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Microbial and nutrient pollution along the coasts of Alicante, Spain
M a r i n e Pollution Bulletin Marine Pollution Bulletin, Volume20, No. 2, pp. 74-81, 1989 Printed in Great Britain.
0025-326X/89 $3.00+0.00 O 1989 Pergamon Press ptc
Microbial and Nutrient Pollution Along the Coasts of Alicante, Spain C. ZOFFMANN**, F. RODP,~GUEZ-VALERAt, M. PI~REZ-FILLOLt, F. RUIZ-BEVIA*, M. TORREBLANCA t and F. COLOM t
Departments of *Applied Chemistry and tMicrobiology, Universityof Alicante, Apdo. 99, Aficante, Spain *To w h o m c o r r e s p o n d e n c e should be addressed.
A systematic study of some pollution indicators (faecal coliforms, enterococci, Nitrogen and Phosphorus) has been carried out for seven years along a tourist crowded coastal region of Spain (Aiicante Province), evaluating the influence of sewage outfalls close to beaches. The study shows the importance of constant monitoring of pollution to achieve an adequate prevention policy. In general there is a tendency to improvement on this coast, attributable to a better sewage disposal network.
The province of Alicante is located in the Southeastern comer of Spain and has 160 km of coast subject to a relatively low level of industrial pollution, but receiving a considerable amount of domestic wastes. The population of the province is over 1 million, mostly concentrated along the coast. Moreover, the intensive tourist exploitation of the area increases population density and further aggravates the problems that occur; the province is visited by over 5 million tourists each year. It is common for many coastal towns to double in population during the summer months. Since the treatment and disposal of waste is mostly in the hands of Town Councils, widely varying degrees of treatment, loads of discharge, and ways of disposal can be found. Given the great importance of the sanitary and ecological quality of these beaches for tourism, and hence the local economy, an intensive monitoring has been carried out during the past 7 yr. Sewage enters the sea at an outfall point and is thence disseminated by various mechanisms which include tidal currents, winds, sedimentation on the sea bottom, etc. The pattern of contamination in a bathing area is a constantly changing one, affected not only by the variations in the different factors mentioned, but also by the continual arrival of fresh material, which in turn becomes diluted with more remotely contaminated seawater. On exposed coasts, an onshore wind may be expected to drive sewage on to the beaches, and the gross pollution, sometimes seen after heavy winds, is a 74
matter of common observation. Sometimes, there are peaks of pollution apparently related to heavy rainfall in the vicinity of stormwater overflows (Moore, 1959). Often raw, untreated wastewater enters these areas as a result of accidental spills, overloading, or blocked sewer lines (Vasconcelos & Anthony, 1985). All these conditions and factors influencing the pollution of coastal waters make the systematic and continuous long-term study of pollution in places such as recreational beaches highly advisable, to assess their state and quality, and to develop a rational programme of improvements of the wastewater disposal facilities. This work is one of a very few reporting a systematic sampling of marine beaches over several years, always at the same sampling points, and covering more than 3400 samples in seven consecutive years, over 160 km of coastline, utilizing the concentration of faecal coliforms as overall parameter indicative of sanitary conditions.
Materials and M e t h o d s
Description of the area studied Since summer 1980, tests have been made on the beaches closest to the city of Alicante (population 250 000, which is doubled in summer), covering a length of coastline of about 14 km facing mainly E and SE. From 1984 onwards, all the beaches in Alicante province (160 km of coastline, including more than 100 km of beaches) have been analysed throughout the year, with a total of more than 50 sampling points. The majority of the beaches are sandy, and densely populated in summer by holiday-makers. The superficial water temperature on the Costa Blanca oscillates between 13°C (February) and 27°C (August). Salinity is relatively high, 37.5-38.0%o. Wave swell depends on wind force, duration, and direction. The prevailing winds are Levant (E), Poniente (W) and Maestral (NW), and to a lesser degree Lebeche (SW) and Norte
(N). Tides are minimal in this area, and variations in sea level are due to atmospheric pressures and winds (variations in excess of 30 cm are rare).
Volume 20/Number
2/February
1989
The principal sea current runs in a NE-SW direction, but close to the coast this is varied by marine and coastal topography. There are numerous short and direct outfalls along the coastline. In fact, the number of long outfalls and outlets of sewage in any way treated is minimal (Ramos, 1981). Sampling
Samples were taken in 1000 ml sterilized (autoclaved) glass flasks with hermetic stoppers, which were submerged to a depth of 20-30 cm in 1 m deep coastal waters, which is the zone where the maximum number of bathers congregate, and transported to the laboratory at a temperature of 4’C, protected from light. Figure 1 shows the area studied. From 1980 to 1983, in Zone A, samples were taken weekly during July and August, fortnightly in June and September, and once during May. There were 10 sampling points during each of those years. From 1984 until the present, samples have been taken along the entire coastline of Alicante province (Zone B), at 50 sampling points throughout the year, weekly during July and August, fortnightly in June and September, and monthly for the rest of the year. Faecal coliforms (FC) were determined by the Most Probable Number (MPN) during the first years (19801983) and by the Membrane Filtration method (MF) using m-FC Agar (Difco) from 1984 onwards. Incubation was at 44.5”C. FC were counted after 24 h incubation.
Faecal Streptococci were determined by the Membrane Filtration method since 1983, using KF Agar (Merck). Incubation was at 37°C. FS were counted after 48 h incubation. Total phosphorus was determined by the Murphy & Riley method, nitrogen by the Kjeldahl method, and calorimetric determination by the Nessler reagent (APHA, 1985).
Results The responsible municipal authorities evidently prefer to keep the fact that sewage is deposited into the sea from general public knowledge, because of the probable negative impact on the tourist trade and thus the local economy. Only three of the thirteen municipalities interviewed provided details of the location and volume of outfalls, short term plans for improvements to the systems, or construction of treatment plants, prolongation of outlet channels4 etc.
Benidorm
Gusrdamar &I
ZONE A
t “.S.Juan
/
beach
_---ElSakfarbeach Roig Cmw 24
Fig. 1 Location
of sampling
66
10 km
area.
75
Marine Pollution Bulletin
Figure 2 shows the major wastewater discharges of Zone A, which has the greatest population density in the province. Before Spain joined the EEC the prevailing legislation provided that: "The concentration of E. coli corresponding to a period of 30 consecutive days should not exceed 1000/100 ml in more than 10% of the samples, nor 200/100 ml in more than 50% of the samplesY (BOE No. 151, 1977). In accordance with these standards we classified faecal coliforms as follows: beaches with values of less than 10 per 100 ml, free from contamination; 10-200, slightly contaminated; 200-1000, highly contaminated; and > 1 0 0 0 , dangerously contaminated. The data regarding concentrations of faecal coliforms and Enterococci at all
the sampling sites and throughout the period studied are summarized in Tables 1, 2. The EEC directives regarding the quality of beach waters are that the following concentrations should not be exceeded: G
I
Periodicity
Total coliforms 100 m1-1 500 10.000 Every 2 months Faecal coliforms 100 m1-1 100 2.000 Every 2 months Faecal streptococci 100 m1-1 100 G: Guide, I: Imperative. Waters are considered suitable for bathing when 95% of the samples, taken at the same site, with at least the frequency specified, give values lower than those of column I and 80% have values under those of column G. It is mandatory that member nations should ensure compliance with the said directive. In relation to the EEC standards, Table 3 shows, for Zone A, the percentage of samples with values of less than 100 and the percentage less than 2000 FC 100 m1-1 during 1980-86, in May-September. Table 4 shows the percentages for the whole area studied. TABLE 3 Percentage of samples with FC 100 ml -~ in ranges shown, during M a y September in Zone A.
