Stan sanitarny wód powierzchniowych w województwie świętokrzyskim

Introduction

Many bacterial species from different biotopes are often identified in surface water. It is due to contact with soil, air, rainfall, and natural microflora of animals and people. Contaminants get into the water most often through human activities like microbiological pollution via industrial waste and wastewater from food companies and households. Microorganisms occurring in water determine their biological properties and the sanitary condition. In densely populated and industrial areas, polluted air plays a very important role, e.g. bacterial plankton suspended in the air in the form of bioaerosols or bacterial fluid that penetrates via rainfall to the surface water. A characteristic feature of these bacteria is their virulence, by which they can infect specific tissues of humans and animals. Typical pathogenic bacteria in water are usually motile, like cylindrical, spiral, or comma-shaped bacterium. Staphylococci, streptococci, enterobacteria Enterobacteriaceae, Helicobacter pylori, Enterobacter sp. are also very common in contaminated waters. Water polluted by excrement increases the risk of spread of pathogenic microorganisms like Salmonella spp., Shigella sp., Campylobacter sp., Vibrio sp., Legionella sp., and Escherichia sp. [1–5]. Escherichia coli is the most important indicator of faecal pollution due to a representative role in intestinal microflora, but they can also be dangerous [6]. These bacteria survive in drinking water for between four and 12 weeks, depending on environmental conditions (temperature, microflora, etc.). Pathogenic E. coli strains mostly cause intestinal diseases, but extraintestinal infection are also common, like uropathogenic Escherichia coli strains, which cause urinary tract infections. One of the most dangerous are Shiga toxin-producing E. coli strains (STEC) [7]. They may lead to life-threatening diseases, including haemolytic uremic syndrome (HUS), especially in young children and the elderly. The waterborne transmission of STEC has been reported, both from contaminated drinking-water and from recreational waters [8]. The problem of insufficient water quality is present not only in African countries but also a lot of European countries have polluted water. This issue is reflected in many government programs and the promotion of environmental protection in the interests of public health. However, public awareness of how to protect health against environmental infectious agents is still poor.

Aim of the research

The aim of the study was to analyse the presence of basic microbiological indicators in the selected water samples collected in autumn, winter, and spring. In our study we present the evidence of microbiological pollution of surface water in Świętokrzyskie voivodeship during the years 2009–2011. The water samples were tested for the presence of coliform, mesophilic, and psychrophilic bacteria.

Material and methods

Study sites and sample collection

The study sites included three rivers (Nida, Bernatka, Wisła) and two water reservoirs (Emerald Lake, Pińczów) located in Świętokrzyskie voivodeship (Table 1). The samples of water were collected in sterile bottles from a depth of 30 cm from the surface of the water during autumn, winter, and spring in 2009–2011. The reservoirs were selected based on occasional contact with the local community and the use of reservoirs for recreational purposes.

Bacterial identification

The 100 μl water samples were plated by spread plate method on selective media: Yeast agar (Biomed) for the total number of mesophilic and psychrophilic bacteria. Plates were incubated at 37°C (mesophilic bacteria) and 22°C (psychrophilic bacteria) for 24–48 h, and the number of bacteria in water was estimated based on the number of grown CFUs (colony-forming units) on the plates. Additionally, the number of coliforms was determined by fermentation tube method. Samples of water were aliquoted to a broth containing lactose and bromocresol purple (LPB, Ejkman broth). The set of five tubes with Durham tubules were supplemented with 10 ml of broth, and one flask was supplemented by 50 ml of broth. All tubes and flask were filled with the same volume of water sample. The cultures were incubated at 37°C for 24 h.
A positive result was a change of broth colour from purple to yellow and the presence of gas bubbles in Durham tubes. In the case of negative results, the cultures were incubated for another 24 h. The most probable number (MPN) of coliform bacteria present was estimated from the number of positive tubes obtained in the confirmatory test, using specially devised statistical tables. Also, the 100 μl water samples were incubated on MacConkey agar to confirm the presence of coliform. All large, red colonies surrounded by turbid zone were cultured on Endo agar to identify the E.coli strains [9]. Analyses were performed according to the Polish Committee of Standardisation Norms PN-EN ISO 9308-3 and PN-EN ISO 9308-1. The norms are included in the Regulations of the Minister of Health of 17 January 2019 on the supervision of the quality of bathing water and places occasionally used for bathing.

