Potassium Ferrate (VI) as the Multifunctional Agent in the Treatment of Landfill Leachate

Removal of phosphate from brewery wastewater by cerium(III) chloride originating from spent polishing agent: Recovery and optimization studies

This paper presents the possibility of using hydrated cerium(III) chloride (CeCl₃∙7H₂O) recovered from a spent polishing agent containing cerium(IV) dioxide (CeO₂) to remove phosphate and other impurities from brewery wastewater (phosphate 43.0 mg/L, total P 19.8 mg/L, pH 7.5, COD_(Cr) 827 mg O₂/L, TSS 630 mg/L, TOC 130 mg/L, total N 46 mg/L, turbidity 390 NTU, colour 170 mg Pt/L. CCD (Central Composite Design) and RSM (Response Surface Methodology) were applied to optimise the brewery wastewater treatment process. The removal efficiency (mainly of PO₄^3-) was the highest under optimal conditions (pH 7.0-8.5, Ce³⁺:PO₄^3- molar ratio of 1.5-2.0). Applying recovered CeCl₃ under optimal conditions yielded a treated effluent in which the concentration of PO₄^3- decreased by 99.86 %, total P by 99.56 %, COD_(Cr) by 81.86 %, TSS by 96.67 %, TOC by 60.38 %, total N by 19.24 %, turbidity by 98.18 %, and colour by 70.59 %. The Ce³⁺ ion concentration in the treated effluent was 0.058 mg/L. These findings suggest that CeCl₃‧7H₂O recovered from the spent polishing agent may constitute an optional reagent for phosphate removal from brewery wastewater. The sludge from wastewater treatment can be recycled for Ce and P recovery. The recovered cerium can be reused for wastewater treatment, creating a cyclic cerium cycle in the process, and the recovered phosphorus can be used, for example, for fertilization purposes. The optimised cerium recovery and application is in accordance with the ideas of circular economy.

Effectiveness of potassium ferrate (VI) as a green agent in the treatment and disinfection of carwash wastewater

Carwash wastewater treatment with potassium ferrate (VI) (K₂FeO₄) was optimized by response surface methodology. The optimum conditions for chemical oxygen demand removal were established a pH 3.5, 0.328 g/L dose of K₂FeO₄, and with a process duration of 48 min. At these conditions, chemical oxygen demand, total organic carbon, total nitrogen, and total phosphorus decreased by 70.3, 58.9, 73.3, 82.0%, respectively; and the putrid odor was reduced. Simultaneously, the total viable count, total coli count, most probable number of fecal enterococci, and the total proteolytic bacteria count decreased by 89.5, 93.1, 92.9, and 95.0 %, respectively. Comparatively, an application of 0.450 g/L FeCl₃·6H₂O corresponding to the iron content in 0.328 g/L of K₂FeO₄ resulted in a decrease of total viable count, total coli count, most probable number of fecal enterococci and the total proteolytic bacteria count only by 38.1, 31.2, 42.9, and 58.0%, respectively. Therefore, flocculation with polyacrylamide anionic flocculant combined with potassium ferrate (VI) oxidation is a more effective alternative to coagulation with FeCl₃ and the same flocculant. The use of potassium ferrate (VI) is a viable option for the treatment of carwash wastewater.

Spatial Succession for Degradation of Solid Multicomponent Food Waste and Purification of Toxic Leachate with the Obtaining of Biohydrogen and Biomethane

A huge amount of organic waste is generated annually around the globe. The main sources of solid and liquid organic waste are municipalities and canning and food industries. Most of it is disposed of in an environmentally unfriendly way since none of the modern recycling technologies can cope with such immense volumes of waste. Microbiological and biotechnological approaches are extremely promising for solving this environmental problem. Moreover, organic waste can serve as the substrate to obtain alternative energy, such as biohydrogen (H2) and biomethane (CH4). This work aimed to design and test new technology for the degradation of food waste, coupled with biohydrogen and biomethane production, as well as liquid organic leachate purification. The effective treatment of waste was achieved due to the application of the specific granular microbial preparation. Microbiological and physicochemical methods were used to measure the fermentation parameters. As a result, a four-module direct flow installation efficiently couples spatial succession of anaerobic and aerobic bacteria with other micro- and macroorganisms to simultaneously recycle organic waste, remediate the resulting leachate, and generate biogas.

Removal of Heavy Metal Ions from Wastewaters: An Application of Sodium Trithiocarbonate and Wastewater Toxicity Assessment

The synthesis and application of sodium trithiocarbonate (Na2CS3) for the treatment of real galvanic wastewater in order to remove heavy metals (Cu, Cd and Zn) was investigated. A Central Composite Design/Response Surface Methodology (CCD/RSM) was employed to optimize the removal of heavy metals from industrial wastewater. Adequacy of approximated data was verified using Analysis of Variance (ANOVA). The calculated coefficients of determination (R2 and R2adj) were 0.9119 and 0.8532, respectively. Application of Na2CS3 conjugated with CCD/RSM allowed Cu, Cd and Zn levels to be decreased and, as a consequence, ∑Cu,Cd,Zn decreased by 99.80%, 97.78%, 99.78%, and 99.69%, respectively, by using Na2CS3 at 533 mg/L and pH 9.7, within 23 min. Implementation of conventional metal precipitation reagents (NaOH, Ca(OH)2 and CaO) at pH 11 within 23 min only decreased ∑Cu,Cd,Zn by 90.84%, 93.97% and 93.71%, respectively. Rotifer Brachionus plicatilis was used to conduct the assessment of wastewater toxicity. Following the application of Na2CS3, after 60 min the mortality of B. plicatilis was reduced from 90% to 25%. Engagement of Na2CS3 under optimal conditions caused the precipitation of heavy metals from the polluted wastewater and significantly decreased wastewater toxicity. In summary, Na2CS3 can be used as an effective heavy metal precipitating agent, especially for Cu, Cd and Zn.