Destructive Water: Water-Caused Natural Disasters, their Abatement and Control (Proceedings of the Conference held at Anaheim, California, June 1996). IAHS Publ. no. 239, 1997. 267

Bacterial and chemical pollution of littoral waters of Lake Ohrid in the area of Pogradec town

ANGJELI VALER, PETRO VASILIKA & BUKLI RAMAZAN Institute of Public Health, Rruga "Aleksander Moisiu" Nr. 80, Tirana, Albania

Abstract Ohrid lake is situated in the eastern part of Albania. It is a tectonic lake, very attractive for tourists, with unique or rare species, and it is under the auspices of UNESCO and the World Bank. In the Pogradec area alone there are about 5 km of sandy beach and the sewerage waste in this area is discharged without treatment. The survey covers this area and aims at pointing out the bacteriological and chemical pollution as well as the risks to public health. Nine zones with three bands for each zone from radiating from the shore (5-7 m, 25-50 m and 150-200 m) were fixed for sample collection. E. coli and Str. faecalis were determined in each sample, while ammonia, nitrite, chlorides, dissolved oxygen, and oxidability were analysed only in nine samples taken from the first band. In the first and second bands, the level of bacteriological pollution generally exceeded the standards for bathing waters recommended by UNEP/WHO, EEC and American authors. In the 150-200 m band the levels of bacteriological contamination are very low, within the above standards. The levels of chemical indices clearly show the influence of organic pollution. Similar levels of bacteriological pollution were also found after 1990. The ratio CF/SF is about 4 which indicates faecal pollution by humans. The concern of the State of Albania, of the World Bank, of the EU and UNDP is important for environmental protection, especially for the protection of public health.

INTRODUCTION

The inclusion of Ohrid Lake under the auspices of UNESCO, the internationalization of the pollution issue, the presence of unique and rare species in the lake (e.g. Salmotruda ohridanus and Salmoletnica type of trout), the solution of pollution issues, the beauty of the lake (a pearl of this region), and the prosperity of the people around this lake are the main reasons for submitting this survey. In our opinion, this survey presents a "peak" situation of microbic pollution of the littoral waters of the Pogradec area.

Ohrid Lake is situated in the eastern part of Albania and a part of it pertains to the former Republic of Macedonia (Fig. 1). It is a tectonic lake and is oligotrophic. It has a surface area of 348 km2, a depth of 294 m (Macedonian Academy of Sciences and Arts, 1974), and an attractive environment for tourists. The scientists of the Institute of Public Health play an important role in identifying and solving a series of issues related to the protection of this lake from pollution.

The originality of the bio-diversity and bio-cenosis or biotype, as well as of the ecological interdependencies of Ohrid Lake have as a fundamental element the crystal like purity of the water. This level of purity constitutes the basic barometer orientating us as to the degree of tolerance in our intervention and is related to the concept of urban health "background motives" in (Mendia, 1974).

268 Angjeli Valer et al.

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Pollution of littoral waters of Lake Ohrid in the Pogradec town area 269

A feasibility study has been concluded and financing by the World Bank of four million US dollars is proposed to improve the situation and expand the study of the pollution. The EU and UNDP are also showing special interest (Mark Kosmo, World Bank EC2AU, 26 July 1995, File: OHER/AID-MEM2.doc).

METHODOLOGY OF THE STUDY

First, all pollution sources of the lake from the urban zone down to Drilon were identified. Nine zones were then fixed for the collection of samples (Fig. 2). Samples were collected in each zone from three bands whose distance from shore were 5-7 m, 25-50 m, and 150-200 m. A total of 108 bacteriological samples and one sample from each zone (nine samples in total) for chemical tests were taken from the 5-7 m band. The samples were taken at a depth of 20-25 cm below the lake surface. Each sample was analysed for E. coli, Str. faecalis, ammonia, nitrites, chlorides, dissolved oxygen and oxidability . The bacteriological tests were conducted using the method of multiple tubes and results were expressed in the MPN index. Ammonia and nitrites were determined using spectrophotometry and chlorides were determined using argentonetry. Dissolved oxygen was determined using the Winkler method, and oxidability was determined using the extraction method (Greenberg et al., 1985; IKHE, 1985a,b).

