Algae farm on wastewater producing clean water and renewable energy.

Algae Bloom Breakthrough: Turning Wastewater into Protein Gold

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Samir D’Costa in Climate & Environment December 2025 • 4 min read.

"Freshwater Macroalgae Offers Sustainable Solution for Nutrient Recovery and Protein Production"


Imagine a world where waste isn't really waste, but a resource waiting to be unlocked. Industries like aquaculture often produce nutrient-rich wastewater, which, if not properly managed, can harm the environment. But what if we could harness this waste, turning it into something beneficial?

Freshwater macroalgae, a largely untapped group of phototrophic organisms, presents a game-changing opportunity. These algae can thrive on waste nutrients and water, yielding biomass suitable for animal feed and renewable chemicals, contributing to a circular economy. This approach aligns with the principles of industrial ecology, where the waste of one process becomes the fuel for another.

A recent study delves into how the freshwater macroalga Oedogonium responds to varying nutrient and carbon levels, achieved by tweaking water exchange rates and adding nitrogen and CO2. The findings reveal optimal conditions for biomass production and protein content, paving the way for integrating macroalgae into wastewater treatment and sustainable protein production.

Unlocking Algae's Potential: Optimizing Growth and Protein Production

Algae farm on wastewater producing clean water and renewable energy.

The research pinpoints that Oedogonium flourishes best with a delicate balance of nutrient flow. Surprisingly, biomass production peaks at low water flow rates (0.1–1 volume per day) when using raw pond water. Boosting CO2 levels in these cultures further enhances biomass production by 2% to 25%, particularly when water exchange is limited. Conversely, adding nitrogen can hinder productivity, especially at lower water exchange rates.

The sweet spot for Oedogonium cultivation lies in water exchange rates between 0.5 and 1 volume per day. At this rate, nutrient uptake is maximized, reaching 1.09 g/m²/day for nitrogen and 0.13 g/m²/day for phosphorus. The resulting biomass boasts impressive uptake efficiencies of 75.2% for nitrogen and 22.1% for phosphorus.

Here are the key conditions for optimal Oedogonium growth:
  • Water Exchange Rate: 0.5-1 volume per day.
  • Nitrogen Flux: Minimum 1.45 g/m²/day.
  • Phosphorous Flux: Minimum 0.6 g/m²/day.
  • Result: Biomass production of 16-17 g DW/m²/day with 25% crude protein content.
The study unveils a simple model: for every gram of dry weight biomass produced, Oedogonium needs 0.09 g/m²/day of nitrogen and 0.04 g/m²/day of phosphorus. Meeting these minimums prevents nutrient limitation, ensures high nutrient uptake, and boosts overall efficiency. This positions freshwater macroalgae as a viable solution for wastewater bioremediation and a sustainable protein source.

The Future is Green: Macroalgae Leading the Way

This research underscores the potential of integrating freshwater macroalgae with aquaculture and other industries producing nutrient-rich wastewater. By carefully managing water exchange rates and nutrient inputs, we can maximize biomass production, create valuable protein resources, and remediate environmental pollutants.

Oedogonium's adaptability to varying conditions makes it an ideal candidate for large-scale cultivation. Unlike some marine species, Oedogonium thrives even with limited water exchange, cutting costs and increasing efficiency. This opens doors for algae-based bioremediation in diverse industrial settings.

As the world seeks sustainable solutions for food production and waste management, freshwater macroalgae offer a promising path forward. By embracing innovative approaches, we can transform waste into valuable resources and create a greener, more sustainable future for all.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1371/journal.pone.0101284, Alternate LINK

Title: Removing Constraints On The Biomass Production Of Freshwater Macroalgae By Manipulating Water Exchange To Manage Nutrient Flux

Subject: Multidisciplinary

Journal: PLoS ONE

Publisher: Public Library of Science (PLoS)

Authors: Andrew J. Cole, Rocky De Nys, Nicholas A. Paul

Published: 2014-07-07

Everything You Need To Know

1

What is Oedogonium, and how is it used?

The freshwater macroalga, Oedogonium, is a phototrophic organism that can thrive on waste nutrients found in wastewater, making it suitable for animal feed and renewable chemicals. The process involves using the Oedogonium to clean wastewater, converting it into valuable protein, aligning with industrial ecology principles where waste from one process becomes the resource for another.

2

What are the optimal conditions for growing Oedogonium?

Optimizing the growth of Oedogonium involves managing the environment it grows in. The key conditions include a water exchange rate of 0.5-1 volume per day, a minimum nitrogen flux of 1.45 g/m²/day, and a minimum phosphorus flux of 0.6 g/m²/day. Maintaining these conditions ensures maximum biomass production, which can reach 16-17 g DW/m²/day with a 25% crude protein content.

3

How much nitrogen and phosphorus does Oedogonium need to thrive?

The study reveals a simple model for Oedogonium. For every gram of dry weight biomass produced, the algae requires 0.09 g/m²/day of nitrogen and 0.04 g/m²/day of phosphorus. Meeting these minimums is crucial because it prevents nutrient limitation, ensuring the algae can efficiently uptake nutrients. It ensures high nutrient uptake and boosts overall efficiency. This allows for wastewater bioremediation and a sustainable protein source.

4

How does water exchange rate affect Oedogonium growth?

Water exchange rate significantly impacts Oedogonium growth. The research shows that optimal biomass production is achieved with water exchange rates between 0.5 and 1 volume per day. This rate maximizes nutrient uptake, leading to impressive efficiencies of 75.2% for nitrogen and 22.1% for phosphorus, making it a critical factor for the process efficiency.

5

How can Oedogonium contribute to a more sustainable future?

By integrating freshwater macroalgae such as Oedogonium with industries that produce nutrient-rich wastewater, such as aquaculture, we can create a circular economy. This involves carefully managing water exchange rates and nutrient inputs to maximize biomass production. This approach not only generates valuable protein resources but also helps remediate environmental pollutants, addressing both environmental and economic challenges.

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