जल उपचार में, ऊर्णन का इष्टतम समय सामान्यतः 30 मिनट दिया जाता है। यदि ऊर्णन का समय इस मान से अधिक बढ़ जाता है, तो फ्लॉक______

The correct answer is option 3) Break up and defeat the purpose of flocculation  

Explanation: 

• Flocculation involves gentle mixing to promote the aggregation of particles into larger flocs.
• If the flocculation time exceeds the optimal duration (30 minutes), prolonged mechanical agitation can shear or break apart the formed flocs.
• This fragmentation results in smaller particles that are less likely to settle effectively in the subsequent sedimentation tank, undermining the goal of flocculation.  

Option 1 is incorrect because flocculation tanks are designed with slow mixing to keep flocs suspended until they reach sedimentation. Settling prematurely would require halted mixing, not extended time.  

Option 2 refers to dissolved air flotation, not sedimentation, and is unrelated to prolonged flocculation.  
Option 4 (sticking to paddles) is less critical compared to shear-induced breakup, which directly impacts process efficiency.  

Thus, over-flocculation leads to floc breakup, reducing sedimentation efficacy.