Wastewater from a primary treatment tank is to undergo secondary treatment in an activated sludge unit. The following data and operational parameters are specified: Two identical units are designed to operate in parallel and to process a combined wastewater flow rate of 0.5 m3 /s; the BOD5 of the effluent suspended solids is 70% of the allowable suspended solids concentration. Assume ideal operation of the reactor units. (a) If the EPA’s secondary treatment standards (average monthly) are to be met. How large must each reactor be (m3 )?

Complete Question

The complete question is shown on the first uploaded image

a

The volume of each reactor is  

b

The rate at which cells must be discharged in the unit is

Explanation:

From the question we are told that

     The  water flow rate of the units is  

     The (Biochemical oxygen demand) of the effluent suspended solid is % of allowable suspended solid concentration

   Given that the flow rate for two identical parallel units then for a single unit the flow rate  would be

Generally the required BOD in terms of  EPA(Effluent Guidelines) is concerned is  

      Now Sludge age of this unit of reactor is mathematically evaluated from this expression  

Where is the Sludge age  

     Substituting values

                 =>  

Now the volume of the reactor is mathematically evaluated from this relation

     Making V the subject of the formula

 Substituting  values

=>      

We can obtain the cell mass  been wasted per day using this  expression

Where is given as  

            is the sludge been wasted per day

                  is the discharge concentration for each unit  

       Substituting values

Now the rate at which they discharge this concentration is  mathematically evaluated as

substituting values

answer:

the answer is d

explanation:

answer:

explanation:

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