Analysis of Nitrogen Removal Efficiency of Advanced Integrated Wastewater Pond Systems (AIWPS) Atsushi Hatano Abstract Due to a lack of proper agricultural and municipal wastewater treatment facilities, a large number of the developing countries’ population is still exposed to water pollution with limiting nutrients such as nitrogen. One of the promising technologies for wastewater treatment is Advanced Integrated Wastewater Pond Systems (AIWPS). The objective of this study is to determine nitrogen removal efficiency and its transformation pathways in AIWPS and to find out if water temperature, pH, and dissolved oxygen (DO) in AIWPS have the influence on those removal efficiency and transformation pathways. The two particular study systems of AIWPS are the Delhi system, which treats municipal wastewater, and the Panoche system, which deals with agricultural wastewater. Their capacity of nitrogen removal from those wastewaters was monitored over a period of 12 months. The Delhi system showed a relatively high total nitrogen and ammonia nitrogen removal of 78.9% and 75%, respectively over the whole period of investigation. On the other hand, the Panoche system removed only 44.6% of total nitrogen, and 56.5% of nitrate and nitrite. Highest removal of both of ammonia nitrogen, and nitrate and nitrite occurred during the warm period (28.3C° average), but the rates of removal of those forms of nitrogen were not correlated to pH and DO. The mechanism of relationship between water temperature and the removal of ammonia nitrogen, and nitrate and nitrite was discussed.Introduction After carbon, hydrogen, and oxygen, the most abundant element in living cells is nitrogen. Thus the availability of various nitrogen compounds such as N2 gas, nitrate, ammonium, and nitrite influences the variety, abundance, and nutritional value of animals and plants. In aquatic ecosystems the major forms of nitrogen available to aquatic creatures are nitrate and ammonia. They are, however, not always present in adequate amounts in natural waters and may limit plant growth, thus nitrogen is considered as one of the limiting nutrients. When there is excessive amount of nitrogen in aquatic systems, high nitrogen level in water gives enormous influences on aquatic environment (eutrophication) and on human health (blue baby) (Horn and Goldman, 1994). Eutrophication can be defined as the process of enrichment of a water body due to an increase in nutrient loading (Horn and Goldman, 1994). A common indicator of this eutrophication is increased phytoplankton population density and speciation often with green, turbid, and foul smelling water and oxygen depletion in water. The source of nitrogen is the liberal use of fertilizers in agriculture combined with increased waste discharges especially after World War 2. Yet this fact that nitrogen is a source of pollution has not been well known by the public. Thus nitrogen sometimes is called the neglected pollutant (Horn and Goldman, 1994). Human health can also be affected by nitrogen pollution. Throughout the world drinking water wells are contaminated (Cunte, 1997), exposing 3 million people only in the U.S. to nitrate contaminated water. The maximum concentration for nitrate of the human drinking water standard is 10mg/L, and of the people exposed above this level, approximately 43500 infants under about 6 months of age are at the risk of developing methemoglobinemia. This condition, which can lead to suffocation, occurs when nitrogen forms methemoglobin, which reduces the oxygen-carrying capacity of the blood (Horn and Goldman, 1994 and Magee, 1977). This oxygen starvation can produce a fatal condition known as blue baby syndrome. In the third world these problems have been becoming major concerns. Especially in China, the largest developing country in the world, still there are many people who lack access to safe waste supply and proper sanitation due to the lack of wastewater treatment facilities and intense use of land for agriculture, and fish farming (Lai 1994). The treatment of nutrient-rich water has been very important for these reasons. Wastewater treatment systems such as High rate algal ponds are widely used for nitrogen removable around the world, and the efficacy of that system is well documented (Lai 1995). High rate algal pondsystem is one of the most cost effective wastewater treatment systems, thus not only for the developing countries but also for other countries the application of high rate algal ponds seems to be a valuable way to treat nitrogen polluted waters for rehabilitation of the water body, sanitation and for reuse as irrigation and drinking water. However, there remains little understanding of the mechanics by which removal occurs or of the factors, which may affect the efficiency of the removal process (Cromar et al. 1996 and Reed 1985). Cromar and Reed stated that the efficiency of nitrogen removal is related to temperature and pH, especially in the summer. Hussanity (1979) also reported that total ammonium removal in particular nitrification, was higher during the summer. Contrary to those findings, Lai and Lam stated that nitrogen removal, nitrification, was more efficient during autumn and early winter, and dissolved oxygen (DO) level was strongly correlated with its removal. It seems there is still the need for further research on the relationship among nitrogen removal, pH, DO, and temperature in high rate algal pond system. The objective of this experiment is to find out the transformation pathways and removal rates of nitrate and nitrite and ammonia nitrogen in a wastewater treatment system, called AIWPS, Advanced Integrated Wastewater Pond System and to determine if the levels of pH, DO and temperature in the system have effects on nitrate and nitrite and ammonia nitrogen transformation pathways and removal efficiency. Methods The purpose of this study is to measure how much total nitrogen is removed by AIWPS, and also it involves the determination of the effects of pH, DO, and temperature in AIWPS on removal efficiency of ammonia nitrogen and nitrate and nitrite. Since ammonia nitrogen is toxic to aquatic organisms and is the major component of nitrogen in one study site, Delhi system, ammonia nitrogen was used to determine correlation tests with pH, DO, and temperature. And also nitrate and nitrite were chosen to be used for the same correlation tests for the other study site, Panoche
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