I had read journal about wastewater phytoremediation, there it said DO is nil but BOD is high (about 200mg/l), how could that happen? Since BOD was in biological oxygen demand and DO was nil how could microorganisms be degrading organic matter if the oxygen is absent?
In fact I am responding to your post not to what the journal says though, you will know from the response that in some instance it is quite likely.
The DO (dissolved oxygen) has a direct relationship with the BOD (biochemical oxygen demand) in that it is determined to test the level of the BOD in water, especially in wastewater when microorganisms and an available food supply are present in water body. The DO is consumed in the process of oxidation of waste in water. Oxygen consumed in the decomposition process robs other aquatic organisms of the oxygen they need to live. Organisms that are more tolerant of lower dissolved oxygen levels may replace a diversity of more sensitive organisms. Normally, oxygen is not a very soluble gas and the DO concentrations are particularly very low in wastewater. To determine the BOD, sample wastewater is tested for the DO on the first day of the sample and the sample water is incubated at 20°C for five days. DO is again determined at the end of 5 days. The difference in dissolved oxygen between the initial measurement and the fifth day measurement represents the BOD.
Suppose, initial and final determinations of the DO both are zero, naturally the biochemical oxygen demand (BOD) will be very high and whatever there is the demand of oxygen for oxidation of a given amount of waste in given volume of water.
Dear Rizal, Please go through the methodology as per APHA it will ensures what exactly happen between DO and BOD, and the methodology itself gives the exact answer for your question.
when in measuring DO and BOD of industrial effluents, most of the times we come across 0 DO level due to high organic content and higher oxidation demand. when DO is 0 we need to increase the DO content of Distilled water and do the same initial and final measurements with dilution of samples, that's why we get higher BOD when DO is nil, moreover we require the exact biological oxygen demand at that sample, sometimes we need to provide microbial seed to know exact BOD.
best wishes
to Dr. Mophin, i see sir, so we need to using dilution to get BOD value because initial DO in pure wastewater is nearly 0,
one more question sir, which one is correct BOD (biological oxygen demand) or (Biochemical oxygen demand)?or both is same context?
thanks for all of your answers sir it really open my mind
So where there is a sample being tested with very high BOD (such as blackwater), dilution with distilled water would be very high (say 60:1) because saturated water can only hold around 10 mg/l oxygen whereas BOD may be 600 mg/l. Am I correct?
DO is consumed during the degradation of BOD (organic matter) by aerobic microorganisms. If more BOD is present then DO is completely consumed. Hence, DO becomes zero. When DO becomes zero anaerobic bacteria starts degrading the if the wastewater still having the BOD..
Anyone came across BOD below lab detection limit in marine water sample
I just wanted to correct, distilled water should not be used rather buffer or saline solution should be used to maintain isotonic environment for cell. Buffer with carbon can't be used. To exemplify acetate buffer.
BOD and DO are inverted related. The more BOD you have in the sample, the less DO you have. Biomass requires Oxygen to grow, so the Oxygen consumption happens as long you have nutrients availabe for the microrganisms.
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