The effect of liquid petroleum refinery effluent on fingerlings of Sarotherodon melanotheron (Ruppel 1852) and Oreochromis niloticus (Linnaeus 1757)

E.A. Ojuola and G.C. Onuoha

AFRICAN REGIONAL AQUACULTURE CENTRE, PORT HARCOURT, NIGERIA
CENTRE REGIONAL AFRICAIN D'AQUACULTURE, PORT HARCOURT, NIGERIA

UNITED NATIONS DEVELOPMENT PROGRAMME
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
NIGERIAN INSTITUTE FOR OCEANOGRAPHY AND MARINE RESEARCH

PROJECT RAF/82/009

APRIL 1987

Hyperlinks to non-FAO Internet sites do not imply any official endorsement of or responsibility for the opinions, ideas, data or products presented at these locations, or guarantee the validity of the information provided. The sole purpose of links to non-FAO sites is to indicate further information available on related topics.

This electronic document has been scanned using optical character recognition (OCR) software. FAO declines all responsibility for any discrepancies that may exist between the present document and its original printed version.

THE EFFECT OF LIQUID PETROLEUM REFINERY EFFLUENT ON FINGERLINGS OF SAROTHERODON MELANOTHERON (RUPPEL 1852) AND OREOCHROMIS NILOTICUS (LINNAEUS 1757).

E. A. OJUOLA ** and G. C. ONUOHA

ABSTRACT

The toxicity of petroleum refinery effluent from Alesa-Eleme (Port Harcourt) Refinery, to two tilapia species, Oreochromis niloticus and Sarotherodon melanotheron, fresh and brackish water species respectively were investigated at an average temperature of 27°C ± 2.5°C under laboratory conditions. LT₅₀ values increased from 29' minutes at 100% effluent concentration to 645 minutes at 10% effluent concentration (Vol/Vol) for O. niloticus and from 48 minutes at 100% to 1,917 minutes at 10% for S. melanotheron. Toxicity of effluent to fish decreased as the effluent aged. LT₅₀ for 2-day and 6-day old effluent for O. niloticus at 63.1% effluent concentration were 30 and 70 minutes respectively.

Median lethal concentrations (LC₅₀) obtained from regressions of effluent concentrations and median lethal times (LT₅₀) for 6-day old effluent at 24, 48 and 96 hours were 5.6, 3.29 and 1.93 percent respectively for O. niloticus, while the corresponding values for S. melanotheron were 9.48, 5.83 and 3.6% respectively.

The safe concentrations of 6 and 15-day old effluents were estimated as 0.19 and 0.29% respectively for O. niloticus, while the corresponding values were 0.36 and 0.35 for S. melanotheron. The 24 and 48 hours LC₅₀ values show that S. melanotheron is more resistant to oil refinery effluent than O. niloticus.

* This study formed a part of a Project Report/Thesis submitted by E.A. Ojuola for Postgraduate Diploma/M. Tech. (Aquaculture) degree of the African Regional Aquaculture Centre/Rivers State University of Science and Technology, Port Harcourt, Nigeria.

** Present address: Federal Department of Fisheries P. M. B. 0240, Bauchi, Bauchi State, Nigeria

INTRODUCTION

Aquatic pollution is of significance to fisheries. It is therefore important to monitor water quality at such discharge sites or outfalls before selecting sites for aquaculture; because areas near such outfalls are subjected to chronic pollution.

Studies have been carried out on the toxicity of oil, oil spill chemicals and industrial waste water (effluent) on different aquatic organisms including those of Ajao et al (1981), Ajao (1985), Oyewo (1986) in Nigeria. Other toxicity studies carried out include that of Gurure (1987). None has however dealt with toxicity of the liquid petroleum refinery effluent on tilapia species, which is a common estuarine and pond-reared fish in Africa.

The aim of this work is therefore to investigate the lethal (acute) toxicity of liquid petroleum refinery effluent from the Alesa-Eleme refinery to two common tilapia species, Oreochromis niloticus and Sarotherodon melanotheron from the fresh and brackish water respectively. The information would give a clue to the approximate concentrations that could be referred to as safe concentration, and would enable prediction of the effluent effect in the field.

