♻️ Ammoniacal nitrogen in sewage sludge — extraction with 2 mol/l potassium chloride — PN-EN 14671

Environment PN-EN 14671

Overview

WHAT THIS TEST IS — SCOPE FROM THE PKN CARD, IN FULL: "Podano procedurę oznaczania ekstrahowalnego amoniaku, z zastosowaniem roztworu chlorku potasu 2 mol/l, w surowych i zmineralizowanych osadach ściekowych. Zakres metody wynosi do 100 g/kg N pod warunkiem odpowiedniego rozcieńczenia ekstraktu w ostatnim etapie pomiarów. Metoda może być przydatna do innych rodzajów osadów ściekowych, jednak zaleca się, aby użytkownik zwalidował metodę stosując te osady" [A procedure is given for the determination of extractable ammonia, using a 2 mol/l potassium chloride solution, in raw and mineralized sewage sludge. The range of the method is up to 100 g/kg N, provided that the extract is suitably diluted in the last stage of the measurements. The method may be suitable for other types of sewage sludge, but it is recommended that the user validate the method using these sludges]. The introduction of the standard explains the purpose: sludge is applied to land as a fertilizer or as a means of disposal, so extractable ammonia has to be controlled.

WHY POTASSIUM CHLORIDE AND NOT WATER (clause 4). The 2 mol/l KCl solution is used in order to determine both the soluble and the ion-exchangeable forms; it also limits biological activity in the extract. Definition 3.1: extractable ammonia is the ammonia released when the homogenized sludge is shaken with 2 mol/l KCl for 1 h at room temperature. The results are expressed as nitrogen.

RESULT ON DRY MATTER. UNDRIED sludge is taken for the analysis, but it is customary to report the result calculated on dry matter — that is why the dry residue is determined according to EN 12880 on a separate portion of the same homogenized sample (clause 4).

SAMPLE — TIME AND TEMPERATURE MATTER (clause 9). The composition of the sludge changes through biological and chemical activity: during transport to the laboratory the samples are kept in cooling containers at a temperature below 4 °C and analysed as soon as possible — within 24 h of sampling. If longer storage is unavoidable, the sample is frozen at –18 °C or below, for at most 4 weeks, and this is recorded in the test report. The sample MUST NOT be dried before homogenization — drying causes a loss of ammonia. For frozen sludges, the standard recommends transferring a portion of the frozen, homogenized sample (corresponding to 0.25 g to 1 g of dry matter) directly into the KCl solution, because nitrogen compounds may be transformed during thawing.

PROCEDURE (clause 10): • m grams of homogenized sludge "as received", corresponding to (0.25 to 1) g ± 2 mg of dry matter — but not more than 20 g of sludge — are weighed into an extraction bottle (e.g. 250 ml, glass or plastic, with a secure closure); without a dry matter result, it can be estimated visually; • (80 ± 1) ml of 2.5 mol/l KCl and (20 – m) ± 1 ml of water are added — so the bottle contains approximately 100 ml of KCl solution with a concentration of 2 mol/l; • it is shaken for (60 ± 5) min at room temperature — a horizontal shaker (20 to 40 rpm, stroke approx. 20 mm), a roller table (approx. 10 rpm) or an "end-over-end" rotary mixer (5 to 10 rpm); the material must not settle or be abraded; • sludges are difficult to filter — the standard recommends centrifuging a portion of the extract and then filtering it through a pleated filter (cellulose, pores 20 µm to 25 µm), discarding at least the first 10 ml; other validated ways of obtaining a clear liquid are permitted (the technique is stated in the test report); DO NOT use vacuum filtration, as it leads to losses of ammonia; • usually the ammonia concentration allows the extract to be diluted 10-fold even before filtration, which greatly speeds up the filtration; • the filtrate is stable for a few hours in a tightly closed polyethylene bottle in a refrigerator at (0 to 4) °C; for longer — in a freezer below –18 °C.

REAGENT (7.2): potassium chloride 2.5 mol/l — dissolve (931.9 ± 1) g of KCl (dried for 1 h at (105 ± 2) °C) in about 3 l of water and make up to 5 l in a volumetric flask; water of grade 2 according to EN ISO 3696.

WHAT THE AMMONIA IN THE FILTRATE IS DETERMINED BY. The standard speaks only of "a suitable method" (clauses 4 and 8.5). In accreditation scopes, PN-ISO 5664:2002 stands next to PN-EN 14671 — distillation and titration (16 entries) — or PN-EN ISO 11732:2007 — flow analysis (3 entries); both methods have separate entries in this database. Technique in the scopes: "Metoda miareczkowa" [Titrimetric method] (18), continuous flow analysis CFA with spectrophotometric detection (3), spectrophotometric (1).

