Influence by ph and dissolved oxygen on faecal coliform removal in algal and macrophyte based wastewater treatment systems’

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Macrophyte based wastewater treatment systems are gaining recognition worldwide because of economic gains. In the traditional algal based ponds harsh environmental conditions of high and fluctuating DO and pH are triggered by sunlight which destroys pathogens. The presence of a macrophyte will prevent direct light penetration. An experiment was therefore conducted to determine the conditions that will occur under macrophyte-based systems and their effect on pathogen removal. Two experiments were conducted to address this problem. The first was the determination of environmental conditions within a bench scale continuous flow system using Pistia, Duckweed and Algae, and the efficiency of faecal coliform removal within the treatment systems. Results obtained indicated acidic (pH = 4.4), neutral (pH = 6.7) and alkaline (pH = 9) in Pistia, Duckweed and Algae respectively. Pistia and Duckweed systems did not show any significant fluctuations in pH during the day. The algal based system rather showed higher values in the afternoon due to photosynthesis. Dissolved oxygen increased in the afternoons in the algal and pistia based systems whiles values decreased at the same time in the duckweed-based ponds. In the second experiment, the effect of pH on faecal coliforms was determined in the treatment systems. The results showed that pH 4 and greater than or equal to 9 are lethal to faecal coliforms. It indicated in effect that environmental conditions created in the macrophyte-based ponds are not as harsh as those created in the algal based ponds. They may therefore not be able to remove pathogens efficiently.
A thesis submitted to the School of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of the Degree of Master of Science in Water Supply and Environmental Sanitation, 2000