Abstract
Experiments undertaken in Poland on fish culture in sugar beet factory wastes show that fish culture in a yearly cycle is possible and that very good treatment effects as well as good fish yields can be obtained. Effluents are collected and stored during autumn and winter. In spring the effluents are diluted according to the self-purification obtained and led to ponds which are then stocked with carp. Before winter the fish ponds are emptied into the recipient and the fish are caught for consumption.
Fish culture in waste effluents should be further encouraged especially in developing countries in order both to control water pollution and to obtain cheap and much needed proteins.
Résumé
En Pologne des expérimentations entreprises en pisciculture avec les rejets d'une usine de betteraves à sucre prouvent qu'il est possible de développer la pisciculture en un cycle annuel et d'obtenir de très bone effets du traitement et aussi de bons rendements en poisson. Les rejets sont assemblés et entreposés pendant l'automne et l'hiver. Au printemps ils sont dilués selon l'auto-épuration obtenu et mis danss des étangs qui sont ensuite peuplés de carpes. Avant l'hiver les étangs sont vidés dans le milieu de décharge et le poisson est capturé pour le consommation.
La pisciculture en eaux résiduaires doit être encouragée surtout dans les pays en voie de développement pour lutter contre la pollution des eaux et aussi pour obtenir économiquement des protéines indispensables.
The wastes from sugar beet factories constitute a problem in many countries. Not only are the wastes very rich in organic matter, they are also produced only during three to four months each year. If a conventional treatment plant is built and designed for the big flow of effluents during this limited time, it will stand idle two-thirds of the year which is not an economical solution. Lagoons with or without artificial aeration are widely used but have led to objectionable smell and the purification process in these lagoons often is so slow that when the wastes have to be discharged to make room for the new season's effluents, they give rise to severe pollution. The problem is worsened by the fact that the factories are located in the beet-producing areas so as to give minimum transport costs for the beets but without due regard to the availability of a suitable recipient watercourse.
These problems were all present for a sugar beet factory near Gołysz, south-west of Kraków, and the pollution in the small recipient stream became very severe although the factory did not discharge its waste directly but spread it on farmland and returned the drainage to the recipient. In 1966 the Research Station of the Polish Academy of Science which is situated in the area (Fig.2) started investigations on the possibilities of treating the wastes from the factory in fish ponds. It has, however, during the experiments, not been possible to take more than about one-third of the effluents into the pond treatment system because other research is carried out in the other ponds.
The sugar factory operates from mid-October until January and has a rather advanced recirculation system resulting in wastes with high content of organic material. For the effluents from the factory the following figures are representative:
| Chemical Oxygen Demand (COD) | 1 400 mg/l |
| Biological Oxygen Demand (BOD) | 960 mg/l |
| Permanganate value | 60 mg/l |
The objectives of the initial experiments were to investigate whether the wastes could be treated in ponds stocked with fish in a one-year cycle, and if dilution of the wastes would be necessary. The experiments were carried out from 1966–1968.
Two similar ponds were filled with wastes during the production season of 1966–67. Pond 1 was filled only with wastes and in pond 2 the wastes were diluted with clean water in the ratio 4:1 wastes:water. In May 1967 the undiluted wastes in pond 1 were still completely void of oxygen and no fish was stocked then. In autumn 1 000 two-year-old carp were stocked and the pond was not utilized by the 1967–68 campaign. In the spring of 1968 another 1 000 carp, this time one-year-old, were stocked. It was thus found that undiluted wastes could not be treated in a one-year cycle and a two-year cycle would have severe economical implications.
In pond 2 the diluted wastes had undergone self-purification so that in May oxygen was present in sufficient concentration to make fish stocking possible. The pond was stocked on 1 June with 650 kg/ha one-year-old carp. The pond was emptied and the fish collected on 1 October. The pond was then left empty during the winter and in spring it was filled with clean water. During the summer the pond was quite normal. It was not affected by its use for waste treatment the preceding year, and it was thus established that for the waste from this factory, treatment in fish pond of waste diluted 4:1 could be undertaken on a one-year cycle.