RESULTS OF THE STUDY

The main sources of urban pollution in the area under study (Fig. 2) are (a) the small collector at Pontili, (b) the stream through Pogradec at Old Tourism where the sewerage wastes are discharged from some dwellings around it, (c) relatively small channels in the concrete covered part of the shore, (d) the Verdova River, (e) the stream through Bucimas village, and (f) the main discharge of the wastewater disposal of Pogradec near Drilon. Table 1 presents the results of the bacteriological analyses, Table 2 presents the results of the chemical analyses, and Table 3 presents the results of E. coli levels during the summers of 1990, 1994 and 1995.

According to UNEP/WHO (1991), the standard for microbiological quality of bathing waters is 100-1000 E. coli per 100 ml water, while the EEC standard allows up to 100 Str. faecalis per 100 ml water (UNEP/WHO, 1991). From the bacterial point of view, E. coli is considered a more significant index for evaluating pollution than the other microorganisms (Pipes, 1982).

In the 5-7 m and 25-50 m bands for eight of the nine water zones studied, the littoral waters of Pogradec had a microbic load surpassing 1000 E. coli per 100 ml. The level 100 Str. faecalis per 100 ml was also exceeded in these same zones and bands. The zone of the villas constitutes the exception. This is due to a less frequent use by people and the absence of urban wastewater discharges; maximal levels in this zone were 150-240 E. coli per 100 ml and 43-240 Str. faecalis per 100 ml. The highest level of bacterial pollution are observed in the 5-7 m band because it is closer to the sources of pollution at some points, while at other points, the band is used more frequently by bathers.

270 Angjeli Valer et al.

Town POGRADEC/'

Snail sewage discharges

2 ) Old tourism

(J) New tourism

y Bar Rainbow

(j|) Camp of pioneers

(J ) Camp of workers

0 Vilas

8 ) River Verdova

— (9) Drilon

NORTH - •

LAKE OF

OHRID

Fie. 2 Sewage discharges and sampling zones on the shore of Lake Ohrid in the area of Pogradec town.

Pollution of littoral waters of Lake Ohrid in the Pogradec town area 271

Table 1 Results of bacteriological analyses.

Zone no.

1

2

3

4

5

6

7

8

9

Zone name

Pontili

Old Tourism

New Tourism

"Rainbow" bar

Camp of Pioneers

Camp of Workers

Villas

Verdova River

Drilon

Distance from shore (m)

5-7 25-50 150-200 5-7 25-50 150-200 5-7 25-50 150-200 5-7 25-50 150-200 5-7 25-50 150-200 5-7 25-50 150-200 5-7 25-50 150-200 5-7 25-50 150-200 5-7 25-50 150-200

Table 2 Results of chemical analyses.

Zone no.

1 2 3 4 5 6 7 8 9

Zone name

Pontili Old Tourism New Tourism Bar "Rainbow" Camp of Pioneers Camp of Workers Villas Verdova River Drilon

Distance from shore (m) 5-7 5-7 5-7 5-7 5-7 5-7 5-7 5-7 5-7

E. coli (MPN):

Minimum

4600 230

0

460 000 11000

4 24 000 11000

1 75 000 23 000

0 1 100

460 0

930 240

0 150 43 0

11000 9 000

0 24 000

1 100 4

Maximum

21000 11000

0 1 100 000

110 000 9

460 000 110 000

3 240 000 110 000

2 7 500 1 100

0 2 400 1 100

0 240 150

0 150 000 12 000

2 460 000 46 000

9

Indicator level (ppm)

Dissol. 02 4.08 3.08 1.76 1.12 4.70 4.20 4.10 3.60 3.20

Str. faecalis (MPN):

Minimum

460 150

0 24 000

1 100 9

1 100 460

1 24 000 2 400

0 1 100

93 0

1 100 410

0 42 23 0

1 100 150

0 1 100

93 4

Oxidab. Ammonia Nitrite

1.6 12.0 9.6 8.0 1.6 1.3 1.6 9.6

12.0

0.05 0.10 0.65 6.30 0.20 0.20 0.05 0.20 0.20

0.016 0.10 0.32 0.06 0.0064 traces 0.016 0.016 0.64

Maximum

11000 240

0 750 000

4 600 23

15 000 1 100

2 46 000 11000

0 2 400

460 0

2 400 1 100

0 240 43 0

12 000 2 400

0 15 000 1 100

23

Chloride

7.5 82.0 8.8

237.12 10.63

9.6 7.09

248.20 14.80

The level of bacterial pollution in the 25-50 m band (be it according to either E. coli, or Str. faecalis indicators) falls to half that in the 5-7 m band. In some cases it is 10 times lower than the 5-7 m band. Generally it remains above the level of

272 Angjeli Valer et al.

Table 3 Results of E. colt (MPN) during the summer of 1990, 1994, 1995.

