There is a ray of hope for hundreds of urban waterbodies, victims of urbanisation and industrial pollution. A combination of bio-ozolyte treatment process and bio-remediation adopted by the State government to save the Ooty Lake, can be used to recover these polluted water bodies.

According to officials, phosphorus and nitrogen are responsible for the rapid growth of water hyacinth, that has invaded many water bodies. The bio-processes will increase the dissolved oxygen (DO), by bringing down the biochemical oxygen demand (BOD) and chemical oxygen demand (COD). DO improves quality of water and replenishes life in water bodies.

On Thursday, Chief Minister Jayalalithaa announced a Rs. 50 crore package for cleaning lakes in the State. But experts point out that the project could achieve success only by preventing people from dumping solid waste and debris into the water bodies.

While bio-remediation comes in handy for treating polluted lake water, bio-ozolyte process is used to treat waste water before being let into the water bodies.

“Since Tamil Nadu has utilized more than 96 per cent of surface water, there is no scope for new reservoirs of over one TMC [thousand million cubic feet] capacity to be built. For storing 1 TMC of rain water, the present cost is Rs. 200 crore,” said R. Elanogvan, Executive Engineer of the Public Works Department.

If urban waste water was treated, around 100 TMC water could be harvested. The total cost of treatment would be between Rs. 9,000 crore and 10,000 crore, which would be half the cost of a new reservoir construction, given the same capacity.

Mr. Elangovan, who was involved in cleaning the Ooty Lake through bio-remediation and bio-ozolyte method, said, “The advantage with the bio-ozolyte process is that it does not require standard design pattern and is flexible to club with any other technology.” This could be accommodated according to the site condition with power or without power, he noted.

One of the biological methods is using microbes (diatoms) available in powder, liquid and Eco Bio Blocks (EBB) infused with special natural micro organisms. EBB blocks are made of volcanic rock zeolite and cement infused with bacteria.

“We may need 250 to 500 blocks per 1 MLD [million litres a day] depending on the condition of the water,” he said.

An Indian technology of using microbes to inoculate the waste water treatment plant is also used. Microbes in the form of powder - 200 gram per 1 MLD - is added in the collection tank for stabilization process. Indian made powder (Bio clean or Nulagi) will be used for starting the process. This will reduce the sludge by degrading the organic matter.

Mr. Elangovan said the diatom would increase the plankton and zooplankton population, a stable diet for fishes. This process would also substantially increase the dissolved oxygen in water. Though water hyacinth was a ravaging weed, its presence ensured that water did not reek. But it would not allow penetration of sun light.

“This plant can be removed and used for generating bio-gas. We can harvest it in every three months,” he said.