Use of Constructed Wetlands to Reduce Pollution of Surface Waters by Tea Factory Effluent in Nandi Hills Tea Estates in Kenya
DOI:
https://doi.org/10.2200/aerj.v2i1.110Keywords:
Constructed Wetlands, Tea Factory Effluent, Water Quality, Nutrients,, Heavy Metals, water PollutionAbstract
The study aimed at investigating the efficiency of treating tea factory effluent using constructed wetlands in Nandi Hills Tea Estates, Kenya. Total Suspended Solids (TSS), Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) were determined in tea factory effluent. Dissolved nitrates and phosphates were analyzed in stream water samples using standard methods for sampling and analysis. Results showed that untreated tea factory effluent had high levels of COD (6732 to 14800 mg/L) and TSS (1078 to 3400 mg/L), and a moderate level of BOD (44 to 53 mg/L). These values reduced after treatment with more than 95% of TSS and COD and 80% of BOD removed by the constructed wetlands. Removal efficiencies for the heavy metals; Cd, Pb, Cu and Zn, were 7.1%, 80.0%, 95.1% and 100% respectively. The high concentration of nitrates (6.6 ± 2.1 mg/L) in a stream receiving factory effluent, compared to the receiving river (0.6 ± 0.7 mg/L) showed that some improvements were needed on the wetlands. The study recommends that sludge flushed out of the sedimentation basin should be directed to a sand bed for filtration and drying and the effluent passed on to the surface cells where more bio-degradation would take place. A mechanism to remove colour from the effluent should also be explored to reduce the turbidity of receiving waters.
References
APHA, AWWA, & WEF (1992). “Standard Methods for the Examination of Water and Waste Water”, 18th Edition. American Public Health Association (APHA), American Water Works Association (AWWA) and Water Environment Federation (WEF), Washington, D.C. Bartram, J.
Ballace, R. (eds), (1996). “Water Quality Monitoring; A Guide to the Design and Implementation of Freshwater Quality Studies and Monitoring Programmes”. UNEP, WHO and Chapman and Hall, London, 383 p.
Brix, H. (1993). Waste Water Treatment in Constructed Wetlands: System Design, Removal Processes and Treatment Performance In: Moshiri, G.A. (Ed.) “Constructed Wetlands for Water Quality Improvement”, Lewis Pub, Boca Raton.
UNESCO, WHO & UNEP (1992). “Water Quality Assessments: A guide to the Use of Biota, Sediments and Water in Environmental Monitoring”. Chapman and Hall, London.
Eastern Produce (K) Ltd. Unpublished Technical Department Records
Follett, R. F., & Walker, D. J. (1989). Ground Water Quality Concerns about Nitrogen. In: Follet, R. F. (Ed). “Nitrogen Management and Ground Water Protection”. Elsevier: Amsterdam.
Fuchs, H. J. (1989). “Tea Environments and Yield in Sri Lanka”. Morgranf Scientific pub.
Haberl, R., Grego, S., Langergraber, G., Kadlec, R.H., Cicalini, A., Dias, S. M., Novais, J. M., Aubert, S., Gerth, A., Thomas, H. and Hebner, A., (2003). “Constructed Wetlands for the Treatment of Organic Pollutants”. Review Article with Case Studies. JSS – J Soils & Sediments 3 (2) 109 – 124.
Ecomed publishers, Landsberg. Accessed at Hach Company (1989). “Hach Water Analysis Handbook”. Hach Company, Loveland.
Khisa, K. (1997). “The Performance of a Constructed Wetland for Treating Wastewaters at Carnivore Restaurant Nairobi, Kenya”.
M.Phil Thesis, Moi University, Kenya. Government of Kenya (2001).
“Nandi District Development Plan, 2002 – 2008”. Ministry of Finance and Planning.
Liao, S., & Chang, W. (2004). Heavy Metal Phytoremediation by Water Hyacinth at Constructed Wetlands in Taiwan. J. Aquat. Plant Manage. 42: 60-68. http://www.apms.org/japm/vol42/v42p60.pdf
Mant, C., Costa, S., Williams, J., & Tambourgi, E. (2005). “Studies of Removal of Chromium by Model Constructed Wetland.” Brazilian Journal of Chemical Engineering. Vol. 22, No. 03, pp. 381 – 387. http://www.scielo.br/pdf/bjce/v22n3/25934.pdf
Masi, F. & Martinuzzi, N. (2007). “Constructed wetlands for the Mediterranean countries: hybrid systems for water reuse and sustainable sanitation”. Elsevier. Desalination 215 (2007) 44–55. http://www.iridra.eu/pubblicazioni/CWs%20in%20the%20Mediterranean%20countries.pdf
Momanyi, T. M. (2002). “Studies on Selected Water Quality Parameters and Heavy Metals in Pulp and Paper Effluents in Relation to the Pollution of the River Nzoia at Webuye”.
M. Phil Thesis, Moi University, Kenya. National Environment Management Authority (2006). “Environmental Management and Co-ordination (Water Quality) Regulations”. Legal Notice No. 120 of 2006. http://www.nema.go.ke/images/stories/pdfs/water_quality_regulations.pdf
Osorio, A. C. (2006). “Influence of the Characteristics of Organic Matter on the Efficiency of Horizontal Subsurface-flow Constructed wetlands”.
Thesis presented as partial requirement to obtain the title of doctor (Ph D) at the Technical University of Catalonia. Castelldefels. http://www.tesisenxarxa.net/TESIS_UPC/AVAILABLE/TDX-0222107-124705//01Aco01de01.pdf
Othieno, C. O. (1992). Soils. In: Willson, K.C. & Clifford, M.N. (Eds) “Tea Cultivation to Consumption”. Chapman and Hall, London.
U.S. Environmental Protection Agency (1998). “Design Manual: Constructed Wetlands and Aquatic Plant Systems for Municipal Water Treatment.” Office of Research and Development, EPA/625/1-88/022. http://www.hydrik.com/downloads/WetlandsDesign_Hydrik.pdf U.S.
Environmental Protection Agency (2000). “Manual. Constructed Wetlands Treatment of Municipal Wastewaters”. Office of Research and Development, EPA/625/R-99/010. Accessed at http://www.epa.gov/nrmrl/pubs/625r99010/625r99010.pdf
Water Research Commission (2005). “Ground Water Pollution: When Water Turns Deadly - Investigating Nitrate in SA Groundwater”. The Water Wheel, p24-27. http://www.wrc.org.za/archives/waterwheel%20archive/nov-dec%2005/Nitrate%20p%2024-27.pdf
Watson, J. T., Reed, S. C., Kadlec, R. H., Knight, R. L., & Whitehouse, A. E. (1989). Performance Expectations and Loading Rates for constructed Wetlands. In: Hammer, D.A. (Eds.) “Constructed Wetlands for Waste Water Treatment; Municipal, Industrial and Agricultural”. Lewis Pub., Michigan.
