Solids

FIG. 7.50.4 Fluidized-bed sludge incinerator.

FIG. 7.50.5 Wet oxidation process.
FIG. 7.50.6 COD reduction from sludge exposed to excess air for 1 hr at various temperatures.
FIG. 7.50.7 High COD reduction and low reaction time with high operating temperatures.

a gas with an increasing CO2 and a decreasing O2 content as the material moves through the reactor.

The wastewater treatment facility selects the operating temperature according to the required COD reduction and reaction time. When the reaction time must be short and the reduction in COD must be substantial, high operating temperatures are required (see Figure 7.50.7). The COD of the effluent leaving the reactor is independent of the incoming COD level at high operating temperatures; therefore, the higher the original COD, the greater the percent reduction.

As consequence of high operating temperatures, the wastewater treatment facility must run the process at high pressures to keep some of the water from vaporizing. The static pressure energy of the exhaust gas can drive the air compressor or generate electric power, while the thermal energy of the reactor effluent can be used for steam generation. Air pollution is controlled because the oxidation takes place in water at low temperatures and no fly ash, dust, sulfur dioxide, or nitrogen oxide is formed.

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