We are a petrochemical company and for treatment of wastewater we have extended aeration with the design of 300 m3/hr effluents with COD 1200ppm but in normal operation, the flow reduces to 100 m3/hr and COD increase to 4000 ppm, I want to know the effect of these changes in biological treatment.
You can assess the impact on biological treatment by BOD because in this test the oxidation factor is bacteria ....and also you can use COD\BOD ratio to assess your plant performance
Published
by Basha Ibra, Environmental complaince sp. at National Water Company (NWC)
Mahmud Ghasempour With so much variation the predictability of the results is definitely a question. Also the varying load is actually a varying food load to the microbes, because of which outlet water quality & parameters will get affected. However, if you put our Bacta cult bioculture (www.amalgambiotech.com) then overall microbial strength becomes high & overall health of the system is always kept in “very good” condition.
By doing this you cannot eliminate the entire problem but you can surely minimise it.
Congenital water by definition is toxic but it's the less problem against hazardous because high concentrations of 4,000 ml hydrocarbon content.
Aeration is not the most effective process, but less for congenital wastewater; aeration effectiveness has more limitations as more concentrated is wastewater.
An obvious observation is your net COD load is about 11 percent greater than your design load, but your contact time increased by 300 percent, providing a longer time for biological treatment. If your design was appropriate for biologically treating the constituents that make up the COD , and had a reasonable factor of safety incorporated into the design with respect to meeting the oxygen demand, the additional 11 percent loading will likely be offset by the much longer hydraulic retention time available for COD uptake and treatment. That being said, if the COD includes constituents that are toxic, and the toxin concentration is proportional to the COD concentration increase, there may be some inhibitory effects that will negatively impact treatment. Unfortunately, it is impossible to confirm the plant will operate as intended with the little information you have provided.
we haven't any problem with COD in the outlet of aeration, but the problem is in the settling tank and turbidty increased, I think with an increase of retention tank the property of bioflocculation will be weak, I want to know the effect for clarification properties .
Thanks a lot for your answer, I am ready to provide information that needed for better decisions. but despite COD and toxic constituents, I want to know increasing of 300 percent in contact time couse what problems in biologecal treatment.
Increasing the contact time means the amount of time to digest the available biodegradable carbon is three time longer. Generally, that is a good thing. The impact also depends on your reactor design. A completely mixed reactor may take a 3:1 increase in load with a 3:1 increase in digestion time better than a plug-flow reactor. If you have, for example, a plug flow reactor that receives 3 times the concentration of substrate, the oxygen demand at the head end of the process could overwhelm and exceed the oxygen supply. Also, you need to determine the nature of the increased COD. Whether it is organic or inorganic can greatly affect the process response to the high concentration. Hope that makes sense.