Effects of a Cyperus Papyrus (Loisel) Swamp on Sewage Effluents.

Abstract

The effectiveness of a papyrus swamp for the removal of nutrients from domestic wastewater was investigated in a small tropical swamp in Kenya, East Africa. The study was conducted in a man-made impoundment transformed in a swamp which receives sewage effluent discharged in a stream. Temporal and spatial distribution of nutrients were determined in the swamp for a period of one year (October 1980 to August 1981). They included the measurement of nitrogen and phosphorus together with temperature, pH, conductivity and dissolved oxygen. Also determined were the removal and release of nutrients by the plants and bottom sediments. St and ard models were used in the determination of the physico-chemical parameters. A comparison between water quality characteristics of the input versus the output from the swamp indicated significant decreases in the mean temperature and conductivity by 20.2% and 23.4%, respectively. Dissolved oxygen was reduced by 84.2%, ammonium by 76.3% and nitrite ions fell by 66.5%. Reduction in orthophosphate was in the order of 79.5% and for total organic phosphorus was 44.4%. The harvested papyrus plants have a biomass of 4,955 g m('-2) (dry weight). The percentage nitrogen content of the various plant organs were: roots, 4.80; rhizomes, 8.39; sheathing scale leaves, 4.49; culms, 4.82 and for umbels, 6.24. The percentages for phosphorus were: roots, 0.093; rhizomes, 0.105; sheathing scale leaves, 0.089; culms, 0.104 and umbels, 0.129. The swamp mud contained 1.48% nitrogen and 0.05% phosphorus. Research findings indicate that papyrus swamps are efficient in nutrient removal for the purpose of wastewater renovation. Nevertheless, they may impose serious public health problems. These problems are associated with the spread of water borne-contact diseases, such as viral-bacteria and parasites. But there is no evidence to show that the discharge of wastewater to a swamp necessarily aggravates the negative public health aspects of the swamp. On the other h and , evidence exists that shows swamps reduce the BOD(,5) and COD to very low levels, and also they remove viruses and bacteria. In short, it can be concluded that papyrus swamps could be used for domestic sewage effluent renovation, if coupled with periodic harvesting.