Sewage Treatment Eye Openers - Dr. Ananth Kodavasal

www.ecotech-india.com EXCELLENCE AND INTEGRITY, SINCE 1986www.ecotech-india.com
PIONEERS & LEADERS IN WASTEWATER TREATMENT
Dr. Ananth S Kodavasal
Director
Sewage Treatment Eye
Openers
www.ecotech-india.com EXCELLENCE AND INTEGRITY, SINCE 1986
An assessment of various technologies
March 2019Presented for ADDA Water Workshop

THREE CARDINAL
LAWS FOR A
GOOD STP
PROPER
DESIGN
PROPER
ENGINEERING
PROPER
OPERATION &
MAINTENANCE

THE ZEROTH LAW
SELECTION OF THE APPROPRIATE
TREATMENT TECHNOLOGY

wrong technology
2500 STPs
IN BANGALORE
350 MLD SEWAGE
80% STPS ARE DEFUNCT
incorrect design
poor engineering
huge operation & maintenance

wrong technology
600 STPs
IN PUNE
100 MLD SEWAGE
80% STPS ARE DEFUNCT
incorrect design
poor engineering
huge operation & maintenance

Bangalore suffers from SBR itis
Pune suffers from MBBR itis
STP diseases – the Dr.’s diagnosis

typical naïve STP tender from architect
“The vendor may select any
process as per their area of
expertise and proprietary
design…”

“…acceptable technologies include
Extended Aeration, SBR, FAB,
SAFF, FBBR, RBC, MBR…”

“…anaerobic systems like UASB,
Septic tank…physical/chemical like
enzyme activated …electrolysis…”

An Experienced Consultant must :
Specify the most appropriate
technology, and not the one the
vendor is “comfortable” with

huge fresh water
savings potential
over Rs. 1600 crore
in STP assets in
Bangalore 20-25% investment
enough to revamp
2000 defunct STPs
protect waterbodies

COMMUNITIES CAN BE 60%
SELF-SUFFICIENT IN WATER
BEYOND 100 KLD, STP
MAKES MONEY
PAYBACK PERIOD
IS MONTHS

Classic EAAS
Anaerobic
CAACO
EADOX
SBR
MBBR/Fixed
MBR
STP TECHNOLOGIES
PREVALENT IN BANGALORE

CLASSIC, CONVENTIONAL
EXTENDED AERATION ACTIVATED SLUDGE
IS BEST

1 | Extended Aeration Activated Sludge
(EAAS)

sludge
recirculation
1. bar
screen
2. grease
trap
3. equalisation
tank
(aerated)
4.
aeration
tank
5. settling
tank
filtratio
n
treated
water
excess sludge
Stages 3 & 4 allow for
extended aeration
sludge recirculation – activated sludge
EAAS SYSTEM

EAAS WITHIN
72 HOURS

2 | Moving Bed Biofilm Reactor (MBBR)

MOVING BED
BIOREACTOR
(MBBR)
PRIMARY SEDIMENTATION ISSUES
SLUDGE HANDLING ISSUES
POORLY DESIGNED & ENGINEERED
NOT APPROPRIATE FOR SMALL STPS
PLASTIC MEDIA TO INCREASE
SURFACE AREA

PROF. HALLVARD ODEGAARD OF NORWAY
INVENTED MBBR IN LATE ‘80S (NOT NEW TECH)
PROPER PRIMARY SEDIMENTATION IS A MUST
UNDER ALL CIRCUMSTANCES
THE MBBRS WE HAVE INSPECTED SKIP THIS AND JUST END UP
TANKERING OUT THE SLUDGE (BAD !)

Original Genuine MBBR
▪ Originally developed by Norwegian University of
Science & Technology with M/S Anox Kaldnes of
Norway (Now Veolia)
▪ Every treatment flowsheet requires primary
solids removal – Crux of an MBBR System

Typical issues with MBBRs in India
▪ No primary sedimentation
▪ Primary sewage solids (faeces) cannot be
digested in small MBBRs in less time
▪ Generic plastic carrier media used (Density,
Roughness, Surface Area - not tailor made )
▪ Cannot transfer more Oxygen in less time using
Coarse Bubble Diffusers

