water management at rainbow drive: in buildotech
TRANSCRIPT
62 l BUILDOTECH l May ’16
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With Bangalore water supply and sewerage board (BWSSB) failing to ‘cope up’ with the water demand of the growing city, lakhs of bore wells and tankers extracting water from the groundwater have led to over exploitation of the groundwater. However, there have been efforts from communities and individuals to sustainably manage the water within their fence. This is one such story of a private gated community in Bangalore
Situated in the south east of the city, the Rainbow Drive (RBD) is a private gated residential layout with an area of 34-acre and total of about 360
housing plots. As of now, 260 plots are
occupied. The layout gets absolutely no
formal water supply from BWSSB and is
completely dependent on its bore wells
as a water source. The site developer had
provided initial infrastructure including:
• Storm water drain network to carry
storm water out of the layout
• Six community yielding bore wells
• Two overhead tanks with piped
water supply connections to all plots
• Piped sewage connection to each
plot
• Two Sewage treatment plants
The plot owners’ associat ion
(POA) that took over the ownership
in 2004 manages the water supply
and sanitation. During the same time,
urbanization started to happen in the
neighborhood, making the POA realize
the intensity of water problems in the
near future.
The members observed that a lot
of reinvestment as well as measures
were needed to build the new water
and sanitation infrastructure and
upgrade the existing one. Therefore,
they did a complete research of the
water issues in the layout, collected
data about consumption, demand,
quantum of waste water generated
daily, issues of water quality, etc. to
get an understanding of the problems.
POA initiated some interventions like
creating a tariff policy, banning of bore
well water use for construction and
forbidding digging individual bore wells.
Water Management Initiatives:The result of this study was:
• Hydrogeologists were called for
who suggested that this space could
support 10-15 bore wells.
• The community bore wells left by
the builder had dried up and water
shortage was being experienced
• Houses had consumption meters at
the household level. And the tariff
was charged at flat Rs. 6/KL. The
study showed that this was minimal
Case Study:
Integrated urban water management
Benchmark of consumption No of households Percentage of households
Up to 135 LPCD 32 14%
Up to 246 LPCD (layout average) 130 59%
Greater than 246 LPCD 89 40%
Some houses were consuming more water than others
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and provided no incentive for the household to save water
• The billing cycle was two months which resulted in accumulated issues of faulty meters and/or demand.
• The most important result was that, the cost of water in the tariff scheme did not capture the cost required for treating the wastewater.
Sewage treatment plant was not adequate and the output water quality was not good enough.
During heavy rains upstream storm waters entered into the layout and caused significant flash flooding at the low end of the layout. This got mixed with the stagnating sewage and caused a lot of problems.
Lowering the demand From the study, it was evident
that 40% of the layout consumed more than the layout average. Two scenarios were looked at to address this. To keep the demand same @246 LPCD or reducing the demand to 150 LPCD. This required investing in rainwater harvesting (RWH) and recharge and gardening making use of treated wastewater. Also, a water
balance analysis was done considering
the future full occupancy.
The ana lys i s showed that
reducing the demand @150 LPCD
with all other water conservation
measures was most beneficial. The
analysis also showed that if effectively
implemented, the net recharge
would be more than the overall
withdrawal. Hence, it was made
mandatory for individual houses
to practice rainwater harvesting as
well as recharge. In addition, POA
invested in groundwater recharge in
the common areas.
Changing Pricing Policy
The bi-monthly bil l ing cycle
was changed to monthly so that
households would come to know
about the faulty meters soon and
fixing could be done immediately.
This also gave an opportunity to
the home owners to be aware of
their consumption with time for
adjustment. The POA moved from
flat rate @6/KL to a block tariff
system corresponding to the actual
production cost of the water. The first
tariff was developed according to the
new slabs:
The plot owners’ association of the Rainbow Drive engaged with Biome Environmental Solutions Pvt. Ltd. to develop rainwater harvesting strategies. Subsequently, with the support of Arghyam Foundation, they engaged in a monitoring exercise in the layout over approximately a year to understand the issues in more detail and evolve relevant solutions.
Consumption slab Tariff
Slab 1 (0-10KL) Rs. 10
Slab 2 (10-20KL) Rs. 15
Slab 3 (20-30KL) Rs. 25
Slab 4 (30-40KL) Rs. 40
Slab 5 (>40KL) Rs. 60
Wells in common stormwater drain invested by household (Individual investment)
Wells in common stormwater drain invested by POA (Collective investment)
Wells in individual house (individual investment)
Borewell water was being used for construction purposes
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In addition, homes investing in RWH and recharge were given a discount of `100. The tariff was revised in 2008, 2012, and 2014 is the latest revision to drive the residents towards recharge and control demand.
The current tariff is:
The water got expensive, almost equal to the tanker water costs at the highest slabs of consumption. The benchmark for what the “highest slab” has changed from 60 KL & above to 25 KL & above
Ban on private borewells and borewell water usage for construction
T h e r e c o m m e n d a t i o n o f hydrogeologist that 10-15 bore wells would be maximum that the layout can sustain led to discussions about
banning of private bore wells within the layout. Community bore well water remained available for domestic purposes. For construction purposes, water had to be sourced from outside at market rates.
Waste water infrastructure investment
The existing STP infrastructure was inadequate and was not treating the water effectively. The result that STP pumping was the single most contributor of the electricity bill, led to a search for new technology which would be of less maintenance and requires less energy. After searching many options, the POA narrowed down to Soil Biotechnology (SBT), and Phytorid. In October 2014, the Phytorid system of 250 KLD capacity became operational. The system receives ~100-150 KLD sewage daily and the treated wastewater is being used for gardening in common areas, gardening in the houses, and a small quantity of treated water is sold to a farmer in the adjacent plot.
Mandatory rainwater harvesting and recharge
Rea l i z i ng tha t the l a you t i s comp l e t e l y dependen t on groundwater, groundwater recharge was critical. RWH and recharge was made mandatory by the POA. As of now, there are in total 250 recharge wells in the individual houses as well as in the common areas (Storm water drain and open spaces).
Consumption slab Tariff
First 15,000 litres `30 per KL
15KL to 25 KL `50 per KL
Above 25 KL `120 per KL
Below graph shows the demand management timeline over a period:
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Impacts of the interventionsIncreased compliance with RWH
There seem to exist a correlation with tariff rates and the compliance with RWH and groundwater recharge. Moreover, the informed citizenry made aware about RWH and its importance led
the initiative. This probably is the highest
density of recharge wells in urban India.
Decreased per capita demand on community water supply
Though the occupancy has increased
over a period, total demand has come down
from 246 LPCD to 150 LPCD.
Increased savings from the STP
The Phytorid technology requires
minimal electricity as compared to the other
conventional sewage treatment plants. The
extent of reuse of this waste water for
gardening and consequent reduction in use
of fresh water for gardening is still being
studied. The POA is now closely monitoring
the quality of treated waste water – so
far it has conformed to KSPCB’s discharge
norms.
Going ahead:The reforms at Rainbow Drive started
in 2004 by efforts of conscious residents of
the layout. The interventions that started
with 20 recharge wells now have reached
to 250. The relationship between shallow
groundwater recharge and the bore well
yields (if any) needs more exploration but,
the demand management with recharge
compliance has worked till now.
Courtesy: Biome Environmental Trust & Rainbow
Drive POA