Process upsets in a full-scale anaerobic digestion bioreactor: over-acidification and foam formation during biogas production

Table 2 Analytical methods for wet chemical analyses of the digestate

Parameter	Sample pre-treatment	Analytical methods and instruments
TS	No	DIN 12880
VS	No	DIN 12879
pH value	Sieved	Microprocessor pH meter pH 95 (WTW, Germany)
VFA/TIC	Sieved	Titration method according to [18]
TOC, TN	Sieved	TOC-VCSH/CSN with a TN unit (Shimadzu, Japan)
NH₄–N	Filtered	DIN 38406 E5. Spektroquant® test kit (measuring range 0.01-3 mg L⁻¹ NH₄-N, Merck. Germany). photometric measurement with MultiLab P5 (WTW, Weilheim, Germany)
Acetate, propionate, butyrate, lactate	Filtered	High-performance liquid chromatography (Shimadzu, Japan); detector: RID-10A; column: VA 300/7.8 Nucleogel Ion 300 OA; eluent: 0.01 N H₂SO₄
Water-soluble elements (Ca, Mg, P, S, K, Na)	Filtered	Inductively coupled plasma atomic emission spectrometry ICP-AES (Spectroflame, Spectro Int., Kleve, Germany)