Results and discussion

The research of the selected water reservoirs and rivers included the analysis of the presence of different bacterial indicators in the water. There are many standardised methods designed for sanitary analysis of water [10–13]; however, we applied only two basic analyses: the total number of mesophilic and psychrophilic bacteria and the total number of coliforms. The results represent a general sanitary condition to indicate the potential epidemiological risk to public health. Samples were collected from five study areas of four different locations in Świętokrzyskie voivodeship (Table 1). The Nida and Pińczów reservoirs were located in the southwest, in the valley of Nida, close to hills. These attractive surroundings are often visited by locals and tourists in the summertime. The river Wisła is located in the eastern border of the voivodeship, near to Zawichost – the small village, located on a flat area. There is also a ferry across the Wisła, which may have an impact on the river environment. It is also visited mainly by tourists in summertime. Bernatka is located in Skarżysko-Kamiennain in the northeast of the Świętokrzyskie voivodeship. This river from which the samples were taken is a mountain river with a rapidly changing water level during heavy rain. The local streams that flow into the river also have an influence on the changing river parameters. The last water reservoir – Emerald Lake – is located in Kielce, the capital of świętokrzyskie. The reservoir is located in a nature reserve, which includes the hill of a sealed mine Wietrznia and the adjacent Międzygórze, being an extension of the Kielce Kadzielnia ridge. It is visited often by inhabitants throughout the year [14]. Summarising, all of the studied water reservoirs are recreational places and therefore they should be subjected to routine sanitary monitoring. The average total number of mesophilic and psychrophilic bacteria in water samples is shown in Figure 1.
The psychrophilic and mesophilic bacteria were present in all cases; however, there were more psychrophilic bacteria, and their number remained constant throughout the year. This is quite because of the low annual temperature of water in Poland. The number of mesophilic bacteria varied widely among the researched places. The most variable results were observed in the Wisła, where the highest value of mesophilic bacteria was 4500 CFU/ml. The lowest value was observed in Emerald Lake and Nida river. Similar studies of water reservoirs in Świętokrzyskie voivodeship were presented in our previous study [15]. The five different reservoirs were investigated based on the presence of mesophilic and psychrophilic bacteria. The number of mesophilic bacteria was in the same range (20–600 CFU/ml), whereas the number of psychrophilic bacteria was much higher, and in some cases they were 20,000 CFU/ml. This value may prove the extensive water eutrophication. The number of psychrophilic and mesophilic bacteria is not a standard determinate for surface water, but it could be used as a further indicator of organic matter contamination and as a source of microorganisms with potentially high adaptive properties [16].
The main indicator of faecal contamination is the number of E. coli CFU per 100 ml [17]. The occurrence of E. coli was analysed on the chromogenic agar by counting specific colonies, and the total number of bacteria was estimated in 100 ml of water. We also analysed the presence of coliforms on the Ejkman broth via the lactose fermentation and released gas. The obtained results (Table 2) were compared to each other and, referenced to the Regulation of the Minister of Health (2019), the limit value of the tested water for recreational purposes is less than 1000 CFU (or MPN) of E. coli per 100 ml of water and less than 400 CFU (or MPN) of Enterocuccus sp. per 100 ml. The faecal contamination of water was detected in all cases; however, exceeding the norm according to the regulation was observed in Wisła, Bernatka, and Emerald Lake, especially during autumn. The presented results were varied in terms of place and time of measurement. Amounts of bacteria above the stabdard limit could be caused by the presence of sewage from households in the area. Additionally, the number of microorganisms in autumn could be caused by the high temperature, which favours the persistence of mesophilic bacteria in water. In the case of Emerald Lake, the high number could be explained by the specific parameters of the reservoir. Emerald Lake is characterised by low water flow, which may have an influence on the accumulation of pollutants. Secondly, it is located in a nature reserve, where wild animals are present, and the natural microflora may contaminate the water. The microbiological condition of Pińczów and Nida seems to be most stable based on the estimated number of E. coli; on the other hand, the MPN of coliforms was highest in these waters. The applied methods, despite the fact that they detect similar microbiological indicators, gave varied results. This may be due to the rapidly changing microbiological parameters of the tested waters and the varied sensitivity of the microbiological growth mediums and the lack of analysis at the same time. The observed contamination could be due to inflow of groundwater, which may have contact with adjoining farmlands fertilised with natural products. In all cases apart from Emerald Lake, the surrounding households are not equipped with sewage systems, which has a major influence on the high number of E. coli and others faecal bacteria. Faecal contamination of water is a potential source of intestinal pathogens such as Salmonella and Shigella species, which may cause epidemic and serious infections. It is extremely relevant because of the serious threat of contaminated water entering the gastrointestinal