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More knowledge about water and wastewater

This overview serves as a guide through the Wasser 3.0 world. All terms included are directly related to our work. This includes topics related to water in general, water without microplastics and micropollutants, as well as overarching points of contact, such as the United Nations sustainability goals or the national water framework directive.

Aquatic ecosystems

Intact ecosystems represent retreats for humans and nature and guarantee the long-term availability of water. The appreciation of ecosystem services as well as the methods for determining the water demand of ecosystems have undergone significant changes in recent times.

A methodologically consistent, up-to-date, and comprehensive description of the status of global water resources and the associated ecosystems is, therefore, a central prerequisite for well-founded regional and global objectives. Without a secure water supply and efficient sewage disposal, successful poverty reduction, social prosperity, healthy economic growth, and efficient environmental protection are not possible.

Wastewater treatment plants

Germany's wastewater volume was around 9.8 billion cubic meters in 2013 and consists mainly of wastewater, extraneous water and rainwater. The pure proportion of wastewater from private households, trade and industry already corresponds to approx. 50% of the total amount of wastewater that is fed to municipal sewage treatment plants. The remaining 50% are composed of almost equal parts precipitation and extraneous water. The wastewater treatment process takes place in the sewage treatment plant. In Germany, this consists of three purification stages in most sewage treatment plants: mechanical, biological, and chemical. After these have passed through, the treated wastewater is fed into the natural water cycle, e.g., in the nearby flowing water, the so-called receiving waters.

It has been known for several years that there are substances in wastewater that can only be removed slightly or not at all during wastewater treatment in the wastewater treatment plant. We are talking about anthropogenic trace substances (or micropollutants) and microplastics.

Environmental quality standards

The classification of the chemical status of a surface water body is based on the environmental quality standards that are regulated in the Surface Waters Ordinance (current OGewV of 20.06.2016).

The EQS or environmental quality standard represents the concentration of a specific pollutant or a specific pollutant group that must not be exceeded in water, suspended matter, sediments, or biota (fish, mussels) for reasons of health and nature protection.

45 priority substances or groups of substances are currently being assessed. These include metals, pesticides, and other chemicals. If the EQS is exceeded for one of the substances or groups of substances, the chemical status of this surface water body is already classified as “not good”.

4th purification stage in sewage treatment plants

The requirements for a fourth purification stage for central wastewater remediation are complex. On the one hand, the cleaning stage must be able to largely remove a wide range of problematic substances; on the other hand, it is also important to avoid undesirable by-products that arise, for example, from chemical or biological conversions, or to make them controllable for the sewage treatment plant operator. In addition, the fourth cleaning stage must be easy to operate for trained personnel and it must be possible to integrate it into an existing system. An appropriate, justifiable, cost / benefit factor must be used.

Now, various methods are available as a fourth cleaning stage for removing pollutants. Based on their respective mechanisms of action, these can be divided into adsorptive, oxidative, biological, and physical.

All processes can be combined with one another, but it must be considered that each, considered individually, has limiting factors that cannot be eliminated even by combining two process approaches. Often the procedural limits are e.g., the uncertainty about by-products in oxidative processes, slip and desorption of powdered activated carbon, high consumption of chemical additives, economic factors or personnel or spatial capacity. Investment costs such as construction costs are also limiting factors for sewage treatment plants with less favorable framework conditions.

Virtual water

The term 'virtual water' describes the amount of water used to manufacture a product - regardless of whether it is industrial or agricultural. An example: Around 16,000 liters of water are used to produce one kilogram of beef. In addition to the water used for watering the animals, the calculation includes the water that is used for the animals in the cultivation of feed.

If you calculate the virtual water consumption, we use almost 4,000 liters of water per day in our latitudes. For the average daily need for basic hygiene, cooking, and drinking, we need around 125 liters of "visible" water.

Water scarcity

At the moment it seems that in most industrialized countries there is hardly any water scarcity, the hygiene conditions are excellent and the industries in the field of water saving and water purification do what the state imposes on them. There is hardly any voluntary commitment to protect the environment and it does not look as if the international community will turn this screw in an impact-oriented way in the next few years. Unless the pollution continues to increase so that the effects on the ecosystem reach people more and more, become visible and noticeable. By then, at the latest, the social pressure will be so high and lead to decisions that really protect the water and our planet.

In the countries of the Global South, the effects of water pollution and water scarcity are already very clearly visible. Since 2000, the world population has grown by more than 1 billion people to a current figure of 7.3 billion people. During the same period, global water demand has increased by around 20 percent. The situation will be exacerbated by the further increase in global water demand forecast by 2050 by an additional 55 percent and the associated increasing conflicts of use.

