How can STP Plants Contribute to Nutrient Recovery and Biofertilizer?

We are currently experiencing a significant change in how we handle nutrients and fertilizers due to the growing global population and increased pressure on agricultural resources. Rather than relying on mining or energy-intensive industrial processes to produce nutrients, we are now looking to municipal sewage treatment plants as a surprising source. These plants are becoming key locations for recovering essential nutrients such as nitrogen, phosphorus, and potassium, which are crucial for fertilizing crops and supporting the world's food production. By extracting these nutrients from the waste streams that sewage plants treat, they are leading the way in creating a new sustainable model through biofertiliser production.

Nutrient Flows Through Sewage Treatment Plants

To understand how sewage treatment plants produce fertilisers, we must first examine the high nutrient loads passing through these facilities each day. Both residential sewage and many industrial wastewaters contain concentrated amounts of nitrogen and phosphorus originating from:

• Human waste products containing urea, faeces, and other nitrogen and phosphorus compounds

• Food and organic matter residues with inherent nutrients

• Liquid waste streams from food/beverage processing, agriculture operations, and other industries

Traditionally, sewage treatment plants simply remove these nutrients from wastewater through chemical and biological treatment processes before discharging the treated effluent. However, they are shifting toward recovering the nutrients in solid form for beneficial reuse as fertiliser.

Nutrient Recovery Technologies at Sewage Treatment Plants

There are a variety of technologies sewage treatment plants employ to extract nutrients for fertilizer production:

Biosolids/Sludge Recovery: During biological sewage treatment, microbes accumulate nutrients that become concentrated in sewage sludge or biosolids. These nutrient-dense residuals can be dewatered and processed into nutrient-rich fertilizer products.

Struvite Recovery: Many plants use controlled chemical precipitation to recover magnesium ammonium phosphate (struvite) from digested sludges. Struvite fertilisers provide plant-available nitrogen and phosphorus.

Ion Exchange and Adsorption: Specialized ion exchange resins, zeolites and other sorbents selectively extract nitrogen compounds like ammonium and phosphates from nutrient-rich streams for recovery into fertilizer-grade solutions or solids.

Nutrient Recovery by Microalgae Cultivation: Sewage treatment plants increasingly couple algae bioreactors that directly uptake nutrients from effluent wastes, producing algal biomass that can then be processed into nutrient fertiliser products.

Advanced Biological Nutrient Removal: Optimized biological nutrient removal maximises microbial accumulation of nitrogen and phosphorus, which gets concentrated in biosolids and side streams for downstream recovery.

Types of Biofertilizers Produced at Sewage Treatment Plants

Using the nutrient recovery technologies above, sewage treatment plants around the world have implemented streamlined processing and production facilities to create a variety of fertilizer products:

Biosolids-Based Fertilizers: Dewatered, stabilized sewage sludge/biosolids from biological treatment can be heat-dried and pelletized into commercial fertilizers.

Struvite Fertilizer Granules/Prills: The recovered struvite is processed for optimal size, hardness, coating and nutrient release characteristics in a final fertilizer prill or granule product.

Ammonium/Nitrate Solutions: Ion exchange processes concentrate nitrogen compounds into liquid fertilizer products like ammonium sulfate or ammonium nitrate solutions.

Algae-Based Biofertilizers: Cultivated algal biomass from sewage treatment can be harvested, dried and granulated or processed into liquid/solid fertilizer products rich in micronutrients.

Additional Benefits of Nutrient Recovery

In addition to creating new revenue streams from fertilizer products, nutrient recovery provides additional environmental and operational advantages for sewage treatment plants such as:

• Reduced nutrient discharge into waterways, minimizing eutrophication risks

• Enhanced biological nutrient removal performance driven by nutrient demand

• Decreased biosolids waste volumes requiring disposal

• Reduced greenhouse gas emissions compared to conventional fertilizers

• Production of high-quality effluent suitable for water reuse in agriculture

• Progress toward circular economy models and sustainability goals

Conclusion:

While pioneering sewage treatment plants have proven the economic and technical viability of recovering nutrients for fertilisers, the model still has immense room for growth globally.  Future advances in microbiology, biorefinery processes, improved fertiliser formulations, and streamlined nutrient extraction technologies will enhance production efficiencies.

Increasingly, regulations are expected to mandate more stringent nutrient removal and recovery requirements for sewage treatment. This policy drive, coupled with intensifying fertiliser needs to sustain agriculture, positions sewage treatment plants at the forefront of the emerging nutrient recovery and biofertiliser industry. Transforming waste streams into renewable fertilizers aligns seamlessly with the water sector's transition toward a circular, sustainable resource recovery future.

To explore customised commercial RO plants, Industrial RO plants, ETP or STP solutions for your needs in your areas and nearby regions, contact Netsol Water at:

Phone: +91-965-060-8473, Email: enquiry@netsolwater.com