Year
Numberof Samples
< 100
<2000
1980 1981 1982 1983 1984 1985 1986
96 105 111 127 127 128 130
38.5 74.5 73.5 61.7 90.6 77.7 81.5
100.0 100.0 100.0 100.0 100.0 98.5 99.2
TABLE 4 Percentage of samples with FC 100 ml -I in ranges shown, during January-December, in Zone B.
Fig. 2 Major discharges in Zone A.
TABLE 1 Percentage of samples with FC 100 ml -~ in ranges shown, during May-September in Zone A.
Year
Number of Samples
<10
10-200
200-1000
>1000
1980 1981 1982 1983 1984 1985 1986
96 105 111 127 127 128 130
10.5 44.0 31.0 20.0 54.0 43.0 47.5
33.5 34.0 42.5 61.5 42.0 40.0 41.5
29.0 12.5 24.0 17.0 3.0 9.0 8.0
27.0 9.5 2.5 1.5 1.0 8.0 3.0
TABLE 2 Percentage of samples with FC 100 m1-1 in ranges shown in JanuaryDecember in Zone B.
76
Year
N u m b e r of Samples
< 100
< 2000
1984 1985 1986
1069 950 1000
92.3 90.7 94.4
99.7 99.6 99.9
TABLE 5 Percentage of samples with Ent 100 ml -~ in ranges shown during M a y September in Zone A.
Year
Number of Samples
< 100
<2000
1983 1984 1985 1986
81 127 128 130
100 93.7 83.1 92.3
100 100 100 100
TABLE 6 Percentage of samples with Ent 100 ml -~ in ranges shown during January-December in Zone B.
Year
Number of Samples
10-200
200-1000
>1000
Year
Number of Samples
< 100
<2000
1984 1985 1986
1069 950 1000
72.0 64.0 65.0
23.5 30.0 32.0
3.5 4.0 2.5
1.0 2.0 0.5
1984 1985 1986
1069 950 1000
97.0 95.5 97.2
99.9 100.0 100.0
Volume 20/Number 2/February 1989
Similarly, Tables 5, 6 give the data for Enterococci. For the latter, each year the percentage of samples with values below 100 Enterococci have been higher than the E E C guideline, the lowest value being 83.08%, only once was there a value of over 2000 Enterococci found: 3000 in Denia. Tables 3, 4 show that, during those years, all, or at the very least, over 98% of samples were below 2000 F.C. 100 ml -~ (i.e. distant from the 95% E E C maximum). The percentage of samples below 100 varied with the zone considered over the years. These tables show a patent diversity of conditions, and values. The true condition of the coast studied is more clearly evident in Tables 1, 2. However, we discuss below some of the more remarkable and interesting cases:
Zone A First, we studied the influence of the various outfalls on nearby beaches, both in respect of the cloud of contamination around each boil and the plume emanating from it. In a previous study, carried out by Ruiz-Bevi~i et al. (1986) concerning the La Albufereta outfall (Outfall No. 2, Fig. 2), the authors calculated the average annual decrease in total coliforms, enterococci, Kjeldahl nitrogen, and total phosphorus, for each of the directions where samples were taken: north, south, east, and west. These values were the average decreases in the fortnightly values of samples taken during twelve consecutive months; samples being taken at 50, 100, and 200 m from the boil. In order to predict the effect of the distribution of the contamination cloud around the boil, a gaussian equation was evolved, taking into account the concentrations of total coliforms at a distance of 350 m from the boil were below 100/100 ml, implying an approximate concentration of faecal coliforms below 20/100 ml (the E E C stipulations observe a ratio of 5 : 1 Total to Faecal. Coliforms); at a distance of 300 m from the boil the concentrations of enterococci were well below 100/100 ml. Applying the parameter of the gaussian equation for nitrogen and phosphorus, we see that these parameters are negligible at 350 m from the boil. A further experiment, following the plume with Rodamine B, showed that at 100 m from the boil the reduction was of the order of 65.8%. Although the above are not mean annual values, applying the Schroeder (1981) equation to a day when the most frequent conditions in the studied area prevailed, we get a decrease rate o f - 0 . 0 1 0 7 for an initial concentration within the boil of 621 000 total coliforms 100 ml -~. If, to obtain an approximate idea of the magnitude of the concentration of total coliforms throughout the plume, we extrapolate this decrease rate to greater distances, we find that at 360 m the concentration would be 13 200; at 600 m, 1000; and at 1300 m, 0.6 TC 100 ml -~. In terms of FC this would be 2640, 200, and 0.12/100 ml. Even with the supposition that no reduction would occur in the water rising in the boil (58.106 T C 100 ml-~: Ruiz-Bevi~i et al., 1986), at a distance of 360 m from the boil there would be in the
order of 106; at 600 m, approx. 105; and at 1300 m, 53/ 100 ml. In terms of Faecal coliforms this represents 2.105, 2.104 and 10/100 ml.
Albufereta beach This is a small beach with a large population living nearby (20 000 inhabitants). The beach was subject to relatively high levels of contamination during 1980, reaching more than 200 Faecal Coliforms 100 ml -I in all the samples (100%) and over 1000 FC 100 m1-1 in 73%. During this time, outfall No. 2 (Fig. 2), with an average flow of 280 m 3 h -1 was only 200 m long (1.7 m depth), and was broken in several places, leaking abundantly. After the extension of the outfall during 1981, pollution levels decreased drastically, only 36% of samples giving values over 200 FC 100 ml-' and 22% over 1000 FC m1-1. Finally, at the end of 1981 the outfall was prolonged to 1336 m (9 m depth) and the FC counts dropped to very low values. In 1982 all the samples showed values below 100 FC 100 ml-k Figure 3 shows the mean values of bacterial pollution during the last 7 yr. The gradual decrease during 1982 and 1983 is attributable to the connection of minor discharges from individual buildings to the main outfall. A malfunction of the underwater outfall detected during 1984 produced an immediate increase in pollution levels, reaching a maximum of 480 FC 100 m1-1, which disappeared as soon as the repair was completed. Postiguet beach This beach is located in the centre of the city of Alicante (250 000 inhabitants) and is among the most crowded beaches on this coast. Daily yield from the capital is approximately 70 000 m 3, rising to 137 000 m 3 in summer. About 40 000 m 3 of treated waste water are used dally for irrigation, leaving about 30 000 m 3 (1250 m 3 h -L) to be outlet into the sea, increasing to 97 000 m 3 day -1 (4040 m 3 h -t) in the period of maximum tourist occupation. At present, outlet No. 4 discharges 450 m 3 h -1 of treated waste water, and the remainder passes through two outlets, one inside the port, and the other south of it. The contamination cloud from outlet No. 2, at more than 2 km distance, does not affect this beach. Nor would a plume heading directly towards the beach adversely affect it, since at 1300 m the TC concentration would be less than 1, as shown above. Although there are normally no waste water discharges into the waters of this beach, there are some important outfalls nearby, outfall No. 3, and a spillway in the immediate vicinity, and the discharge from a large hotel located directly on the beach (Fig. 2), also the main harbour dock makes a breakwater contributing to the accumulation in the resulting corner of pollution carried by the predominant winds and currents. The contamination cloud from outfall No. 3 (Fig. 2) would not have any effect on this beach either, since the distance is slightly over 1 kin, except that when predominant winds bring the outfall towards the beach, there would be a slight increase in coliform content. Figure 4 shows the mean values of bacterial pollution during the last 7 yr. In fact this beach gives the highest values of bacterial indicators in the province. In 77
Marine Pollution Bulletin
1980, 85% of the analysed samples gave more than 200 FC 100 ml -~ and 36% more than 1000 FC 100 ml -]. That these are the highest mean values registered would seem to be attributable to a direct discharge caused by a malfunction of the sewage collectors in this area. In later years the values have been lower, but show no tendency towards sustained improvement. A slight decrease was found only during 1985 and 1986, probably due to a better management of a sewage treatment plant of the hotel sited on the dock (Fig. 2). Tiro de Pich6n Beach (T.P.) This is a small beach not normally used for
1000 800 600
b
LL.