MBBR issues (cont’d)
▪ Fine Bubble Diffuser cannot be used due to
media interference (have to use less efficient
coarse bubble diffuser)
▪ Shallow MBBR tanks – less efficient oxygen
transfer
▪ Primary solids (faeces) slip out of MBBR tank
▪ Dead microbes slough off from MBBR tank

MBBR issues (cont’d)
▪ Plate/tube settler cannot be used for Biomass
settling ( This is WTP legacy for chemical sludge)
▪ Sludge/solids adhere to plate/tubes and then
become septic and escape out
▪ Thin slurry from plate settler difficult to dewater
▪ Sludge requires thickening, digestion,
conditioning before dewatering

Plastic Carrier Media for MBBR
developed by
Anox Kaldness

Fig. 1 – What is
actually used in
MBBRs in India
Fig. 2 – What should be used:
Anox Kaldness MBBR media
with microbial coating

The Big Question then?
Question #1
If dead or dying microbes along with some living
microbes on the outside can float out of any
MBBR tank, why can they not do the same in the
settling tank? MBBR Tank Cross Section is much
larger!

The Big Question then?
Question #2
If microbes can attach to plastic media under
turbulent conditions in the MBBR tank, why will
they not attach to the plastic tube/plate in the
secondary settler under calm, quiescent
conditions?

MBBR sludge difficult to handle
▪ Without primary settling, human faeces slip out
of MBBR tank
▪ Solids slipping out of MBBR tank are inherently
difficult to settle, fluffy, light, do not dewater
▪ Need thickening, digestion, conditioning

MBBRs we have seen in recent times
▪ No primary sedimentation
▪ Less than 50% treatment
▪ Filter press never used
▪ Sludge tankered out (ILLEGAL!)

MBBRs we have seen in recent times
▪ Not one MBBR STP working per design
▪ Have converted many MBBRs to EAAS
▪ In Pune-Hinjewadi 220 KLD, and 435 KLD in
Kharadi

EAAS versus MBBR

Lifecycle of microbes

A genuine, well-engineered MBBR

A genuine, well-engineered EAAS

EAAS : SUSPENDED GROWTH REGIME
SLUDGE RECIRCULATION
MBBR : ATTACHED GROWTH REGIME
PRIMARY SEDIMENTATION
NO SLUDGE RECIRCULATION
Key differences EAAS vs MBBR

3 | Sequencing Batch Reactor (SBR)

1
fill wastewater
2
react
3
settle
4
decant
5
idle
waste
sludge
treated
water
aeration
aeration
NO ISSUES WITH TECHNOLOGY
AIMS TO SAVE SPACE & ENERGY
SEQUENCING BATCH REACTOR (SBR)

MOTORISED DECANTERS NEEDED
SLUDGE ENTERS
DECANT WATER
BUT RUDIMENTARY DECANTERS USED
FOULS TERTIARY FILTERS & OPERATOR WILL JUST
BYPASS
DECANT TANK WITH SLUDGE GOES SEPTIC

Motorised
Decanter
required for proper
treatment, but never
used

DECANT
VELOCITY
3000
TIMES
SETTLING
VELOCITY
DECANT ISSUES

AREA AND POWER MYTHS
OVERSIZED COLLECTION TANK FOR SMALL STPS TO
DEAL WITH 8 HOURS OF EFFLUENT
POWER SAVINGS ONLY WITH
TWO SETS OF AIR BLOWERS
AREA & POWER BENEFITS ONLY FOR
LARGE PLANTS BEYOND 10 MLD

INAPPROPRIATE FOR SMALL STPS – RESIDENTIAL,
COMMERCIAL
DISTINCT PEAK FLOWS REQUIRE LARGER
EQUALISATION TANK
DECANT ONLY 33% OF AT VOLUME →LARGER
AERATION TANK NEEDED
ODOUR NUISANCE, MORE ENERGY, LARGER
FOOTPRINT, MORE EQPTS

