Environmental engineering is one of the most popular, complex and fast growing disciplines in engineering. The scope of environment includes issues from public health, aesthetics, and impact of all development activities, pollution control legislation, standards, regulations, guidelines and their enforcement. Traditionally the application of engineering principles for the protection and enhancement of the quality of environment and protection of public health was called as sanitary engineering or public health engineering. Around 1968 this was changed to environmental engineering.

For conceiving environmental engineering, one has to consider the definition of engineering itself. Engineering may be defined as the application, under limits of scientific principles for the planning, design, execution, operation and maintenance of structures, equipment and systems for the development and benefit of the society. Here the word benefit is more important than the development. The so-called development in some cases may not be in real benefit of the society.

The environmental engineer plans, designs, executes, operates and maintains the water, wastewater and solid waste management plants. Clean, bacteriologically safe, potable drinking water protects and enhances public health. Liquid and solid waste management is a necessary step for healthy living. They also deal with air pollution control. The resulting pure cleaner air is conducive to people’s good health and prevents the building and other materials from the harmful effects of air pollution. The environmental engineer cares for the energy requirements of the society and the ways and means to protect the environment against the various pollutions created through the production and consumption of various goods and comfort conditions. It is the duty of environment engineer to assess the environmental impacts of the various development and other activities. In general one has to work to have sustainable and holistic development. Of course there are always constraints of resources, knowledge, human nature, social and racial considerations that limit the achievement of these goals.

Therefore the environmental engineering is defined as the application of scientific and engineering principles, under limits, for the protection and enhancement of the environment that includes the biotic and abiotic both components.

The environment exists in dynamic equilibrium of its biotic (living) and abiotic (non-living) elements. The solar energy induced photosynthesis synthesizes the carbon as the plant tissue and we get matter in various forms from the trees. The carnivores, humans and animals consume the edible matter. They convert it into the energy required to sustain their lives. Their excreta comes near to the nature and the natural scavengers, bacteria and others convert it into inorganic matter like nutrients due to the biological decomposition. The roots of the plants, to form the edible matter again, extract these nutrients. Like this the nutrient cycle, material cycle, energy cycle and other cycles like hydrological cycle keep on existing until there is a great shock given by the human beings.