BIOME, WIPRO, MAPSAS and other lakes communities have come together to try and understand how bio-remediation technologies can be applied to deal with the sewage inflow into some of the rejuvenated/to be rejuvenated lakes around Sarjapura Road.
Hence on 25th November the first meeting was arranged to discuss bioremediation methods, to bring together the community working on different lakes in Bangalore on a same platform and decide on the further agenda for 15 lakes selected for the project was the objective of the meeting.
Following are the key points/deliberations happened during the meeting:
A. The lakes that have been narrowed down for this project are:
B. An initial discussion was led by Priya from MAPSAS who explained about the links between the lakes through kaluves and hence the importance of controlling the sewage entering in the lakes.
C. Mr. Vishwanath explained about viewing lakes as an ecosystem with space for biodiversity, treatment, recharge zones, etc. He cited example of Jakkur lake wherein a treated sewage water from BBMP maintained STP goes into a constructed wetland and then into the lake. He suggested that things that can be studied for lake should include percolation study, water balance, nitrate and phosphate removal, biodiversity, etc.
D. Some legal issues were also discussed:
- Areas without BWSSB underground drainage network are not allowed to dispose of their sewage either with or without treatment. Zero discharge i.e. 100% reuse of wastewater generated within the premises
- Areas with BWSSB underground drainage network are allowed to dispose of their sewage with at least secondary treatment
- The discharge standards for sewage treated water are close to drinking water standards
E. An important part of the meeting was presentations by vendors implementing bio-remediation technologies. Presentations were made by Visionearthcare on soil biotechnology (SBT), Hydrocreatives on Phytorid, and CDD on Decentralized wastewater treatment system (DEWATS).
Soil biotechnology (SBT): Have done for Herohalli Lake in Bangalore.
Their detailed presentation can be found http://www.slideshare.net/biomeshubha/sbt-for-lakes-bioremediation
a. No external aeration is required as the different porous layers in the medium/bed help in aeration.
b. One time media installation. No need to change soil media frequently
c. No sludge formation
d. Space: 1 sq.m/KLD
e. No foul odor
f. Have established 65 plants across India. Also experience in designing for lakes
g. Not designed for removal of nitrates and phosphates specifically yet it works in their removal
h. Herohalli plant details: Design capacity-1.4 MLD, Area- 1650 sq. m, cost- 3 crores, power consumption-125 units/day
Their detailed presentation can be found here: http://www.slideshare.net/biomeshubha/phytorid-for-bioremediation-of-lakes
a. Plants have been designed particularly for BOD reduction and some amount of COD reduction also happens
b. Power Cost: Rs. 1/KL
c. Sedimentation tank: needs to be cleaned once in a year
d. Issues with phytorid bed: Plants grow over a period and hence need to be cut as suited by the community. The disposal of cut plants is similar to other plants.
e. No foul odor as water is not seen from above, no exposure
f. Bacterial addition: once in a lifetime of the plant
g. Space: for sedimentation tank/underground primary settling tank- 0.2/0.3 sq.m/KL and for phytorid bed- 0.9 sq.m/kl
h. Cost per MLD: 1.3 crores
i. Sensor based system
j. Capacity range: 3 KLD -1.5 MLD
k. The system needs to be placed in open as it needs sunlight for the plants to grow
l. Water load fluctuation: the plants can survive without water (especially this may happen in dry season) for two months. Even if little amount of water is available, the plants can survive on fewer nutrients.
m. If slope/gradient is available then no pumping is required
Decentralized wastewater treatment system (DEWATS):
Their detailed presentation is available here: http://www.slideshare.net/biomeshubha/how-dewats-can-be-implemented-to-bioremediate-lakes
a. Shared case study of Bandhwa Talab in Raipur, Chattisgarh.
b. This system based on phytotechnology which uses Canna indica plant which has shallow fibrous root system
c. No color, odor and pathogens after passing the water through the bed of plant
d. Based on requirement design can be customized
e. The flow should be checked daily, sludge removal from the settling tank (primary treatment) is also required
f. Treats only organic waste, domestic sewage
g. Cost varies with capacity
F. Further deliberations and studies are needed on:
1. Assuming that some amount of sewage already exists within the lakes, which of the systems would be useful?
2. It is essential to conduct water balance study for every lake. Water balance means, calculating percentage of water coming, sewage coming, water percolating, evaporation, etc.
3. Understanding the suitability of the system based on cost, maintenance, power consumption and mostly its ability to handle water load fluctuation, etc.
Based on primary data collection from each of the implemented technologies, water balance for some of the lakes and finally deliberations on bio-remediation technologies would help in seeking most suitable method to tackle the issue at hand.
We would like to thank the participants:
Vendors: Sharan Kumar from Visionearthcare for SBT, Mr. Himanshu from Hydrocreatives for Phytorid, Mr. Andrew Jacobs from CDD for DEWATS
Devarabisanahalli lake/Adarsh residents
Halanayakanahalli lake group
Priya representing MAPSAS
Students from Christ University