Ph 700

The pH of the samples (water and sediment) was measured on-site using pH strips [Hi-Media], which were further analyzed in the laboratory using a pH meter [(EUTECH instruments pH 700)]. The temperatures of the water and sediment samples were recorded using a thermometer during sample collection. TDS, SO₄²⁻, ammoniacal nitrogen, NO₃, NO₂, and Cl were analyzed as per standard protocols [26 ]. The analyses of Ca, Mg, Zn, Mn, Fe, B, Cu, Co, Mo, Cd, Cr, Al, B, Ni, Pb, Hg, Li, Va, Se, Si, and As were followed as per AOAC 990.08 standards [27 ]. TOC, TKN, conductivity, and salinity were recorded as per IS 2720 [28 ], AOAC 955.04 [29 ], APHA 2510B [30 ], and APHA 2520B [31 ] standards.

Wastewater samples were collected from KwaDlangezwa Wastewater Treatment Plant and Tendele Coal Mine Wastewater Plant in KwaZulu-Natal, South Africa. Parameters such as total nitrogen (N), biochemical oxygen demand (BOD), phosphorus (P) and chemical oxygen demand (COD) were measured before and after treatment with the bioflocculant. The measurements were performed using a spectrophotometer (Spectro-quant Phero 300, Merck KGaA, Darmstadt, Germany) and a pH meter (Eutech Instruments pH 700, Singapore) [36 (link)]. About 3 mL of 1% (w/v) AlCl₃ ions and 2 mL of 0.4 mg/mL bioflocculant solution were mixed with 100 mL of wastewater sample in a 250 mL conical flask. The mixtures were agitated at 200 rpm for 3 min, and the speed was thereafter reduced to 40 rpm for 5 min. The flasks were left at room temperature to stand for 10 min for sedimentation. For comparison, conventional flocculants such as alum and ferric chloride (0.4 mg/mL) were used. Thereafter, the percentage removal efficiency of the bioflocculant on; N, BOD, P and COD was measured by reading the optical densities at 680 nm. The following formula was used to calculate the bioflocculant removal efficiency [37 (link)];
$$\mathrm{Removal} \mathrm{efficiency} \left(\mathrm{RE}\right) (\%)=\left[\frac{Co-C}{Co}\right] \times 100,$$
whereby Co and C are the values before and after the flocculation process measured at 680 nm, respectively [38 (link)].

The seawater pH was monitored with a pH meter (pH 700, Eutech Instruments, Singapore) and total alkalinity (TA) was calculated by titrations (Gao et al., 2019 (link)). Other parameters of the carbonate system were obtained with CO2SYS software (Pierrot, Lewis & Wallace, 2006 ), the equilibrium constants K₁ and K₂ for carbonic acid dissociation (Roy et al., 1993 (link)).

Glyphosate was purchased from Sigma Aldrich Chemie GmbH, 45521, Buchs, Switzerland. Dilution series of up to 0.3 mM were prepared in local tap water (Lyngby Taarbæk municipality, Denmark) with no further treatment or purification. Water characterization can be seen in the Supplementary Material, Table S1. Tap water was also considered as the background in all measurements. Omethoate was purchased from Sigma Aldrich, 36181. Aminomethylphosphonic acid (APMA) was purchased from Sigma Aldrich, 324817. A concentration of 0.3 mM was prepared using local tap water with no further treatment or purification. All electrochemical measurements were taken with a potentiostat (PalmSens 3, PalmSens, Houten, The Netherlands). Commercial, screen-printed electrodes based on gold working and counter electrodes and a silver reference electrode were used to conduct the measurements (DRP 220AT, Dropsens, Asturias, Spain). The pH measurements were carried out using a pH meter (EUTECH Instruments pH700, Singapore). The conductivity of the water was measured using a conductivity meter (Meter Lab CDM210, Radiometer Copenhagen, Lyon, France).