Wastewater treatment – the invisible benefits of civilisation (Part 2)

• Extension…
• New Ages (15th century – end of World War I )
• Recent centuries (1918 to the present day)
• Modern Wastewater Treatment Technologies
• Conclusion

In this article “Wastewater treatment – the invisible benefits of civilisation (Part 2)”, we will continue to look at how wastewater treatment has evolved and developed in the last and the most recent centuries.

The New Century (15th century – end of World War I)

The real beginning of the need for wastewater treatment came with the Industrial Revolution in the 19th century.
The population moved to the cities in search of work. As a result, cities expanded rapidly and industries began to mass produce products, adding to the already existing pollution. Most of the waste water simply flowed into rivers, lakes or the sea, despite its harmful effects on nature and people. Untreated sewage has caused huge pollution problems and allowed the rapid spread of diseases and harmful organisms.

As Britain was the first industrialised country, it was the first to suffer the full consequences of urbanisation. The cholera epidemics of 1832, 1849 and 1855, which killed many people, added to the stench of the cities. One of these epidemics, in 1847, was a major breakthrough. John Snow, an English physician, discovered that cholera and typhoid fever were caused by drinking water contaminated by sewage. And sewage enters drinking water wells via groundwater from sewage pits. A few years later, Louis Pasteur’s research confirmed this hypothesis. He found that cholera and typhoid fever are caused by dangerous micro-organisms in wastewater. These discoveries led to changes in legislation in many countries and, since the 19th century, laws in various countries have restricted the construction of sewage pits in areas without sewers. This led to the design and construction of sewage systems in London and other major cities in Europe and the USA.

Initially, these sewage systems were simply gravity sewers. They used rainwater to discharge sewage directly into surface waters without treatment. But as pollution of water bodies increased, some cities started to treat wastewater before discharge. Already at the end of the 19th century, chemical treatment and precipitation techniques were introduced.

London in the 19th century

Recent centuries (1918 to the present day)

Early 20th century industrialisation

The industrialisation of the early 20th century, population growth and the development of agriculture posed new challenges for wastewater treatment.

But most importantly, people realised that untreated sewage is harmful to the environment and drinking water and can cause many problems. First of all, untreated wastewater can pollute rivers, lakes and seas. Such pollution can lead to a reduction in animal and plant diversity and, in some cases, even to the extinction of species. Secondly, hazardous substances in wastewater can leach into groundwater, contaminate groundwater sources and affect drinking water sources.

Therefore, recognising the importance of wastewater treatment, scientists have concentrated their efforts on developing more and more modern and efficient technologies.

One of the most important discoveries that has revolutionised the wastewater treatment industry
And one of the most important discoveries that revolutionised the wastewater treatment industry was made in 1912. Edward Arden and William T. Lockett, researchers at the University of Manchester, discovered the activated sludge wastewater treatment process. This is a biological wastewater treatment process that uses active micro-organisms, bacteria and viruses to remove organic matter and pollution from wastewater. And after the First World War, this method was widely used in the USA and Canada as well as in western European cities. This wastewater treatment process, discovered in 1912, is still in use today.

It was a breakthrough in wastewater treatment technology, but as cities expanded, industry developed and the population grew, so did the requirements. Not only environmental protection and the continuous improvement of wastewater treatment plants, but also efficiency improvements, energy savings and the quality of the wastewater treated.

Wastewater treatment plant with tanks for sludge aeration and biological treatment

Modern wastewater treatment technologies

Wastewater treatment today is a complex and multifaceted process involving several steps that ensure that the treated wastewater is safe for the environment and for people.

1. Pre-treatment (Preliminary Treatment): This stage involves the removal of large solids and floating materials. This is done using sieves, grates and sand traps. The aim is to reduce the amount of pollutants in the effluent so that the subsequent stages of the treatment process work more efficiently.
2. Secondary treatment: Secondary treatment involves treating the wastewater with biological processes that use micro-organisms to break down organic pollutants. The most popular method is the activated sludge process, which uses micro-organisms to break down organic matter. This process allows the removal of most biological pollutants.
3. Tertiary treatment: This is an additional stage of treatment designed to remove the remaining contaminants that secondary treatment has failed to remove. Tertiary treatment may involve a variety of technologies such as chemical cleaning, filtration, adsorption by carbon filters, ultraviolet disinfection or chlorine.
4. Sewage sludge treatment: The treatment process generates sewage sludge, which also needs to be treated properly. The sludge can be stabilised using anaerobic (without oxygen) or aerobic (with oxygen) treatment. For example, anaerobic treatment, also known as anaerobic digestion, takes place in closed reactors where micro-organisms break down the organic material to produce biomethane, which can be used as an energy source. The sludge is also dewatered and compacted to reduce its volume and improve the efficiency of further processing. Drying and densification help to reduce transport and disposal costs.
5. Environmental Protection and Technological Development: Current technology and research is continuously being developed to reduce the energy consumption of treatment plants, increase treatment efficiency and reduce emissions. New technologies such as membrane filtration, nanotechnology and advanced biological techniques are achieving even better results.

Integrated Pretreatment System

Conclusion

Looking at the evolution of wastewater treatment technologies from ancient civilisations to the present day, we can see how important and complex this process has been throughout human history. The sewage systems of ancient Rome and the challenges of the Middle Ages show how important it was to find ways to manage wastewater efficiently in order to keep cities clean and citizens healthy.

During the Industrial Revolution, the growing urban population and increasing industrial pollution forced people to find new solutions. Discoveries in the 19th century, such as the research of John Snow and Louis Pasteur, showed that polluted water could cause serious diseases and led to the development of more modern wastewater treatment systems. As a result of this research, many cities have introduced sewerage systems and treatment plants that have significantly reduced pollution problems and prevented the spread of disease.

In the 20th century, wastewater treatment technologies continued to improve, with new methods such as the activated sludge process revolutionising wastewater treatment. Today, we have advanced and efficient systems that make it possible to remove most of the pollutants and even turn wastewater into a useful resource.

In summary, wastewater treatment is a key factor in quality of life and environmental protection. These technologies are constantly being developed to ensure that water resources are safe and clean for future generations. We can be grateful for the clean environment in which we live by appreciating the achievements of ancient civilisations and the efforts of modern scientists.

We hope that this journey through the history of wastewater treatment technology has helped you to understand how much has been done to reach the current level.