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NPA
(Nitrogen and Phosphorus Removal using Aluminum alloy)
This is a sewage treatment technology that removes phosphorus caused by aluminum nanoparticles from the electrode plate by immersing the aluminum nanoalloy plate to which the rated direct current voltage is applied to the nanoprecipitation equipment, which is an electrolysis tank, through the process consisting of an anoxic tank, aerobic tank, and a nanoprecipitation equipment comprising aluminum-iron alloy.
Operating parameters HRT(hr) MLSS(mg/ℓ) DO(mg/ℓ)
Anoxic tank 2.0 2,200 ~ 5,100 (3,200) 0.1 or less
Aerobic tank 4.0 4,120 ~ 7,240 (4,686) 2.0 ~ 4.2
Iron-aluminum elution tank 0.14 ~ 0.35 (0.2) - 2.1 ~ 4.1
Reactor tank SRT: 10 ~ 30 days, F/M ratio: 0.09 ~ 0.2kg.BOD/kg.MLSS
Settling tank Settling tank residence time 3 hours, water surface load: 14 ~ 20㎥/㎡ per day

Configuration and function

Process Name Process Description Effect
Anoxic tank
  • Reduced facility costs as there is no anaerobic tank
  • Increased nitrogen removal efficiency as the anoxic tank utilizes carbon source for nitrogen removal
  • Reduced anaerobic facility costs and operation management costs and reduced residence time Reduced by approx. 1-2 hours
  • Denitrification effect is achieved by using all the carbon sources consumed when phosphorus is released. 10% increase
Aerobic tank
  • Nitrous oxidation by microorganisms
  • Aluminum and nanoparticles are combined with phosphorus to remove phosphorus
  • Oxidation and decomposition of organic matter
  • Aluminum-nanoparticle precipitation equipment
  • Organic matter and nitrification
  • Nitrogenated water is returned to the anoxic tank internally.
Nano alloy precipitation equipment
  • Elution of aluminum-nanoparticles for phosphorus removal
  • Precision controlled by controlling voltage and current
  • The residence time of the nanoprecipitation device is reduced by 8-20 minutes.
  • A phosphorus removal comparison experiment found that sludge generation is less than when using coagulant.
  • Phosphorus removal rate is over 95% regardless of the microscopic residence time (SRT)
  • Phosphorus removal is performed in the nanoprecipitation device (NPR), ensuring a phosphorus removal efficiency of more than 95% at all times.
  • High phosphorus removal efficiency regardless of temperature
Final settling tank Solid-liquid separation/sludge return/surplus sludge drawing
  • Advantageous when removing water as it contains aluminum and nanoparticles.
  • The nanomaterials hold onto pin-flocs and the sedimentation property of the sludge is improved.

Phosphorus removal principle

  • Precipitation of aluminum and nano ions
    - Al ions are continuously deposited from the anode aluminum plate by passing a direct current through electrochemical dissolving action.
  • Phosphorus removal by physical reaction (mostly)
    - Removal of phosphorus by physical reaction in which aluminum nanoparticles formed through bonding with precipitated aluminum ions are combined with oxygen and phosphorus and removed through settling.
  • Phosphorus removal by chemical reaction (partial)
    - Removal of phosphorus by chemical reaction in which aluminum nanoparticles are combined with soluble phosphorus that is removed

Phosphorus removal mechanism

Nitrogen removal principle

  • Ammonia removal
    4OH- is generated.
    2. Oxidation of ammonia by electrolysis
    3. A large amount of ammonia is oxidized by oxidation of OH- radicals.
    4. Ammonia decomposition is enhanced when salt is present.
    5. Aluminum is eluted according to the Faraday method.
  • Denitrification
    1. Aerobic tank : Nitration NH4+ + 2O2 -----> NO3- + 2H+ + H2O
    2. Anoxic tank : Denitrification NO3-+6H++5e-  0.5N2+3H2O

Nitrogen removal mechanism

Processing efficiency

Item Influent concentration (mg/ℓ) Discharge water concentration (mg/ℓ) Removal rate (%)
Range Average Range Average Range Average
BOD 85.8～133.6 105.0 6.3 ~ 9.9 9.0 89.4 ~ 93.0 91.4
CODMn 44.3～63.4 54.7 4.8 ~ 7.9 5.0 85.6 ~ 90.7 90.8
SS 76.9 ~ 101.7 93.8 7.5 ~ 12.0 7.5 87.6 ~ 92.3 90.2
T-N 29.8～36.4 33.2 9.3 ~ 11.8 9.2 65.8 ~ 73.1 72.2
T-P 2.64 ~ 3.05 2.87 0.16 ~ 0.23 0.19 95.4 ~ 98.5 93.3

Design of NPA

Certification No.

  • Patent No. 10-152877