Zone no.

1

2 3

4

5

6 8

Zone name

Pontili

Old Tourism New Tourism

Bar "Rainbow"

Camp of Workers

Villas Verdova River

Distance from shore

5-7

5-7 5-7

5-7

5-7

5-7 5-7

Year: 1990 Sample no.

-

-2

3

2

1

-

E. coli

-

-1 100

46 000 4 600

1 100 000 400

46 000 43

-

1994 Sample no.

2

1 2

2

_

-1

E. coli

24 000 46 000

460 000 110 000

2 400 460 000

•

-110 000

1995 Sample no.

2

-2

1

-

-1

E. coli

24 000 46 000

-240 000

1 100 000 460 000

•

-1 100 000

above-mentioned microbiological standards for E. coli and Str. Faecalis (see below). In the 150-200 m band, the lake waters appeared entirely free from the microbic

burden found in almost all the zones. A small bacterial contamination (up to 9 E. coli and 23 Str. faecalis per 100 ml) is observed in the zone of the Old Tourism and that of Drilon, where, in our opinion, it is influenced by the flow of the respective river waters, which disperses pollution in an accelerated way.

Results of bacteriological analyses are supported also by the results of chemical indicators (Table 2) which bear a special significance for the human organic pollution. In the case of chemical analyses we are not provided the possibility of comparing the levels according to distances because the samples are taken only in the 5-7 m band. However the results clearly reflect the compromising of water purity even from the chemical point of view. Almost all the samples show a reduction of ordinary levels of dissolved oxygen in the surface waters, particularly at the Old Tourism, the New Tourism, "Rainbow" Bar, the Verdova River and Drilon. High levels of chloride are witnessed in the Old Tourism, "Rainbow" Bar and Verdova River. Ammonia and nitrites, which are significant indices of fresh organic contamination, are observed in all the zones, irrespective of the changes of levels in the various zones.

The contamination sources in the zones of the Pontili, the Old Tourism, the Verdova River and Drilon are due to urban discharges. In zones "Rainbow" bar, camp of Pioneers and Camp of Workers the pollution is due to the high frequency of use by bathers. The New Tourism zone presents more complex contamination, for there are some minor wastewater discharges on the one hand and a high frequency of use by bathers, on the other hand.

The highest levels of bacterial pollution, from 460 000 to 1 100 000 E. coli per 100 ml, were witnessed in the zone of Old Tourism and in Drilon where the sewerage wastewaters are discharged. But high levels of bacterial pollution are witnessed even in the "Rainbow" bar zone, which is highly frequented by bathers. The high levels of chlorides (237.12 ppm), ammonia (6.3 ppm), oxidability (8-12 ppm) and the low level of dissolved oxygen (1.12 ppm) are also reported here.

Pollution of littoral waters of Lake Ohrid in the Pogradec town area 273

DISCUSSION

The problem of water pollution is considered by the WHO as the most important (Fish, 1979), whereas the Council of Europe considers the protection of freshwaters as a super regional or international problem (Council of Europe, 1976).

According to UNEP/WHO (1991), the standard for microbiological quality of bathing waters is 100-1000 E. coli per 100 ml water, while the EEC standard allows up to 100 Str. Faecalis per 100 ml water (UNEP/WHO, 1991). From the bacterial point of view, E. coli is considered a more significant index for evaluating faecal water pollution than the other microorganisms (Pipes, 1982).

The bacterial and chemical pollution of Pogradec shore is conditioned both from the untreated sewerage wastewater discharges and the contribution of bathing people. The authors think that the level of 1000 E. coli per 100 ml should not be accepted as a standard criterion. According to US authors, bathing waters should not exceed the level of 200 faecal coliforms per 100 ml water in order to prevent the transmission of pathogen organisms during an accidental swallowing of water (Liptak, 1974). More than 30 kinds of infection can be transmitted through water to mankind (WHO, 1989) and the transmission of contagious diseases through freshwaters is much more probable than through salty sea water, because the latter has more antigonistic factors (Vyershikova et al., 1967).

