60.
AN STP DESIGN WITH A LITTLE HELP FROM GOOGLE
Regular
followers and readers of my blogs would have no doubt read the piece about an
STP titled “Designing by the Book”. In keeping with advancement of technology, here
is an STP proposed to be designed with a little help from Google.
Many
well wishers have often asked me why I do not respond to RFQ’s ( Request for
Quotation) for STP’s floated by Architects and their Plumbing Consultants. I
present to you below a recent RFQ I came across for a High end apartment
complex of a Grade I Builder sent out by a leading Architect and his Plumbing
consultant. The specifications for the
STP in the RFQ will accept anything from
a SIPANI BADAL three wheeled car to a PORSCHE 911 and everything in between if
I were to borrow the equivalent from the automobile world.
Under
the circumstances, dear reader you will agree that the odds of a snowflake in
hell are infinitely higher than Ecotech ( our Company) landing a contract
through this tender route.
The
following is a true, entirely authentic and unedited extract from an RFQ we
were regaled with from a respected Architectural firm in Bangalore. The only camouflaging I have done is to the
names of the actors in this farce and some figures to protect their identity and their good name (
although I am not entirely sure why).
The camouflaged bits are in red font by me..
“XXXXXXX APARTMENTS”
BY
M/S YYYYYY DEVELOPERS
at BANGALORE
REQUEST FOR QUOTATION ON DESIGN BUILD BASIS FOR
230KLD
SEWAGE TREATMENT PLANT
Date : Does it really matter for this kind of trash ?
Client: M/s. YYYYYYYY ( same
as above)
Architects: ZZZZZZZZ ( In sleep mode)
PHE
Consultants: 000000000.... ( Not enough zeroes in this world
for ranking)
Introduction:
The
proposed project is a residential Apartment located Anywhere in Bangalore comprising of 999 Flats
with common amenities like clubhouse, Gym & swimming pool etc.
The
total water requirement is as mentioned in the below table.
Description
|
Values
|
Units
|
No. of
Flats
|
999
|
Nos.
|
No. of
persons per villa
|
5
|
Nos.
|
Water
Usage per person per day
|
200
|
LPCD
|
Water
used for domestic uses
|
2,21,000
|
LPD
|
Design
factor for additional reserve capacity
|
5%
|
|
Additional
reserve capacity
|
11,050
|
LPD
|
Total
Flow in ltrs/Day
|
2,32,050
|
LPD
|
Total
Design Capacity of Plant
|
230
|
KLD
|
The project is a gated community which has no
access to sewer system hence requires establishing a STP onsite. Further it is
also envisaged to use the reclaimed water for landscaping by spray or drip kind
of irrigation system and if need be for flushing in future.
Plant
design parameters:
Influent to the STP shall be domestic sewage
generated in the Flats and common amenity areas, an approximate characteristics
of the likely expected sewage is given below. The influent sewage parameters
may vary time and season, the plant shall be capable of accommodating organic
loading to the tune of 30% and a hydraulic shock load of 30 to 40% with minor
operational adjustments.
Parameters
|
Inlet (Expected)
|
Outlet (Required)
|
|
Reuse
|
Landscaping
|
||
BOD, ppm
|
250
|
<10
|
<20
|
COD, ppm
|
500
|
<100
|
<200
|
TSS, ppm
|
500
|
<10
|
<20
|
Oil &
Grease, ppm
|
>10
|
<3
|
<5
|
pH
|
6.5 - 8.5
|
6.0 - 9.0
|
6.0-9.0
|
E-Coli
|
NA
|
NIL
|
NIL
|
Residual
chlorine, PPM
|
-
|
<1 mg/lt
|
1 mg/lt
|
The expected outlet water requirements shall be
met by the plant while operating in the range up to the designed capacity. The
output performance shall not vary by more than 20% under shock loads.
The output is to be treated as 50% for reuse and
50% for landscaping quality water generation.
