Phytoplankton: A Natural Solution for Nutrient Pollution in Wastewater Treatment
- Dr. Algae
- Jun 26, 2025
- 8 min read
Updated: Dec 22, 2025
Wastewater treatment facilities across the United States process 34 billion gallons daily. However, they discharge significant levels of nitrogen and phosphorus into lakes and waterways.
EPA data shows that 58% of river and stream miles and 40% of lake acres contain excess nutrients. These excesses trigger harmful algal blooms and serious water quality problems. While municipal treatment systems remove many contaminants, they consistently fail to eliminate these nutrients completely.
Phytoplankton offers a natural solution to nutrient-polluted water bodies that receive treated wastewater. These microscopic organisms absorb excess ammonia, nitrite, nitrate, and phosphate. They take in what conventional treatment methods leave behind. Phytoplankton work within existing ecological processes. They restore water balance while avoiding the harmful effects of chemical treatments like copper sulfate. These chemical treatments damage beneficial organisms such as zooplankton, which are essential to fish fry and other organisms.
Cities and counties face increasing economic pressure from water management costs. American households spend approximately $500 annually on wastewater collection and treatment. Moreover, facilities generate 13.8 million tons of biosolids yearly.
Phytoplankton offers municipalities a cost-effective strategy. It addresses nutrient pollution while supporting both recreational water use and agricultural irrigation needs. This biological method creates sustainable solutions for communities dealing with the impacts of wastewater discharge on their water resources.
The Problem with Nutrient Pollution in Treated Wastewater
Nutrient pollution causes serious ecological problems in freshwater systems. This is the case even with advances in wastewater treatment technology. Treatment facilities discharge excess nitrogen and phosphorus, fueling cascading environmental damage across water bodies.
How Ammonia and Phosphate Affect Freshwater Lakes
Ammonia and phosphate act as fertilizers in water bodies. They drive excessive algae growth, potentially leading to eutrophication. Ammonia can shift from its relatively harmless ammonium (NH4+) form to toxic ammonia (NH3) as lake conditions change. Toxicity in fish can occur at concentrations as low as 0.016 mg/L [11]. This toxicity elevates with higher pH and temperature [11].
Fish exposed to ammonia suffer physical damage. Their gills, liver, kidneys, and other organs can be affected [15]. Even sublethal ammonia levels can reduce swimming activity, disrupt feeding behavior, and impair their ability to escape predators [15].
Phosphates drive algal blooms through bacteria that consume dissolved oxygen. When large algae populations die and decompose, they create dead zones where aquatic life cannot survive [2]. Certain algae species also produce toxins harmful to wildlife and humans who come into contact with affected water [3].
Sources of Nutrient Pollution in City and County Water Bodies
Municipal wastewater treatment facilities release nitrogen and phosphorus from human waste, food residues, and cleaning products [4]. Stormwater runoff carries nutrients from fertilized lawns, pet waste, and urban surfaces directly into water bodies without filtration [15]. Also, combined sewer overflows discharge untreated sewage during heavy rainfall events [15]. Improperly maintained septic systems also contribute significantly, with 10-20% failing during their operational lifetime [4].
These sources result in nutrient overload, affecting 40% of rivers, streams, and lakes nationwide [6].
Why Traditional Wastewater Treatment Isn't Enough
Traditional wastewater treatment plants lack advanced tertiary treatment systems. These systems are necessary to eliminate contaminants of emerging concern, heavy metals, and harmful bacteria [7]. Most facilities, therefore, cannot completely remove nutrients.
As a result, treated wastewater releases significant nitrogen and phosphorus into receiving water bodies. Standard treatment methods become especially problematic during population growth when facilities face increased volumes without corresponding technological upgrades.
Standard treatments struggle with the complex interactions between different pollutants. They also cannot adapt to seasonal variations in wastewater composition. This leaves communities and agricultural operations relying on these water sources facing serious economic and environmental challenges due to degradation.
Phytoplankton as a Natural Solution for Lake Restoration
Phytoplankton provides a biological approach to restoring lakes affected by nutrient-rich wastewater discharge. These microscopic organisms work within natural ecological cycles. They restore water balance instead of simply removing contaminants through chemical intervention.