MATERIALS AND METHODS

Test Organisms

Fingerlings of the freshwater fish Oreochromis niloticus of total length 8.8 to 12.0cm (mean - 10.4cm) and 10 – 15g body weight (mean - 11.0g) were collected from the ponds of the African Regional Aquaculture Centre (ARAC) Aluu, Port Harcourt; while the fingerlings of the brackishwater fish Sarotherodon melanotheron of total length 6 – 10cm (mean - 8.0cm) and 5.7 – 12.0g body weight (mean - 8.9g) were collected from Buguma fish farm situated about 20km away from ARAC in the riverine area. The two sets of fish species were kept separately in two large circular plastic pools each for four weeks for acclimation in fresh water, and brackish water of salinity 10.2‰ respectively before the tests were carried out. The water in the plastic pools was changed every 48 hours. The temperature was not controlled. Both species of fish were fed with pellets containing 35% protein prepared at the Nigerian Institution for Oceanography and Marine Research (NIOMR). Feeding was stopped 24 hours prior to commencement of the tests and during the test period.

Test Media

The liquid petroleum refinery effluent was collected in three 40-litre plastic containers from the Nigerian Petroleum Refining Company (NPRC) now Nigerian National Petroleum Corporation (NNPC) at Alesa-Eleme near Port Harcourt, on three occasions. The physico-chemical characteristics of the waste-water (effluent) are shown in Table I.
Procedures of chemical analyses followed were those described by Golterman et al (1974), APHA (1976) and William et al (1981). The effluent samples not utilized immediately were kept referigerated at 4°C between usage.

Experimental Procedure

Seven twelve-litre glass aquaria tanks (20cm × 20cm × 30cm) were used as test containers. Test solutions containing various percentages of the effluent by volume based on logarithmic scale (APHA, 1976) were prepared using aerated dechlorinated tap water as dilution water for the fresh water fish (O. niloticus) and aerated brackish water (S = 20.2‰) as dilution water for the brackish water fish (S. melanothe~on). The volume of each test solution was 10 litres. The test solutions were not aerated so as to avoid volatilization of the toxic hydrocarbon components, but the solutions were changed with fresh ones every 24 hours, as this was the best option of indirect oxygenation available. A fish was presumed dead when there was neither opercular nor bodily movement after gentle prodding. Dead fish were removea, and time to mortality of individual fish recorded, body length and weight taken. Observations continued for a maximum period of one week (10,000 mins.) for concentrations in which all the exposed fish did not die.

Statistical Analysis

Results were analysed and calculated from the arithmetic and probit plots of percent dead fish against time to death to obtain the median lethal time (LT₅₀), which is defined as the time at which mortality is recorded for 50% of the exposed fish to each of the toxicant concentration and the lethal concentration (LC₅₀), concentration of test media at which mortality is recorded for 50% of the test animals. The LC₅₀ was obtained from the regressions of median lethal times and concentrations in a double log plot (Fry et al, 1942). The safe concentrations were calculated from the 96hr. LC₅₀ using the application factor of 0.1 EIFAC, 1983. The regression equation was calculated following the method of Snedecor and Cochran (1980).

RESULTS

The results of the chemical analyses of the effluents are shown in Table I.
Table II gives an example of the raw data obtained on time death in minutes of O. niloticus exposed to six different concentrations of the refinery effluent (from 10.0% to 100.0%). The resistance times (time to death in minutes) of individual fish are plotted against percent fish dead for O. niloticus and S. melanotheron respectively. Such arithmetic plots gave the characteristic sigmoid curves (Figs. 1, 2 and 3) as obtained by earlier workers, (Bliss, 1937). The sigmoid curves also shift towards the time axis as the lethal concentration become less. The sigmoid curves were converted into simple straight lines when the percent mortality on probability scale was plotted against logarithm of time to death (Fig. 4).

The median lethal times (LT_50s) were obtained by calculation of the geometric means. Values obtained from the arithmetic, and probit plots were quite close when compared to the geometric mean (Table III). Table IV gives the various values of the median lethal times (LT₅₀).

