Hq30d flexi meter

Water quality examinations were performed according to APHA [48 ]. The spectrophotometer DR 2800 Hach Lange (www.hach.com) was used for the assessment of parameters such as chemical oxygen demand (COD), ammonia–nitrogen (NH₄–N), nitrate–nitrogen (NO₃–N), ortho–phosphate–phosphorus (PO₄–P), total suspended solids (TSS) and colour. The 5–day biochemical oxygen demand (BOD) was determined with the OxiTop IS 12–6 system according to Wissenschaftlich–Technische Werkstätten (WTW), Weilheim, Germany. Turbidity was determined with a Turbicheck Turbidity Meter (Lovibond Water Testing, Tintometer Group). Electric conductivity (EC) was measured by the conductivity meter METTLER TOLEDO FIVE GOTM (Keison Products, Chelmsford, Essex, England, UK). Hydrogen ion (pH) and redox potential (Eh) were determined with a sensION+ benchtop multi–parameter meter (Hach Lange, Düsseldorf, Germany). Dissolved oxygen (DO) was recorded by a HQ30d Flexi Meter (Hach Lange, Düsseldorf, Germany).

The physicochemical properties (including pH, conductivity, and the concentrations of anions and metal cations) of the four water samples were analyzed. The pH values were measured using a pH meter (FiveGo F2 pH Meter; Mettler Toledo Instruments, Shanghai, China) after calibrating with buffer solutions of pH 4.01, 6.86, and 9.18 (Mettler-Tolrdo). The conductivity was determined using a conductivity meter (HQ30d Flexi Meter, HACH Company, Loveland, CO) (Cao et al., 2021b (link)). Besides, the concentrations of the anions in water were determined by ion chromatography (Dionex, Thermo Fisher Scientific Inc. Shanghai, China) (Xu et al., 2017 (link)). They were analyzed after calibration with a standard solution containing 5 mg/L each of HCO₃⁻, Cl⁻, NO₃⁻, and F⁻. The metal cation composition (Ca²⁺, K⁺, Mg²⁺, and Na⁺) of the brewing water was analyzed by inductively coupled plasma mass spectrometry (ICP-MS; Thermo Jarrell Ash Corp. USA). The analytical conditions were as follows: a charge injection device detector; low wavelength maximum integration time: 15 s; high wavelength maximum integration time: 5 s; nebulizer pressure: 28 psi; pump speed: 100 rpm; auxiliary gas flow: 1 L/ min; and RF power: 1150 W.