Why We Should Recycle Agricultural Wastewater and How Microalgae Can Help

Greenhouse wastewater treatment using microalgae

Why are our water resources under pressure?

Water is essential for life. Humans survive only about three days without water intake. Animals and plants need it as well. Industry also needs it to generate energy, manufacture goods or grow crops.

With the growing population, the demand for freshwater is constantly increasing. According to a United Nations forecast from 2015, the global freshwater resources will decline by 40% by 2030 if the trends of water usage continue. At the same time, climate change is affecting the global water cycle and thus our freshwater resources. For instance, droughts are becoming more frequent and are lasting longer.

Water pollution is also putting a great strain on our water resources. Agriculture is one of the biggest polluters of water, according to a report by the European Environmental Agency from 2018. Farmers add nitrogen, phosphorus and other nutrients to the irrigation water to help plants grow healthy and produce good yields. However, plants do not absorb all the nutrients in the irrigation water. The remaining nutrients can then enter into rivers and lakes. Nitrates, for example, are the primary pollutant, affecting 18% of European groundwater.

Too many nutrients in water bodies create dead zones

When too many nutrients accumulate in water bodies, plants and algae grow excessively, creating “dead zones”. In these zones oxygen is scarce, and fish and other animals fight to survive. Microalgae, just like plants, need nitrogen and other nutrients. A higher concentration of nitrogen, is a feast for microalgae and they bloom.

But we can use microalgae’s need for nitrogens to our advantage, and that‘s what the REALM project is all about: Developing greenhouse wastewater treatment using microalgae.

Greenhouse wastewater treatment using microalgae

The REALM team is working towards a new cultivation facility where microalgae grow in agricultural effluent. As they grow in this controlled facility, the microalgae remove the fertilisers from the water. In doing so, microalgae prevent the accumulation of fertilisers in the environment, keeping freshwater bodies clean.

We are developing this concept with wastewater from soilless greenhouses. In their proximity, we install microalgae cultivation systems such as big re-circulation ponds, called raceway pond. In these ponds, a paddle wheel propels the microalgal culture. They are particularly suitable for low-cost operations, as investment and operation costs of raceway ponds are lower than for other systems.

Once the nutrient concentration has reached legal limits, farmers can safely resuse the recycled water or release to the environment. From the produced microalgae, we develop bio-fertiliser, bio-pesticides and feed for aquaculture, because microalgae are rich in proteins, fatty acids and nutrients, but also compounds that protect plants or support their growth.

Once we developed and tested our concept, we will share a business model plan, so other people can benefit from our results.