The median lethal times are plotted against corresponding effluent concentrations in a double log plots (Fig. 5) and regression lines fitted through the plots. Fig. 5a shows the regression lines for both species of fish exposed to 2-day old effluent, 5b for 6-day old effluent and Fig. 6c for 15-day old effluent. Fig. 6 shows the regression lines fitted for S. melanotheron to different concentrations and different ages of the effluent. The regression equations are presented in Table V from which the LC₅₀ (lethal concentration that will kill half the population of fish) for 96 hours, 48 and 24 hours can be calculated.
The LC₅₀ values obtained are presented in Table VI. The safe concentration can then be obtained by multiplying the LC₅₀ for 96hr by an application factor of 0.1 after EIFAC (1983). Values obtained for the two species of fish are presented in Table VII.

TABLE I: Characterization of Refinery Effluents collected on various dates.

TABLE II: Time to death (mins) Percent mortality and Size of fish O. niloticus exposed to 100% effluent

TABLE III: Comparison of median lethal times, TL₅₀ (minutes) of O. niloticus exposed to various concentrations of effluent, as obtained from the arithmetic plots, probit plots and from geometric means

Effect of 1-day old effluent on O. niloticus

TABLE IV: Median lethal times, LT₅₀ (mins) of O. niloticus and S. melanotheron exposed to various concentrations and different ages of refinery effluent

TABLE V: Regression equations of effluent concentration against LT₅₀ for O. niloticus and S. melanotheron fingerlings exposed to various concentrations of effluent

where y = logarithm of effluent concentration in percentage
X = logarithm of median lethal time (LT₅₀) in minutes

TABLE VI: 24, 48 and 96 hours Median Lethal concentration (LT₅₀) in % of the refinery effluent for fingerlings of O. niloticus and S. melanotheron

TABLE VII: 96hr Safe Concentration in % of Effluent

FIG 1: TIME MORTALITY CURVES OF Oreochromis niloticus FINGERLINGS FOR VARIOUS CONCENTRATIONS OF OIL REFINERY EFFLUENT OF 1-DAY OLD.NOS. NEXT TO THE CURVES INDICATE CONCENTRATIONS, CROSSES INDICATE MEDIAN LETHAL TIMES LT₅₀ IN MINUTES

FIG 2: TIME MORTALITY CURVES OF Sarotherodon melanotheron FINGERLINGS FOR VARIOUS CONCENTRATIONS OF OIL REFINERY EFFLUENT OF 2-DAY OLD. THE NOS. NEXT TO THE CURVES INDICATE EFFLUENT CONCENTRATIONS. CROSSES INDICATE MEDIAN LETHAL TIMES (LT₅₀) IN MINUTES.

FIG 3: TIME MORTALITY CURVES OF Sarotherodon melanotheron FINGERLINGS FOR VARIOUS CONCENTRATION OF OIL REFINERY EFFLUENT OF 15-DAY OLD. THE NUMBERS NEXT TO THE CURVES INDICATE EFFLUENT CONCENTRATION. CROSS INDICATE MEDIAN LETHAL TIMES (LT₅₀) IN MINUTES.

FIG 4: PLOTS OF PERCENT MORTALITY IN PROBIT AND LOGARITHM OF TIME TO DEATH (MIN) FOR Oreochromis niloticus FINGERLINGS; EXPOSED TO VARIOUS CONCENTRATION OF 1-DAY OLD REFINERY EFFLUENT. THE NUMBERS NEXT TO THE CURVES INDICATE THE OIL REFINERY EFFLUENT CONCENTRATION (%). THE CROSSES INDICATE THE MEDIAN LETHAL TIME (LT₅₀) IN MINUTES

FIG 5: PLOTS OF LOGARITHM OF OIL REFINERY EFFLUENT CONCENTRATIONS (%) AND LOGARITHM OF MEDIAN LETHAL TIMES IN (MINS) FOR FINGERLINGS OF Oreochromis niloticus AND Sarotherodon melanotheron EXPOSED TO 2, 6, 15-DAY OLD REFINERY EFFLUENT

FIG 6: PLOTS OF LOGARITHM OF OIL REFINERY CONCENTRATIONS (%) AND LOGARITHM OF MEDIAN LETHAL TIME (MINS) FOR FINGERLINGS OF Sarotherodon melanotherodon EXPOSED TO EFFLUENT OF DIFFERENT AGES. THE NUMBERS NEXT TO THE CURVES INDICATE THE AGE OF THE EFFLUENT IN DAYS.

