Joanna Świetlik

In recent years, metal alloys used for drinking water distribution are gradually being replaced by PVC and HDPE pipes. In areas of distribution networks made of plastic, consumer complaints related to a significant deterioration of organoleptic parameters of water are frequently recorded. The decline in water quality is most likely the result of chemical and biological processes occurring on the inner walls of the transmission pipes coexisting with the disappearance of disinfectant residues. Plastic pipes are also characterized by high failure rates associated with aging of polymeric materials under operating conditions. Published reports indicate disturbing phenomena occurring in plastic pipes: oxidative aging of polymers, degradation of antioxidant coatings, release of organic compounds to water as well as surface damage and scaling, generating microplastic particles. PE and PVC networks are also susceptible to biofilm formation, characterized by a high phylogenetic diversity of microorganisms. Studies presented in the literature, indicating the risks resulting from the exploitation of PE and PVC pipes, are mainly based on model tests. There is a lack of works, which would complementarily explain all the phenomena occurring in working water pipes made of plastics. The aim of this review is to present the current state of knowledge regarding the phenomena and processes that can occur in PE and PVC pipes in service and their relevance to the safety and quality of drinking water in distribution networks, as well as to identify areas that require further analysis to enable water producers to deliver an appropriately high‐quality product to consumers.This article is categorized under: Engineering Water > Water, Health, and Sanitation Science of Water > Water Quality Water and Life > Conservation, Management, and Awareness

The paper presents the results of a long-term study covering the development, implementation and operation of the second stage of water treatment (i.e. ozonation and subsequent granular active carbon (GAC) filtration) in the “Mosina” water treatment station supplying drinking water to the city of Poznań. The basis for the modernisation of the system was the high reactivity of the natural organic matter (NOM) present in the treated water with the disinfectant (in this case chlorine dioxide) resulting in an increased demand for ClO₂ and reduced microbiological stability of the water. During the study it was shown that simple carboxylic acids are generated during ozonation and their presence can be an indicator of the microbiological stability of the treated water. However, these compounds are effectively removed from water during filtration through biologically active GAC filters. It was also shown that the best and cheapest parameter allowing to control water quality at individual stages of its treatment is UV absorbance, which shows reactive components of NOM removal efficiency in the technological sequence. The effectiveness of the modernisation of the technological system was evaluated on the basis of the disinfectant demand as well as on the basis of selected carboxylic acids concentration in the intake points on the water supply network fed with water from the WTS “Mosina”. At the last stage of the study, it was observed that the concentration of carboxylic acids in the distribution network was significantly reduced and stabilised, and a low dose of chlorine dioxide did not cause their re-formation. As a result of the modernisation, a new balance was achieved between the disinfectants used and the NOM compounds present in the treated water. Thus, the results confirmed that properly conducted pilot studies are a required element in planning of modernisation changes for water supply facilities.

The ozonation of aromatic compounds in low-pH water is ineffective. In an acidic environment, the decomposition of ozone into hydroxyl radicals is limited and insufficient for the degradation of organic pollutants. Radical processes are also strongly inhibited by halogen ions present in the reaction medium, especially at low pH. It was shown that even under such unfavorable conditions, some compounds can initiate radical chain reactions leading to the formation of hydroxyl radicals, thus accelerating the ozonation process, which is referred to as so-called “self-enhanced ozonation”. This paper presents the effect of bromides on “self-enhanced ozonation” of benzoic acid (BA) at pH 2.5. It is the first report to fully and quantitatively describe this process. The presence of only 15 µM bromides in water inhibits ozone decomposition and completely blocks BA degradation. However, the effectiveness of this process can be regained by ozonation in the presence of phosphates or sulphate. The addition of these inorganic salts to the bromide-containing solution helps to recover ozone decomposition and BA degradation efficiency. As part of this research, the fractions of hydroxyl, sulphate and phosphate radicals reacting with benzoic acid and bromides were calculated.

Samples from the two main watersheds that provide Athens Water Supply and Sewerage Company (AWSSC) with raw water were examined for Dissolved Organic Carbon (DOC) and for their molecular weight distribution (MWD). In addition, water samples from water treatment plants (WTPs) and from the water supply network were examined for trihalomethane (THMs) levels. The main purpose of this study was to reveal the molecular composition of natural organic matter (NOM) and identify the individual differences between NOM from the two main Athens watersheds. High-performance size exclusion chromatography (HPSEC), a relatively simple technique, was applied to determine different NOM fractions' composition according to molecular weight. Various THM levels in the supply network of Athens are illustrated as a result of the different reservoirs' water qualities, and a suggestion for a limited application of chlorine dioxide is made in order to minimize THM formation.

A new model for the investigation of the impact of corrosion on water quality, based on application of cast iron filings, is proposed. The use of filings ensures a large specific surface area which permits observation of changes in water quality in a relatively small amount of material. Two models differing in idea and construction are presented in this paper. The detailed results from the one model where thin layer water flows over the cast iron filings are shown. The rate of water quality changes during stagnant periods could be controlled by different amounts of filings. The results received in the model experiment are compared with those from a real fragment (100 m) of distribution system. Deterioration of water quality observed in model conditions is similar to that in real distribution network. Increase of iron concentration, turbidity, and decrease of oxygen and nitrate concentration were observed in both systems during stagnation periods. No changes of water quality were observed during flow conditions. Elemental and phase composition of corrosion scales collected from both systems was also comparable.

Open Access Agricultural Journals published by Institute of Agricultural Economics and Information

Zearalenone (ZEA) is a mycotoxin produced by some Fusarium species in food and feed. The toxicity of ZEA and its metabolites is related to the chemical structure of the mycotoxin, which is similar to naturally occurring oestrogens. Currently, there is increasing awareness of the presence of fungi and their toxic metabolites in the aquatic environment. One of the sources of these compounds are the effluents from wastewater treatment plants. The average annual efficiency of zearalenone reduction in the Łęczyca plant in our three-year study was in the range from 51.35 to 69.70 %. The threeway analysis of variance (year, month, and kind of wastewater) shows that the main effects of all factors and all interactions between them were significant for zearalenone and dissolved organic carbon content. Our findings suggest that wastewater is not the main source of surface water pollution with zearalenone. Future research should investigate the means to reduce ZEA and its migration from the fields through prevention strategies such as breeding for crops, plant debris management (crop rotation, tillage), and/or chemical and biological control.