HomePhotometry & ReflectometryAmmonium in Sewage Sludge

Ammonium in Sewage Sludge

Photometric determination using the indophenol blue method

Photometric determination of ammonium in sewage sludge


Ammonium is a key parameter in water testing, as it can have adverse effects on marine ecosystems at high levels. One major issue is eutrophication, excessive plant and algal growth.1 As a result, determining ammonium levels during the process of sewage treatment is critical to maintaining aquatic environments. In this application note, we describe quantification of ammonium in sewage sludge with the Spectroquant® photometry system and ammonium test kits.

Experimental Method

Ammonium nitrogen (NH4-N) occurs partly in the form of ammonium ions and partly as ammonia. A pH-dependent equilibrium exists between the two forms. In strongly alkaline solution ammonium nitrogen is present almost entirely as ammonia, which reacts with hypochlorite ions to form monochloramine. This in turn reacts with a substituted phenol to form a blue indophenol derivative that is determined photometrically. Due to the intrinsic yellow coloration of the reagent blank, the measurement solution is yellow-green to green in color.

The method is analogous to EPA 350.1, APHA 4500-NH3 F, ISO 7150-1, and DIN 38406-5.

Reagents, Instruments and Materials

Test Kits

One of the following test kits is necessary for this analysis:

  • Ammonium Cell Test Method: photometric 0.20 - 8.00 mg/l NH4-N: 0.26 - 10.30 mg/l NH4+ Spectroquant® (1.14558)
  • Ammonium Cell Test Method: photometric 0.5 - 16.0 mg/l NH4-N: 0.6 - 20.6 mg/l NH4+ Spectroquant® (1.14544*)
  • Ammonium Cell Test Method: photometric 4.0 - 80.0 mg/l NH4-N: 5.2 - 103.0 mg/l NH4+ Spectroquant® (1.14559)
  • Ammonium Test Method: photometric 0.010 - 3.00 mg/l NH4-N: 0.013 – 3.86 mg/l NH4+ Spectroquant® (1.14752)
  • Ammonium Test Method: photometric 2.0 - 150 mg/l NH4-N: 2.6 - 193 mg/l NH4+ Spectroquant® (1.00683)

*Not compatible with Move 100


One of the following instruments is necessary for this analysis:

  • Spectroquant® VIS Spectrophotometer Prove 100 (1.73016)
  • Spectroquant® UV/VIS Spectrophotometer Prove 300 (1.73017)
  • Spectroquant® UV/VIS Spectrophotometer Prove 600 (1.73018)
  • Spectroquant® Photometer NOVA 30 (1.09748)
  • Spectroquant® Photometer NOVA 60 (1.09751)
  • Spectroquant® Photometer NOVA 60A (1.09752)
  • Spectroquant® Colorimeter Move 100 (1.73632)


  • Rectangular cells 10 mm (1.14946) and/or
  • Rectangular cells 20 mm (1.14947) and/or
  • Rectangular cells 50 mm (1.14944)
  • Folded filter, Whatman® pre-pleated qualitative filter paper, Grade 1573 ½ (WHA10314745)
  • EMSURE® Water for analysis (1.16754)

Sample preparation

  1. In a 1000-ml volumetric flask, mix 50 g of the sample with water for analysis and fill up to the volume
  2. Let the insoluble parts settle and decant 250 ml of the supernatant solution
  3. Then add 2.5 g of charcoal activated for soil tests and stir for 10 minutes, before filtering through a folded filter


Determine with the above-mentioned test kits.


Ammonium content in mg/l NH4 = analysis value in mg/l NH4 x 20



Camargo JA, Alonso Á. 2006. Ecological and toxicological effects of inorganic nitrogen pollution in aquatic ecosystems: A global assessment. Environment International. 32(6):831-849.
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