Dr Sarath Obeysekera

At present, the Sri Lanka Land Development Corporation (SLLRDC) has proposed intercepting polluted stormwater and sewage entering Beira Lake by constructing a perimeter pipeline to collect these discharges and divert them for appropriate treatment or disposal. The proposal also includes desludging and dredging the lake to remove contaminated sediments accumulated over many years.

However, pumping seawater into the lake as a flushing mechanism would be a serious mistake. Rather than solving the problem, it would transport contaminated water and suspended pollutants into the canal network, Colombo Harbour, and the Port City waterfront, causing further environmental degradation. Such a measure should therefore not be considered as a sustainable solution.

 Continuous aeration and oxygenation of Beira Lake is indeed one of the most practical methods for improving water quality, provided the root causes of pollution are also addressed.

My colleague Vamadeevan based in UK  who worked in offshore industry provided this valuable advise

His experience comes from the Cormorant A offshore platform in the North Sea. The platform legs contained stagnant seawater where anaerobic conditions developed, producing highly toxic hydrogen sulphide (H₂S). Before corrective measures were taken, three workers tragically lost their lives due to H₂S exposure. We successfully eliminated the problem by continuously injecting oil-free compressed air into the stagnant water, maintaining dissolved oxygen levels and preventing the formation of hydrogen sulphide.

A similar approach can be adopted for Beira Lake.

The proposed system would include:

● Installation of solar-powered floating aerators or diffused-air aeration units at strategic locations throughout the lake.

● Fine-bubble diffusers placed near the lake bed to circulate the water column and increase dissolved oxygen levels.

● Solar panels mounted on floating platforms or nearby structures to provide continuous, low-cost operation.

● In severely polluted zones, oxygen concentrators or pure oxygen injection could be considered to accelerate recovery, although this is more expensive than air aeration.

● Continuous monitoring of dissolved oxygen, pH, biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammonia, and hydrogen sulphide levels to assess improvements.

Aeration alone, however, will not permanently solve the problem. It must be combined with:

● Preventing untreated sewage and stormwater pollution from entering the lake.

● Removing accumulated organic sludge from the lake bed where necessary.

● Controlling nutrient inputs to reduce algal blooms.

● Restoring aquatic vegetation and improving ecological balance.

The benefits would include:

● Elimination of foul odours caused by hydrogen sulphide.

● Prevention of fish kills.

● Improved water clarity.

● Reduced mosquito breeding in stagnant zones.

● Restoration of Beira Lake as an attractive recreational and tourism asset.

Based on international experience, significant improvements could be achieved within several months, while complete ecological restoration may take one to three years depending on the existing pollution load and the effectiveness of source control.

This approach is technically proven, environmentally friendly, and economical, especially when powered by renewable solar energy. It deserves serious consideration by the Sri Lanka Land Development Corporation (SLLRDC), Urban Development Authority (UDA), Central Environmental Authority (CEA), and the Colombo Municipal Council (CMC) as part of an integrated lake restoration programme.

Regards

Dr Sarath Obeysekera