Nanocolor chromafil membranefilter gf pet 0.45 μm

TSS was quantified using standard methods (Apha, 2005 ). Sludge was separated using sieves of 0.25 mm (to separate flocs < 0.25 mm from granules > 0.25 mm) or 1 mm (to separate large granules > 1 mm from small granules, flocs and debris). Sieving of the different sludge fractions was performed by gently pouring the sludge into the sieve, and then washing the sieve with additional tap water. The particles retained by the sieve were collected by back-washing the cake that formed on the sieve with tap water. Size fractions were then quantified using TSS measurements. Total and soluble COD was measured using cuvette tests (LCK 114, 314, Hach-Lange, Germany, Kits). X_B was defined as the difference between total and soluble COD, measured after filtration at 0.45 μm using membrane filters (Macherey Nagel, Nanocolor Chromafil membranefilter GF/PET 0.45 μm, Germany). Samples were collected in 50 mL vials and homogenized for 1 min at 10′000 rpm (Ultra-Turrax, Ika, Germany) prior to total COD measurement. In our study, X_B refers to all COD fractions larger than 0.45 μm, including biodegradable and unbiodegradable fractions of particulate COD and possibly a fraction of the colloidal COD (Levine et al., 1985 ).

Samples of influent and effluent were analysed for COD, total nitrogen (TN) and total phosphorus (TP) using photochemical tests (Hach Lange, Germany, LCK 114, 314, 338, 238, 348, 349). Soluble COD (sCOD) was measured after filtration at 0.45 μm (Macherey Nagel, Nanocolor Chromafil membranefilter GF/PET 0.45 μm, Germany). Cations (NH₄⁺-N) and anions (NO₃⁻-N, NO₂⁻-N, PO₄^3--P) were measured using flow injection analysis (Foss, FIAstar flow injection 5000 analyzer, Denmark) and anion chromatography (Methrom, 881 compact IC, Switzerland), respectively. VFAs were measured using headspace solid-phase microextraction (HS-SPME) followed by gas chromatography coupled to flame ionization detection (GC-FID) (Trace 1300 GC, Thermo Scientific, USA) (Feng et al., 2008 (link)).

Samples for dissolved organic carbon (DOC), nitrite, nitrate and ammonium measurements were filtered at 0.45 μm (Nanocolor Chromafil membrane filter GF/PET 0.45 μm, Macherey Nagel, Düren, Germany) for sample conservation and stored at 4°C before the chemical analysis. DOC was measured using a total organic carbon analyzer (Shimadzu TOC-L, Kyoto, Japan). Ammonium was measured by gas-diffusion flow injection (Foss, Hillerød, Demark). Nitrite and nitrate were measured by means of ion chromatography (Metrohm 881, Herisau, Switzerland).
Free and total chlorine were measured immediately after sampling using a portable spectrophotometer (DR 1900, Hach, Loveland, USA) with corresponding test kits (DPD, 0–2 mg/L free chlorine, Hach, Loveland, USA).