Sewage
treatment processes:
The vendor may select any process as per their
area of expertise / proprietary design. The vendor shall submit a detailed
process description and flow sheet considering the site conditions.
The vendor may also choose from the list of
available methods for treatment or propose any other alternative.
Biological: Aerobic
- Extended aeration
- SBR (Sequential Batch Reactor)
- FAB (Fluidized Aerobic bed)
- SAFF (Suspended Aeration Fixed Film)
- FBBR (Fluidized bed Bio Reactor)
- RBC (Rotating Biological Contactor)
- MBR (Membrane Bio Reactor)
Biological
Anaerobic systems
- UASB
- Septic tank
Physical
/ Chemical:
- Enzyme activated treatment
Electrical:
- Electrolysis
The sludge generated in the STP shall be suitably
treated to ensue that it can be properly disposed along with municipal solid
waste. Sludge drying beds are not permitted. Sludge volume reduction by aerobic
/ anaerobic digestion in small plants are not viable hence the same may be
considered for plants above 250 kld.
The vendor shall also furnish detailed design
calculations along with the offer which shall be scrutinized by the PHE
consultants. In the event of the vendor not willing to share the design
calculations they shall guarantee the performance of the system by a Bank
Guarantee of a value as per the client discretion and shall be decided based on
the vendors reputation and the performance of the existing plants.
NOW SOME PERTINENT
OBSERVATIONS AND QUESTIONS FROM ASK ( that is me : of “ When
Kodavasal talks, people listen” fame)
(
Pls. note I have overlooked and condoned some minor lapses in this document
which may have crept in due to a mindless cut and paste job done by the Consultant
: Ex : “No. of persons per villa”. Is
this not an apartment ?)
1.
Since when has Karnataka State Pollution Control Board ( KSPCB) relaxed its Rules and
left toilet use option of treated water to the discretion of the plumbing consultant ?
2.
What can be the seasonal variation in the characteristics of domestic sewage
from an apartment complex ? Due to
variations in Temperature ? The monsoons ? Seasonal changes in dietary pattern of the residents
?
3.
Why must the STP accommodate and handle only 30 % of the organic load ? Why not
100 % ? And where does one offload the balance 70 % ?
4.
30 – 40 % of excess Shock loads are better handled by proper Design and
Engineering of the STP rather than by
twiddling with some unspecified and abstruse “minor operational adjustments”
5.
Obviously the Consultant is not wise to the KSPCB “ Urban Reuse Standards” for
quality of treated water enforced now for more than 6 years, and has prescribed
his own set of standards.
6.
I fail to understand the grammar of the consultant’s 50 % for Reuse and 50 %
for landscaping jargon. In Technical papers
and documents one expects exactitude and precision and not vague descriptions.
7.
About the wide choice of STP technologies left to the bidder, less said the
better. One wonders however at these
possibilities and has these nagging questions :
- Had there been a more powerful search engine, say Google +++, would the list have been longer ?
-
Does the Consultant possess adequate knowledge, competence, skill and expertise
to assess the pros and cons of the various technologies that may be proposed by
sundry bidders. And if the answer is
YES, why has he not done this exercise
and homework himself and Zeroed in on the one most Optimal and Practicable
technology option for an STP of this size in this setting ?
-
Under the Biological aerobic options, what is the difference between an FAB and
FBBR ? Am I missing some key but obscure
differences in Design and engineering between the two competing technologies ?
-
A septic tank option for a 230 KLD STP ?????
…
and so on. Professional etiquette and decency prevents me from completely disrobing the consultant.
UPSHOT OF THE STORY
My
Company steadfastly refuses to participate in such open tenders for precisely the
above reasons. What chance does a good
STP with proper scientific design and engineering features have against these
odds and at the hands of an incompetent consultant ?
Dr.
Ananth S Kodavasal October
04, 2015
Director
– Ecotech Engg. Consultancy Pvt. Ltd.
Bangalore
560 066
Mob
: 98450-62033
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