400 200 i
1981
1980
!
1982
'1985" '1986'
119831 '1984' Year
Cala Palmera This is a little cove located in one of the most picturesque areas of the coast, Cape Huertas. At the tip of this Cape there is an underwater outfall at 800 m discharging 350 m 3 h -1 untreated sewage (Fig. 2). The depth of this outfall (approx. 25 m) and the current which carries the plume far from the coast maintain the
500 400
8
swimming. However, it was included in this study from 1984 onwards because a sailing school for children is located here, which implies some contact with the water. There is an underwater outfall opposite this beach (600 m) which discharges an average of 220 m 3 h - t untreated sewage (Fig. 2). As shown in Table 1, the values at this site are rather high considering the distance at which the outfall is located. Since outlet No. 3 is slightly inferior to outlet No. 2 both in depth and and volume, we may assume that the average concentration at the boil is similar. As in the previous cases, the contamination cloud does not affect the shoreline, but in the event of a consistent SE wind, shore concentrations could reach 200 CF 100 ml -I. This rate of contamination was traced to temporary discharges through an overflow shaft directly on the shore and a spillway outletting at the foot of this shaft. This area is relatively enclosed, which helped maintain high levels of pollution in the sampling site. Between 1984 and 1986, the highest FC 100 ml - t values in this area were registered in 1985; of a total of 19 samples analysed that year, 74% were over 1000 FC 100 ml-L In summer 1985 the shaft was extended, and during the summer of 1986 the use of the spillway was drastically restricted, resulting in the reduction of pollution here to a great degree, as shown in Fig. 5.
3o0
b
u_ 200 100
,--, J
F
M A
VI M
__
J J A Month
S
0
N
700
D
600
5OO
8 "--
160
~
120
U u. 300
80 40
J
VlnIlnnH F
M A
M
J
J
A
S
0
N
400
Jf
200 100 1980
D
1981
1982
-E
30
~
2o
1984
1983 Year
Month
40
,I IJ 1985
1986
160 8 120 L)
U.
u.
10
J
F
M
A
M
J
J
A
S
0
N
D
78
I
1984
Month Fig. 3 Albufereta Beach. Annual mean summer values of FC 100 ml -~, and monthly fluctuations 1984-6.
80
1985
1986
Year Fig. 4
Postiguet Beach. Annual mean summer values of FC t00 ml -~, and monthly fluctuations, 1984-86.
Volume 20/Number 2/February 1989
area relatively free of pollution. This outlet (No. 1) is greater in both volume and depth than No. 2, so the concentration of contaminants at the boil may be considered similar. However, the contamination cloud does not affect Cala Palmera beach. Due to the coastal outline it is unlikely that a plume could penetrate the cove. For this to occur, a considerable variation in the direction of prevailing winds would be needed, but in such an event, the concentration at the shoreline would be approx. 80 FC 100 ml-L However, over the years, a tendency to increase has been detected in the pollution levels at this sampling site. In 1984 occasional high values were observed, due to breakdown of the outfall, with recovery of normal values as soon as this was repaired, although with a constantly increasing trend (Fig. 6). This information was passed to the local
Denia Located 100 km NE of Alicante, with 23 000 inhabitants, this town, although usually giving very low (nil or almost nil) rates of contamination, shows occasional increases which at times have exceeded 1000 FC 100 ml-~, regardless of season. The fluctuations observed in FC and FS values, and their relative ratios have led us to believe that this contamination was not recent. It has not so far been possible to identify the causes, although most probably they could be failures of the treatment plant, giving rise to the dumping of untreated waste into the sea. Figure 7 shows the changes in recent years.
>1200
600
/
\
500
-E
O O
400
[
u. 200300
]
100 1984
1985 Year
1986
Fig. 5 Tiro de Pich6n Beach (T.P.). Annual mean values of FC 100 ml-L
140 120 100 O O ~D LK
80 60 40 20 1984
authorities, who promptly found the reason: a growing number of cottages and small housing estates were being built and their wastes were not connected to the general sewage network. The highest values except for those during the breakdown of the outfall were reached in 1985, often around 200 FC 100 ml-I and occasionally even 1000 FC 100 ml-L Since then the connection of the small outlets to the general sewage system has been enforced, and the pollution levels have decreased to the very reasonable average of 10 FC 100 ml-~, with a maximum of 25. This case shows how relatively small sewage discharges can rapidly spoil picturesque and valuable holiday sites, which can, however, be rescued simply by enforcing the law against independent sewage discharges.
1985 Year
140 120
Benidorm 42 km NE of Alicante, Benidorm is an example of a quite acceptable rate of cont~amination, in spite of the extensive tourist and recreational use of the resort (34 000 residents, but an average population of 200 000 in summer and 80 000 in winter. Two sample points were maintained in each of the two main beaches, Poniente and Levante, and one in La Cala, a smaller cove. In spite of the massive influx of holidaymakers, the well planned location of the town's sewage outfall (Sierra Helada, Escaleta Point) (Fig. 1), which discharges 1250 m 3 h -1 in winter and 2000 m 3 h -I in summer of untreated waste water (since 1988 most of it has a secondary treatment) into the NE-SW current, so that residues could only return towards the coast under rare weather conditions, keeps the town's coastal waters clear, with average monthly values below 20 FC 100 m1-1 during the months of maximum occupation in 1984. August 1985 exceeded this average, with mean values of 85 for the four samples taken at each of the five stations (total 20 samples) and in 1986 also with 20
I00
200
O
o
80
160
60 40 20
8
120
u..
80 40
1980
1981' "1982" '1983' 1984 Year
1985
J19861
Fig. 6 Cala Palmera. Annual mean summer values of FC 100 ml-L and monthly fluctuations, 1984-86.
1984
II
1985 1986 Year Fig. 7 Denia. Annual mean values of FC 100 ml-L
79
Marine Pollution Bulletin
samples, the July average was 70 and August 90. Even so, the averages for the summer months: June, July, August and September was 37 in 1985 and 58 in 1986 (Fig. 8). Santa Pola The city of Santa Pola is located 19 km SW of Alicante. Although its beaches do not reach extreme states of contamination, this is nevertheless one of the zones of the coastline studied where notable contamination is most frequent, due principally to the southern orientation of its beaches, and the existence on some of them of small localized direct outfalls. Figure 9 shows the contamination values during 1984, 1985, and 1986. Torrevieja This municipality of 12 000 residents, 48 km SW of Alicante, maintains mean annual values of less than 16 FC 100 m1-1 on its two main beaches (El Cura and Los Locos) (Fig. 10), from a total of 40 samples in 1984 and 1986, and 38 in 1985. Since 1984, 625 m 3 h -~ of sewage have been treated. An annual average of 250 m 3 h -1 are dumped into the sea. Torrevieja's beaches exemplify the well planned placement of the town's sewage disposal system, particularly since the beaches are within the urban centre and in summer the population increases threefold.
