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WHY TRADITIONAL BIOLOGICAL WASTEWATER TREATMENT PLANTS FAIL TO COPE WITH MODERN WASTEWATER?

Modern wastewater is increasingly becoming a cause of environmental disruption due to technological advances that have fundamentally changed the composition of wastewater and made it complex in configuration.

Over the last 30 years, new types of industrial pollutants, heavy metals, phenols, fluoride preparations, petroleum products, complex fats, preservatives and food additives of various types of origin (not organic), pharmaceuticals and antibiotics have appeared in wastewater.

The basic principle of operation of traditional wastewater biological treatment plants (WWBTP) is based on biological decomposition of organic compounds by microorganisms (bacteria and protozoa) with active oxygen supply and breakdown of pollutants to simple substances - water, methane, hydrogen sulphide, carbon dioxide. For this reason, WWBTP technologically have limitations on the input parameters in terms of pollution levels, COD (chemical oxygen demand), BOD (biochemical oxygen demand) and chlorides. The maximum that modern WWBTPs are capable of is to treat effluents with a COD of 1800 mg/l or less. Unfortunately, the presence of the latest anthropogenic pollutants in wastewater makes the COD of wastewater much higher than the limit value, which leads to poor quality of wastewater treatment. As a result, the treated water at the outlet of the WWBTP does not meet the legal rules and requirements for discharge to land or surface water and groundwater. The unremoved pollutants from wasrewater together with the activated sludge get to the wetlands and biofilters, where they significantly pollute the environment, creating an environmental disaster.

A separate and the most acute problem of our time is the content of microplastics in wastewater. These tiny particles are not captured and are not removed at the existing WWBTPs neither by mechanical or biological method, nor by physical-chemical pretreatment or disinfection. WWBTPs are not technologically adapted to treat and dispose of non-biodegradable solids such as plastics.

It is also worth noting that seasonal, industrial and climatic (prolonged droughts or heavy precipitation and floods) fluctuations in wastewater volumes (e.g. 2 up to 4 times) make it difficult and sometimes even impossible to treat these wastewaters at the biological treatment plant. A sharp increase or decrease in the volume of wastewater leads to hydraulic and organic overloads at biological treatment plants and to a significant deterioration in the efficiency of the wastewater treatment process.

To summarise, we note that traditional wastewater treatment plants are no longer able to cope with the challenges of technological progress, the level of urbanisation and population growth.

The main reasons are as follows:

1. Obsolescence of biological treatment technology

The first WWBTP was designed by humanity in the mid-18th century and were designed to remove traditional pollutants such as inorganic substances and biodegradable organic compounds. WWBTP has not changed structurally to this day, but they are used universally and widely around the world.

2. Increase in the number and complexity of pollutants

With the development of industry and population increase, the volume of wastewater is steadily increasing worldwide. At the same time, there are many new man-made, chemical and inorganic pollutants, including pharmaceuticals and microplastics, that standard WWBTPs are not designed to remove and dispose of.

3. limited regulatory requirements

Regulatory requirements for wastewater treatment in many countries still focus on classical pollution indicators (BOD, COD, chlorides, etc.) and do not include new types of pollutants. This means that even if WWBTPs are certified, they are in any case releasing substances into the environment that pose a risk to human health and ecosystems.

4. The need for effluent neutralisation

Modern wastewater today contains viruses and other pathogenic microflora dangerous to human and animal health. For this reason, wastewater must first of all be neutralised before treatment. Traditional WWBTPs for neutralisation of wastewater are not technologically adapted from the word "absolutely" and are not able to cope with the given task.

5. Technological and design limitations

Standard WWBTPs are not able to cope with multiple fluctuations in wastewater volumes, due to the inability to maintain the number of necessary bacteria, or to increase it in case of need. The design disadvantages also include the inability of WWBTP to operate in the Far North climat, where bacteria are unable to live and multiply.

THE MODERN WORLD IS FACED WITH THE CHALLENGE OF APPLYING THE LATEST TECHNOLOGIES OF WASTEWATER TREATMENT, WHICH SHOULD REPLACE MORALLY AND TECHNOLOGICALLY OUTDATED BIOLOGICAL TREATMENT PLANTS.