One
of the main issues confronting lakes in Bangalore is to do with the
water inflow - both in terms of quality and quantity (current as well as
anticipated in the future). While the main channels bring rainwater to
these lakes they also carry with them significant amounts of solid waste
and sewage. Over a period of time untreated sewage leads to the
eutrophication of the lakes. The changes in the topography of the lake
catchments (due to urban development) has also led to significant
reduction in the runoff from upstream lakes thereby rendering the lakes
dry.
With
an intent to explore bio remediation solutions to treat the incoming
water before it enters the lake, we try to understand the parameters
important in identifying a lake for restoration and then coming up with a
suitable framework to evaluate the multiple technologies to facilitate
bio remediation.
The following graphic illustrates the different factors that have an impact on various aspects of the lake
Since
a diverse set of factors are at play here, it is important to have a
framework in identifying the lakes which are in dire need for immediate
action and subsequently the most suitable technological and regulatory
solution for rejuvenating the lake.
Identification of Lakes:
The Ministry of Environment and Forests has set guidelines for Lake Conservation.
This could be a reference point for framing the parameters to help identify the lakes for immediate conservation action.
Criteria
|
Description
|
Hydrological Criteria
|
A perennial lake can be given more weightage than a seasonal one
Larger and deeper lakes to have priority. For instance, greater than 10 hectares in surface area and 3 meters in depth
|
Scientific Criteria
|
Lake to be observed for Eutrophication
Also lake water quality to be monitored with importance to
|
Administrative Criteria
|
High demand from a Public forum/ Local Stakeholders towards lake conservation
Lake serves domestic uses, recreation, bio diversity hotspot
|
Technology Evaluation:
The
rejuvenated lakes are in all probability going to be managed by a non
governmental body and hence apart from the efficacy of the treatment
itself, the ease and cost effective maintenance aspect will have extreme
importance.
Some of the factors (which are open to further deliberation) are listed below:
Criteria
|
Description
|
Capital Expenditure
|
Total
cost of commissioning of the Treatment System (Includes Cost of civil
construction and Installation of Electromechanical components/ Plumbing/
Vegetation etc
|
Operation and Maintenance
|
Yearly
recurring cost for the entire lifecycle of the Treatment System
(Includes cost of Consumables, Electricity, Manpower, Annual Repair and
anything else as applicable)
The ease of operation and maintenance of the system - which is determined by -
- the requirement of skilled manpower
for continuous manning of the system
- duration and frequency of downtime
for maintenance/ repair
- Frequency and quantum of Sludge Disposal
- need for replacement of components
- need for vendor support
|
Footprint
|
The land area that is required for commissioning the system.
|
Treatment Efficiency
|
The ability of the system to treat the low quality sewage inflow. Some of the quality parameters that need to be dealt with:
|
Design Tolerance
|
The ability of the Treatment System to be able to handle wide fluctuations in Input Water Quality and Quantity without -
|
Other Factors
|
Does the vendor have prior experience in commissioning such projects?
Will the system emanate foul odor?
Will the system be a breeding ground for mosquitoes?
Does the system require an stabilization phase? If yes, what is the duration?
|
References:
http://cpcb.nic.in/upload/NewItems/NewItem_116_Guidelinesof%20waterqualitymonitoring_31.07.08.pdf
http://www.moef.nic.in/sites/default/files/nlcp/NLCP_guideline.pdf
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