How much incoming BOD can be removed by the primary treatment process when chemical coagulants are used?

The primary treatment process for wastewater typically focuses on physical separation of solids and particulates from the liquid waste. When chemical coagulants are introduced into this process, they enhance the removal of suspended solids and some dissolved organic matter. This technique primarily involves the addition of substances that cause smaller particles to clump together, making them easier to remove.

In terms of Biological Oxygen Demand (BOD), which is a measure of the organic matter in water that can be biologically degraded, the use of chemical coagulants can lead to a more efficient removal during primary treatment compared to physical methods alone. With the proper application of coagulants, a treatment plant can achieve a removal of BOD that reaches up to 50%. This level is significant because it means that nearly half of the organic material present can be eliminated before the water moves on to secondary treatment processes, which can further reduce BOD levels more effectively.

The distinction here is that while some other treatment methods or processes may allow for higher percentages of BOD removal, primary treatment typically does not reach the levels indicated by options suggesting up to 75% or 100%, as these figures are associated with more advanced stages of wastewater treatment rather than the primary phase alone.