Sunday, February 8, 2015

Framework for Identifying Lakes and Solutions for Rejuvenation

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.

Hydrological Criteria
  • Water Availability

  • Lake Size

  • Lake Depth

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
  • Inflow of Domestic/ Industrial waste
  • Dumping of Municipal Solid Waste

Lake to be observed for Eutrophication
Also lake water quality to be monitored with importance to
  • Dissolved Oxygen
  • Biological Oxygen Demand
  • Chemical Oxygen Demand
  • Faecal Coliform
  • pH
Administrative Criteria
  • Public Demand

  • Lake End Use

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:

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
  • Expenditure   

  • Act of O&M   

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
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:
  • Biological Oxygen Demand
  • Chemical Oxygen Demand
  • Total Suspended Solids
  • Nitrates
  • Phosphates
  • Total Faecal Coliform
  • pH
Design Tolerance
  • Input water Quality
  • Input water Quantity   

The ability of the Treatment System to be able to handle wide fluctuations in Input Water Quality and Quantity without -
  • Degradation of treated water quality
  • Breakdown of system (Plants not being able to tolerate chemical load, scaling/ corrosion of plumbing fixtures etc)
Other Factors
  • Past Experience

  • Odor
  • Mosquitoes

  • Stabilization Phase

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?


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