tract, e.g. after swallowing by people swimming in the examined water reservoirs and rivers [18]. Our previous results [15] also included the analysis of the total number of E. coli. The number of E. coli in one reservoir was high in spring (average 40 CFU/ml). In the present case, the number of coliforms was significantly high in all reservoirs. The widespread and continuous presence of coliform bacteria in water reservoirs indicates continuous contamination with faeces. The water reservoirs are monitored by sanitary stations; however, this issue seems not to be very attractive among the scientific community in Poland. The study by Wolny-Koładka (2016) included, besides E. coli and coliforms, also E. faecalis, C. perfringens, Staphylococcus spp., and Salmonella spp. The presence of the analysed bacteria was correlated with the air and water temperature, as well as with the recreational use of water during the holidays. Because of the high prevalence of the microbiological indicators, poor water quality was specified, and the author concluded that it is reasonable to include the Nowohucki Reservoir into a constant sanitary monitoring programme [19]. Augustyn et al. (2016) also included a wider range of microbiological analyses: coliforms, thermo-tolerant coliform, faecal enterococci, and Salmonella spp., in the Wisłoka river. They concluded that human-origin contamination had the main impact on the sanitary condition of the studied waters. However, their study was dedicated to estimating the water parameters and factors influencing them in the context of drinking water [20]. Most of the published research of sanitary analysis of water from various sources comes from countries with poor hygiene standards and highly contaminated water, and with insufficient resources [19, 21–27]. All authors emphasise that the quality and quantity of water in general all over the world is insufficient for people. The absence or presence of indicators in water does not always have to correlate with presence or absence of pathogenic microorganisms, and their presence does not always pose a public health risk [28]. Nevertheless, we cannot forget about the existing threat, and we should consider ways to improve the sanitary quality of water in Poland [11, 29]. Poland is among the countries with insufficient water resources, which are characterised by significant seasonal variation and uneven territorial distribution [30]. Among the 139 lakes analysed in 2010 only 4% had a very good ecological status (class I). Lakes with moderate ecological status of water (quality class III) accounted for 50% of all monitored lakes. Lakes with poor ecological status class V accounted for 9% of the examined lakes. Wastewater discharge to surface water is still noted due to the lack of a sewage system. In 2012, it was noted that sewage treatment plants support only 69% of the population in a country that mainly inhabits urban areas [30]. The sanitary infrastructure in Poland is improving every year; however, the activities of the Ministry of Health and the Environment and the State Sanitary Inspectorate seems to be insufficient to control the spread of pathogens in water. The basic and often the only analysis applied in sanitary and epidemiological stations is the assessment of the occurrence of faecal microorganisms, mainly Escherichia coli and Enterococcus sp. These analyses included the routine monitoring only of water reservoirs classified as recreational by the European Union.
Summarising, there can be many sources of water contamination, starting from contact with the natural microflora of animals and people, and ending with insufficient municipal waste management. In many small villages in Poland there is no sewage system, and the contaminants enter the soil next to the ground water and surface water. It is a potential source of pathogens, which may cause serious gastrointestinal tract diseases. The presence of pathogenic bacteria in surface waters that are used for recreational purposes could be dangerous, especially for children and adults with immunodeficiency. The most common pathogens are, e.g. Salmonella spp., Shigella spp., Vibrio cholerae, and Escherichia coli. In recent years an increase in antibiotic resistance to bacteria isolated from the environment has been observed. It is obvious that this may cause complications in the treatment of waterborne infections [31]. Other bacterial pathogens such as Legionella sp., Aeromonas sp., Pseudomonas aeruginosa, and Mycobacterium avium are indigenous aquatic organisms that can both survive and proliferate in water [32]. It is important to educate people about the risk of waterborne infection, as well as wastewater management. Increased financing for the development of sewage systems in small towns and increased supervision of the sanitary condition of water in reservoirs used for recreational purposes have an important influence on the protection of the environment and public health.

Conclusions

Taking into account our preliminary and general research, it can already be said that the estimated sanitary condition of the studied water reservoirs was contaminated by faecal pollution and can be dangerous for human health. The studied places are often visited by people, so these places should be monitored or marked as biohazards.

Acknowledgments

We would like to thank students Joanna Niedziela-Wąsacz, Katarzyna Wąsowska, Remigiusz Ziewiecki, and Monika Żurawska for their assistance in the experimental work.
This work was supported by the program of the Minister of Science and Higher Education under the name “Regional Excellence Initiative in 2019-2022”, project number: 024/RID/2018/19, financing amount: 11,999,000.00 PLN

Conflict of interest

The authors declare no conflict of interest.

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