Water volume: 50000 litre
Feed: 32 % protein
Daily feeding: 700 gm
if the TAN: Nitrite: Nitrate:: 0.25:10:0)
what will be the carbon required to maintain the ratio C:N of 10:1?
Now i have calculated the following steps
Total N in the system= 10.25 ppm or (10.25 mg/ l)
total volume is 50000 litre
so total nitrogen is 50000*10.25=512500 mg or 512.5 gm
So we have 512.5 gm of total nitrogen in the system
Now total "C" is adding daily in the form of feed
Say: Feed contains 50% carbon and 32 % protein and approx 70% feed is getting waste/ day
So 700*70/100=512.5 gm feed getting waste, as 50 % carbon is there in the feed so 512.5*50/100=256.25 Gm Carbon is going in the system/ day
So the current C:N ratio is 256.25/512.5= approx 0.5:1
So to maintain a ratio of 10:1 C:N we required 5150 gm of carbon
Suppose we are using Molasses of (28% C) as a carbon source Than
5150*100/28=18392gm or 18.3 kg of molasses is required?
Please help me out critically in this calculation .....is my calculation is fine or i am missing any aspect or concept.
@ Vivek, I think your calculation is ok. You may take 18.4 kg of molasses instead 18.3 you have mentioned.
Since you have not written what you actually want to do as a process with this water it is difficult to guide. I just note that you feed also will contain Nitrogen if it contains proteins since they will be hydrolysed and release ammonia.
Hello Kim Sir
Actually this is the second part of my previously asked question?
Sir i am looking to manage or required to know the amount of Carbon source as per the available Total Nitrogen content (Ammonia +Nitrite+nitrate) to maintained a ration of C:N 15:1 under bio floc system for culture of my fishes.
In my biofloc water sample analysis i found (Ammonia =.25 ppm; Nitrite: 10 ppm and nitrate was 0ppm. Hence, the total nitrogen is the sum of the above three that is 10.25 ppm.
Finally, the below 2 approaches are there to manage the C:N ratio
1) First to calculate the Feeds (Protein and Carbon %) to add the required quantity of Carbon in the system to manage a ratio of C:N ::15:1
2) Direct calculation of the amount of nitrogen which is ultimately coming from the given feed, left over feed and excreta in the form of (TAN+Nitrite+Nitrate in mg/l) in the water system to adjust the required quantity of Carbon in the system to manage a ratio of C:N ::15:1
I have applied the second method to calculate. I hope the explanation is clear
I do not know from where you get that you need this ratio of C:N of 15, but in most cases this C is actually not C, but COD - Chemical Oxygen Demand that is referred to and what the actual COD in the Molasses is will again depend on the origin of this molasses.
Kim Sir, I am sorry to say I am talking about BIOFLOC system and as per my little knowledge "C" means Carbon, not the COD - Chemical Oxygen Demand. Thank you for giving your suggestion and for your valuable time.
Vivek Shrivastava Sir,
you are calculating the nitrogen directly from the tank water. I think it can be calculated from the feed given also. Protein content in the feed is well known. Hence from that data, the total protein given to the system can be calculated. from the protein, 16% will be the nitrogen. So the total nitrogen also can be calculated. From the total nitrogen, 70% will be wasted. From that total nitrogen inside the pond can be calculated.
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