What is Phytoplankton and How Does It Work?
Phytoplankton are single-celled algae that form the foundation of aquatic food webs. These primary producers absorb nutrients, convert carbon dioxide to oxygen through photosynthesis, and provide food for zooplankton. Phytoplankton respond naturally to environmental changes. Hence, they are effective indicators of water health [8].
These organisms produce oxygen through photosynthesis. This enhances the aerobic degradation of pollutants by beneficial bacteria [9]. Their rapid reproduction cycle enables quick absorption of excess nutrients that would otherwise fuel harmful algal blooms. Additionally, phytoplankton support biodiversity by providing essential food for zooplankton, which then feed fish and other aquatic organisms.
Natural Method to Outcompete Harmful Algae
Traditional copper treatments cause immediate declines in algal populations but trigger massive increases shortly thereafter [10]. Copper-based treatments reduce beneficial zooplankton, eliminating natural algae controllers [10].
On the other hand, phytoplankton strains like Chlorella vulgaris reduce cyanobacteria dominance by 87% in nutrient-rich waters without harming beneficial organisms [11]. Concentrated phytoplankton from Hydralife Solutions competes with harmful algae. It reproduces while absorbing excess nutrients, offering a sustainable solution to problematic algae. Phytoplankton stabilize oxygen levels through continuous photosynthesis without causing harmful die-offs that deplete oxygen [11].
Role in Ammonia Removal and Phosphate Reduction
Phytoplankton effectively absorb nitrogen and phosphorus from wastewater as they grow [12]. They convert toxic ammonia nitrogen into organic matter. This process removes the harmful compound while producing nutritious food for zooplankton [11].
Phytoplankton functional groups adapt to different nutrient conditions. Specific groups thrive in varying nitrogen and phosphorus concentrations [8].
Phytoplankton access both inorganic and organic nutrient pools through direct uptake, enzymatic hydrolysis, and symbiotic relationships with microbial communities [13].
Impact on Harmful Algal Blooms and Water Clarity
Harmful algal blooms occur when nutrient imbalances favor toxic species like Anabaena, Oscillatoria, and Microcystis [12]. Phytoplankton communities compete directly with these harmful species for nutrients, effectively starving them [11].
Research indicates that land-water transition areas improve phytoplankton quantity and quality. This leads to increased zooplankton biomass and trophic transfer efficiency [14]. Dense phytoplankton communities limit light penetration to submerged weeds, naturally controlling macrophyte growth without chemicals [11].
A 2021 study of irrigation ponds found that managed phytoplankton communities reduced cyanobacteria by 50% within six months. Additionally, they decreased sediment copper levels by 30% [11]. This demonstrates phytoplankton's potential for sustainable lake restoration without chemical intervention.
How Phytoplankton Transforms Treated Greywater and Blackwater Lakes
Municipal water bodies contaminated by wastewater discharge pose complex challenges that phytoplankton addresses through natural biological processes. These microscopic organisms actively compete with harmful algae while establishing balanced aquatic ecosystems.
Case Studies of Phytoplankton in Municipal Lake Systems
Lake Jeziorak Mały demonstrates phytoplankton's effectiveness in urban water restoration. Researchers implemented stormwater pretreatment separators and fountain-based aeration systems. This effort produced substantial decreases in harmful cyanobacteria proportions alongside increased diversity of beneficial phytoplankton groups [15]. These changes led to greater water visibility, improved oxygenation, and reduced orthophosphates, transforming the lake from polytrophic to a more balanced eutrophic state [15].
Biological Water Treatment Results
High-Rate Algal Pond technology showcases impressive nutrient removal capabilities. Phytoplankton-based systems remove 26.6-75.7% of nitrogen with a median of 61.23%. They also achieve a range of 21.89-94% ammonia removal with a median of 77% [1]. Phosphorus removal ranges from 10.48-97.2% with a median of 42.73% [1]. This directly addresses the primary driver of harmful algal blooms.
