Combined physico-chemical treatment of secondary settled municipal wastewater in a multifunctional reactor

Evaluation of a hydrodynamic cavitation-type bubble generator in a prototype bench-scale flotation unit for poultry processing wastewater treatment

Dissolved Air Flotation (DAF) systems are designed to remove oil and grease (O&G) and total suspended solids (TSS) in wastewater treatment. These systems require saturation tanks, water pumps, and high-pressure compressors to control the pressure, hydraulic retention time, and airflow parameters. DAF process efficiency depends on complex operational controls associated with these components, and the most critical aspect of an effectively operating DAF unit is a generated bubble size. This work presents the design and operational test of a flotation unit prototype that replaces the saturation tank and high-pressure compressors present in DAF with the CARMIN microbubble injector, the evaluation of the proposed system's TSS and O&G removal efficiency was carried out considering different initial configurations of the injector to change the generated microbubble size, four synthetic wastewater solutions, and poly aluminum chloride as a flocculant to establish the potential of this system for the poultry processing wastewater treatment. Mean microbubble size results were obtained from 47.41 µm to 116.17 µm. The average removal efficiency of TSS exceeded 65% under a high concentration of suspended particles (1,560 mg/l) and 80% under a lower TSS concentration (795 mg/l). Meanwhile, 70% and 90% of O&G were removed from high (400 mg/l) and low (100 mg/l) initial O&G concentrations, respectively. These removal levels are similar to those reported in the literature for DAF for poultry processing wastewater, albeit with a simple configuration and better controllability and scalability.

Removal of microplastics from secondary wastewater treatment plant effluent by coagulation/flocculation with iron, aluminum and polyamine-based chemicals

Microplastic (MP) removal by coagulation/flocculation followed by settling was studied in a secondary wastewater treatment plant (WWTP) effluent matrix. MP concentration in size range <10 µm in wastewater is currently unknown due to the exclusion of this size range in many studies and due to difficulties in MP quantification. WWTP effluent samples were spiked with a known amount of polystyrene spheres of two different sizes 1 µm and 6.3 µm. The samples were treated with inorganic and organic coagulants typically used in WWTPs, i.e., ferric chloride, polyaluminum chloride, and polyamine. The effect of pH was studied with ferric chloride by changing the pH from 7.3 to 6.5. In this study, MP removal was monitored using flow cytometry. The role of chemicals in MP removal at WWTPs has not been in the focus of previously reported MP studies. Our results showed that all tested coagulants enhanced the removal of MPs with dosages applicable to tertiary treatment. The highest removal efficiency obtained was 99.4%, and ferric chloride and polyaluminum chloride were more efficient than polyamine. Performances of ferric chloride and polyaluminum chloride were close to each other, with a statistically significant difference at a certain dosage range. Our findings suggest that chemical coagulation plays a key role in the removal of MPs, and the process can be optimized by selecting the right coagulant and pH.

Controlling micropollutants in tertiary municipal wastewater by O3/H2O2, granular biofiltration and UV254/H2O2 for potable reuse applications

A comprehensive pilot study was carried out to experimentally assess the potential of newly developed treatment trains integrating two-stage AOPs and biofiltration to reach potable reuse water quality standards from municipal wastewater. The processes consisted of a two-stage AOPs with (carbon or limestone) biofiltration, the first AOP (O₃/H₂O₂) serving as pre-treatment to biofiltration and the second AOP (UV₂₅₄/H₂O₂) serving as post-biofiltration finishing step to ensure advanced disinfection. A comprehensive monitoring campaign was put in place resulting from the combination of targeted, non-targeted and suspect screening measurements. It was found that 13 organic micropollutants were detected from a list of 219 suspects although at ng/L level only. For the treatment conditions piloted in this study (O₃ = 13 ± 0.5 mg/L, H₂O₂ = 11 ± 0.4 mg/L for the O₃/H₂O₂ process, and UV = 410 ± 63.5 mJ/cm², H₂O₂ = 5 mg/l for the UV₂₅₄/H₂O₂ process), it was possible to estimate the overall removal efficacy for each unit process, which was found to follow this order: RO (99%)  > BAC (87%) > O₃-H₂O₂ (78%)  > BAL (67%)  > UV/H₂O₂ (43%)  > AOP contact chamber (19%)  > UF(0%), with the treatment train integrating two AOPs and granular biofiltration with activated carbon (O₃/H₂O₂ + BAC + UV₂₅₄/H₂O₂) showing superior performance with a 99% abatement in total micropollutants. No ecotoxicologically-positive response was generally observed for any of the effluent samples from the tested trains, even when pre-concentration factors up to 100-1000 times were employed to increase the sensitivity of the bioassay methods.