Agata Rosińska

Total organic carbon (TOC) present in surface water consists of different fractions like dissolved organic carbon (DOC) or biodegradable dissolved organic carbon (BDOC). BDOC may have an impact on the bacteriological quality of water as it can be a source of carbon and energy for microorganisms. It is important to consider this parameter in case of the distribution of drinking water. The aim of this research was to compare the qualities of chosen surface water in Poland and Germany in terms of concentration of total organic carbon and its fractions. The samples were taken from the reservoir in Poland and Rhine River in Germany. The first one is a source of drinking water for humans. The research showed that, considering the analyzed compounds, the water from the river has better quality.

An analytical method that can allow one to determine simultaneously chosen organic micropollutants has been developed to measure their concentrations in water. Standard mixture of 16 polycyclic aromatic hydrocarbons (PAH) and nine polychlorinated biphenyls (PCB) was added to distilled water in a specific amount. The solid phase extraction (SPE) method was applied. Isopropyl alcohol and methanol were used to precondition SPE extraction columns. PAH and PCB were eluted from the column fillings using dichloromethane. Extracts were condensed to a volume of 2 mL. Prepared samples were analyzed with the use of gas chromatography and mass spectrometry. The achieved percent recovery of PAH was from around 7% in the case of chrysene to 100% in the case of naphthalene. The achieved percent recovery of PCB was from about 51% in the case of PCB 101 to 92% in the case of PCB 156.

The aim of the research was to determine the efficiency of a coagulation process with powdered activated carbon for the removal from surface water of benzo(a)pyrene and 16 polycyclic aromatic hydrocarbons (PAHs), including the sum of four standardized in the Council Directive 98/83/EC on the quality of water intended for human consumption: benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(g,h,i)perylene, and indeno(1,2,3-cd)pyrene. For the study, surface water was used, whose composition was modified with standard solution PAH MIX A. In the first stage, for water modified with standard PAH mixture, the coagulation process was conducted. As the coagulants Al₂(SO₄)₃·18H₂O, hydrolysed salts, and polyaluminum chlorides (PAX1910 and PAX19F) were used. In the second stage, the adsorption process was conducted. Powdered activated carbon was used (CWZ-22 and CWZ-30). In the third stage, the coagulation process and the adsorption process were combined. The best effects for the reduction concentrations of the sum of four normalized PAHs, as well as of benzo(a)pyrene, were obtained by applying coagulation carried out with PAX19F and aided by powdered activated carbon CWZ-30. The removal efficiency for these compounds was, respectively, 93.8% and 95.8%.

The aim of the research was to compare selected coagulants efficiency in indicator and chosen dioxin-like PCB removal from surface water. As coagulants, there were used aluminium sulfate and 5 hydrolyzed polyaluminium chlorides, with trade names: PAX-XL1, PAX-XL10, PAX-XL19, PAX-XL60, PAX-XL69. For the research, surface water was used, collected from dam reservoir. The water composition was modified with standard mixtures PCB MIX24 and MIX13, in order to obtain concentration of each congener equal to 300 ng/dm3. The PCB MIX24 mixture was composed of indicator congeners solution: 28, 52, 101, 118, 138, 153, and 180, whereas the MIX13 mixture - solution of three dioxin-like PCB 77, PCB 126, and PCB 169. It was demonstrated that the application of aluminium sulfate allowed for reaching better effects for purifying water of PCB, than with the usage of pre-hydrolyzed salts, polyaluminium chlorides. Out of the studied coagulants, the best effects for indicator PCB removal were obtained with the application of aluminium sulfate, total PCB concentration was decreased by 65%. The highest efficiency for indicator congeners removal (90%) was obtained for PCB 138 and 153. After the application of hydrolyzed polyaluminium chlorides PAX-XL1, PAX-XL10 decrease in higher chlorinated PCB concentration was obtained, in the range of 23 to 74%. Selectivity of chosen PCB congener removal, depending on applied coagulant, was demonstrated; with the usage of aluminium sulfate, removal of heptachlorobiphenyl PCB 180 at the level of 34% was obtained, whereas with the application of PAX-XL1 and PAX-XL10 higher reduction efficiency for this congener was obtained, i.e. 83 and 74% respectively. For dioxin-like PCB, after application of aluminium sulfate, total concentration reduction by 74% was obtained, efficiency of this congeners removal amounted to from 54 (PCB 77) up to 72% (PCB 126), similar results were obtained after the usage of PAX-XL1. The lowest PCB removal from water rate was stated for coagulants PAX-XL60 and PAX-XL69.

Suitability of powdered activated carbon CWZ-30 for enhancing the coagulation process used for the removal of contaminants from surface water was evaluated. Aluminium sulphate, aluminium chloride and pre-hydrolysed polyaluminium chloride (PAX18 and PAX-XL1905) were used as coagulants, and the following parameters were analysed in water sampled from the Kozłowa Góra dam reservoir (Poland): concentrations of heavy metals (Cu, Cd, Ni, Pb) and indicator PCBs (28, 52, 101, 118, 138, 153, 180). The highest reduction in heavy metal concentration was obtained with the use of PAX-XL1905. It amounted, in case of copper, cadmium, nickel and lead, to 64, 39, 18 and 85%, respectively. Enhancement of coagulation with powdered activated carbon CWZ-30 in the amount of 30 mg L⁻¹, increased the efficiency of these metals removal up to 79, 53, 26 and 95%, respectively. The best results for total PCB concentration removal were obtained with the use of PAX18. Application of powdered activated carbon also allowed to obtain better effects of PCB removal from water. Therefore, the coagulation process enhanced with powdered activated carbon had crucial impact on the reduction of analysed heavy metals concentration and indicator PCBs.

The main goal of water treatment plants is water intake from water’s natural sources and its preparation for consumers. After the water treatment process, water has to meet requirements of legal standards regarding chemical and microbiological composition. The quality of water from water pipes depends on: its initial composition, the way of treatment, storage, the condition of water system, terminal, and plumbing. The choice of the technological process of water treatment depends on raw water quality, which is often different at the consumer’s tap from the one delivered to the distribution system since water undergoes complex physical, chemical, and biological processes. This results in, so-called, secondary water contamination in a distribution system. In this article, the value changes of selected chemical water quality parameters have been presented during both ozone and sodium hypochlorite disinfection. Water samples were collected from underground water intakes. The results showed that disinfection processes did not negatively affect water quality. The number and the extent of changes to the water quality parameters were similar in the case of both ozone and sodium hypochlorite disinfection processes. All examined water samples showed an increase in total hardness following the treatment process and a decrease in the TOC content in water in the distribution process.