Drb200 cod reactor

Chemical oxygen demand (COD) was measured by the US-EPA Standard Method 5220 using a HACH DRB200 COD reactor and HACH DR3900 spectrophotometer. Ammonium (NH3-N), total nitrogen (TN) and total phosphorus (TP) were determined by HACH standard kits using the HACH DR3900. Orthophosphate (PO4 3-) was measured using ion chromatography (IC) (Thermo Fisher, Australia). The system was equipped with a Dionex AS-AP auto-sampler and a Dionex AS19 IC column (7. The optical density and dry weight of microalgae culture were determined daily using a UV spectrophotometer (UV 6000 Shimadzu; Australia) at a wavelength of 680 nm and by gravimetric analysis, respectively to assess microalgae growth. For the optical density measurement, 3 mL of homogeneous microalgae cell suspension was transferred into a cuvette to measure the optical density. For gravimetric analysis, 50 mL of microalgae cell suspension was filtered through a 1.1 m pre-weighed glass filter paper. The filter paper was then dried at 60 °C for 4 hours to a constant mass. A linear regression coefficient (R 2 ) of 0.96 was confirmed between the optical density and dry weight biomass.

The TS, VS, ammonia, and alkalinity were analyzed according to Standard Methods for the Examination of Water and Wastewater (APHA, 1999) . COD was analyzed using test kits (Ultra High Range, HACH, Loveland, CO, USA) with a HACH DRB200 COD Reactor and a HACH DR3900 spectrophotometer. Biogas production was recorded and normalized to STP conditions based on the local climatological data. The composition of biogas was analyzed using a gas chromatograph (GC126N, INESA, Shanghai, China) equipped with a thermal conductivity detector and a 2 m*3mm TDX-01 column (INESA, Shanghai, China) . The volatile fatty acids (VFAs) were determined using the direct injection method as previously described (Mu et al., 2018) . The composition of VFAs was characterized by GC-FID (6890B, Agilent Technologies, Palo Alto, CA, USA) using helium as carrier gas and a capillary column (DB-FFAP, 30 m × 0.25 mm × 0.25um, Agilent Technologies, Palo Alto, CA, USA). To visualize cell attachment to CMs, samples were prepared according to previously described method (Chen et al., 2014) , and the scanning electron micrographs were taken using Field Emission Scanning Electron Microscope (ZEISS Sigma, Germany).

Key water quality parameters of the primary effluent were measured according to standard methods. COD was measured using a Hach DRB200 COD Reactor and Hach DR3900 spectrophotometer (program number 435 COD HR) following the US-EPA Standard Method 5220. Adequate dilutions and adjustments were made to minimise chloride interference during sample measurements. A Shimadzu analyzer (TOC-V CSH ) was used to determine TOC concentration. An inductively coupled plasma-optical emission spectroscopy (ICP-OES) system (ICP-OES 710, Agilent, Australia) was used to determine the sodium ion concentration in the samples. Temperature, pH, and electrical conductivity were measured using an Orion 4-Star pH/conductivity meter (Thermo Scientific, Waltham, MA).