FIG. 7.49.4 Clarified effluent BOD and COD concentration as a function of solids content of heat treated sludge into the thickener.

turns and sludge piping are fabricated of heavy thickness due to the erosive forces of grit and sand in the feed sludge.

Wet-combustion systems are fabricated from stainless steel.

Table 7.49.3 shows operating data for the Porteous process.

As previously mentioned, this process is more economic than the chemical conditioning of sludges to improve their dewatering characteristics. Heat-treatment fuel costs are further reduced if the dewatered cake is incinerated and the waste heat is recovered. The final sludge cake is ultimately disposed as a low-grade soil conditioner, land fill material, or fuel. The high temperature used in the process sterilizes the sludge from pathogenic germs and weed seeds.

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