Collect algae from the middle portion of algal colony and wash several times with distilled water and filter via filter paper

You can harvest the 30% of the total volume per day, and recover the culture with the 30% of fresh culture media. This could be a semi-continuous culture. Yo need to maintain sterile conditions of the photobioreactor and the fresh and sterile nutrients container. You can connect the all systems with sterile silicon tubes that you can sterilize in autoclave.

What is the measurement of the area of the algaculture you do. If it a small one, use algae-net. If it is a bigger one, flocculation can be preferred.

You can harvest microalgae by flocculation if it is a pilot-scale culture, and gravity Sedimentation for voluminous water or wastewater tanks culture. Flocculation can be also used to increase the efficiency of gravity sedimentation.

With my personal experience I would recommend the use of Flocculation to easily and effectively harvest microalgal cultures. Low cost flocculants such as NaOH and KOH can be used. However, there are many chemicals and salts that can be used as flocculants. You can refer research papers to learn more about them.

You can also use centrifugation or filtration to harvest cultures. However, these techniques require more resources and time.

Hope my answer is helpful.

In my case it's just to recolt microalgae from FRESHWATER to produce biofuel so I can imagine culture's idea later and I want simples methods because can't realise the photobioreactor etc @RACHAN ,@LAURA,@MD please I speak currently french and I trie to ameliore my English

The simplest method is to use algae net. But if you are collecting it from a canal or a pond o a river, you need to have boat at first. That is why I asked the size of your pond.

Bonjour Premice, je me permets de te répondre en francais pour plus de simplicité. Pour la récolte de microalgues à échelle de laboratoire (autour de 5L), il est préférrable de faire usage d'une centrifuge. Mais si c'est plus que cela, il vaut mieux utiliser plusieurs techniques en séquence: sédimentation/floculation ensuite centrifugation.

A noter que si tu cultives des microalgue qui sont moins de 5um, il serait mieux d'utiliser la floculation en modifiant le pH ou d'utiliser des produits chimiques pour agglomerer les cellules. Une fois les cellules ont sedimenté, tu peut utiliser la centrifuge.

Salutations,

Ritesh

Merci beaucoup monsieur @Ritesh