Niina Dulova

Emerging micropollutants in water/wastewater: growing demand on removal technologies

Developing advanced treatment technologies for improving the removal of micropollutants in water/wastewater is important. A suitable treatment is more likely to be used as the polishing step in the treatment scheme. Advanced oxidation technologies (AOTs) are relevant for removing micropollutants. The ability of direct UV photolysis and selected AOTs to degrade pharmaceuticals, endocrine-disrupting compound and herbicide has been studied and compared. The tested methods resulted in the degradation of the studied micropollutants; however, none of the methods was preferred for the removal of all tested compounds. The UV-active processes have strong potential for removal of the studied micropollutants. The utilisation of a moderate hydrogen peroxide admixture resulted in a more reliable treatment.

Combined Physicochemical Treatment of Textile and Mixed Industrial Wastewater

Wastewaters derived from a textile factory and an industrial park were subjected to treatment with ferric chloride coagulation; ozonation; ferric chloride pre-coagulation/Fenton-based process/lime post-coagulation; Fenton-based process/lime post-coagulation; and ferric chloride pre-coagulation/ozonation. Schemes with the Fenton-based process proved the most efficient for treatment of both wastewater samples. The characteristics of wastewater samples treated by a Fenton-based process at H2O2/COD weight ratio 0.5:1 complied with the discharge limits stated by regulations for wastewater directed to local sewerage. The Fenton-based process/lime post-coagulation scheme proved more efficient than ferric chloride pre-coagulation/Fenton-based process/lime post-coagulation system. The increase of H2O2/COD weight ratio to 2:1 resulted in 5 and 10% of residual COD and DOC, respectively. All studied processes and combined physicochemical treatment schemes, except single ozonation, resulted in toxicity reduction and biodegradability improvement in both wastewater samples. The operational costs of applied treatment schemes were calculated and indicated the Fenton-based process schemes as the most feasible and cost-effective.

Catalytic degradation of picric acid by heterogeneous Fenton‐based processes

The efficiency of goethite, magnetite and iron powder (Fe0) in catalysing the Fenton‐based oxidation of picric acid (PA) in aqueous solution was studied. The effect of pH, hydrogen peroxide concentration, and catalyst type and dosage on treatment efficacy was investigated. The adsorption of PA from aqueous solution by heterogeneous catalysts was also examined. The results demonstrated negligible PA removal in H2O2/α‐FeOOH and H2O2/Fe3O4 systems independent of process pH, and hydrogen peroxide and catalyst dosage. The PA adsorption effects of both iron oxides turned out to be insignificant for all studied pH values and catalyst dosages. The H2O2/Fe0 system proved efficient at degrading PA, but only under acidic conditions (pH 3). The results indicated that, due to rather fast leaching of ferrous ions from the iron powder surface, PA degradation was carried out mainly by the classic Fenton oxidation mechanism in the bulk solution. The adsorption of PA onto the iron powder surface may also contribute to the overall efficiency of PA degradation.

Application of Fenton’s Reaction for Food-processing Wastewater Treatment

Abstract Depending on the process type and raw materials involved, various types of wastewater are discharged from food industry. In the present study the feasibility of Fenton-based treatment, as a part of combined treatment schemes, to degrade high organic content, to eliminate suspended solids, and to improve the overall quality of food-processing plant wastewater was assessed. Fenton oxidation step used in treatment schemes improved significantly the quality of the effluent, enabling additional 62-79% and 53-69% reduction of chemical oxygen demand (COD) and dissolved organic carbon (DOC), respectively, when the H2O2/COD w/w ratio of 2:1 was used. The results show feasibility of the Fenton oxidation to decrease substantially the organic load and improve the biodegradability of the effluent.

Application of Ozonation, UV Photolysis, Fenton Treatment and other Related Processes for Degradation of Ibuprofen and Sulfamethoxazole in Different Aqueous Matrices

Abstract Two pharmaceuticals ibuprofen (IBP) and sulfamethoxazole (SMX) were treated with ozone and advanced oxidation processes (AOPs): UV photolysis, O3/H2O2, O3/UV, O3/H2O2/UV, H2O2/UV, the Fenton and photo- Fenton process. The efficacy of AOPs for degradation of pharmaceuticals as well as the impact of the matrix (pure water, urea and wastewater) on drugs’ decay was evaluated. The experimental study has been carried out using concentration of the pharmaceuticals in the level of 100 mg/L. IBP was more resistant to all types of treatment than SMX. Ozonation was effective for removal of SMX and IBP when carried out under alkaline conditions. The ultimate elimination of SMX could be achieved with UV photolysis, whereas more rapid removal of IBP was attained with H2O2/UV. The complete SMX removal and more than 90% IBP degradation by the ordinary Fenton treatment were reached with oxidant overdosing only. Additional UV-radiation improved substantially the performance of the Fenton oxidation for elimination of both pharmaceuticals. The elimination rates determined in the pure water cannot be directly used to predict the oxidation of SMX and IBP in the wastewater.