4O 30
0 0
~
20
IJ.
1984
1985
1986
Year Fig. 8 Benidorm. Annual mean values of FC I00 ml -=.
8O l 0 0
60
~ 40 Lt.
20
Fig.
jl[
1985 1986 Year 9 Santa Pola. Annual mean values of FC 100 m1-1. 1984
2O E
15
8 u..
lO 5 1984
1985
1986
Year
Fig. 10 Torrevieja. Annual mean values of FC 100 ml -l.
80
Nutrient content Under natural conditions, Mediterranean waters are poor in nutrients, a characteristic shared by the majority of tropical seas not fertilized by outcrops. This scarcity of nutrients is responsible for the ecological characteristics typical of this type of sea, including, among other obvious effects, the transparency of the water, and overall blue tone, contrasting with the green tint of plankton rich waters. The conservation of these characteristics is obviously essential therefore from the tourist point of view, even without taking into account the possible ecological repercussions to fishing, etc. At the sampling stations, when FC concentrations were high, so also were nutrient values. At the majority of sampling points the average phosphorus content was less than 40 p.g 1-1 and nitrogen less than 150 ~tg 1-l. In the San Gabriel area, which was used for bathing until about 20 yr ago, FC concentrations have been consistently below 200, between 1982 and 1986, except in 1983, when the average was 295. During these years average phosphorus and nitrogen concentrations varied between 100-128 ~tg P 1-1 and 175-450 ~tg N 1-1, due to the fact that the largest outfall of urban sewage on the coastline studied is located here--outfall No. 4 (Fig. 2). This outfall has an underwater length of 2 m. Until 1983 all the sewage discharged here, almost 1000 m 3 h -~, was untreated. In 1984, as a result of the commissioning of treatment station T1 (Fig. 2), (secondary treatment), the rate was 450 m 3 h -1 treated sewage and 170 m 3 h -1 untreated, the remainder being used for irrigation. Since 1986, station T1 is treating a larger amount of sewage, and recycling the treated waters for irrigation, so that currently the outfall is only 450 m 3 h -l, secondarily treated residual waters. Since 1984 therefore, all the residual waters outlet by outfall No. 4 (Fig. 2) are subjected to secondary treatment, and contain chloride, which reduced the bacterial content, but not that of nutrients. In general terms, in contrast with the previous section, in this respect the situation is not encouraging. Although the waters cannot be considered eutrophic, nonetheless the values are almost without exception higher than those natural for these waters, obtained at the island of Tabarca (a Marine Reserve since April 1986 (Fig. 1), (BOE No. 112)): 20 ~tg P i-I and 85 gg N 1-1 (Zoffmann et al., 1985). Discussion
The coastal sector we have studied can be considered a typical example of Mediterranean coast subjected to an intermediate level of urban pollution, with a marked summer increase and with a relatively low industrial contribution. This model can be widely extended throughout the Mediterranean coast in several countries. Also, given the time-span and the number of samples, the results can be considered valid reflections of tendencies and mean values. By studying the values of the pollution indicators in beach waters, we have attempted to evaluate the effect of wastewater discharges. It seems clear that the coastal structure is a critical factor in deciding the degree to which beaches
Volume 20/Number 2/February 1989
are affected. Torrevieja and Benidorm are typical exam- municipal beaches, and thanks to a close degree of colpies where relatively large discharges of untreated laboration between the competent municipal authorities sewage cause little ill effect on the sanitary quality of the and laboratories, in the detection and prevention of beaches, which in the case of the second town is attri- existing or predicted problems. With similar collaborabutable to the exceptional location of the outfall, at the tion the occasional abnormally high values seen in other tip of a cape where the sea floor drops to 25 m depth municipalities could be avoided. almost on the shore line. It is remarkable that as a general rule in the whole Examples of the opposite case are Albufereta and area studied, the beaches to the north of the capital had Postiguet beaches, enclosed within a bay formation, so higher pollution values than those to the south. Possibly that even small discharges produce high levels of pollu- the general orientation of the coast, more open to the tion indicators, and consequently poor sanitary and east in the southern part, could contribute to this aesthetic conditions. Albufereta, however, has been difference. restored to very reasonable limits for an enclosed and shallow area. A second treatment station, T2 (Fig. 2), is This work was supported by the Excmo. Ayuntamiento de Alicante currently under construction, which, in the near future, and the Excma. Diputaci6n Provincial de Alicante. will commence treatment of the sewage at present being discharged through the outfalls 1, 2 (Albufereta), and 3 APHA (1985). Standard Methods for the Examination of Water and (rig. 2). Wastewater, t6th edn. American Public Health Association, WashAnother different situation is that created by the disington, DC. charge of treated wastewater, such as in the area of San BOE No. 151 (1977). Orden de 29 de abril de 1977 por la que se aprueba la "Instrucci6n para el vertido al mar, desde tierra, de aguas Gabriel in Alicante. Here the values of microbial polluresiduales a travrs de emisarios submarinos', pp. 14247-14256. tion indicators were in general acceptable, but the levels BOE No. 112 (1986). Orden de 4 de abril de 1986 por la que se establece una reserva marina en la Isla de Tabarca. p. 16769. of nutrients were very high, with a degradation of the B. (1959). Sewage contamination of coastal bathing waters in ecology and aesthetic values of these waters. It is true Moore, England and Wales. A bacteriological and epidemiological study. however that the rocky beaches located in this area have Jour. Hyg. 57,435-472. never been used extensively for recreational purposes, Ramos, A. (1981). Contribuci6n al conocimiento de la franja litoral de la provincia de Alicante (Costa E. espafiola). In El medioflsico de la and are therefore of low tourist value. Furthermore, the comarca de Alicante (C. Auernheimer and A. Escarrr, eds), pp. 196'Integral Water Project' currently being developed in 225. Excmo. Ayuntamiento de Alicante and Universidad de Alicante. Alicante city, will permit the treatment and recycling for F., Zoffman, C., Rodn'guez-Valera, F. & Marcilla, A. irrigation of all sewage waters, eliminating the necessity Ruiz-Bevifi, (1986). Contaminants on the sea surface around an underwater outfor any direct marine outfalls. Within the space of two fall. Mar. Pollut. Bull. 17,107-112. years, Alicante will be the first Spanish city to treat the Vasconcelos, G. S. & Anthony, N. C. (1985). Microbiological quality of recreational waters in the Pacific Northwest. J. Water Pollut. Control whole of its sewage. Fedn. 57, 367-377. The favourable evolution of the trend in zone A over Zoffrnann, C., Ramos, A. A. & Rodn'guez-Valera, F. (1985). Datos preliminares oceanogrfificos y de contaminaci6n marina en la Isla the study period is evident. This is clearly due to the Plana o Nueva Tabarca (Alicante). In La reserva marina de la Isla interest in achieving and maintaining the highest posPlana o Nueva Tabarca (Alicante) (A. A. Ramos, ed.), pp. 95-110. sible sanitary standards for the waters of Alicante Ayuntamiento de Alicante, Universidad de Alicante.
