Recycling Treatment Plants


# Vrishabhavathy Valley


a) V. Valley - T.T.P

The Board has commissioned during may 2003 a 60 MLD T.T.Plant at an estimated cost
of Rs.35 Crores. Funds required for implementing this project is arranged
through KUIDFC/HUDCO under Megacity scheme and under the Indo french protocol.

Recycled water is proposed to be supplied to M/s Karnataka Power Corporation
Limited and M/s Pulikeshi Power Corporation for their power generation plants to
be located at Bidadi & Kumbalgod industrial areas repectively.

Plant Description

The existing Vrishabhavathy Valley waste water treatment plant can (located on
Mysore Road), treat an average of 180 MLD (terminal capacity of more than 60 MLD)
of sewerage.

Part of the treated flow is the sewage drained through Vrishabhavathy Valley. The
sewage from KM Halli is also lifted and conveyed to the plant for final disposal.

Conventional Bio-filter process has been adopted for secondary treatment.
Mechanical screens (coarse and fine), Detritor, Primary clarifiers, Bio-filters,
Secondary clarifiers, Primary and Secondary sludge, Re-circulation pump house,
Digestors and Drying beds are provided.

The plant is designed to produce an effluent having BOD of not more than 20 mg per
litre and suspended solids not exceeding 30 mg per litre. The effluent is discharged
into the V-Valley at RL794.00 and is in accordance with IS4764-1973 standards.

Salient Features of V Valley

Vrishabhavathy valley Tertiary Treatment plant- water for non potable purposes.

Bangalore city has limited raw water sources to meet its ever growing population. City
is almost completely depending on river Cauvery , located more than 100 kms., away
from the city for its requirements. This involves an exorbitantly high energy costs
for pumping of water. Recycling and reuse of wastewater becomes absolutely
imperative. Extremely finite source of raw water prompted BWSSB to undertake a
major step hitherto unseen in our country, towards recycling of wastewater on such
a mega scale.

Of the two tertiary treatment plants(TTPs) in Bangalore one at Yelahanka and another
at v.valley have been planned and executed by BWSSB, the 60 million litre per day
(MLD) capacity plant at v.valley is 2nd in the row and biggiest in the country both in
size and technology.

Tertiary Treatment Process

The V.Valley tertiary plant has been designed and constructed by M/s ONDEO
Degremont , at a total cost of Rs.35 Crores. The project is funded under
Indo-French protocol and with assistance from HUDCO. The secondary effulent
converge from the existing 183 MLD capacity plant is being treated here to tertirary
levels by using a combination of biological and physio-chemical treatment . the
treatment chain in this plant consists of trickling filter, DENSADEG high rate clarifier ,
FLOPAC biological reactor and chlorine based disinfection.

The secondary treated sewage is fed into an aerobic attached growth trickling filter,
which is the first stage of tertiary treatment. The wastewater flows through a plastic
cross flow type media , where attached active biomass feed on organic pollutants.
The downward flowing wastewater carries with it excess biomass, which develop as
a result of bacterial activity. The output from the trickling filter is fed into the high
rate clarifier DENSADEG unit and passes through a flash mixer before entering
the clarification unit. The DENSADEG unit combines two facilities in a single
tank-separation of floc from water using lamellar separators and counter current flow
to separate water from sludge and thickening of sludge that settles at the bottom
through a picket fence equipped scrapper . Clarified water from DENSADEG flows
into biological filtration unit FLOPAC. Settled sludge is continuously recycled back
to flocculation reactor and excess sludge is sent to dewatering.

The FLOPAC is a downward flow aerobic biological filter and is a combination of
pre-aeration unit and biological filtration unit with sand as filter media. The
pre-aeration tank is provided with an air pipe network with air diffusers for aeration
of water and diffuser network is supplied with required quantity of air through Air Blowers.

The oxygen saturated water from the pre-aeration tank flows trough a channel to biological filter and is fed from the top . as the water flow through the media
fine, suspended solids are filtered out and active biomass in the presence of
dissolved oxygen in water degrades the organic pollutant. Filtered water from the filter
is collected in a common treated water channel, which leads into filter water
collection tank. The overflow from filtered wash water collection tank flows into
dis-infection chamber.The treated water from FLOPAC is finally treated with
chlorine solution in the dis infection chamber . The chamber is provided with baffling ,
to increase the length of travel of water before it reaches water collection tank, and also
to have effective dis-infection action of chlorine.

Treatment of Sludge:

The excess sludge from thickerner section of DENSADEG is pumped for
mechanical dewatering . The dewatering machine is a continuous belt filter type
super press. The dewatered sludge undergoes sludge conditioning before final disposal.

Quality of influent Wastewater and tertiary treated wastewater characteristics.

Parameter	Raw Wastewater	Treated wastewater
BOD5	380 mg/l	<5mg/l
COD	800 mg/l
Suspended solids	480 mg/l	<5mg/l
Turbidity		<2 NTU
pH	6.8- 7.5	7-8
Fecal coliform		<25 MPN / 100ml
Colifrom index		2.2-23 MPN / 100 ml.

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