As the 21st century moves steadily into its second decade, some trends that will affect the way we live and our quality of life are becoming very apparent.
The first of these is that increasingly rapid urbanization is a fact of life in both developed and developing countries. More and more people are flocking to cities in search of a better life.
The send is that the birth rate, especially in the developing world shows no signs of slowing down.
The net effect is that we have more people crowding into increasingly densely populated areas.
One of the effects is that systems for the treatment of sewage are coming under increasing pressure. Much of the infrastructure that is used for the treatment of human waste (and in particular cases industrial effluent) is aging remarkably quickly. Some urban planners have indicated that the median age of this infrastructure and equipment is more than 50 years old.
This makes it essential that sewage treatment, which is the removal of contaminants from the water and the production of water that is environmentally friendly (or in some cases fit for human consumption) takes place in a rigidly controlled environment.
The most common methods for the treatment of sewage are mechanical / physical, chemical and finally biological. These treatment types can be broadly defined as primary treatment, secondary treatment, and tertiary treatment.
Primary treatment consists of containing the sewage in a basin where particulate matter is allowed to settle and lighter substances such as petrochemical matter float to the top of the water column. The matter at the top is skimmed off, and the heavier matter at the bottom of the tank is discharged or undergoes further treatment.
Secondary treatment uses water-based biological organisms to consume organic contaminants. In the United States, the general rule is that by the time primary and secondary treatment has been completed approximately 85% of organic solids should have been removed from the water. In some instances, the water will be further treated to remove these biological organisms before the water is discharged or further treatment takes place.
Tertiary treatment is especially important when the treated water is going to be released into a biologically sensitive environment, Examples of this sort of environment include mangrove swamps or into the ocean where delicate ecosystems such as coral reefs are present. Tertiary treatment can include the use of chemicals and lagoons. Other types of tertiary treatment also include the use of sand filtration and the removal of nitrogen before discharge.
This water can then be used for agricultural purposes. Water treated in this way has become extremely popular for use in golf courses.
Sewage treatment is a process of continual improvement and refinement. There is a wide variety of developing technologies which are being rolled out across the world to make the process more efficient and reduce treatment times. An example of this is the use of activated carbon filters or ozone to remove so-called ‘micropollutants.’
As urbanization continues, it is becoming increasingly clear that these innovations are going to become essential if those living in large cities are to enjoy a good quality of life.