Phytoplankton simultaneously purify water through direct contaminant uptake. They also facilitate the bacterial degradation of organics by generating oxygen through photosynthesis [1]. The resulting biomass can be harvested for biofuel production, creating circular economy benefits [1].
Improving Biodiversity and Supporting Zooplankton
Phytoplankton communities create positive effects throughout aquatic ecosystems. Their diversity directly influences zooplankton communities. Zooplankton serve as the crucial intermediary between algae and fish populations [17].
Diatoms support rotifer development while green algae and certain cyanobacteria foster the populations of microcrustaceans like Copepoda and Cladocera [17]. This relationship maintains efficient energy transfer from phytoplankton to zooplankton. It supports productivity at higher trophic levels [18] and sustains recreational fishing opportunities and overall ecosystem health.
Community and Agricultural Benefits of Phytoplankton-Based Lake Management
Phytoplankton-based lake management delivers practical benefits that extend beyond water quality improvements. Communities gain access to cleaner recreational waters. Farmers receive improved irrigation sources that support crop production since phytoplankton act as a biostimulant to soils.
Water Quality Restoration for Recreational and Irrigation Use
Phytoplankton systems eliminate the risk of harmful cyanobacteria blooms. These blooms produce dangerous toxins affecting humans and animals [12]. Lakes managed with phytoplankton show dramatic improvements in water clarity. This creates safe conditions for swimming, fishing, and boating activities that generate permit and user fee revenue [19].
Property values increase around well-maintained water bodies. They become sources of civic pride and enhance the quality of life for residents [5].
Municipal Cost Savings and Sustainable Operations
Cities and counties benefit from phytoplankton's preventative approach to lake management. Traditional reactive treatments require costly emergency interventions when algae problems become severe. Meanwhile, phytoplankton provides consistent, predictable maintenance costs [19]. This proactive biological method addresses problems before they escalate.
Municipalities reduce their reliance on chemical treatments and energy-intensive processes, resulting in more sustainable operations than conventional methods [9].
Cleaner Water Sources for Local Farming Operations
Agricultural areas surrounding phytoplankton-managed lakes experience significantly fewer toxic algae contamination issues [21]. Farmers benefit from irrigation water that reduces crop contamination risks and associated testing expenses. Water from phytoplankton-balanced systems contains beneficial nutrients in stable forms. These nutrients support plant growth without the problematic effects of untreated wastewater discharge.
Nutrient Recovery Through Struvite Formation
Struvite (MgNH4PO4) recovery from wastewater streams offers farmers an alternative to conventional phosphorus fertilizers [22]. This crystalline mineral functions as a slow-release fertilizer. It contains 5.7% nitrogen and 12.6% phosphorus by weight [23]. Field applications demonstrate that struvite-based fertilizers perform comparably to synthetic products. They also reduce runoff concerns due to lower water solubility [22]. Nutrient recovery through struvite formation prevents pollution while providing agricultural communities with sustainable fertilizer sources [24].
Conclusion
Phytoplankton provides municipalities with a natural method to address wastewater nutrient pollution in lakes and waterways. These microscopic organisms absorb excess ammonia, nitrate, and phosphate. They support aquatic ecosystems through continuous oxygen production and food web enhancement.
Cities and counties benefit from lower water management costs compared to reactive chemical treatments. Phytoplankton systems require less intervention once established. They provide predictable budgeting for water resource management. Municipal lakes transform into community assets, generating revenue through recreational use while supporting agricultural irrigation needs.
Farmers gain access to cleaner irrigation water that reduces crop contamination risks. The potential for nutrient recovery through struvite formation creates sustainable fertilizer alternatives. This practice supports circular economy practices, benefiting agricultural productivity.
Copper sulfate and similar chemicals create harmful boom-and-bust cycles that damage beneficial organisms. Phytoplankton communities work continuously to prevent harmful algal blooms while maintaining water quality through natural ecological processes.
This biological approach addresses the root cause of nutrient pollution rather than treating symptoms after problems develop. Communities seeking cost-effective solutions for wastewater-fed lakes should consider phytoplankton as their primary management strategy for sustainable water quality improvement.