Secondary Waste Treatment by Biological Processes

FIGURE 5.8 Trickling filter for secondary waste treatment. Wastewater is sprayed from holes in a rotating pipe onto a bed of rocks or other solid materials coated with microorganisms that metabolize biodegradable materials in the wastewater. 

The structure of the trickling hlter is such that contact of the wastewater with air is allowed and degradation of organic matter occnrs by the action of the microorganisms. 

FIGURE 5.10 Pathways for the removal of BOD in biological wastewater treatment. 

The sewage sludge (which is often referred to by the more palatable term biosolids ) produced in wastewater treatment processes requires disposal or use such as for soil conditioner. This issue is discussed in more detail in Section 5.14. 

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