81
0025-326X/89 $3.00+0.00 O 1989 Pergamon Press ptc
Microbial and Nutrient Pollution Along the Coasts of Alicante, Spain C. ZOFFMANN**, F. RODP,~GUEZ-VALERAt, M. PI~REZ-FILLOLt, F. RUIZ-BEVIA*, M. TORREBLANCA t and F. COLOM t
Departments of *Applied Chemistry and tMicrobiology, Universityof Alicante, Apdo. 99, Aficante, Spain *To w h o m c o r r e s p o n d e n c e should be addressed.
A systematic study of some pollution indicators (faecal coliforms, enterococci, Nitrogen and Phosphorus) has been carried out for seven years along a tourist crowded coastal region of Spain (Aiicante Province), evaluating the influence of sewage outfalls close to beaches. The study shows the importance of constant monitoring of pollution to achieve an adequate prevention policy. In general there is a tendency to improvement on this coast, attributable to a better sewage disposal network.
The province of Alicante is located in the Southeastern comer of Spain and has 160 km of coast subject to a relatively low level of industrial pollution, but receiving a considerable amount of domestic wastes. The population of the province is over 1 million, mostly concentrated along the coast. Moreover, the intensive tourist exploitation of the area increases population density and further aggravates the problems that occur; the province is visited by over 5 million tourists each year. It is common for many coastal towns to double in population during the summer months. Since the treatment and disposal of waste is mostly in the hands of Town Councils, widely varying degrees of treatment, loads of discharge, and ways of disposal can be found. Given the great importance of the sanitary and ecological quality of these beaches for tourism, and hence the local economy, an intensive monitoring has been carried out during the past 7 yr. Sewage enters the sea at an outfall point and is thence disseminated by various mechanisms which include tidal currents, winds, sedimentation on the sea bottom, etc. The pattern of contamination in a bathing area is a constantly changing one, affected not only by the variations in the different factors mentioned, but also by the continual arrival of fresh material, which in turn becomes diluted with more remotely contaminated seawater. On exposed coasts, an onshore wind may be expected to drive sewage on to the beaches, and the gross pollution, sometimes seen after heavy winds, is a 74
matter of common observation. Sometimes, there are peaks of pollution apparently related to heavy rainfall in the vicinity of stormwater overflows (Moore, 1959). Often raw, untreated wastewater enters these areas as a result of accidental spills, overloading, or blocked sewer lines (Vasconcelos & Anthony, 1985). All these conditions and factors influencing the pollution of coastal waters make the systematic and continuous long-term study of pollution in places such as recreational beaches highly advisable, to assess their state and quality, and to develop a rational programme of improvements of the wastewater disposal facilities. This work is one of a very few reporting a systematic sampling of marine beaches over several years, always at the same sampling points, and covering more than 3400 samples in seven consecutive years, over 160 km of coastline, utilizing the concentration of faecal coliforms as overall parameter indicative of sanitary conditions.
Materials and M e t h o d s
Description of the area studied Since summer 1980, tests have been made on the beaches closest to the city of Alicante (population 250 000, which is doubled in summer), covering a length of coastline of about 14 km facing mainly E and SE. From 1984 onwards, all the beaches in Alicante province (160 km of coastline, including more than 100 km of beaches) have been analysed throughout the year, with a total of more than 50 sampling points. The majority of the beaches are sandy, and densely populated in summer by holiday-makers. The superficial water temperature on the Costa Blanca oscillates between 13°C (February) and 27°C (August). Salinity is relatively high, 37.5-38.0%o. Wave swell depends on wind force, duration, and direction. The prevailing winds are Levant (E), Poniente (W) and Maestral (NW), and to a lesser degree Lebeche (SW) and Norte
(N). Tides are minimal in this area, and variations in sea level are due to atmospheric pressures and winds (variations in excess of 30 cm are rare).
Volume 20/Number
2/February
1989
The principal sea current runs in a NE-SW direction, but close to the coast this is varied by marine and coastal topography. There are numerous short and direct outfalls along the coastline. In fact, the number of long outfalls and outlets of sewage in any way treated is minimal (Ramos, 1981). Sampling
Samples were taken in 1000 ml sterilized (autoclaved) glass flasks with hermetic stoppers, which were submerged to a depth of 20-30 cm in 1 m deep coastal waters, which is the zone where the maximum number of bathers congregate, and transported to the laboratory at a temperature of 4’C, protected from light. Figure 1 shows the area studied. From 1980 to 1983, in Zone A, samples were taken weekly during July and August, fortnightly in June and September, and once during May. There were 10 sampling points during each of those years. From 1984 until the present, samples have been taken along the entire coastline of Alicante province (Zone B), at 50 sampling points throughout the year, weekly during July and August, fortnightly in June and September, and monthly for the rest of the year. Faecal coliforms (FC) were determined by the Most Probable Number (MPN) during the first years (19801983) and by the Membrane Filtration method (MF) using m-FC Agar (Difco) from 1984 onwards. Incubation was at 44.5”C. FC were counted after 24 h incubation.
Faecal Streptococci were determined by the Membrane Filtration method since 1983, using KF Agar (Merck). Incubation was at 37°C. FS were counted after 48 h incubation. Total phosphorus was determined by the Murphy & Riley method, nitrogen by the Kjeldahl method, and calorimetric determination by the Nessler reagent (APHA, 1985).
Results The responsible municipal authorities evidently prefer to keep the fact that sewage is deposited into the sea from general public knowledge, because of the probable negative impact on the tourist trade and thus the local economy. Only three of the thirteen municipalities interviewed provided details of the location and volume of outfalls, short term plans for improvements to the systems, or construction of treatment plants, prolongation of outlet channels4 etc.
Benidorm
Gusrdamar &I
ZONE A
t “.S.Juan
/
beach
_---ElSakfarbeach Roig Cmw 24
Fig. 1 Location
of sampling
66
10 km
area.
75
Marine Pollution Bulletin
Figure 2 shows the major wastewater discharges of Zone A, which has the greatest population density in the province. Before Spain joined the EEC the prevailing legislation provided that: "The concentration of E. coli corresponding to a period of 30 consecutive days should not exceed 1000/100 ml in more than 10% of the samples, nor 200/100 ml in more than 50% of the samplesY (BOE No. 151, 1977). In accordance with these standards we classified faecal coliforms as follows: beaches with values of less than 10 per 100 ml, free from contamination; 10-200, slightly contaminated; 200-1000, highly contaminated; and > 1 0 0 0 , dangerously contaminated. The data regarding concentrations of faecal coliforms and Enterococci at all
the sampling sites and throughout the period studied are summarized in Tables 1, 2. The EEC directives regarding the quality of beach waters are that the following concentrations should not be exceeded: G
I
Periodicity
Total coliforms 100 m1-1 500 10.000 Every 2 months Faecal coliforms 100 m1-1 100 2.000 Every 2 months Faecal streptococci 100 m1-1 100 G: Guide, I: Imperative. Waters are considered suitable for bathing when 95% of the samples, taken at the same site, with at least the frequency specified, give values lower than those of column I and 80% have values under those of column G. It is mandatory that member nations should ensure compliance with the said directive. In relation to the EEC standards, Table 3 shows, for Zone A, the percentage of samples with values of less than 100 and the percentage less than 2000 FC 100 m1-1 during 1980-86, in May-September. Table 4 shows the percentages for the whole area studied. TABLE 3 Percentage of samples with FC 100 ml -~ in ranges shown, during M a y September in Zone A.
