How does a sewage treatment plant remove phosphorus and nitrogen?

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1. 1

   Sewage treatment (Wikipedia)

   WikipediaPublished Oct 10, 2026Checked Oct 11, 2026

   “Sewage treatment is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable for discharge to the surrounding environment or an intended reuse application, thereby preventing water pollution from raw sewage discharges. Sewage contains wastewater from households and businesses and possibly pre-treated industrial wastewater. There are a large number of sewage treatment processes to choose from. These can range from decentralized systems (including on-site treatment systems) to large centralized systems involving a network of pipes and pump stations (called sewerage) which convey the sewage to a treatment plant. For cities that have a combined sewer, the sewers will also carry urban runoff (stormwater) to the sewage treatment plant. Sewage treatment often involves two main stages, called primary and secondary treatment, while advanced treatment also incorporates a tertiary treatment stage with polishing processes and nutrient removal. Secondary treatment can reduce organic matter (measured as biological oxygen demand) from sewage, using aerobic or anaerobic biological processes.”

2. 2

   Vibrating membrane bioreactors enhance nutrient removal and energy efficiency in municipal wastewater treatment.

   Nature communications (Lin et al.)Published Jul 20, 2026Checked Oct 11, 2026

   “Here, we report approximately 800 consecutive days of full-scale (7500 m3 d-1) parallel operation of the vibrating MBR (VMBR) and the conventional aerated MBR (AMBR) systems, systematically comparing their pollutant removal performance, long-term filtration stability, membrane fouling mechanisms, and full life cycle environmental impacts. Results showed that the VMBR demonstrated enhanced nutrient removal, lowering effluent total nitrogen by 22% and reducing the chemical dosage for phosphorus removal by 40% compared with the AMBR. It also exhibited enhanced fouling resistance, with a 20% higher average specific flux than that of the AMBR throughout the operation. Mechanism analysis revealed that the VMBR generated effective, uniform shear at the membrane surface while preserving the sludge floc structure, thereby mitigating membrane fouling. Consequently, the VMBR reduced specific energy consumption for fouling control by 75% and the overall carbon footprint by 30%. We validate that VMBRs represent a scalable, energy-efficient and sustainable technology for future wastewater treatment.”

3. 3

   Water hardness-mediated EBPR-BIPP synergistic phosphorus removal and microbial community response.

   Journal of environmental management (Zhang et al.)Published Sep 21, 2026Checked Oct 11, 2026

   “Sequential extraction and speciation analysis (31P MAS-NMR, XRD, XPS) revealed phosphorus transformation from soluble to stable calcium- and magnesium-bound forms, predominantly hydroxyapatite (HAP) and struvite (MAP), with the MAP proportion increasing at higher hardness. Under high hardness, PPK and PPX activities increased by 109.1% and 80.7%, respectively, and the relative abundance ratio of PAO/DPAO-associated taxa to GAO/DGAO-associated taxa increased from 0.24 to 2.5. A 190-day operation confirmed the synergistic interactions between BIPP and EBPR. Microbial analysis revealed that the relative abundance of GAO/DGAO-associated taxa decreased from 5.0% to 2.0%, while the phoR gene showed its highest relative abundance (0.45%) under high-hardness conditions, suggesting a potential association between extracellular chemical fixation and intracellular storage. This study elucidates the hardness-driven synergistic mechanisms, providing a theoretical basis for EBPR optimization in high-hardness regions.”

4. 4

   Sulfide-driven partial denitrification serves as a remedial strategy for suboptimal partial nitrification-anammox performance.

   Bioresource technology (Wang et al.)Published Sep 9, 2026Checked Oct 11, 2026

   “The partial nitrification-anammox (PNA) process applied to low C/N municipal wastewater treatment is often constrained by unstable nitrite supply and nitrate accumulation. In this study, a coupled suboptimal partial nitrification, sulfide-driven partial denitrification, and anammox (sPN-SPDA) process was developed in a step-feed sequencing batch reactor, in which sulfide was introduced as an electron donor during the second feeding stage. A high nitrogen removal efficiency of 93.2 ± 1.2 % was achieved, with effluent total inorganic nitrogen reduced to as low as 5.1 ± 0.5 mg/L. Microbial community analysis demonstrated the enrichment of sulfide-driven partial denitrification (SPD)-related denitrifiers after sulfide addition, particularly Thauera (16.3 %), which supported the conversion of NO3--N to NO2--N. Metagenomic analysis showed increased abundances of nitrate-reduction genes napA and napB, consistent with improved nitrite availability for anammox. Overall, this study provides a promising strategy to alleviate nitrite limitation caused by suboptimal partial nitrification and to achieve advanced nitrogen removal from low C/N municipal wastewater.”

5. 5

   Robust nitrogen removal through simultaneous denitrification and anammox driven by alkaline sludge fermentation liquid at varying nitrification levels.

   Bioresource technology (Li et al.)Published Aug 1, 2026Checked Oct 11, 2026

   “Here, a stable simultaneous denitrification-anammox system driven by alkaline sludge fermentation liquor (ASFL) under varying nitrification levels (PN, complete nitrification, and their coexistence) has been presented. Through a 240-day continuous operation treating municipal wastewater, this system achieved high nitrogen removal efficiency, ranging from 96.9 ± 2.0% under PN to 95.7 ± 2.4% under coexistence of PN and complete nitrification. Isotope tracing and microbial analyses indicated that ASFL-supported heterotrophic denitrification was the dominant nitrogen removal pathway, whereas anammox activity remained detectable but contributed only to a limited extent under the investigated conditions. Metagenomic analysis revealed functional shifts in nitrogen metabolism while the core carbon metabolic potential remained largely conserved. Combined with an optimized iron-assisted strategy for effluent polishing, this ASFL-driven simultaneous denitrification-anammox framework provides a sustainable, circular pathway for energy-efficient nitrogen removal, addressing the inherent vulnerability of mainstream PN applications.”

6. 6

   Sewage sludge treatment (Wikipedia)

   WikipediaPublished Oct 10, 2026Checked Oct 11, 2026

   “Sewage sludge treatment describes the processes used to manage and dispose of sewage sludge produced during sewage treatment. Sludge treatment is focused on reducing sludge weight and volume to reduce transportation and disposal costs, and on reducing potential health risks of disposal options. Water removal is the primary means of weight and volume reduction, while pathogen destruction is frequently accomplished through heating during thermophilic digestion, composting, or incineration. The choice of a sludge treatment method depends on the volume of sludge generated, and comparison of treatment costs required for available disposal options. Air-drying and composting may be attractive to rural communities, while limited land availability may make aerobic digestion and mechanical dewatering preferable for cities, and economies of scale may encourage energy recovery alternatives in metropolitan areas. Sludge is mostly water with some amounts of solid material removed from liquid sewage. Primary sludge includes settleable solids removed during primary treatment in primary clarifiers.”