Sewage Flashcards
wastewater
liquid from wastes of humans, cant be drained without being treated into environment
industrial water
can contain toxic substances such as petro, plastics
domestic water
sewage, “grey water” (washing, cooking)
contaminants of water
soils, biodegradable organics, pathogens/parasites, pollutants, refractory organics, heavy metals, dissolved organics
Primary Treatment
Physical
- screening: removal of large objects
- sedimentation: of grit, solids
Secondary Treament
Biological
- trickling filter (aerobic), or
- activated sludge (aerobic)
- sludge digestion (anaerobic)
- disinfection (chemical)
Tertiary Treatment
Chemical, biological, physical
-any physicochemical or biological process employing bioreactors, precipitation, filtration, or chlorination procedures similar to those employed for drinking water treatment
Sewage process
1) Pretreatment: raw sewage settles (2)larger sediment at the bottom by gravity
3) primary treatment: suspended soils sink and go to anaerobic sludge digester to go to landfill/converted to fertilizer (6)
4) a) wastewater is sprayed onto bed with microbe that consume organic waster
b) activated sludge mixes with air to support bacteria that consume suspended organic wastes
c) cleanest water from settling after b) and sent to be disinfected
5) a)effluent is discharged to river/natural water sources
5b) sludge from primary/secondary is sent to anaerobic digester where bacteria consume organic wastes
6) sludge is incinerated, sent to sanitary landfill, converted to fertilizer
Tricking filter
primary effluent water goes in and distributed through filtration bed and effluent is sent to disinfection
-include biofilms
Activated sludge process
goes through aeration tank->settling tank->
clear effluent goes to chlorinator and activated sludge goes through aeration tank again or to anoxic sludge digestor
Flocs
substrata to which other bacteria, protozoa, small animals attach; Zoogloea important in formation
main removal process in aeration tank
adsorption of soluble organic matter to floc; some mineralization, incorporation
Biochemical oxygen demand
amt of dissolved O2 required by microorganisms stabilizes organic matter in sewage/water
BOD5
O2 demand measured over 5 days at 20deg in the dark
Anaerobic Sludge Digestor
Top to bottom:
gas outlet-scum layer-supernatant (where sludge goes in)-actively digesting sludge-stabilized sludge-sludge comes out
Digestion:
complex organics-hydrolysis>monomers-fermentation> acetate, H2+CO2 -methanogenesis> methane+carbon dioxide