EAAS versus SBR (qualitative)
Sl. Existing SBR Proposed EAAS Remarks
1
Inappropriate Technology for
res. complexes
Most suitable for Mini, Small STP* See PPT*
2 Large Footprint Smaller footprint
3 High energy Less energy
4 Unscientific decant system* N.A See PPT*
5 Very thin sludge Thick Sludge * Easy to dewater *
6 High Solids carryover * Clear water Filters Stressed *
7 Frequent Backwash filters Less Frequent Operators will bypass
8 Large Collection tank Smaller collection tank Collection tank receiving raw sewage generates max. odour
9 Very High failure rate Almost NIL if designed well * Robust performance 24/7 for decades *
10 3 Nos. Air blower 400 Derate to 275cmh each * Less noise, less vibration *
11 Membrane life Short* Membrane life longer Cyclic air flux rates *
12
Long stabilisation period after
upset
Short recovery period * Less downtime * Loss Minimised
13
Does not deliver quality water
24/7 for in sustained manner
Our first EAAS for ITC – Frazer town still delivering after 30
years
Least life cycle cost
14 N.A.
Converted Several SBR to EAAS with 100 % success* - Latest
500 KLD Phoenix market City
Yet to see a good SBR working to 100 % design capacity*

EAAS versus SBR (quantitative)
Sl. Item Existing Proposed SBR Larger by Remarks
SBR EAAS
1 Footprint, Sqm 315 250 0.26
Could have been less if designed from
scratch
2
Tank
constructed
volume, cum
1200 770
56% (140 % if EAAS
designed from scratch)
Could have been less at 500 cum if
designed from scratch
3
Connected
load
43 KW 42 KW --
Could have been less @ 35 KW if
designed from scratch
4
Energy Used,
Units
526 338 0.56
Energy can be reduced further with new
1.5 HP pump
5
No. of
equipment
10 9 0.11
Could have been less if designed from
Scratch
6 Filters size 1.3m Dia 1.3 m Dia
1.3 dia is undersized for SBR since
filtration hours must be shorter

SLUDGE HANDLING ISSUES
FLAT BOTTOM SBR
THIN EXCESS SLUDGE
CONVENTIONAL EAAS
THICK EXCESS SLUDGE

EAAS IN ACTION
TREATED WATER SAMPLE FROM
BANGALORE’S BIGGEST MALL
AFTER HEAVY SATURDAY NIGHT RUSH
SBR STP UPGRADED TO EAAS BY US IN OCT 2017.
ECOTECH HAS BEEN PERFORMING O&M OF
THIS STP SINCE THEN

4 | Anaerobic Treatment

not suitable for urban
residential & commercial
buildingsanaerobic
treatment
unfit for urban reuse
foul odour
black colouration
black solid particles
3 STPs modified by us
200 KLD, 350 KLD, 500 KLD

6 | Anaerobic Bio-Reactor (ANBR) for
micro STPs

DEWATS of Ludwig Sasse

50 KLD ANBR
HDFC SCHOOL
HADAPSAR

60 KLD ANBR
KUNDALAHALLI
BANGALORE

7 | Electrocoagulation (EADOX)

similar to chemical
coagulation
EADOX
electrocoagulation
removes only solids and
colloids
six STPs studied by us – all defunct
does not remove dissolved organics
unsustainable electrode costs
tertiary filters
overload costs

6 | Membrane Bio-Reactor (MBR)

NO PROBLEM WITH
TECHNOLOGY
MEMBRANE
BIOREACTOR (MBR)
GOOD FUTURE PROSPECTS
RELIABILITY & COST ISSUES:
NOT MATURE FOR SMALL
STPS

MBR Flowsheet

Typical Membrane Cassettes

Key Takeaways
▪ From a long-term perspective, EAAS is still the
best available, practicable, and most appropriate
technology
▪ Anaerobic, CAACO, EADOX are unsuitable
▪ SBR, MBBR inappropriate for micro & mini STPs
▪ MBR is for the future but only when all current
issues are resolved

But isn’t Modern Technology
always better?

METRO (CONVENTIONAL TECHNOLOGY)
MOST APPROPRIATE FOR WITHIN TOKYO
BULLET TRAIN (MODERN TECHNOLOGY)
GREAT FOR TOKYO TO OSAKA (INTER-CITY)

EAAS is the best technology
for mini and small STPs
10-80 KLD Micro
100 – 1000 KLD Mini
1000 – 5000 KLD Small

www.ecotech-india.com EXCELLENCE AND INTEGRITY, SINCE 1986www.ecotech-india.com
THANK YOU
for patiently listening
Dr. Ananth S Kodavasal, Ecotech

Sewage Treatment Eye Openers - Dr. Ananth Kodavasal

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