INTERFERENCES AND HAZARDS (clauses 5 and 6). At typical concentrations, the substances present in sludges should not interfere with the extraction; a high ammonia concentration usually limits interference in the final measurement, but the standard requires recovery checks. Sludges may contain pathogens and flammable substances; gases from microbiological activity build up overpressure in closed bottles — a bursting bottle threatens infectious fragments and aerosols, which is why glass bottles are avoided and the samples are stored at (0–4) °C in containers that allow gases to escape.

EDITIONS (state of the PKN cards on 25.09.2026). PN-EN 14671:2007 — Polish version, publication 25-06-2007, 13 pages, KT 121 Water Quality — Chemical Testing — Inorganic Substances, introduces EN 14671:2006 [IDT], without the "Wycofana" [Withdrawn] header; it replaced PN-EN 14671:2006 (English version of 11-08-2006, 11 pages; withdrawn 25-06-2007). At the publisher (the CEN catalogue run by iTeh, read on 25.09.2026): EN 14671:2006 published 28-06-2006 (CEN/TC 308 "Characterisation of sludges"); stage 90.93 — decision to confirm after the systematic review (enquiry from 13-06-2022, closing 23-09-2026).

HOW ACCREDITATION SCOPES CITE THE STANDARD. Measurement of 25.09.2026 on the database of PL accreditation scopes (1310 laboratories with entries): 22 entries at 15 laboratories, all with the notation "PN-EN 14671:2007". The subject of the test is most often "Osady ściekowe" [Sewage sludge] (14), several entries — waste with code 19 08 05 (stabilized municipal sewage sludge); the methodology "Zawartość azotu amonowego" [Ammoniacal nitrogen content] (21 of 22). The declared ranges — in % or in g/kg — have lower limits from 0.005 % to 0.5 % (from 0.05 g/kg to 1.0 g/kg), and upper ones from 1.6 % to 15 % (from 50 g/kg to 150 g/kg). Three entries indicate as the determination method neither PN-ISO 5664 nor PN-EN ISO 11732.

THE KEY OF THE "LABORATORIES" TAB: "PN-EN 14671" — 15 laboratories and 22 entries, without foreign entries.

WHAT WE DO NOT GIVE. We had a fragment of the text of EN 14671:2006 made available by the publisher: the foreword, the introduction and clauses 1–10.3 (up to the sentence on the 10-fold dilution of the extract). We do not have the rest of 10.3 and 10.4 (reference to the determination method), the formula for expressing the result (clause 11) or the data of the interlaboratory study (Annex A). We do not give the formula or the precision.

Method principle

Homogenized, undried sludge (0.25–1 g of dry matter) is shaken for 60 ± 5 min at room temperature with about 100 ml of 2 mol/l KCl solution; the extract is centrifuged and filtered (without vacuum), and the ammonia is determined in the filtrate by a suitable method (e.g. PN-ISO 5664, PN-EN ISO 11732). The result is expressed as nitrogen, usually calculated on dry matter determined according to EN 12880.

Applications

• Raw and digested (mineralized) sewage sludge — extractable ammonia expressed as nitrogen
• Assessment of sludges before application to land (fertilization, disposal)
• Other sludges — after validation by the user (note in the scope of the standard)

Key parameters

Standard

Standard number

PN-EN 14671:2007 (wersja polska; wprowadza EN 14671:2006 [IDT]; zastąpiła PN-EN 14671:2006 w wersji angielskiej)

Title (PL)

Charakterystyka osadów ściekowych — Wstępne przygotowanie próbki do oznaczania amoniaku ekstrahowalnego roztworem chlorku potasu 2 mol/l

Title (EN)

Characterization of sludges — Pre-treatment for the determination of extractable ammonia using 2 mol/l potassium chloride

Step-by-step procedure

1. Sample

   Transport below 4 °C, analysis within 24 h; no drying before homogenization. For longer storage — freezing at ≤ –18 °C, max. 4 weeks.

   🌡 Temperature: < 4 °C

2. Dry residue

   From a separate portion of the same homogenized sample — according to EN 12880 (for calculating the result on dry matter).

3. Test portion and solution

   Sludge corresponding to 0.25–1 g of dry matter (not more than 20 g) into the bottle; (80 ± 1) ml of 2.5 mol/l KCl and (20 – m) ± 1 ml of water.

4. Extraction

   Close and shake at room temperature.

   ⏱ Time: (60 ± 5) min

5. Clarification

   Centrifuge a portion, filter through a pleated filter, discard at least 10 ml; usually the extract can be diluted 10-fold before filtration. No vacuum.

6. Determination

   Ammonia in the filtrate — by a suitable method (in accreditation scopes: PN-ISO 5664 or PN-EN ISO 11732); result as nitrogen. WE DO NOT GIVE the formula (clause 11).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Sludges may contain pathogens — gloves, work limiting aerosols, microbiological safety rules
• Gases from microbiological activity build up overpressure — risk of bottles bursting; avoid glass, use containers that allow degassing
• Flammable gases — explosion-proof equipment in the surroundings (note in 6.1)

Frequently asked questions