Sustainability of Murram Mbeya- Pumice for Phosphoru sorption in wetlands

Murram and Mbeya-Pumice substrates are prospective filter media in constructed wetlands. The study of phosphorus sorption behaviours and properties of the substrates were carried in laboratory scale. Three different sizes( 1-2mm, 2-4mm, and 4-8mm) of Murram and Mbeya-Pumice substrates were tested using batch experiments in the laboratory. For the phosphorus sorption isotherms, the results show that Murram substrates has higher sorption capacity than Mbeya Pumice substrates. The sorption capacity for the Murram and Mbeya-pumice substrates were 2.55gp/kg and 2.2g p/kg respectively for. For 1-2 mm and 4-8 mm grain sizes about 50% of phosphorus sorption in Murran substrates, 50% of phosphorus sorption occurs in the first 17 and 18 hours, respectively. Compared to 4-8mm and 2-4 mm grain sizes, temperature did not significantly influence phosphorus sorption for 1-2 mm grain size. Phosphorus desorption did not occur when the maximum sorption capacity was not reached. Both Murran is recommended to be used as a substrate to be used as substrate in constructed wetlands to remove highly phosphorus concentration range >20 mg p/L while Mbeya- Pumice substrates recommended to be used in constructed wetlands to remove low phosphorus concentrations in the range (0-20mg p/L.