Algae: Nature's Pollution Solution

Algae are an important part of the ecosystem, but certain pollutants can cause an overgrowth of algae, known as algal blooms. This can have detrimental effects on aquatic life and human health.

Nutrient pollution, specifically an excess of phosphorus, can cause an explosion in algae growth. This is because phosphorus is one of the most important nutrients for plant growth. When there is too much phosphorus in a body of water, algae and other aquatic plants can grow out of control, using up all the oxygen and blocking out sunlight from other organisms.

Acid rain is another pollutant that can kill off algae and other living things if the pH level is outside the normal range. Farmers' use of fertilisers can also become a pollutant if there is too much water runoff into nearby streams and rivers.

Algal blooms can be toxic, producing toxins that are harmful to fish and other animals. They can also be non-toxic and still negatively impact aquatic life by blocking out sunlight and clogging fish gills.

Dead zones are areas of water where aquatic life cannot survive due to a lack of oxygen, also known as hypoxia. These are often caused by significant nutrient pollution and are a particular problem for bays, lakes and coastal waters.

Nitrogen is another primary nutrient of concern in nonpoint source pollution and can also cause algal blooms. Controlling nutrient inputs is challenging because they often come from multiple sources that are hard to identify and control.

So, while algae are an important part of the ecosystem, certain human activities can cause an overgrowth of algae, which can have harmful effects on both the environment and human health.

Algae can remove heavy metals from wastewater

Algae can be used to remove heavy metals from wastewater. Heavy metals, such as lead, cadmium, and arsenic, are released into the environment through human activity and can have detrimental effects on both aquatic ecosystems and human health. To combat this, algae can be used as a low-cost, eco-friendly, and efficient method for removing heavy metals from wastewater.

The unique structural and biochemical properties of algae enable them to remove heavy metals through various mechanisms, including physical adsorption, ion exchange, complexation, precipitation, phycoremediation, and bioaccumulation. Physical adsorption involves metal ions being physically bound to the polyelectrolytes present in microbial cell walls through electrostatic interactions. Ion exchange occurs when metal ions are harmonised in the organisation of complex groups through interaction between metal ions and proteins on biological surfaces. Complexation is the association of two or more species that results in the establishment of a complex. Precipitation can occur through a process that is either reliant on cellular metabolism or chemical reactions between heavy metals and the surface of an algal cell. Phycoremediation involves the use of living microalgae to remove and detoxify heavy metals, while bioaccumulation is a metabolism-dependent process where metal ions are taken up by microbial cells inside the cell.

To enhance the efficiency and specificity of heavy metal removal, algal modification techniques such as pre-treatment, immobilization, and genetic modification can be employed. Pre-treatment involves modifying raw biomass through physical, chemical, or combined activation processes to increase the efficacy of heavy metal removal. Immobilization is the process of stabilising algal cells, which can improve their biosorption capacity, photosynthetic activity, and bioactivity. Genetic modification of algae can be achieved through gene overexpression or the creation of transgenic algae through the introduction of foreign DNA.

Overall, the use of algae for heavy metal removal from wastewater is a promising approach due to its unique structural and biochemical characteristics, and the ability to regenerate algal biomass provides a sustainable solution to the issue of algal disposal.

Algae can reduce the amount of nitrogen and phosphorus in water

Algae are essential for maintaining the health of aquatic ecosystems. However, an excessive amount of algae can be detrimental. This phenomenon, known as an algal bloom, can be caused by an abundance of nitrogen and phosphorus in the water.

Nitrogen and phosphorus are vital nutrients for the growth of algae and aquatic plants. While these nutrients are naturally present in aquatic ecosystems, human activities can lead to an excess of these nutrients, causing algae to grow faster than the ecosystem can handle. This excess of nutrients is known as eutrophication and can have several negative consequences.

One of the main issues with algal blooms is that they can reduce the oxygen levels in the water. As the algae grow and multiply, they consume more oxygen, leading to hypoxic or "dead" zones where there is not enough oxygen for aquatic life to survive. Additionally, algal blooms can block sunlight from reaching underwater plants, hindering their growth. The algae can also clog the gills of fish, making it difficult for them to breathe.

