Wastewater treatment with algae - synergies for the future

Clean water due to wastewater treatment with algae

Wastewater treatment with algae holds great potential, not only to purify wastewater, but also to reduce environmental impacts and promote the sustainable use of valuable resources. At a time when clean water is an increasingly scarce resource and environmental protection is crucial, algae can make an efficient contribution to solving these challenges. Harnessing the natural capabilities of algae opens up a wide range of possibilities that can positively shape our future.

What types of wastewater are there?

There are different types of wastewater, these can be distinguished according to their origin and composition. Domestic wastewater refers to wastewater that comes from private households. This includes waste water from toilets, showers, washbasins and kitchens.

Stormwater refers to rainwater or meltwater that runs off roads, roofs and other surfaces. It can also pick up contaminants in the form of pollutants from the environment.

Industrial and commercial wastewater is generated in factories, businesses and other industrial facilities. It can contain a wide range of pollutants, depending on the manufacturing processes and activities involved.

Cooling water is a special type of wastewater used in industrial facilities to cool machinery and processes. It can have various chemical compounds and temperature variations.

Proper treatment and disposal of these different types of wastewater is crucial to minimise environmental impact and maintain water quality. Wastewater treatment with algae can make a resource-saving contribution to this.

What are the different types of water pollution?

Conventionally, water pollution is thought of as polluted surface waters such as rivers, lakes and oceans. Water pollution can be caused by a variety of pollutants, including chemicals from households, industries and agriculture (such as soaps and detergents), heavy metals, faeces and rubbish, microplastics and other toxic substances.

Water that does not flow on the surface and is visible can also be polluted. Subsurface pollution refers to the contamination of groundwater that is found in the soil below the earth’s surface. This type of pollution can be caused by similar sources of pollutants as described above, and it affects groundwater used as a source of drinking water.

Chemicals released by households (e.g. detergents), industries and agriculture (fertilisers) actively contribute to water pollution. These chemicals can be toxic and affect water quality, as well as harm the ecosystem whose role is actually to keep water clean.

Industries in particular can release heavy metals such as lead, mercury, cadmium and others into water bodies. These metals are toxic and can have serious environmental impacts. Heavy metal pollution is a major problem, especially in industrialised countries. However, due to the pollution of seas and rivers, this local problem is increasingly becoming a global problem.

The discharge of faeces and waste into water bodies can lead to bacterial and viral contamination, which in turn can endanger human and environmental health. This is especially a problem in remote and economically weaker regions of the world, as maintaining sewage systems and treating water is a complex and costly undertaking.

Microplastics are small plastic particles that are often broken off from larger plastic products or can be found in cosmetics and other products. These tiny particles can end up in water bodies and have negative impacts on aquatic life and the environment. Microplastic contamination and pollution is a problem for which there is still no concrete solution.

What is the general process to clean or treat wastewater?

The treatment and purification of wastewater is a complex process that can vary according to the degree of purification and the technologies used, depending on the type of wastewater, local regulations and available resources. However, the following steps outline the general structure and functions of a process to treat wastewater.

Filtration of solids:
First, the wastewater undergoes a mechanical process to remove solids such as suspended solids, sand and coarse impurities. This is usually done through screens, rakes and sedimentation tanks to separate particles.
Chemical water treatment:
After the coarse removal of solids, chemical processes are used to remove other impurities. The addition of flocculants causes fine particles to stick together into larger aggregates, facilitating their removal. Precipitants are added to form insoluble compounds that can then precipitate and be separated. Oxidising agents are used to break down organic compounds and eliminate pollutants. The process of ion exchange removes dissolved ions and heavy metals from the water by exchanging them for other ions.
Bioremediation:
Bioremediation uses microorganisms such as bacteria and algae to break down organic contaminants and toxins in wastewater. This is often done in biological clarifiers where microorganisms use the organic matter as food.
Disinfection:
Chemical and biological treatment is often followed by disinfection to kill pathogenic microorganisms such as bacteria and viruses. This can be done by adding chlorine, UV irradiation or ozone.

How can algae be used for wastewater treatment?

Wastewater treatment with algae, such as Chlorella sp., can be done in different ways. Algae can help in the chemical upgrading of water in the oxidation step, but also decompose and absorb toxins and other pollutants in the process of bioremediation.

Algae perform photosynthesis, absorbing carbon dioxide and releasing oxygen. This increases the oxygen content in the wastewater, which makes it more difficult for anaerobic bacteria to multiply. In addition, the oxygen produced by the algae allows aerobic bacteria to break down organic waste and absorb nitrogen and phosphorus, improving water quality.

Algae have the ability to break down pollutants through their metabolism. This can help to remove certain pollutants from wastewater. However, algae not only break down pollutants, but can also bind them. Pollutants such as heavy metals and organic compounds are absorbed and bound in the cells of the algae and thus removed from the wastewater.

