What Sludge Is

Sewage becomes offensive due to its own instability together with the objectionable concentration of suspended materials. In addition, the potential presence of disease producing organisms makes sewage dangerous. Removal or stabilization of sewage matters may be accomplished in treatment works by a number of different methods or by a suitable combination of these methods. 

If instead we can sell the waste, then we not only have eliminated these costs, but in addition have generated a positive cash flow into our operation for the sale of the waste. This is what we mean by pollution prevention practice. 

Of concern, however with any sludge management issue, are the costs for recovery of potentially valuable by-products as in the case of the cable plant and the costs associated with concentrating the sludge to a form that it can be handled in post processing operations. 

There is an old saying among pollution control engineers that practiced pollution prevention long before it became fashionable. That saying is - If you see a dollar lying on the ground, it s worth your while to bend over and pick it up - but NOT if you have to break your back to do it.  

We will address some of these issues later on in this chapter. But for now, simply recognize the fact that the most basic part of waste water treatment is solids removal. Solids are removed in primary and secondary treatment tanks, but without such effective removal there is no treatment process efficiency. 

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