Another concern with algal blooms is the production of toxins. Certain species of algae, such as cyanobacteria, can produce toxic compounds that are harmful to fish, shellfish, and other animals, including humans. These toxins can move up the food chain, affecting larger animals and potentially impacting human health.

To mitigate the negative impacts of algal blooms, it is essential to reduce the amount of nitrogen and phosphorus entering water bodies. This can be achieved through several means, such as:

• Choosing phosphate-free soaps and detergents: Phosphates are chemicals that promote algal growth and can be swept into waterways if not properly treated or disposed of.
• Using fertilizer responsibly: Fertilizers contain high levels of nitrogen and phosphorus, which can contribute to algal blooms if used in excess.
• Properly managing animal manure: Manure contains nitrogen and phosphorus, and if not managed correctly, can be washed into waterways during rain events.
• Improving wastewater treatment: Sewer and septic systems should effectively remove nitrogen and phosphorus before discharging water into waterways.
• Reducing the use of fossil fuels: Nitrogen is a byproduct of burning fossil fuels, and power plants, industries, and automobiles are major sources of nitrogen pollution.

Algae can be used to treat industrial and agricultural wastewater

Algae can be used to treat wastewater for a range of purposes, including:

• Removal of coliform bacteria
• Reduction of both chemical and biochemical oxygen demand
• Removal of N and/or P
• Removal of heavy metals

Algae are known to sequester heavy metals and are efficient absorbers of them. They can be grown in ponds with little nutritional input or maintenance.

Algae can also be used to monitor water quality.

Algae can be used in alternative culture and treatment systems, such as:

• Hyperconcentrated cultures
• Immobilized cell systems
• Dialysis cultures
• Tubular photobioreactors
• Stabilization ponds

Algae can be used to treat human sewage

In a sewage treatment facility, organic matter is first anaerobically digested to produce methane, which can be used as fuel. The carbon dioxide produced as a byproduct of this process is then pumped back into the wastewater to feed the algae. This algae can either be specially selected strains or what grows naturally in the ponds. The latter is more cost-effective as it does not require a closed system to avoid contamination.

Once the algae have grown, they can be harvested and the oils separated to produce biofuel. The remaining organic matter can be burned to generate electricity. This process not only treats the sewage water but also produces enough methane to power vehicles and electricity.

Algae are also significant organisms for the biological purification of wastewater. They can accumulate and remove toxic substances such as heavy metals, pesticides, and radioactive materials from the water. Algae are also able to remove nutrients like nitrogen and phosphorus from wastewater, which can be used as fertiliser for agricultural purposes.

Algal-bacterial ponds are designed to keep and improve wastewater over a certain period. While wastewater is treated via physical, chemical, and biological processes, algal-bacterial ponds rely on natural conditions. Stabilisation ponds, where dissolved compounds and suspended solids are stabilised in completely aerobic conditions, are called "oxidation ponds". When stabilisation occurs in anaerobic or facultative conditions, the ponds are called "waste stabilisation ponds".

Algae can remove coliform bacteria from wastewater

Wastewater treatment processes play a crucial role in removing these bacteria and other harmful microorganisms. Algae are effective in this treatment process due to their ability to utilise inorganic nitrogen and phosphorus for growth, removing these nutrients from the wastewater. This is particularly important as the discharge of wastewater loaded with inorganic nitrogen and phosphorus can lead to eutrophication and the growth of unwanted plants, such as algae and aquatic macrophytes.

Additionally, algae can create conditions that are unfavourable for the survival of coliform bacteria. For example, Moawad (1968) observed that environmental factors favourable for algal growth were unfavourable for the survival of coliforms. Furthermore, the presence of algae can increase the pH of the water during photosynthesis, which can also contribute to reducing coliform bacteria.

Overall, the use of algae in wastewater treatment offers a cost-effective and elegant solution for removing coliform bacteria and other pollutants, such as heavy metals and toxic organic compounds, from wastewater.

Frequently asked questions