'Green' coagulant application with activated carbon: dosing sequence and removal of selected micropollutants and effluent organic matter from municipal wastewater.

Combination of 'green' coagulation and powdered activated carbon adsorption was tested for removal of benzophenone (BP), benzophenone-3 (BP-3) and caffeine (CF) from treated municipal wastewater at realistic concentration levels (1-2 µg/L). At the same time it was tracked how the process affected effluent organic matter (EfOM) by measuring chemical oxygen demand (COD). Green coagulant was produced from dry common bean seed in laboratory. Combined coagulation-adsorption experiments were performed by applying different dosing sequences of process materials. Removal of hydrophobic BP and BP-3 by separate adsorption (from 79 to 98%) was not significantly hindered by the addition of the coagulant (activated carbon dose of 5 or 20 mg/L). However, in some cases negative effects were observed for hydrophilic caffeine, depending on the carbon dose, dosing sequence and presence of total suspended solids (TSS). Thus, when coagulant was firstly added into water without TSS before low activated carbon dose of 5 mg/L, caffeine removal dropped from 26% to 5%. Conversely, when TSS were present in the water sample, the removal of caffeine was not hindered under the same PAC dose and dosing sequence. The importance of the process optimisation related to removal of organic micropollutans of different hydrophilicity has been shown in this paper. Removal of around 30% of COD regardless of the dosing sequence was achieved.

Fate of Benzophenone, Benzophenone-3 and Caffeine in Lab-Scale Direct River Water Treatment by Hybrid Processes.

Emerging microcontaminants benzophenone (BP), benzophenone-3 (BP-3) and caffeine (CF) are widely used anthropogenic markers from a group of pharmaceuticals and personal care products. They have different logD values and charges at neutral pH (2.96 neutral for BP; 3.65 negative and neutral for BP-3; 0.28 and neutral for CF). The goal of this study was to assess the efficacy of coagulation/flocculation/sedimentation (C/F/S), adsorption onto two types of powdered activated carbon (PAC)/sedimentation (PAC/S) and the combination of these two processes in different dosing sequences (PAC/C/F/S) and with/without ultrafiltration (powdered activated carbon/ultrafiltration-PAC/UF, coagulation/UF-CoA/UF) for the removal of selected micropollutants from river water. It was shown that the removal efficiency of benzophenones by coagulation depends on the season, while CF was moderately removed (40-70%). The removal of neutral BP by two PACs unexpectedly differed (near 40% and ˃93%), while the removal of BP-3 was excellent (>95%). PACs were not efficient for the removal of hydrophilic CF. Combined PAC/C/F/S yielded excellent removal for BP and BP-3 regardless of PAC type only when the PAC addition was followed by C/F/S, while C/F/S efficiency for CF diminished. The combination of UF with PAC or coagulant showed also high efficacy for benzophenones, but was negligible for CF removal.

Removal of selected emerging micropollutants from wastewater treatment plant effluent by advanced non-oxidative treatment - A lab-scale case study from Serbia.

The presence of 48 emerging micropollutants was tested in influent and effluent from primary and secondary treatment at a municipal wastewater treatment plant (WWTP) in Serbia. Sixteen emerging micropollutants (active pharmaceutical ingredients, bisphenols, parabens and UV filters) had concentrations >LOQ (max. conc. 33.4 µg/L). The removal efficiency of primary treatment ranged from 2.0% - 96.0%. In the case of secondary treatment, except for ketoprofen (61.0%), diclofenac (62.6%) and carbamazepine (-20.0%), all other measured micropollutants had removal efficiency above 77.0%. Advanced non-oxidative lab-scale treatments were investigated. Powdered activated carbon (PAC) adsorption achieved removal efficiencies in the range 52.4-99.9%, novel coagulation with natural coagulant isolated from beans achieved removal efficiencies in range 3.2-99.9%, conventional coagulation with ferric chloride 3.12-96.4%, combined adsorption/coagulation 2.69-99.9% and combined PAC/ultrafiltration (PAC/UF) 60-99.9%. For most of the micropollutants, their removal efficiencies were similar to that reported in the literature. Novel natural coagulant showed significant potential compared to the conventional coagulant during a short episode of sub-optimal WWTP operation. When natural coagulant was applied as a part of an adsorption/coagulation hybrid process, there was no negative effect on PAC adsorption, while for conventional coagulant that was not always the case. Also, a structure property relationship (SPR) study revealed correlations between the removal efficiency of the majority of treatments applied and total polar surface area (TPSA) of the micropollutants.

Insight into selected emerging micropollutant interactions with wastewater colloidal organic carbon: implications for water treatment and analysis.

This study reports how adding a membrane filter (0.45-µm cellulose nitrate filter) between a glass fibre filter and the solid phase extraction (SPE) cartridge affected the GC/MS analysis of 48 emerging organic micropollutants in wastewater. Most of them are widely used as active pharmaceuticals, cosmetic and packaging material ingredients including classes of parabens, benzophenones and bisphenols among other chemicals tested. A high artificial organic carbon (OC) content in wastewater (DOC = 280 ± 14 mg/L) was investigated to gain insight into micropollutants/colloidal OC filter cake interactions. The results show that even with the use of matrix-matched calibration, the introduction of a second (membrane) filtration step can affect the analysis. Both positive, negative and no effects on the theoretical concentrations calculated from the calibration curves with and without additional filtration were observed. Positive effects on the concentration for the same analyte peak area relative to its surrogate standard were the consequence of a reduced signal for the same concentration, while the negative effects are the consequence of increasing signal for the same concentration. Effect types were dependent on the concentration and the nature of the analytes. Results show that bisphenols and parabens significantly interact with colloidal OC. Statistical analysis of molecular descriptor distribution with effect type showed that micropollutants that have a stronger interaction with colloidal OC have significantly higher ability to act as hydrogen bond donors (HBD) and have larger molar volume (MV). All compounds that experienced either positive or negative effects have a significantly higher median logD. However, further exploration within a single class of compounds (parabens, benzophenones and bisphenols) revealed that selected descriptors are unrelated to an effect type. Pearson's correlations showed that a correlation exists for certain concentration levels and groups of compounds between a negative effect and MV and logD and a positive effect with MV, MW and rotatable bond (RB) count.