Loktak lake, at Manipur, which is 300 km2 in area, is under stress due to human encroachment, deforestation, raw sewage disposal, agricultural runoff, and siltation. Due to these, many services to the community as well as the lake quality have deteriorated. About 70% of the lake is covered with a floating heterogeneous mass of vegetation, organic debris and soil locally known as Phumdis. These Phumdis are at various stages of decomposition and occur in various sizes and thickness. There has been a growing concern to protect and save this natural resource by the people of Manipur. There is a need to minimize or totally eliminate the organic load that enters the lake in the form of non-point and point source pollutants. The paper discusses a lake restoration plan based on decentralised bioreactor systems. Harvested floating aquatic biomass can be utilized for conversion to fuel and compost in plug flow bioreactors. Plug flow bioreactors, which are suitable for plant biomass, established in a modular manner around the lake perimeter, nutrient harvest could be made into a sustainable practice. Laboratory studies have shown that the key species of phumdis have the right TS and VS ratio of 80-95% and the potential to produce biogas. In addition to removal of plant nutrients, bioreactors can also be used to treat sewage. Bioreactors established in a decentralised manner can treat sewage and arrest organic matter flow into the lakes.

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