Dr900 colorimeter

Extractable SOC, inorganic chemical species, CO₂ and CH₄ were analyzed, as described previously (Yang et al., 2016 (link)). In short, headspace CO₂ and CH₄ were analyzed with a SRI 8610C gas chromatograph equipped with a flame ionization detector (SRI Instruments, Torrance, CA). Soil samples were extracted with either 0.1 M KCl (pH ~ 5.0) or 10 mM NH₄HCO₃ (pH ~ 7.3) solution to determine soluble soil organic compounds and dissolved inorganic species. Total dissolved organic C (DOC) was measured by a Shimadzu TOC-L analyzer (Shimadzu Corp., Kyoto, Japan). Alcohol compounds were analyzed with an Agilent gas chromatograph (Agilent Technologies), and organic acids were measured by ion chromatography using a Dionex DX500 system (ThermoFisher Scientific, Madison, WI). Simple sugars such as glucose and cellobiose were analyzed on a high-performance liquid chromatograph (Waters, Milford, MA). Dissolved Fe(II) and total Fe concentrations were quantified using phenanthroline method following the HACH procedures 8146 and 8008, respectively, on a HACH DR 900 colorimeter.

The monitoring of general water chemistry and ambient conditions was performed daily: temperature, pH, and conductivity were measured using an Orion pH-meter 420 (ThermoFisher Scientific Ltd., Waltham, WA, US). The composition of dissolved nutrients (phosphate, nitrate, nitrite, and ammonium ions) and their depletion were monitored using a HACH DR-900 colorimeter (HACH Co., London, ON, Canada). Analysis of water ions (Ca, Mg, K, P, and metals) was conducted by inductively coupled plasma mass spectrometry (ICP-MS) at the Manitoba Chemical Analysis Laboratory (MCAL) of the University of Manitoba. Water samples for ion analysis were acidified with 16N HNO₃ (1% acidification).
The experimental framework was completed on three different media. The RFWW was designed taking into account both BBM and natural fish wastewater (FWW) physico-chemical parameters. To eliminate the possible influence of pH on S. quadricauda and L. minor physiology and steroid performance, the pH of all the media tested was adjusted to 7 with 1 N HCl or 1 N NaOH solutions. All pH-adjusted media were equilibrated for 1 day prior to being used in the tests.

Oxidative reduction potential (ORP), pH and conductivity were measured using a Myron L 6PFCE Ultrameter II (Myron L Company, Carlsbad, CA, USA). The sensor wells were rinsed 3× with sample prior to measurement.
Free chlorine was measured using the N,N‐diethyl‐p‐phenylenediamine (DPD) method (HACH method 8167) with a HACH DR 900 colorimeter (HACH, Loveland, CO, USA) according to the manufacturer's instructions. Blanks consisting of sample effluent without DPD reagent were run prior to each sample to zero the instrument. Free chlorine pillow packs (HACH) were added to 10 ml of sample effluent, allowed to react for 1 min, then run using program 87 Chlorine F&T PP MR. Samples above the range of detection (2.2 mg/L) were diluted with diH₂O, and the instrument was zeroed with the diluted sample prior to the addition of reagent. Exposure time (C·t) at time n was calculated by determining the area under the concentration/time curve (Le Dantec et al. 2002):
$C·t_n=\left(C_{n-1}·t_{n-1}\right)+\left[\frac{C_n+C_{n+1}}{2}\right]·(t_{n+1}-t_n)$
Total solids (TS) were determined according to the EPA method (EPA 2001) by evaporating triplicate samples (5–10 ml) at 103–105°C in tared aluminum weighing dishes. Total suspended solids (TSS) were determined in triplicate by weighing liquid samples (∼10 ml) in tared tubes, washing the samples through tared 0.7‐μm filter paper (Fisher), and weighing the filter papers after drying at 103–105°C.