MICROALGAE TECHNOLOGY

Pre-treated drain water (project 2) contains, besides nutrients (nitrogen and phosphorus) also some contaminants. Direct discharge into water bodies has to be avoided because it will lead to excessive algae growth or eutrophication of water bodies due to the high nutrient concentrations. The nutrients, together with the still remaining pollutants (heavy metals, micropollutants and pathogens), make the receiving waters unsuitable for animal and human use.

The Indian climate is very suitable for microalgae as there is plenty of sun for these microscopic plants to grow. Because algae grow very fast, they take up nutrients from water very efficiently making them an excellent water treatment platform. When the nutrients and pollutants are removed, nutrient poor water is produced which is suitable for safe discharge or reuse. The produced water is suitable for reuse in various agricultural, industrial and domestic settings. With additional treatment (project 1B) this water becomes suitable as a potable source of water.

As algae take up nutrients, they grow and thereby form algae biomass. By recovering this biomass, added value can be created. The biomass is rich in nutrients and can be used as fertilizer, energy or as resource for industry (e.g. bioplastics). This ‘renewable resource’ aspect of microalgae technology fits with the principals of the bio based economy/circular economy.

Microalgae are unicellular photosynthetic microorganisms. They fix almost 50% of global carbon emission and produce about 80% of the oxygen we breathe every day. Microalgae absorb sunlight and fix CO₂ in aquatic media to convert photon energy into chemical energy. Besides light and CO₂, microalgae need nutrients for growth, such as nitrogen and phosphorus. Both these nutrients are available in excess in drain water.

Fig. Microscopic Pictures of different microalgae species

Microalgae technology is ideal for wastewater treatment in warm temperate climates were warmth and light are in abundance. Algae technology results in higher nutrients assimilation efficiencies than other technologies. Additionally, microalgae photobioreactors are also efficient at removing persistent pharmaceuticals, such as diclofenac and carbamazepine, human pathogens and heavy metals.

To make this technology possible research is needed. The current bottlenecks for using microalgae technology for water treatment are the technology’s footprint, the light intensity needs and the energy intensive separation step of biomass and treated liquid. In this project, the research will focus on these aspects.

We will compare the PBRs performance efficiency of suspended microalgae versus self-sedimenting algal-bacterial community. We will research how native species perform in relation to lab species in terms of nutrient recovery and pollutants removal. By using natural occurring microalgae species and a more oxidizing growing environment in the closed PBR we expect to enhance the degradation of persistent pollutants. We will also evaluate the level of contamination of the algae biomass and its limitations for field application.

Initial algae treatment systems will be able to handle up to 100 litres per day. This initial design will serve as a test case for a 1000 litres per day pilot photo bioreactor system that is efficient in removing nutrients and pollutants while making biomass harvesting affordable.

Safe reuse of effluent

The microalgae water treatment system can deliver water that is safe to discharge in rivers. This will have an immense positive impact on the overall water quality of the receiving rivers. Because the produced water does not contain nutrients, it is also suitable for reuse in various industrial and domestic purposes. With proper additional treatment, even drinking water becomes an option. 

Source of income

The recovered algae biomass can be used as fertiliser and other algae based components as pre-cursor for industrial processes. Algae biomass trade could become a local source of income.

Knowledge creation & dissemination

The developed knowledge could be used by various stakeholders and partners to further develop and implement the technology. In turn, this will contribute to a safe water supply and clean water bodies.