Experimental bioreactor

Container

This project innovates with a homemade bioreactor for bioremediation, using laboratory techniques adapted to be more accessible and economical. It uses the microalgae Chlorella vulgaris, contained in agar agar spheres, to purify the water of the El Clavel stream. The central installation is a 2 liter fish tank, chosen for its transparency to optimize photosynthesis. With aeration and agitation systems, it allows monitoring algae growth and water purification. After experimenting for 6 days, the cleaning efficiency and viability of this technique for small-scale water treatment are analyzed, proposing a sustainable option for communities with limited resources.

Aeration

To emulate the stirred tank fermenters of previous research, this bioreactor incorporates a bubbling aeration system, with an aquarium air pump capable of adjusting the flow of oxygen and CO2. This air pump, carefully selected for its capacity of between 4 to 20 liters per hour, guarantees adequate oxygenation and prevents water stratification, essential to keep algae in suspension and in optimal conditions for photosynthesis.

In addition, the pump has a diffuser that disperses the flow evenly, promoting an equitable distribution of nutrients and light. The configuration allows the intensity of aeration to be adjusted to avoid stress on the microalgae and maintain the integrity of the agar spheres where they are immobilized. The strategic positioning of the pump and the use of diffusers ensure effective agitation without creating dead zones, crucial for a homemade bioreactor intended for bioremediation research and application.

PH

Experiments in bioreactors maintained controlled pH and temperature conditions, crucial to optimize the growth and photosynthesis of Chlorella vulgaris, typically between a pH of 6.5-8.5 and temperatures of 20-30°C. pH significantly influences metal biosorption, with maximum performance at pH 7.5, indicating optimal slightly alkaline conditions for the removal of metal ions by Chlorella Vulgaris. Adjusting pH is essential in bioremediation and is commonly performed with sodium bicarbonate to raise it or citric acid to lower it, with continuous monitoring being key to the effectiveness of the process.

Temperature

A thermometer is used to control the temperature at values of 24 ± 2°C.
To increase it, there was a thermal blanket with a thermostat for aquariums, which was not necessary to use. The temperature was constant. The optimal range for the growth of Chlorella Vulgaris is generally between 20-30°C.
Thermal Blankets for Aquariums: They are an effective option for maintaining a constant temperature and can be particularly useful if the bioreactor temperature needs to be raised above ambient temperature.

Lightning

To achieve photosynthesis, it was illuminated with low intensity LED lights.

It was decided to maintain lighting for 16 hours with 8 hours of darkness. Illumination was ensured by a set of LED lights, providing a specific irradiance.

Evaporation

A transparent cover was used for the bioreactor that allowed light to pass through but reduced evaporation. We made sure the cover had some openings to allow gas exchange and prevent overheating of the system.