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Algae Based Sewage Treatment

Up flow Anaerobic Sludge Blanket reactor (UASB) coupled Diatom algae PBR sewage treatment technology

In countries with a warm climate throughout the whole year like India, high waste water allows and favors anaerobic treatment of the entire sewage flow. Anaerobic treatment systems such as UASB do not require an energy consuming aeration system and can be constructed much simpler than aerobic treatments.

They convert the organic matter into biogas, which can be recovered. UASB reactors can treat all type of high-strength wastewater. It can be used at large-scale or as decentralized treatment systems for domestic wastewaters; yet domestic treatment is still relatively new and not always successful with domestic wastewater of lower strength. Although it is effective in reducing BOD, COD and TSS the main draw back in this system was minimal reduction of nutrients N and P. so the nutrient rich effluent needs to be further treated to consider its reuse.

Our proposed technology is based on using this nutrient rich effluent to grow diatom algae by Nualgi technology. This process enables N and P removal and as diatoms consumes
CO2 and release oxygen COD and BOD will also be reduced further.

Diatom Algae for Nutrient removal or sewage treatment:

Growing micro-algae / phytoplankton such as Diatom Algae in the sewage will enable the nutrients in the sewage to be consumed and the oxygen produced will satisfy the BOD and COD and provide Oxygen to fish.

Phytoplankton is the natural food for fish and Diatoms are the best group of Phytoplankton.

Thus sewage polluted lakes will become clean and have plenty of fish.

About 50% of the photosynthesis on Earth takes place in water – lakes and oceans and Diatom Algae account for about 50% of the algae in water bodies.

Treated sewage with BGA and Green algae can’t be released into public water bodies.

Advantages of treating sewage with Diatoms:

Nualgi Technology:

Treatment process:
The effluent from the UASB is let in to a series of raceway ponds were diatom algae is grown and as diatom algae needs N and P as food they consume the nutrients present in effluent and during photosynthesis they consume CO2 and release O2 this dissolved O2 helps in further reduction of BOD and COD. The biomass generated from diatoms can be further processed for value added products like Omega 3 Fatty acids and Biodiesel. It can also be used for feed supplement in aquaculture, poultry and dairy industry.

Biogas produced from the UASB contains 35% of CO2 so by removing this CO2 we can improve the calorific value of the gas. For this purpose we can use diatoms which consume CO2 as carbon source. To this CO2 removal we have to use a closed tubular PBR system were raw biogas can be diffused in the effluent and diatoms are grown in this effluent medium in a continuous process and at the end the refined biogas can be collected (fig.1).

Figure.1. Showing the schematic diagram of USAB coupled with Tubular PBR and Raceway reactor. We want to explore both Tubular PBR and race way pond bioreactor systems as race way ponds because of its more retention time, surface area and light penetration are more efficient in Nutrient removal compared to Tubular PBR.

But capturing of CO2 reduced refined biogas is only possible in a closed PBR system so both the possibilities will be explored depending on area available, effluent quantity, biogas input and nutrient load.

The diatom biomass generated from the PBR will be harvested using either a settling filter tank for raceways and through cloth filters from tubular PBR and this biomass can be used for development of values added products for aquaculture, neutaceutical and biofuel purposes.