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Influence of UV-chlorination sequence application on swimming pool water quality was investigated. In addition, an analysis of operating costs of such system was conducted. The study was based on a real facility, i.e. the swimming pool of AGH University of Science and Technology in Krakow. In the facility, water disinfection with calcium hypochlorite was carried out, assisted by UV irradiation. Switching the UV lamps temporarily off allowed for comparative studies on the quality of pool water disinfected by pure chlorination and by the UV and chlorination sequence. For these two variants of the swimming pool water disinfection several physico-chemical and microbiological parameters were analyzed, including the disinfection by-products. Cost analysis included the consumption of chemical agents and the UV lamp operation. It was established that the UV technology did not contribute to the expected improvement in the pool water quality in terms of the combined chlorine removal, however it did cause an increase in the concentration of selected organic chlorination by-products. Moreover, application of the UV lamp to the pool water treatment system increased the chlorine demand and, consequently, the consumption of calcium hypochlorite. Combined with the need to exchange lamp filaments, it raised the operating costs of the pool water treatment technology. [ABSTRACT FROM AUTHOR]

In this study, the MIEX®DOC process was applied to test the removal potential of halogenated organic water disinfection by-products (trihalomethanes, haloacetic acids, haloacetonitriles, haloketones, chloropicrin and chloral hydrate) precursors. The experiments were conducted using model and surface water samples. The samples of untreated water and the MIEX®DOC process effluent were chlorinated with sodium hypochlorite which resulted in residual free chlorine of 3-5 mg L-1 after 24 h. After this time, the water was analysed to check the presence of chlorination by-products using the gas chromatography method. Subsequently, the formation potential was calculated for each group of halogenated organic compounds. The efficiency of the MIEX®DOC process in removing the disinfection by-product precursors was dependent on the type and quality of raw water. The MIEX®DOC process showed the highest removal efficiency for trihalomethanes (68%-90%), haloacetic acids (76%-82%) and chloral hydrate (62%-88%) precursors. Lower removal efficiencies were observed for the precursors of haloacetonitriles (42%-72%), haloketones (26%-73%) and chloropicrin (9%-74%). [ABSTRACT FROM AUTHOR]

Application of UV radiation for water disinfection becomes more and more popular in Polish treatment plants that supply drinking water. UV disinfection is often sequentially coupled with chemical disinfection to prevent secondary growth of bacteria in water distribution systems. However, there are cases where directly after the UV disinfection water is pumped into a distribution system, without any additional chemical protection. The article presents results of the research on the influence of UV radiation on variations in water microbial stability in the distribution system supplied by Raba water treatment plant. Water samples were irradiated in laboratory conditions in the photochemical reactor (Heraeus) with the UV low-pressure lamp TNN 15/32. The UV doses of 400 J/m2, 1860 J/m2 and 10,000 J/m2 were applied. Water microbial stability was determined on the basis of heterotrophic bacteria growth rate in the period of up to 18 days. An analysis of the results demonstrated that UV radiation could adversely affect water microbial stability in distribution systems. The highest number of heterotrophic bacteria, over three-times higher compared to a purely ozonated sample, was recorded in the water sample irradiated with 400 J/m2. Higher doses of UV radiation as well as ozone/UV sequence improved water microbial stability, most likely due to organic matter mineralization. [ABSTRACT FROM AUTHOR]

Variations in halogen chlorination by-product formation potential after UV disinfection in four water treatment plants were studied. Formation potential of the following compounds has been examined: trihalomethanes (trichloromethane, bromodichloromethane, dibromochloromethane, tribromomethane), haloacetic acids (monochloroacetic acid, monobromoacetic acid, dichloroacetic acid, trichloroacetic acid, bromochloroacetic acid, dibromoacetic acid), haloacetonitriles (trichloroacetonitrile, dichloroacetonitrile, bromochloroacetonitrile, dibromoacetonitrile), haloketones (1,1-dichloropropanone, 1,1,1-trichloropropanone), chloral hydrate and chloropicrin. Water samples prior to and after UV irradiation were chlorinated with sodium hypochlorite at a dose resulting in 3÷5 gCl2/m³ of free residual chlorine after 24 h. The highest increase in the formation potential of all examined chlorination by-products was observed in water where the highest UV irradiation dose was applied. Additionally, it was stated that prior chemical oxidation may lead to increase in the examined product formation potential. It was proved that UV disinfection may also lead to increase in the amount of product bromide derivatives in water of high bromide content. Finally, nitration of organic compounds was demonstrated for water samples after UV irradiation. This phenomenon may lead to increase in nitrogen-containing chlorination byproduct content. [ABSTRACT FROM AUTHOR]

• Constructed wetlands have great potential to treat wastewater. • Halophytes can be used to treat saline wastewater with high efficiency. • Halophyte biomass has different uses after harvesting (i.e. bioenergy production). In many parts of the world wastewater is not treated at all or only to a limited extend because there are no resources available to establish an efficient wastewater treatment plant and there are also insufficient resources for operation and maintenance costs. Constructed wetlands (CWs) are nature-based solutions to treat wastewater in a highly cost-efficient manner. They can be very efficient and effective when well designed and maintained. Latin America is rich in saline natural wetlands. These can be used as prototypes for CWs treating saline process or wastewater. Similar to natural saline wetlands CWs can deliver several ecosystem services. This review focuses on saline wetlands and will first present the protagonists, the salt-tolerant plant species belonging to the halophytes with respect to their physiological and biochemical functions in wetlands. In a second step, their remediating activities which are used in many ways by local people will be shown in an exemplary manner. A number of CWs established in different regions, including Latin America, will be introduced as case studies. Halophytes are already being used in a number of CWs as biofilter but their usage could be increased, for example to treat aquaculture effluents and the biomass has a high potential for valuable compounds (i.e. metabolites) or for bioenergy production. Lastly, aspects of sustainability and ecosystem services of saline natural and constructed wetlands are shown with an emphasis on charting a way forward for the future holistic implementation of saline systems in Latin America. [ABSTRACT FROM AUTHOR]