Liquid waste- problems and treatment.ppt

1. Liquid waste

2. Liquid waste treatment
•Water bodies
•DO
•BOD
•Anaerobic
•Lotic, lentic
•Treatment- 3 stages
•Primary, sec-BOD dec; tert-> mineral,
recalcitrant organic removal

5. primary
•Screen
•Scum, grease
•Grit settle
•BOD dec
•If only org.solid- upto 70-80%; domestic
sewage- 30-40%

6. Screening

8. Settling tank

9. Secondary treatment
•biological
•anaerobic
•Aerobic
•Fixed film type-Trickling filter, RBC,
Submerged aerobic filters, Fluidized bed
reactor
•Suspended sewage treatment systems
•Oxidation lagoon, Activated sludge

16. RBC

19. Submerged Aerobic Filters

20. Fluidized bed reactor
•Support- pumice, sand , plastic; pump water
up (anaerobic); air/O2 (aerobic)
•Rate- no shear off but fluidised
•SA large
•USB
•More mo

22. Suspended cell sewage treatment
•Oxidation lagoons- cheap, long retention time
•O2- diffusion (slow), photosyn-> if less O2 ->
odor
•Dep on temp

23. •treated sewage-> may be recharge ground
water
•Sewage- primary settling-> series of holding
ponds-> microbial biomass settle-> infiltration
pond-> nat. soil, sand-> groundwater
•Problem- clogging-> periodic rest

26. Activated sludge
•Flocs
•Gram –ive rods- coliforms, Ps, Z.ramigera
•Flocs- attached cilliates- suspended bactetia
•Pathogen – dec (can’t survive), also reduce in
settling
•Settling of floc- problem- ‘bulking’ (filamentous bac,
fungi)? highC:N, C:P, low DO
•Sludge- settled-. Recycled, incineration, anaerobic,
composting, landfilling

28. floc

32. Bulking causing m.o.

34. modifications
•UNOX- O2
•ICI
•Anaerobic
•eutrophication
•Removal of P, N
•Alt aerobic, anaerobic (add. Org)
•P- Acinetobacter-Moraxella- Mima
•PHB, P-release (anaerobic), P uptake (aerobic)

35. UNOX

39. Anaerobic digesters
•Slow, less E, E gen
•Septic tank- residue to leaching field (aerobic,
far)
•Imhoff tank

44. •Anaerobic lagoons
•Odor
•Meat packing plant effluents

45. Tertiary treatment
•Non-biodegradable organic comp, mineral
•Activated C-filters
•P- ppt Ca, Fe
•N- stripping- NH3 at high pH
•Breakpoint chlorination- HOCl (1:1)
•Dec BOD- NOD
•Heavy metals- mo sorbed

46. •HOCl +NH
3-> NH
2Cl +H
2O
•HOCl + NH
2Cl-> NHCl
2 +H
2O
•2NHCl
2 +H
2O-> N
2 + HOCl + 3H
+
+ 3Cl
-

47. Disinfection
•After sec or tert.
•Cl
2, NaOCl, Ca(OCl)
2
•ClO
-
, HOCl=> free residual chlorine
•Oxidant
•Org matter, NH
3, Fe
2+,
S, Mn
•Some org-> part. Oxidised-> toxic, difficult

48. •Cl
2 + H
2O-> HOCl +HCl
•NaOCl +H
2O -> HOCl + NaOH