DISCUSSION

The chemical analysis of the effluent indicated that the effluent was saline. Salinity ranged from 1.96 to 2.87‰ with a mean of 2.36 ± 0.34‰. The salinity of the effluent reduced as dilution of effluent with water increased. Thus for O. niloticus ambient salinity was different in the different tests, but it was possible that this did not affect the results remarkably.
Dissolved oxygen of the effluent water was low, ranging from 2.55 to 2.75mg/l. It is known however that Tilapia can tolerate low oxygen levels, even less than 1ppm (Kutty and Mohammed, 1982; Kutty and Saunders, 1982). The lethal effect of the effluent water on the fish could not have arisen solely from low oxygen content. Other parameters likely to contribute to lethality include the ammonia content, high pH, oil and grease. Tilapias and cyprinids have been known to tolerate ammonia concentrations to the range of 1 – 5 ppm (Kutty and Mohammed, 1982). Boyd (1979), Balarin and Hatton (1979), Craig and Baski (1975) among others have shown the critical pH and temperature values at which fish cannot survive.

The total alkalinity and total hardness provide information on the buffering capacity and on the amount of solids present in the water. Total alkalinity is a valuable index used for measuring productivity of water by many workers, and a value above 100mg CaCO₃1/ is bellieved to be associated with high biological productivity. A³value of 40mg CaCO₃/1 is also considered appropriate to induce a good biological productivity than waters of lower alkalinity (Moyle, 1946; Mairs, 1966; Boyd, 1979).
Heavy metals including lead (Pb), Copper (Cu), Zinc (Zn), Iron, (Fe), and Chrcmium (Cr), were determined (although not included in this report), and were found to be in trace amount (Onuoha, 1986, Unpublished). The characteristics of the effluent water, the high oil content not withstanding, compared favourably with those of the refinery laboratory routine investigations, and are said to be within accepted limits (Edet, 1985, CONCAWE, 1980).

The present results show the toxicity of the refinery effluent, which is confirmed by the workers like Pessah et al (1973). The results indicated that the survival time for both species increased as the concentrations of the refinery effluent decreased. The LT₅₀ values for O. niloticus and S. melanotheron exposed to 63.1% concentration of 2-day old effluent were 30 and 48 minutes respectively, and for 10% effluent concentration of same age, the median lethal times for O. niloticus and S. melanotheron were 645 and 1917 minutes respectively. The median lethal times (LT₅₀) for the two species also differed with reference to the age of the effluent. These results prove that S. melanotheron was more resistant than O. niloticus. It is possible that salinity might have been a contributive factor to the survival and resistance of S. melanotheron. Experiments investigating the relationship between oil and salinity, and effluent and salinity, show that oil and effluent are more toxic at the extremes of an animal's salinity tolerance range, the range which differ between species (Baker, 1972). Toxicity however decreased as the effluent aged as reflected in Fig. 5. This might have been due to the evaporation of volatile hydrocarbons and possible degradation of toxic compounds. This finding is similar to the work carried out on toxicity of the refinery effluent to phytoplankton population (Onuoha, 1986, Unpublished).
The regression equations of effluent concentration against LT₅₀ for the two species of fish show that the relation of lethal times to concentrations are species specific (Table V). The values of correlation coefficient ‘r’ suggest that the variables are highly correlated in all cases. The LC₅₀ values for specific time of exposure (24, 48 or 96 hours), under various test conditions can be obtained using the regression equations (Table VI). Based on these LC₅₀ values, safe concentrations have been calculated (Table VII). concentrations below this level are expected to permit successful growth, reproduction and other life processes of the fish. Obviously, these values have to be less than the 96 hour LC₅₀. Observations made on the effect of the liquid petroleum refinery effluent on the early development of Clarias gariepinus (egg and fry), show that effluent concentrations of 5% and above (Vol/Vol) were quite toxic to hatching success and to 3-day old fry of Clarias gariepinus. Effluent concentrations of 1% and 0.1% had no effect on 3-day old fry (Onuoha and Nwadukwe, 1987 Unpublished).

The purpose of toxicity testing is to predict the effects of a toxic substance on natural communities of animals and plants from the results of simple experiments. The effects of effluent depend on many factors other than the obvious ones of effluent constituents and volume. The siting of the outfall, the type of receiving area, and its associated community of plants and animals, and the movements and quality of the receiving water, all have to be considered.

