Modeling and Control Studies of an Integrated Biological Wastewater Treatment System

The economic opportunity and quality of human life depend upon the continued availability of a life-sustaining environment. Understanding how we and other organisms affect, and are affected by, our environment is an important first step toward maintaining a sustainable future. As environmental engineers, we have to deal with natural systems and also expand our conceptualization of environmental engineering to include societal, legal and financial aspects. Water, by its very nature, is vital for the survival of life on the earth. If today, the struggle amongst the nations is for the resources such as oil, a survey of the United Nations suggests that in the future, it will be a struggle for drinking water. This shows how much importance we have to pay to the water and water quality to assure our future generation of a life-sustainable environment to live upon. As industrialization and population growth continues, the problem of eutrophication, which is the accelerated ageing of lakes and estuaries, etc., due to excess plant and algal growth has been and going to be witnessed all over the world. This is the result of discharges of nutrients like nitrogen and phosphorus to these water bodies. Hence, environmental engineers are working hard in designing the wastewater treatment system that could remove these pollutants in an efficient and cost effective way. The components in wastewater treatment processes may be conveniently categorized as physical, chemical and biological operations, but understanding the principles governing their behaviour is a prerequisite for successful process design. Biological wastewater treatment has seen a significant growth in the last 25 years. Particular occurrence was recognition of the many events that can happen simultaneously in biological processes and the role that the design engineer has in determining which predominates. The impact on process design of this recognition demanded that the present and future environmental engineers begin to think in multiple events rather than compartmentalizing them. These necessitate the need for better understanding of microbiology and reactor engineering to achieve the improved results in biological wastewater treatment. In the part of literature review, emphasis has been made to understand the nature of biochemical operations, kinetics, stoichiometry and some conflicts of the major reactions occurring in different environments and design processes. However, the important aspect of understanding and appreciating the complex interactions occurring among the micro-organisms that form the ecosystems in the biological process operations has been discussed in length in the section recent research part. Some conflicts have arisen in a single biological wastewater treatment system that simultaneously removes nitrogen and phosphorus. Therefore, resolving these conflicts and enhancing the process performance are the primary goal of this project work. An effort has been made to modify the process design and combine continuous stirred tank reactor and rotating biological contactors to overcome these conflicts. The combined hybrid system will provide two kinds bacteria population: suspended activated sludge bacteria and biofilm bacteria. Together, these can improve the efficiency of simultaneous removal of nitrogen and phosphorus from the municipal wastewater.

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