Chapter 16. Degasification, odour control, evaporation (32 pages)

1.Air or gas strippers, removing CO₂
1.1.CO₂ eliminators
1.2.Airstrippers
1.3.Gas and vapor strippers
1.3.1.Gas strippers
1.3.2.Vapor strippers
2.Measuring odours and odour control
2.1.Sources of emission of odorous compounds produced by a wastewater treatment plant
2.1.1.Raw effluent inlet and pre-treatment (grit removal, oil removal and primary settling)
2.1.2.Biological treatment and associated clarifier
2.1.3.Sludge treatment
2.2.The main pollutants
2.3.Analysis
2.3.1.Chemical analysis
2.3.2.Olfactometric analysis
2.4.Ventilation
2.4.1.Aims
2.4.2.The different types of ventilation
2.5.Regulations
2.5.1.On rooms and on ventilation
2.5.2.French legislation on odours
2.6.Odour control
2.6.1.Physical-chemical treatment in scrubbing towers: the Azurair C
2.6.2.Activated carbon treatment: the Azurair A
2.6.3.Biological treatments: the Azurair B
2.6.4.A few typical results
3.Thermal degasifiers
3.1.Horizontal degasifying heater
3.2.Packing degasifier
4.Seawater evaporators
4.1.General
4.2.Marine vapor scrubber (figure 8)
4.3.Multi-effect distillation (MED) (figure 9)
4.4.Multi-effect distillation with thermally compressed steam (MED- TCS) (figure 10)
4.5.Multi-stage flash distillation with recirculation (MSF) (figure 11)
4.6.Mechanical steam compression (MSC) (figure 12)
5.Evaporator-crystalliser
5.1.Zero liquid discharge
5.2.Example: recycling yeast factory vinasse (distilling slops)

This chapter examines the gas-liquid exchanges that are applied in very different ways, depending on their purpose:

eliminating a gas from water through stripping at normal temperature: CO₂ removal or gas adsorption in a «gas scrubber», especially applicable to the removal of odour-emitting gases (odour control);
oxygen removed by vapor stripping in thermal degasifiers operating at temperatures close to boiling point;
and, by extension to the latter, water evaporation, mainly seawater, for producing drinking or process water, or also for concentrating or even crystallising salts in effluents and, accordingly, avoiding discharge of any liquid into the environment, using evaporator-crystallisers.