It will also be worthwhile studying the possible sub-lethal effect of the refinery effluent on the tilapias and other fish occurring in the effluent discharge area.

ACKNOWLEDGEMENTS

We wish to thank all the laboratory staff for their support. We would also like to thank Dr. M. N. Kutty for his advice, contributions and critical reading of the manuscript. We wish to thank the Nigerian Petroleum Refining Company (NPRC), Alesa Eleme, now Nigerian National Petroleum Corporation (NNPC) who supplied us with the refinery effluent.

Finally we would like to thank the Director, Federal Department of Fisheries, and Management of the Nigerian Institute for Oceanography and Marine Research/African Regional Aquaculture Centre (NIOMR/ARAC) for their sponsorship, support and use of facilities.

REFERENCES

Ajao, E. A.; Oyewo, E: O. and Orekoya, T. (1981). The effect of oil formation water on some marine organisms. 2pp. In proceedings of an International Seminar on the Petroleum Industry and the Nigerian Environment.

Ajao, E. Z. (1985). Acute toxicity tests of a textile mill wastewater effluent and a ‘detergent wash’ with a hermit crab Clibinarius africanus (Aurivillius). NIOMR Tech. Paper No. 21, 11pp.

American Public Health Association (APHA) (1976). Methods for the examination of water and wastewater. 14th ed. 1193pp.

Balarin, J. D. and Halton, J. P. (1979). Tilapia. A guide to their biology and culture in Africa. Unit of Aquatic Pathology, University of Stirling, Stirling, Scotland. 174pp.

Bliss, C. I. (1973). The calculation of the time mortality curve. Ann. Appl. Biol. 24, 815 – 852.

Boyd, C. E. (1979). Water quality in warm water fish ponds. Agricultural Experiment Station. Auburn University, 369pp.

CONCAWE (1980). Sampling of liquid effluents from Refineries. Report No. 7/80.

Craig, C. R. and Baski, W. F. (1975). The effect of depressed pH on the Flag fish reproduction, growth and survival. Water Research 11, 621 – 626.

Edet, S. O. (1985). Unpublished report of routine laboratory monitoring of the Alesa-Eleme Refinery, Port Harcourt, 18pp; presented at the Nigerian National Petroleum Corporation (NNPC) Seminar held in Kaduna 1985.

EIFAC (1983). European Inland Fisheries Advisory Commission Revised Report on fish toxicity testing procedures. EIFAC Technical Paper No. 24, revision 1.

Fry, F. E. J.; Brett, J. R. and Clawson, G. H. (1942). Lethal limits of temperature for young gold fish. Rev. Can. Biol. 1, 50 – 56.

Golterman, H. L.; Clymo, R. S. and Ohnstad, M. A. M. (1978). IBP Handbook No. 8. Methods for physical and chemical analysis of fresh waters. Blackwell Scientific Publications, Oxford 2nd Edition 213pp.

Gurure, R. M. (1987). Influence of two organo-chloride pesticides, Thiodan and Lindane on Survival of fingerlings of Oreochromis niloticus, and Tilapia zilli. African Regional Aquaculture Centre. Working Paper ARAC/WP.6/87.

Kutty, M. N. and M. P. Mohammed (1982). Respiratory quotient and Ammonia quotient in Tilapia mosambica (Peters) with special reference to Hypoxia and recovery. Hydrobiologia, 76: 3 – 9.

Kutty, M. N. and K. M. S. Hamsa, (1972). Influence of ambient oxygen and spontaneous activity on the metabolism of five marine teleosts. Indian J.Fish. 19: 76 – 85.

Mairs, D. F. (1966). A total Alkalinity Atlas for marine lake waters. Limnol. Oceanogr., 11: 68 – 72.

Moyle, J. B. (1946). Some Indices of Lake productivity. Trans Amer. Fish. Soc., 76: 322 – 334.

Oyewo, E. O. (1986). The acute toxicity of three oil dispersants. Environ. Pollution (Series A) 41, 23 – 31.

Pessah, E.; Loch, J. S. and J. C. Macleod (1973). Preliminary Report on the acute toxicity of Canadian petroleum refinery effluents to fish. Tech. report No. 408.

Snedecor, G. W. and W. G. Cochran (1980). Statistical methods. 7th ed. The Iowa State University Press, USA. 507pp.