The overexploitation of global water resources is already shaping the appearance of the earth. The water shortage not only has consequences for individuals, ecosystems, and economic development. Inadequate basic water supply is also a factor that can weaken the stability of political systems. By 2050, 40 percent of the world's population is expected to live in areas with water stress. The increasing amount of problematic ingredients combined with water scarcity creates an explosive mix. The question of whether water is a human right or an economic good is only one of many when it comes to protecting our environment and us humans.

Effects of water scarcity: lack of basic sanitation

Worldwide around 1.2 billion people are threatened by extreme water scarcity and around 748 million people have no access to clean drinking water.

However, the number of those who must live without basic sanitation, i.e. they have neither a toilet nor a connection to the sewage disposal system, is more than twice as high at 2.5 billion. The consequences of this for the people affected, but also for the economic and ecological development of their home countries, are enormous.

Cities in the Global South are particularly affected. There, in a relatively confined space, both the water consumption and the degree of pollution as well as the amount of wastewater produced are particularly high. There is often a lack of adequate infrastructures for wastewater disposal and recycling, so that the inhabitants of these cities usually only have dirty water at their disposal. A reliable drinking water supply and efficient wastewater disposal go hand in hand. This is also reflected in goal 6 of the UN sustainability goals of clean water and sanitary facilities.

Water cycle

The term water cycle describes the transport and storage of water. In the meantime, the water changes its physical state, so water is never lost. Water from seas, rivers and lakes evaporates and rises into the atmosphere as water vapor. The resulting humidity is transported to the mainland by the wind.

When the humid air meets cold layers of air, it pushes itself over them and rises, just as it does when it hits mountain slopes or is warmed up over warm ground. When the air rises, it cools down. Cold air can absorb less water vapor than warmer air, so the water vapor contained in the air condenses at a certain height. This creates clouds.

If the water droplets are large enough, precipitation occurs. The water falls back to the earth in the form of rain, snow, or hail. The water collects there and then flows back into the sea via rivers and streams.

Water quality

Water quality can be viewed as a measure of the suitability of water for a particular use based on selected physical, chemical, and biological properties.
Various analytical tests are usually carried out to assess the water quality or the condition of a body of water. This includes the determination of chemical oxygen demand (COD) or biological oxygen demand (BOD) as well as pH value, turbidity, conductivity, water hardness, total nitrogen, and total phosphorus.

These basic analyses give a first impression, but not a comprehensive insight. In order to be able to make a comprehensive statement about water quality, further investigations (including analysis for micropollutants, microplastics), but also classifications of the values with regard to the environmental quality standards, must be carried out.

A distinction is made between chemical and ecological status. The environmental quality standards are used for the chemical status; the Water Framework Directive serves as the basis for the ecological status in Germany and the EU.

Water Framework Directive

The Water Framework Directive (WFD) describes measures for an integrated water protection policy. It was launched in the European Community on December 22nd, 2000, the day of its publication in the Official Journal. With the approach of integrated water protection policy in Europe, which also transcends national and international borders, the European Community would like to achieve a coordinated management of the waters within the river catchment areas.

The classification of the concept of the ecological status or potential of rivers, lakes, transitional and coastal waters anchored in the WFD is based on so-called biological quality components of the aquatic flora and fauna. The fish, invertebrates, macrophytes or phytoplankton living in the water are good indicators for making statements about the quality of the water. The species composition and frequency of species is, therefore, recorded and assessed for all groups of organisms, the age structure of the community for fish and the biomass for phytoplankton.

Water pollution

While in Africa and other developing countries the contamination of the water with pathogens (still) represents the greatest danger (sewage, infectious diseases), in European and other industrialized countries the pollution of the water with chemicals is the main problem. The pollution of the water by drugs, perfluorinated and polyfluorinated substances, nitrates and microplastics is very present in the media. So far, it has mainly been analytical methods that are not yet sufficient and have told us little or nothing about the actual degree of exposure. With the expansion of the municipal sewage treatment plants on three levels (mechanical, biological, and chemical), it was thought that the pollutant cocktail could be brought under control.

But, as it turns out today, there are many more factors that must be taken into account, and the concentrations of problematic ingredients and their complexity in terms of distance and behavior in the environment are continuously increasing.

The improved analytics prove it. It is not only the supposedly high concentrations (e.g., phosphates) that must be removed in the sewage treatment plant in order to curb eutrophication (the accumulation of nutrients leading to the creation of dead zones), but the micropollutants, the very small amounts, are causing us more and more problems because they are often more toxic and dangerous.