The use of algae in wastewater treatment, especially in so-called algae wastewater treatment plants, can help to improve water quality and reduce pollutants. This process is called “phycoremediation” and uses the natural abilities of algae to clean and treat wastewater.

What types of algae have already been used to treat wastewater with algae?

Different types of algae have already been used in wastewater treatment. Microalgae, such as different types of chlorella and spirulina, are often used for wastewater treatment. They are well suited to remove organic compounds and nutrients from wastewater.

Some types of macroalgae, such as various brown algae and green algae, have been considered for their efficiency in absorbing heavy metals. These algae could be used in bioremediation to remove heavy metals from water and clean the oceans. It should be noted that not all macroalgae absorb and bind heavy metals to the same extent.

Some thermophilic algae, such as Galdieria sulphuraria, which thrive in extreme environments, have been studied in research projects on wastewater treatment. These algae are adapted to high temperatures and could be useful in specific applications for treating warm or industrial wastewater.

The choice of algae species depends on the specific requirements and objectives of wastewater treatment. Due to their versatility and efficiency, microalgae are usually the most commonly used algae in wastewater treatment, while other types of algae can be used in specific situations or for the removal of certain pollutants.

What form must the algae be in to treat wastewater?

The form in which algae are used to treat wastewater can vary, depending on the specific requirements and objectives of the process. In general, live algae, dried algae and algae extracts can be used in different situations and applications.

Living algae are often used in biological clarifiers or ponds to remove organic contaminants and nutrients from wastewater. These algae are able to perform photosynthesis and thus produce oxygen and support aerobic bacteria. Living algae can also break down organic matter and help improve water quality.

In some cases, dried or inactivated algae can be used to absorb pollutants from wastewater. Dried algae can bind certain heavy metals and other pollutants in their cells. This mechanism of absorption is one way to remove pollutants from wastewater.

Some algae extracts, or algae-based products, can be used in wastewater treatment to treat specific contaminants. These extracts may contain certain enzymes or substances extracted from the algae that help in the degradation processes or in the removal of pollutants.

The choice between live and dead algae depends on the wastewater treatment objectives. Live algae are able to support biodegradation processes and produce oxygen, which is beneficial in many cases. Dried algae or extracts can be used in situations where specific pollutants need to be removed or when live algae are not practical.

What are the advantages of wastewater treatment with algae over conventional treatment processes?

Wastewater treatment with algae can create interesting synergies and circular economy effects. The algae can decompose organic contaminants and absorb nutrients from the wastewater and grow in the process. This algae mass can then be used as a valuable resource, for example to produce biofuels, animal feed or fertilisers. This helps to reduce waste and close material cycles.

Wastewater treatment with algae is based on natural processes such as photosynthesis and biological degradation. Compared to conventional treatment processes, which often require the use of chemical treatment agents, algae-based systems require fewer chemicals. This can lead to lower environmental impacts and lower operating costs.

Algae are efficient organisms that can decompose organic pollutants and extract nutrients from them, thus converting them into biomass. This contributes to resource conservation by converting waste products into valuable raw materials. Furthermore, the cultivation of algae in wastewater treatment plants can help to make wastewater treatment processes more sustainable. It is important to remember that this is not possible with all types of pollutants. Heavy metals, for example, can only be absorbed, which makes it possible to bind the pollutants, but makes the biomass useless for applications afterwards, re-entering the food cycle.

Overall, wastewater treatment with algae can be an environmentally friendly, cost-efficient and resource-saving alternative to conventional wastewater treatment processes, especially if the algae mass produced can be reused for various purposes.

How can wastewater treatment with algae be integrated into other processes?

The integration of wastewater treatment with algae into further processes can take place in various ways. Synergetic processes are particularly interesting, as algae can not only play a role in treating the water, but can also be a source of raw materials for further products.

In an aquaponics system, fish are kept in tanks and the wastewater from the fish tanks is fed into algae cultures. The algae use the nutrients in the fish faeces as fertiliser to grow. At the same time, the algae clean the water by absorbing nutrients and pollutants. After the algae’s growth process, they can be harvested and used again as fertiliser. This leads to a closed cycle in which fish, algae and plants benefit from each other.

This approach is a good example of how wastewater treatment with algae not only enables the upgrading of water, but also the reuse of nutrients and the generation of sustainable resources. Algae can help promote a sustainable circular economy and can be particularly beneficial in urban environments or areas with limited resources.

Wastewater treatment with algae – A sustainable solution for clean water and resource management

The future of wastewater treatment with algae promises exciting developments. It not only enables the cleaning of wastewater, but also the creation of resources. The integration of algae into additional processes such as aquaponics and urban agriculture shows that this method can be a cornerstone for future-oriented resource management. Algae can help close material cycles, turn waste into value and minimise environmental impact in the process.

At a time when water resources are scarce and environmental protection is crucial, wastewater treatment with algae not only offers a sustainable solution for clean water, but also opens up a promising future perspective for the sustainable use and conservation of our resources.

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