J. Turek-Szytow

Oxidation of sulfamethoxazole by UVA radiation and modified Fenton reagent: toxicity and biodegradability of by-products

Improvement of sulfamethoxazole (4-amino-N-(5-methylisoxazol-3-yl)-benzenesulfonamide-SMX) biodegradability using a modified Fentons reaction has been studied. The modification consists of replacing hydrogen peroxide with atmospheric air and adding copper sulphate as a reaction promoter. Two series of experiments were carried out. The first (Series 1) was conducted using only the catalysts with aeration. In the second series (Series 2), cycles of UVA radiation and aeration were used. During UVA radiation, the removal of sulfamethoxazole proceeds less rapidly than in only aerated solution. After 1.5 h of these two processes, the SMX degradation was 23% in Series 2 and 59% in Series 1. The opposite trend was observed for mineralization and the removal of DOC was about 5% higher in Series 2 than in Series 1. The FTIR spectra of the extracts of reaction products yielded by four organic solvents of varying polarity revealed a wide diversity of functional groups in the post-reaction mixture in comparison to the extracts from sulfamethoxazole solution. Based on FTIR analysis, several oxidation products of sulfamethoxazole are proposed. Apparently, hydroxyl radicals initially attack sulphonamide bonds, resulting in the formation of sulfanilic acid and 3-amino-5-methylisoxazole. Irrespective of the reference organism used in toxicity tests, the post-reaction mixture in the Series 2 was more toxic than the post-reaction mixture in Series 1. In contrast, the biodegradability calculated as BOD(5)/DOC ratio, was higher for post-reaction mixture 2 and amounted to 0.43.

Solid inorganic peroxy compounds in environmental protection

Solid inorganic peroxy compounds in environmental protection The paper presents a solid inorganic peroxy compounds description (calcium peroxide, magnesium peroxide and sodium percarbonate) focused on the properties and environmental application, particularly for the degradation of polycyclic aromatic hydrocarbons (PAHs) and phenols in soil environment. Modern technological processes require the use of compounds that are safe for the environment, non-toxic, easily degradable to the products, which themselves have no adverse environmental effect. Peroxides, as the chemical compounds, produce an effect on the enzymatic activity of the environment into which they are introduced. A good indicator of the activity of soil, bottom sediment or activated sludge, may be the dehydrogenase activity, which is a reflection of the general physiological state of microorganisms. Peroxides can be applied both in a pure form, as well as in mixtures with certain other groups of compounds. To enhance their efficiency they can be mixed with nitrogen, phosphorus or potassium carrying compounds.

Qualitative analysis of activated sludge using FT-IR technique

The ability to measure and control the composition of activated sludge is an important issue, aiming at evaluating the effectiveness of changes occurring in the sludge, what determines its usefulness to treat wastewater. In this research, diffuse reflectance infrared Fourier transform (FTIR–DRIFT) technique was used, which relies on measuring the reflectance of the powdered substance’s surface layer and capturing spectra in range of infrared wave. First, spectra correlation table of the substances mostly occurring in wastewater was developed to assess the main components of the tested samples of activated sludge. The simplest compounds containing functional groups characteristic for particular chemical classes were chosen: peptides (peptone and albumin), fats (glycerin and fatty acids), carbohydrates (glucose and sucrose), nitrogen compounds (NaNO3 and NH4SO4), sulfur compounds (Na2SO4 and Na2S2O3), silicate, etc. The spectra of those substances were captured and characteristic absorption bands for respective bonds in the function groups were assigned. Second, samples of activated sludge from lab-scale membrane bioreactors (MBRs), which purifies petroleum wastewater, were taken. Samples were properly prepared (lyophilization and homogenization) and their spectra were captured. During spectra analysis, previously developed correlation table was used. In obtained spectra of activated sludge, absorption bonds characteristic for amides, peptides, carbohydrates, fats, and aliphatic was identified. The spectra profile of the sludge sample from MBR feed with petroleum wastewater was slightly different from the control MBR sample’s spectra. Intensity of bands in the area characteristic for aliphatic compounds and phenols was clearly higher. This study proves the usefulness of FT-IR technique to observe changes in the chemical composition of activated sludge.