According to Geldreich et al. (1969) and Pipes (1982), the ratio CF/SF is more than 4 in bacterial human pollution and less than 1 in those of animal origin, hence the main contamination sources of lake waters remain the human ones. The levels of BOD-5, COD, phosphates, total azote and azotic ammonia of the sewerage wastewaters are similar to the levels provided by the literature for this category of water (Gjebrea et al., 1990).

The synthesis of the water quality data leads us to deduce that the stable solution for the protection of this system would be the avoidance of discharges to the lake, be it even through prior purification in special purification installations. Even in this case, the elimination of nitrites is difficult (WHO, 1986). In addition, the presence of viruses or other pathogens has been observed even after the treatment in these purification installations (WHO, 1979). From the results of the analyses it is observed that the contribution of the bathers to polluting the lake waters is not insignificant. Therefore a better distribution of use in the beach zone should be organized.

The tests of 1990, 1994 and 1995 (Table 3) reflect a similar situation with that of former years, although the number of samples taken is small. In some cases the levels of bacterial contamination exceed those of the bacterial pollution observed prior to the year 1990.

CONCLUSIONS

The Pogradec shore waters exceed the bacteriological standards and present risks to the Public Health.

- The levels of the chemical indexes in near-shore waters clearly show the influence of organic pollution.

274 Angjeli Valer et al.

- The ratio CF/SF is above 4 and indicates faecal pollution by humans. - The main sources of pollution are the discharges of untreated sewerage waters,

so the project of the World Bank for their treatment is full justified from the health point of view.

- The contribution from bathers to the pollution of the near-shore water is not insignificant and a better distribution of the use of the beach zone should be organized.

Acknowledgement The authors thank the specialists at the Primary Health Care of Pogradec town (Dr Rexhina Todolli and Dr Violeta Kerxhalli) for the offered analytical data after 1990.

REFERENCES

Council of Europe (1976) European Symposium on the Organization of the Protection Water, Final Report. Council of Europe, Strasbourg.

Fish, R. A. (1979) Déchets Toxiques et autres Déchets Dangereux. ICP/CEP 402, OMS, Copenhagen. Geldreich, E. et al. (1969) Concept of fecal streptococci in stream pollution. J. Wat. Pollut. Control Fed. 41, 336-352. Gjebrea, A. et al. (1990) Potenciali ndotes i ujrave ne qytetin e Pogradecit (Polluting potential of waters in the town of

Pogradec) (in Albanian). In: Sympozfum i IKHE: Problème te Ndotjes se Ujrave Siperfaqesore (IKHE Symp.: Problems of surface water pollution). Tirana.

Greenberg, A. E. et al. (1985) Standard Methods for the Examination of Water and Wastewater, 16 edn, 374-406, 878-882. American Public Health Association.

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Liptak, B. G. (19740 Environmental Engineer Handbook, vol. I, Water Pollution, 354-356. Macedonian Academy of Sciences and Arts (1974) Symposium on the Problems of regulation of Lake Ohrid (Skopje), 39,

355. Mendia, L. (1974) Alcuni aspetti del risanamento ambientale seminario internazionale. In: Diffusione e Trattamento

dell'Infezione Colerica (Rome, 24-25 April), 107-122. Pipes, O. W. (1982) Bacterial indicators of pollution, 22-27. UNEP/WHO (1991) Epidemiological studies related to environmental quality criteria for bathing waters, shellfish,

growing waters and edible marine organisms (activity D). MAP Technical Reports Series no. 53, p. 21. Athens. Vyershikova, A. E. et al. (1967) Sanitarnaya Mikrobiologia (Sanitary microbiology) (in Russian). WHO (1979) Human viruses in water, wastewater and soil. Report of a WHO Scientific Group, Geneva, 5-21. WHO (1986) Removal of Nitrates from Drinking Water (Budapest, 2-5 September 1986). WHO (1989) Disinfection of rural and small community water supply. Manual for Design and Operation, 4-7.