Biofilters Flashcards
What are hard for biofilters to treat?
Aliphatics and aromantics
What are the 4 phases to consider in reactor?
Air-waste stream flow in/out
Solid support ‘packed bed’
Biofilm
Water (+ nutrients in water for biotrickle bed)
What happens if the pressure drop increases in bed?
Fixed speed blower - lower flowrate = less contaminant being degraded and likely not meeting control standards
Variable speed blower - low flowrates - will speed up to try and increase flowrate, lots of power $$
Biofilter failures?
Physical - Moisture and pressure drop
Biological - pH or nutrients
What are the process parameters of bed?
EBRT = V/Q = 30-120s Inlet concentration = 0.01 - 5 g/m3 Mass loading = Cin/EBRT Surface loading = Q/area Avg = 1 m/min Removal eff = (cin-cout)/Cin Elimination capacity = (Cin-Cout)/EBRT Avg < 100 g/m3 h Bed depth = 1m (0.5-1.5) Area = Q*EBRT/Depth
Pretreatment?
Particulates - can cause clogging
Temperature
Humidity (want 100%)
What different flow directions are required?
Hot water saturated gas = upflow, ground can be heat sink and collect condensate at bottom
Humidify dry gas = downflow, drying concentrates at inlet so can spray water over bed
High mass loading = downflow, high activity = extra heat = more water
H2S, NH3 = upflow, H+ increase accumulates at bottom easier to wash out
What methods are used for pH control?
Extra irrigation - wash acid from bed (leachate problems)
Buffering - add lime (needs to be < 10% volume of bed)
Thicobacillus bacteria - happy at pH 1-3 - but what construction material cam you use and cant treat hydrocarbons
Advantages of biofilters? (4)
Low capital and operating expenses
No additional fuel or NOx emissions
Minimal additional waste generated
Regional councils familiar with technology
Disadvantages of biofilters? (5)
Emissions must be biologically treatable Must not be ignored/neglected Can generate leachate Can require large footprint Preconditioning can be significant