Year
Numberof Samples
< 100
<2000
1980 1981 1982 1983 1984 1985 1986
96 105 111 127 127 128 130
38.5 74.5 73.5 61.7 90.6 77.7 81.5
100.0 100.0 100.0 100.0 100.0 98.5 99.2
TABLE 4 Percentage of samples with FC 100 ml -I in ranges shown, during January-December, in Zone B.
Fig. 2 Major discharges in Zone A.
TABLE 1 Percentage of samples with FC 100 ml -~ in ranges shown, during May-September in Zone A.
Year
Number of Samples
<10
10-200
200-1000
>1000
1980 1981 1982 1983 1984 1985 1986
96 105 111 127 127 128 130
10.5 44.0 31.0 20.0 54.0 43.0 47.5
33.5 34.0 42.5 61.5 42.0 40.0 41.5
29.0 12.5 24.0 17.0 3.0 9.0 8.0
27.0 9.5 2.5 1.5 1.0 8.0 3.0
TABLE 2 Percentage of samples with FC 100 m1-1 in ranges shown in JanuaryDecember in Zone B.
76
Year
N u m b e r of Samples
< 100
< 2000
1984 1985 1986
1069 950 1000
92.3 90.7 94.4
99.7 99.6 99.9
TABLE 5 Percentage of samples with Ent 100 ml -~ in ranges shown during M a y September in Zone A.
Year
Number of Samples
< 100
<2000
1983 1984 1985 1986
81 127 128 130
100 93.7 83.1 92.3
100 100 100 100
TABLE 6 Percentage of samples with Ent 100 ml -~ in ranges shown during January-December in Zone B.
Year
Number of Samples
10-200
200-1000
>1000
Year
Number of Samples
< 100
<2000
1984 1985 1986
1069 950 1000
72.0 64.0 65.0
23.5 30.0 32.0
3.5 4.0 2.5
1.0 2.0 0.5
1984 1985 1986
1069 950 1000
97.0 95.5 97.2
99.9 100.0 100.0
Volume 20/Number 2/February 1989
Similarly, Tables 5, 6 give the data for Enterococci. For the latter, each year the percentage of samples with values below 100 Enterococci have been higher than the E E C guideline, the lowest value being 83.08%, only once was there a value of over 2000 Enterococci found: 3000 in Denia. Tables 3, 4 show that, during those years, all, or at the very least, over 98% of samples were below 2000 F.C. 100 ml -~ (i.e. distant from the 95% E E C maximum). The percentage of samples below 100 varied with the zone considered over the years. These tables show a patent diversity of conditions, and values. The true condition of the coast studied is more clearly evident in Tables 1, 2. However, we discuss below some of the more remarkable and interesting cases:
Zone A First, we studied the influence of the various outfalls on nearby beaches, both in respect of the cloud of contamination around each boil and the plume emanating from it. In a previous study, carried out by Ruiz-Bevi~i et al. (1986) concerning the La Albufereta outfall (Outfall No. 2, Fig. 2), the authors calculated the average annual decrease in total coliforms, enterococci, Kjeldahl nitrogen, and total phosphorus, for each of the directions where samples were taken: north, south, east, and west. These values were the average decreases in the fortnightly values of samples taken during twelve consecutive months; samples being taken at 50, 100, and 200 m from the boil. In order to predict the effect of the distribution of the contamination cloud around the boil, a gaussian equation was evolved, taking into account the concentrations of total coliforms at a distance of 350 m from the boil were below 100/100 ml, implying an approximate concentration of faecal coliforms below 20/100 ml (the E E C stipulations observe a ratio of 5 : 1 Total to Faecal. Coliforms); at a distance of 300 m from the boil the concentrations of enterococci were well below 100/100 ml. Applying the parameter of the gaussian equation for nitrogen and phosphorus, we see that these parameters are negligible at 350 m from the boil. A further experiment, following the plume with Rodamine B, showed that at 100 m from the boil the reduction was of the order of 65.8%. Although the above are not mean annual values, applying the Schroeder (1981) equation to a day when the most frequent conditions in the studied area prevailed, we get a decrease rate o f - 0 . 0 1 0 7 for an initial concentration within the boil of 621 000 total coliforms 100 ml -~. If, to obtain an approximate idea of the magnitude of the concentration of total coliforms throughout the plume, we extrapolate this decrease rate to greater distances, we find that at 360 m the concentration would be 13 200; at 600 m, 1000; and at 1300 m, 0.6 TC 100 ml -~. In terms of FC this would be 2640, 200, and 0.12/100 ml. Even with the supposition that no reduction would occur in the water rising in the boil (58.106 T C 100 ml-~: Ruiz-Bevi~i et al., 1986), at a distance of 360 m from the boil there would be in the
order of 106; at 600 m, approx. 105; and at 1300 m, 53/ 100 ml. In terms of Faecal coliforms this represents 2.105, 2.104 and 10/100 ml.
Albufereta beach This is a small beach with a large population living nearby (20 000 inhabitants). The beach was subject to relatively high levels of contamination during 1980, reaching more than 200 Faecal Coliforms 100 ml -I in all the samples (100%) and over 1000 FC 100 m1-1 in 73%. During this time, outfall No. 2 (Fig. 2), with an average flow of 280 m 3 h -1 was only 200 m long (1.7 m depth), and was broken in several places, leaking abundantly. After the extension of the outfall during 1981, pollution levels decreased drastically, only 36% of samples giving values over 200 FC 100 ml-' and 22% over 1000 FC m1-1. Finally, at the end of 1981 the outfall was prolonged to 1336 m (9 m depth) and the FC counts dropped to very low values. In 1982 all the samples showed values below 100 FC 100 ml-k Figure 3 shows the mean values of bacterial pollution during the last 7 yr. The gradual decrease during 1982 and 1983 is attributable to the connection of minor discharges from individual buildings to the main outfall. A malfunction of the underwater outfall detected during 1984 produced an immediate increase in pollution levels, reaching a maximum of 480 FC 100 m1-1, which disappeared as soon as the repair was completed. Postiguet beach This beach is located in the centre of the city of Alicante (250 000 inhabitants) and is among the most crowded beaches on this coast. Daily yield from the capital is approximately 70 000 m 3, rising to 137 000 m 3 in summer. About 40 000 m 3 of treated waste water are used dally for irrigation, leaving about 30 000 m 3 (1250 m 3 h -L) to be outlet into the sea, increasing to 97 000 m 3 day -1 (4040 m 3 h -t) in the period of maximum tourist occupation. At present, outlet No. 4 discharges 450 m 3 h -1 of treated waste water, and the remainder passes through two outlets, one inside the port, and the other south of it. The contamination cloud from outlet No. 2, at more than 2 km distance, does not affect this beach. Nor would a plume heading directly towards the beach adversely affect it, since at 1300 m the TC concentration would be less than 1, as shown above. Although there are normally no waste water discharges into the waters of this beach, there are some important outfalls nearby, outfall No. 3, and a spillway in the immediate vicinity, and the discharge from a large hotel located directly on the beach (Fig. 2), also the main harbour dock makes a breakwater contributing to the accumulation in the resulting corner of pollution carried by the predominant winds and currents. The contamination cloud from outfall No. 3 (Fig. 2) would not have any effect on this beach either, since the distance is slightly over 1 kin, except that when predominant winds bring the outfall towards the beach, there would be a slight increase in coliform content. Figure 4 shows the mean values of bacterial pollution during the last 7 yr. In fact this beach gives the highest values of bacterial indicators in the province. In 77
Marine Pollution Bulletin
1980, 85% of the analysed samples gave more than 200 FC 100 ml -~ and 36% more than 1000 FC 100 ml -]. That these are the highest mean values registered would seem to be attributable to a direct discharge caused by a malfunction of the sewage collectors in this area. In later years the values have been lower, but show no tendency towards sustained improvement. A slight decrease was found only during 1985 and 1986, probably due to a better management of a sewage treatment plant of the hotel sited on the dock (Fig. 2). Tiro de Pich6n Beach (T.P.) This is a small beach not normally used for
1000 800 600
b
LL.
