1. The document discusses various types of wastewater treatment processes including oxidation ditches, oxidation ponds, aerated lagoons, and septic tanks. 2. Oxidation ditches are essentially extended aeration activated sludge processes using endless ditches and rotors for aeration. Rotors are designed to impart velocities between 0.3 to 0.4 m/s. 3. Oxidation ponds, also called waste stabilization ponds, are open earthen basins that use natural means like wave action and sunlight to facilitate the aerobic and anaerobic treatment of sewage and biodegradable wastes.

1. UNIT – III
Environmental Engineering – IIEnvironmental Engineering – II
Prof S S JAHAGIRDAR
BE (CIVIL), ME(ENV.)PhD(persuing)
NK Orchid college of Engg. and Tech.NK Orchid college of Engg. and Tech.
Solapur

2. A Oxidation ditchA. Oxidation ditch
B Oxidation pondsB. Oxidation ponds
C. Aerated lagoonsg
D. Septic tanks (Already
covered for two batches during
practical hrs)

3. Essentially an extended aeration
activated sludge processg p
Consists of endless ditches for the
aeration tank and a rotor for aerationaeration tank and a rotor for aeration
mechanism.
N PST i d dNo PST is needed.
Rotors designed to impart 0.3 to 0.4g p
m/s velocity.
Rotors have dia = 70 cm and speed =Rotors have dia. = 70 cm and speed =
75 rpm

4. Rotors are manufactured in 30 cm intervals
up to 4.5 m length.p g
The width of ditch divided by the rotor
length ratio= 1.5 to 2.8.length ratio 1.5 to 2.8.
Standard oxygen transfer capacity of rotor =
2 8 kg of oxygen / m length @ 16 cm depth of2.8 kg of oxygen / m length @ 16 cm depth of
immersion.
This rotor has been found to impartThis rotor has been found to impart
adequate circulation for 120 to 150 cu.m. of
ditch volumeditch volume.
Power requirement/m length of rotor = 1.35
kWkW
Depth = 1 to 1.2 m

8. Is an open, flow throughp , g
earthen basin of controlled
shape specifically designedshape, specifically designed
and constructed to treat
sewage and biodegradablesewage and biodegradable
industrial wastes.
Mixing by natural means (No
artificial oxygen supply)yg pp y)

9. AerobicAerobic
AnaerobicAnaerobic
facultativefacultative

11. Bacteria algaeBacteria- algae
Symbiosis

12. D th i h ll i 0 5 t 1 2Depth is shallow i.e. 0.5 to 1.2 m
L/B ratio = 3:1L/B ratio 3:1
Algal population is present
Rest microorganism system is
similar to ASPsimilar to ASP

13. Ratio of surface area toRatio of surface area to
volume, larger ratio, better
will be the oxygen diffusionwill be the oxygen diffusion
into lagoons
T b l it tiTurbulence – agitation,
generally provided by waveg y p y
action.
Penetration of sunlight in thePenetration of sunlight in the
pond.
BOD:N:P:K:: 100:5:1:1BOD:N:P:K:: 100:5:1:1

14. Anaerobic decomposition takesAnaerobic decomposition takes
place in two steps,
Decomposition of organic wasteDecomposition of organic waste,
by acid producing bacteria to
organic acids andorganic acids and
Further decomposition of these
acids to the end products ofacids to the end products of
methane, carbon dioxide and
water by methane formerswater by methane formers.

15. Less surface area than aerobic ponds.
Depth ranges from 2.5 to 5 m.
L/B ratio = 2:1
Summer season - BOD loading = 1000
to 2000 kg/ha/day with detentions ofg y
2 to 5 days.
Efficiency of BOD removal is @ 65 toEfficiency of BOD removal is @ 65 to
80 %
Winter season - BOD loading = 500 toWinter season - BOD loading = 500 to
1000 kg/ha/day with Efficiency of
BOD removal @ 45 to 65 %BOD removal @ 45 to 65 %

16. Organic loading is @ 10 timesOrganic loading is @ 10 times
more than aerobic pond.
Optimum pH range is 6.6 to 7.6

17. Combined features of aerobic andCombined features of aerobic and
anaerobic ponds.
D h 1 1 5Depth =1 to 1.5 m
Aerobic zone at topp
Anaerobic at bottom
Fac ltati e bet een abo e t oFacultative between above two
zones.

20. Intermediate systemIntermediate system
between oxidation ponds and
ASP.
Floating aerators areFloating aerators are
provided fixed on rafts or
floats.
Depth 2 5 to 4 mDepth 2.5 to 4 m.

22. Detention time 2 to 10 days
Oxygen required = 0 7 to 1 3Oxygen required = 0.7 to 1.3
kg/kg of BOD5 removed.
Power requirement = 0.75 to
2.25 kW/1000 m32.25 kW/1000 m3
BOD removal efficiency = 75 to
8 %85 %
SST is neededSST is needed

24. Detention time 3 to 5 days
Oxygen required 0 8 kg/kg ofOxygen required = 0.8 kg/kg of
BOD5 removed.5
Power requirement = 0.8 to 1
kW/1000 m3kW/1000 m3
BOD removal efficiency = 75 toy
90 %
No SST but sludge has to beNo SST but sludge has to be
cleaned after some years

25. 1 Classify stabilization ponds according to the nature of1. Classify stabilization ponds according to the nature of
biological activity. Explain any one in detail.
(Nov 2010, 8 marks)( , )
2. Explain oxidation pond in detail.
(May 2010, 5 marks)
3. Write short notes on
1. Aerated lagoon (May, Nov 2010, 4 marks)
W bili i d2. Waste stabilization pond
(Nov 2009, 4 marks)
3 Oxidation ditch (May 2009 6 marks)3. Oxidation ditch (May 2009, 6 marks)
4. Draw complete process flow sheet for wastewater
treatment with 1) oxidation ditch and 2) trickling) ) g
filter as secondary treatment.
(May 2008, 4 marks)