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Section II

Floating Wetlands for Management of Algal Washout from Waste Stabilization Pond Effluent: Case Study at Hikkaduwa Waste Stabilization Ponds

Authors:

Sujatha Kalubowila ,

Water Supply & Drainage Board., LK
About Sujatha
Civil Engineer,
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Mahesh Jayaweera,

University of Moratuwa, LK
About Mahesh
Senior Lecture, Department of Civil Engineering
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Chandrika M. Nanayakkara,

University of Colombo, LK
About Chandrika
Senior Lecturer, Department of Plant Sciences,
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Dhanesh N. De S. Gunatilleke

National Water Supply & Drainage Board,, LK
About Dhanesh
Specialist (Sewerage Designs)
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Abstract

Waste stabilization ponds are advantageous waste water treatment processes, especially for developing countries. Nevertheless, in spite of the well known advantages of the implementation of the stabilization pond system, the effluent of this system has a significant amount of algae and high nutrients. Disposing this effluent with high contents algae and nutrients to the receiving waters can hinder the water reuse for a wide range of different applications, it is essential to look for a post treatment method that can provide considerable removal of algae, nutrients and organic matter from the effluent and at the same time, assure that the treatment system as a whole will maintain the advantages of the pond treatment processes. In this context, this research study was planned and intended to introduce a floating treatment wetland in which water hyacinth plants (Eichhornia crassipes) were used as macrophyte or vegetation in the part of the maturation pond area to control algae and nutrients in the effluent.

With the application of the floating wetland the removal efficiencies were found to have increased in the maturation pond in terms of BOD and COD from 13.3% to 62.9% and 13.6% to 57.5%, respectively. In the case of TP and TN there were no significant reductions achieved prior to the establishment of the wetland but, reductions of 74.8% for TP and 55.8% for TN were achieved since the establishment of floating wetland. It was also possible to achieve a reduction of algal cell densities of 900 units/ml to zero unit/ml for the algal species of Spirulina and for Oscillatoria, the reduction was from 290 units/ml to 0 units/ml. In case of Chlorella and Pandorina, density reductions were 830,000 units/ml to 68,000 units/ml and 4300 units/ml to 280 units/ml respectively. Accordingly, the reduction efficiencies for Spirulina, Oscilltoria, Chlorella and Pandorina were reported to be improved from 31.8% to 100% and 4.5% to 100%, 34.2% to 91.8% and 42.2% to 93.5%, respectively. Application of this research can therefore be possible to polish waste stabilization pond effluent economically in order to re-use for various beneficial uses except potable use.

DOI: http://dx.doi.org/10.4038/engineer.v46i4.6811

ENGINEER, Vol. 46, No.04, pp. 63-74, 2013

How to Cite: Kalubowila, S. et al., (2013). Floating Wetlands for Management of Algal Washout from Waste Stabilization Pond Effluent: Case Study at Hikkaduwa Waste Stabilization Ponds. Engineer: Journal of the Institution of Engineers, Sri Lanka. 46(4), pp.63–74. DOI: http://doi.org/10.4038/engineer.v46i4.6811
Published on 21 Oct 2013.
Peer Reviewed

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