Ferrous ion-activated persulphate process for landfill leachate treatment: removal of organic load, phenolic micropollutants and nitrogen

ABSTRACT The innovative treatment technology based on sulphate radicals induced oxidation was applied for the treatment of landfill leachate. The performance of chemical oxygen demand (COD) and dissolved organic carbon (DOC) removal in the Fe2+-activated persulphate system was moderate; however, the results of dissolved nitrogen (DN) and total phenols removal showed significant efficacy (≤39% and ≥87%, respectively). addition to the system enhanced the treatment efficacy and resulted in supplementary 15% of COD and 5% of DN removal. Hydroxyl radical-based H2O2/Fe2+ treatment of the landfill leachate was performed as well; the results indicated higher removal efficacy of COD and DOC compared to the system. However, practical application of the H2O2/Fe2+ system is considerably influenced by temperature rise and excessive foam formation. Generally, the ferrous ion-activated persulphate treatment could be a promising technology for ex situ as well as in situ landfill leachate treatment applications.

Photochemical degradation of nonylphenol in aqueous solution: The impact of pH and hydroxyl radical promoters

The degradation of nonylphenol (NP) in aqueous solution with UV, H2O2/UV, and Fenton/photo-Fenton processes was studied. The efficacy of direct and hydrogen peroxide photolysis proved to be dependent on the pH value. The addition of H2O2 to UV treatment improved NP degradation. The application of UV photolysis and the H2O2/UV system at pH 7 resulted in low pseudo first-order rate constants at 10-4 sec-1. In the experiments at elevated pH values the pseudo-first order rate constants increased to 10-3 sec-1. The efficacy of the Fenton process was lower in comparison with UV and hydrogen peroxide photolysis. The addition of UV irradiation to the H2O2/Fe2+ system substantially improved NP degradation efficacy. In terms of performance, the photo-Fenton process was similar to the H2O2/UV process. The most favourable process for complete nonylphenol degradation considering both operational cost and treatment efficacy was H202/UV at pH 11 and 250 micromol/L H2O2.

Degradation of diclofenac in aqueous solution by homogeneous and heterogeneous photolysis

Abstract Background: Pharmaceuticals have arisen as emerging environmental pollutants due to their potential impact on humans, animals and microorganisms even at low concentrations.

Hazardous waste landfill leachate treatment by combined chemical and biological techniques

AbstractThe efficacies of coagulation, ozonation, Fenton treatment, activated sludge process, Fenton treatment–activated sludge process (CHEM-BIO) and activated sludge process–Fenton treatment (BIO-CHEM) to treat hazardous waste landfill leachate were investigated and compared. The results of the biodegradability test revealed a high content of readily biodegradable organic matter in semicoke landfill leachate, and thus, aerobic biological oxidation was found to be a more reasonable and cost-effective technique for leachate treatment than direct chemical processes (ozonation, Fenton treatment). However, in terms of treatment efficacy, both chemical and biological processes resulted in a high residual organic load, indicating an insufficient leachate quality improvement. The treatment performance of the combined schemes (BIO-CHEM and CHEM-BIO) proved more effective and ensured the removal efficacy percentage met that required by EU legislation as well as the specific target discharge limits of the measured...

Treatment of high-strength wastewater by Fe2+-activated persulphate and hydrogen peroxide

Ferrous ion-activated persulphate and hydrogen peroxide were studied for the treatment of real high-strength industrial effluent. The Fenton process demonstrated greater organic load removal, biodegradability improvement and toxicity reduction as well as lower treatment cost than the activated persulphate system. However, the use of an activated persulphate process was more favourable due to the exothermic effect intrinsic to the Fenton reaction, which resulted in a rapid increase in the temperature of the high-strength wastewater along with excessive foam formation. Overall, for the H2O2/Fe2+ and processes, the application of a chemical oxygen demand (COD)/oxidant/Fe2+ weight ratio of 1/0.4/0.075 resulted in a COD removal of 58 and 50%, a 7-day biochemical oxygen demand/COD ratio increase from 0.14 to 0.3 and 0.23, and an increase in the EC50 (Daphnia magna) by 6.5-fold and 2.9-fold, respectively. The stepwise addition of the oxidant and activator was favourable for the Fenton process and resulted in negligible improvement in the wastewater treatment efficacy in the activated persulphate system.