Reliable - good correlation was obtained against the standard BOD5 test for a given water source. Cost effective - low cost encourages more frequent monitoring of treatment plant efficiency and allows rapid response to changing conditions.
Correlation with the Standard BOD5 Method
Additional Benefits Acid hydrolysis of the tested water converts all the bio-polymers in the water flora into biodegradable nutrients. The high sensitivity of the test enables extensive dilution of the sample, thus minimizing possible inhibitory effects due to toxicity or turbidity of the tested water.
Step 1 - sample preparation Boil sample with 0.1 M HCl for 1 hr. To break polymers into oligomers and monomers. Neutralize acid with base and adjust pH.
Step 2 - Test Set Up Dispense diluted assay buffer into a set of tubes designated for - Negative control Positive control (I.e., carbon cocktail standard) Sample dilution set
Step 3 - Bacteria Preparation Hydrate freeze dried bacteria with hydration buffer. After mixing the bacterial suspension, incubate at 28°C for 30 min.
Step 4 - Bacteria dispensing Rapidly dispense bacteria into tubes containing negative control, carbon cocktail standard, and dilution set of sample., and double dilutions of treated sample.
Step 5 - Incubation After mixing the contents of each tube by vortex or hand, incubate at 26-28°C (in either air incubator or water bath).
Step 6 - Data recording Record light level after 1 hr and 2 hrs.
Data Analysis Principle The minimal extrapolated organic carbon concentration of the standard (carbon cocktail solution) is equated with the minimal sample concentration that exhibited a detectable signal. Using this value, the final BOD concentration in the original sample is calculated.
Automatic analysis with dedicated Excel module
Summary Because of the 5-day lag, BOD5 results are seldom of any use for real time process adjustment or decision making. CheckLight developed a unique technology for determination of BOD in water in only 3-4 hours. Data analysis is straightforward: the higher the luminescence, the higher the concentration of utilizable carbon. Acquiring this vital information in real time enables timely corrective measures in waste water processing, lowering running costs, and elimination of risk of heavy fines due to BOD limit excess.
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