400 200 i
1981
1980
!
1982
'1985" '1986'
119831 '1984' Year
Cala Palmera This is a little cove located in one of the most picturesque areas of the coast, Cape Huertas. At the tip of this Cape there is an underwater outfall at 800 m discharging 350 m 3 h -1 untreated sewage (Fig. 2). The depth of this outfall (approx. 25 m) and the current which carries the plume far from the coast maintain the
500 400
8
swimming. However, it was included in this study from 1984 onwards because a sailing school for children is located here, which implies some contact with the water. There is an underwater outfall opposite this beach (600 m) which discharges an average of 220 m 3 h - t untreated sewage (Fig. 2). As shown in Table 1, the values at this site are rather high considering the distance at which the outfall is located. Since outlet No. 3 is slightly inferior to outlet No. 2 both in depth and and volume, we may assume that the average concentration at the boil is similar. As in the previous cases, the contamination cloud does not affect the shoreline, but in the event of a consistent SE wind, shore concentrations could reach 200 CF 100 ml -I. This rate of contamination was traced to temporary discharges through an overflow shaft directly on the shore and a spillway outletting at the foot of this shaft. This area is relatively enclosed, which helped maintain high levels of pollution in the sampling site. Between 1984 and 1986, the highest FC 100 ml - t values in this area were registered in 1985; of a total of 19 samples analysed that year, 74% were over 1000 FC 100 ml-L In summer 1985 the shaft was extended, and during the summer of 1986 the use of the spillway was drastically restricted, resulting in the reduction of pollution here to a great degree, as shown in Fig. 5.
3o0
b
u_ 200 100
,--, J
F
M A
VI M
__
J J A Month
S
0
N
700
D
600
5OO
8 "--
160
~
120
U u. 300
80 40
J
VlnIlnnH F
M A
M
J
J
A
S
0
N
400
Jf
200 100 1980
D
1981
1982
-E
30
~
2o
1984
1983 Year
Month
40
,I IJ 1985
1986
160 8 120 L)
U.
u.
10
J
F
M
A
M
J
J
A
S
0
N
D
78
I
1984
Month Fig. 3 Albufereta Beach. Annual mean summer values of FC 100 ml -~, and monthly fluctuations 1984-6.
80
1985
1986
Year Fig. 4
Postiguet Beach. Annual mean summer values of FC t00 ml -~, and monthly fluctuations, 1984-86.
Volume 20/Number 2/February 1989
area relatively free of pollution. This outlet (No. 1) is greater in both volume and depth than No. 2, so the concentration of contaminants at the boil may be considered similar. However, the contamination cloud does not affect Cala Palmera beach. Due to the coastal outline it is unlikely that a plume could penetrate the cove. For this to occur, a considerable variation in the direction of prevailing winds would be needed, but in such an event, the concentration at the shoreline would be approx. 80 FC 100 ml-L However, over the years, a tendency to increase has been detected in the pollution levels at this sampling site. In 1984 occasional high values were observed, due to breakdown of the outfall, with recovery of normal values as soon as this was repaired, although with a constantly increasing trend (Fig. 6). This information was passed to the local
Denia Located 100 km NE of Alicante, with 23 000 inhabitants, this town, although usually giving very low (nil or almost nil) rates of contamination, shows occasional increases which at times have exceeded 1000 FC 100 ml-~, regardless of season. The fluctuations observed in FC and FS values, and their relative ratios have led us to believe that this contamination was not recent. It has not so far been possible to identify the causes, although most probably they could be failures of the treatment plant, giving rise to the dumping of untreated waste into the sea. Figure 7 shows the changes in recent years.
>1200
600
/
\
500
-E
O O
400
[
u. 200300
]
100 1984
1985 Year
1986
Fig. 5 Tiro de Pich6n Beach (T.P.). Annual mean values of FC 100 ml-L
140 120 100 O O ~D LK
80 60 40 20 1984
authorities, who promptly found the reason: a growing number of cottages and small housing estates were being built and their wastes were not connected to the general sewage network. The highest values except for those during the breakdown of the outfall were reached in 1985, often around 200 FC 100 ml-I and occasionally even 1000 FC 100 ml-L Since then the connection of the small outlets to the general sewage system has been enforced, and the pollution levels have decreased to the very reasonable average of 10 FC 100 ml-~, with a maximum of 25. This case shows how relatively small sewage discharges can rapidly spoil picturesque and valuable holiday sites, which can, however, be rescued simply by enforcing the law against independent sewage discharges.
1985 Year
140 120
Benidorm 42 km NE of Alicante, Benidorm is an example of a quite acceptable rate of cont~amination, in spite of the extensive tourist and recreational use of the resort (34 000 residents, but an average population of 200 000 in summer and 80 000 in winter. Two sample points were maintained in each of the two main beaches, Poniente and Levante, and one in La Cala, a smaller cove. In spite of the massive influx of holidaymakers, the well planned location of the town's sewage outfall (Sierra Helada, Escaleta Point) (Fig. 1), which discharges 1250 m 3 h -1 in winter and 2000 m 3 h -I in summer of untreated waste water (since 1988 most of it has a secondary treatment) into the NE-SW current, so that residues could only return towards the coast under rare weather conditions, keeps the town's coastal waters clear, with average monthly values below 20 FC 100 m1-1 during the months of maximum occupation in 1984. August 1985 exceeded this average, with mean values of 85 for the four samples taken at each of the five stations (total 20 samples) and in 1986 also with 20
I00
200
O
o
80
160
60 40 20
8
120
u..
80 40
1980
1981' "1982" '1983' 1984 Year
1985
J19861
Fig. 6 Cala Palmera. Annual mean summer values of FC 100 ml-L and monthly fluctuations, 1984-86.
1984
II
1985 1986 Year Fig. 7 Denia. Annual mean values of FC 100 ml-L
79
Marine Pollution Bulletin
samples, the July average was 70 and August 90. Even so, the averages for the summer months: June, July, August and September was 37 in 1985 and 58 in 1986 (Fig. 8). Santa Pola The city of Santa Pola is located 19 km SW of Alicante. Although its beaches do not reach extreme states of contamination, this is nevertheless one of the zones of the coastline studied where notable contamination is most frequent, due principally to the southern orientation of its beaches, and the existence on some of them of small localized direct outfalls. Figure 9 shows the contamination values during 1984, 1985, and 1986. Torrevieja This municipality of 12 000 residents, 48 km SW of Alicante, maintains mean annual values of less than 16 FC 100 m1-1 on its two main beaches (El Cura and Los Locos) (Fig. 10), from a total of 40 samples in 1984 and 1986, and 38 in 1985. Since 1984, 625 m 3 h -~ of sewage have been treated. An annual average of 250 m 3 h -1 are dumped into the sea. Torrevieja's beaches exemplify the well planned placement of the town's sewage disposal system, particularly since the beaches are within the urban centre and in summer the population increases threefold.
