Conclusion

Poor water quality and frequent foam formation in Varthur Lake highlights of poor environmental status with nutrient enrichments due to the sustained discharge of partially treated or untreated sewage, industrial effluents, agriculture and floriculture run-off (non-point sources), solid waste dumping, etc. Foam with aerosols is being dispersed by winds has been affecting residents in the locality exposing them to health hazards and also traffic congestion. The surfactants are responsible for foam formation in lakes. Foam samples compared to that of Varthur lake water has higher concentrations of chemical contaminants and nutrients. This underscores the need for preventing abuse of P use in detergents manufacturing as the global stock of P is limited and is required for manufacturing medicines and fertilizers (to sustain agricultural productivity). The current work underlines the need of P recovery from the lakes, which will be beneficial for different stakeholders to meet the food demand and to ensure food security. Measures like removal of phosphorus from municipal and industrial wastewater, adopting ways to recover P and ban of phosphorus in detergents and use of sustainable alternatives P to meet the burgeoning demand. There is an urgent need for enacting stringent legislations to regulate phosphate content in detergents and also ban of P based detergents in markets.

Recommendations

Different strategies need to be evolved to minimize eutrophication in water bodies through minimizing P in the environment, which help in saving waterbodies including Varthur lake in India and some of the suggestions are:

      1. Solutions at consumption level:
  • Ban of phosphorus use in the manufacture of detergents and other cleaning agents,
  • Use of non-phosphate based builders like Zeolite A to manufacture detergents,
  • Proper labeling of detergent packages (Ecolabel) including enlisting of all ingredients,
  • awareness among customers to opt for detergents with minimum amount of polluting ingredients,
  • Stringent implementation of ‘polluter pays’ principle,
  • Minimize the use of phosphate fertilizers and use of sewage sludge ash as P source.
  1. Measures to rejuvenate lakes include:
  • Rejuvenation of lakes based on the scientific principles,
  • Dredging of lake removes nutrient rich bottom sediments, it can increase the storage capacity, aid in groundwater recharge, while reducing the internal nutrient loading,
  • Restricting the entry of untreated solid and liquid waste/sewage directly into water bodies,
  • Allowing only treated water to enter the lake through integrated wetlands to minimize the nutrient loadings,
  • Creating constructed wetland of native species to treat partially treated or untreated wastewater,
  • Adopting ways to control agricultural and urban runoff to lakes by creating buffer of riparian vegetation,
  • Installation of aerators at different locations in the lake to enhance the dissolved oxygen levels and recreation services of water bodies,
  • De-weeding at regular intervals to control the profuse growth of macrophytes and subsequent decay resulting to C, N and P inputs to water and sediments,
  • Implementing pollution mitigation measures for reducing phosphorus (and nitrogen) loadings in the environment.
  1. Recommendation for P recovery and reuse:
  • Removal of phosphorus from municipal and industrial wastewater by passing through wastewater treatment plants to recover and reuse P and water,
  • Recovery of phosphorus (and nitrogen) from domestic and industrial wastes to meet agricultural requirements,
  • Extraction of microbial biosurfactants from wastes helps in industries, medicine, food processing industries, agriculture and phytoremediation.

ACKNOWLEDGEMENTS

Authors are grateful to (i) The ENVIS Division, The Ministry of Environment, Forests and Climate Change, Government of India, (ii) Indian Institute of Science and (iii) the Ministry of Science and Technology (DST), GoI for the sustained support to ecological research.