4O 30
0 0
~
20
IJ.
1984
1985
1986
Year Fig. 8 Benidorm. Annual mean values of FC I00 ml -=.
8O l 0 0
60
~ 40 Lt.
20
Fig.
jl[
1985 1986 Year 9 Santa Pola. Annual mean values of FC 100 m1-1. 1984
2O E
15
8 u..
lO 5 1984
1985
1986
Year
Fig. 10 Torrevieja. Annual mean values of FC 100 ml -l.
80
Nutrient content Under natural conditions, Mediterranean waters are poor in nutrients, a characteristic shared by the majority of tropical seas not fertilized by outcrops. This scarcity of nutrients is responsible for the ecological characteristics typical of this type of sea, including, among other obvious effects, the transparency of the water, and overall blue tone, contrasting with the green tint of plankton rich waters. The conservation of these characteristics is obviously essential therefore from the tourist point of view, even without taking into account the possible ecological repercussions to fishing, etc. At the sampling stations, when FC concentrations were high, so also were nutrient values. At the majority of sampling points the average phosphorus content was less than 40 p.g 1-1 and nitrogen less than 150 ~tg 1-l. In the San Gabriel area, which was used for bathing until about 20 yr ago, FC concentrations have been consistently below 200, between 1982 and 1986, except in 1983, when the average was 295. During these years average phosphorus and nitrogen concentrations varied between 100-128 ~tg P 1-1 and 175-450 ~tg N 1-1, due to the fact that the largest outfall of urban sewage on the coastline studied is located here--outfall No. 4 (Fig. 2). This outfall has an underwater length of 2 m. Until 1983 all the sewage discharged here, almost 1000 m 3 h -~, was untreated. In 1984, as a result of the commissioning of treatment station T1 (Fig. 2), (secondary treatment), the rate was 450 m 3 h -1 treated sewage and 170 m 3 h -1 untreated, the remainder being used for irrigation. Since 1986, station T1 is treating a larger amount of sewage, and recycling the treated waters for irrigation, so that currently the outfall is only 450 m 3 h -l, secondarily treated residual waters. Since 1984 therefore, all the residual waters outlet by outfall No. 4 (Fig. 2) are subjected to secondary treatment, and contain chloride, which reduced the bacterial content, but not that of nutrients. In general terms, in contrast with the previous section, in this respect the situation is not encouraging. Although the waters cannot be considered eutrophic, nonetheless the values are almost without exception higher than those natural for these waters, obtained at the island of Tabarca (a Marine Reserve since April 1986 (Fig. 1), (BOE No. 112)): 20 ~tg P i-I and 85 gg N 1-1 (Zoffmann et al., 1985). Discussion
The coastal sector we have studied can be considered a typical example of Mediterranean coast subjected to an intermediate level of urban pollution, with a marked summer increase and with a relatively low industrial contribution. This model can be widely extended throughout the Mediterranean coast in several countries. Also, given the time-span and the number of samples, the results can be considered valid reflections of tendencies and mean values. By studying the values of the pollution indicators in beach waters, we have attempted to evaluate the effect of wastewater discharges. It seems clear that the coastal structure is a critical factor in deciding the degree to which beaches
Volume 20/Number 2/February 1989
are affected. Torrevieja and Benidorm are typical exam- municipal beaches, and thanks to a close degree of colpies where relatively large discharges of untreated laboration between the competent municipal authorities sewage cause little ill effect on the sanitary quality of the and laboratories, in the detection and prevention of beaches, which in the case of the second town is attri- existing or predicted problems. With similar collaborabutable to the exceptional location of the outfall, at the tion the occasional abnormally high values seen in other tip of a cape where the sea floor drops to 25 m depth municipalities could be avoided. almost on the shore line. It is remarkable that as a general rule in the whole Examples of the opposite case are Albufereta and area studied, the beaches to the north of the capital had Postiguet beaches, enclosed within a bay formation, so higher pollution values than those to the south. Possibly that even small discharges produce high levels of pollu- the general orientation of the coast, more open to the tion indicators, and consequently poor sanitary and east in the southern part, could contribute to this aesthetic conditions. Albufereta, however, has been difference. restored to very reasonable limits for an enclosed and shallow area. A second treatment station, T2 (Fig. 2), is This work was supported by the Excmo. Ayuntamiento de Alicante currently under construction, which, in the near future, and the Excma. Diputaci6n Provincial de Alicante. will commence treatment of the sewage at present being discharged through the outfalls 1, 2 (Albufereta), and 3 APHA (1985). Standard Methods for the Examination of Water and (rig. 2). Wastewater, t6th edn. American Public Health Association, WashAnother different situation is that created by the disington, DC. charge of treated wastewater, such as in the area of San BOE No. 151 (1977). Orden de 29 de abril de 1977 por la que se aprueba la "Instrucci6n para el vertido al mar, desde tierra, de aguas Gabriel in Alicante. Here the values of microbial polluresiduales a travrs de emisarios submarinos', pp. 14247-14256. tion indicators were in general acceptable, but the levels BOE No. 112 (1986). Orden de 4 de abril de 1986 por la que se establece una reserva marina en la Isla de Tabarca. p. 16769. of nutrients were very high, with a degradation of the B. (1959). Sewage contamination of coastal bathing waters in ecology and aesthetic values of these waters. It is true Moore, England and Wales. A bacteriological and epidemiological study. however that the rocky beaches located in this area have Jour. Hyg. 57,435-472. never been used extensively for recreational purposes, Ramos, A. (1981). Contribuci6n al conocimiento de la franja litoral de la provincia de Alicante (Costa E. espafiola). In El medioflsico de la and are therefore of low tourist value. Furthermore, the comarca de Alicante (C. Auernheimer and A. Escarrr, eds), pp. 196'Integral Water Project' currently being developed in 225. Excmo. Ayuntamiento de Alicante and Universidad de Alicante. Alicante city, will permit the treatment and recycling for F., Zoffman, C., Rodn'guez-Valera, F. & Marcilla, A. irrigation of all sewage waters, eliminating the necessity Ruiz-Bevifi, (1986). Contaminants on the sea surface around an underwater outfor any direct marine outfalls. Within the space of two fall. Mar. Pollut. Bull. 17,107-112. years, Alicante will be the first Spanish city to treat the Vasconcelos, G. S. & Anthony, N. C. (1985). Microbiological quality of recreational waters in the Pacific Northwest. J. Water Pollut. Control whole of its sewage. Fedn. 57, 367-377. The favourable evolution of the trend in zone A over Zoffrnann, C., Ramos, A. A. & Rodn'guez-Valera, F. (1985). Datos preliminares oceanogrfificos y de contaminaci6n marina en la Isla the study period is evident. This is clearly due to the Plana o Nueva Tabarca (Alicante). In La reserva marina de la Isla interest in achieving and maintaining the highest posPlana o Nueva Tabarca (Alicante) (A. A. Ramos, ed.), pp. 95-110. sible sanitary standards for the waters of Alicante Ayuntamiento de Alicante, Universidad de Alicante.
81