Primary production was found to start in both ponds as soon as dissolved oxygen became available. The chlorophyll content was up to four times that found in normal ponds and oxygen saturation was also very high (reached 800 percent in pond 1 during the second summer).
There was a very high production of zooplankton. Daphnia magna had mass development giving a reddish colour to the water. This development also occurred momentarily in early spring but stopped suddenly when available oxygen was used up. Bottom fauna developed in pond 1 in July the first summer; only then was oxygen available at the bottom. Only two species developed (Chironomus plumosus and Glyptotendipes) and biomass reached as high as 135 g/m2. The second summer bottom fauna developed in March, the fauna became gradually more diversified, and by the end of July, it had a composition like in a normal pond. In pond 2 bottom fauna developed earlier than in pond 1 and maximum biomass reached 70 g/m2. Chironomus plumosus was dominant but other species were also present. During the second summer an entirely normal bottom fauna developed in the pond. Oligochaete did not develop in either of the ponds.
The first series of experiments proved that diluted wastes could be treated in a yearly cycle, and that this was not possible with undiluted wastes. The fish production during this experiment was 400 – 500 kg/ha without artificial feeding. This should be compared with ordinary fish farms in this region of Poland where a production of 500 kg/ha is obtained with chemical fertilization.
The second series of experiments were started in 1969 with the objective to find the optimum rate of dilution. During this experiment the wastes are collected in one storage reservoir where it undergoes anaerobic self-purification during winter and spring. The fish ponds are empty during winter and are filled in late spring with wastes diluted according to the BOD remaining after self-purification obtained during winter and early spring. It is thought that this should be the best sequence of operation and the technique has already been applied to other sugar factories in Poland. The rate of dilution needed will depend on the composition of the waste, which varies between different factories, and also on the climatic conditions which affect the rate of self-purification.
The reduction in BOD is sufficient so that the fish ponds can be emptied into small rivers in autumn without any pollution problems occurring. The drainage from the fields irrigated with fresh wastes, on the other hand, when discharged still have BOD ca 600 mg/l.
In warmer climates this process should be even more advantageous. The higher temperatures would speed up the initial self-purification process and the growth rate of fish would be higher. Dr. S. Wróbel, who is in charge of the investigations, thought that investigations should be carried out on this process in tropical and semi-tropical areas. The problems with strong organic wastes in these areas are well documented and are likely to increase with time, as are the protein deficiencies in the developing countries.
There are indications that the interest in use of wastes for protein production will increase (Allen, 1970) but better communication and unified efforts between engineers and biologists are needed if the conventional hesitant attitude is to be changed.
Allen, G.H., 1970 The constructive use of sewage with particular reference to fish culture. Contribution to the FAO Technical Conference on Marine Pollution and its Effects on Living Resources and Fishing. Rome, 9–18 December 1970. FIR:MP/70/R-13.
Grabacka, E., 1970 Mikrobentos w stawach ze ściekami cukrowniczymi. [Micro-benthos in ponds filled with effluents from sugar beet factory]. Summary report on the Eighth Polish Hydrobiologists Congress in Białystok, September 1970
Kyselowa, K., 1970 Plankton stawów zasilanych ściekami cukrowniczymi. [Plankton in ponds filled with sugar beet factory wastes]. Summary report on the Eighth Polish Hydrobiologists Congress in Białystok, September 1970
Lewkowicz, S., 1970 Procesy samooczyszczania ścieków cukrowniczych w stawach. [The selfpurification of sugar beet wastes in ponds]. Summary report on the Eighth Polish Hydrobiologists Congress in Białystok, September 1970
Zięba, J., 1970 Fauna denna w stawach zasilanych ściekami cukrowniczymi. [Bottom fauna in ponds filled with sugar beet factory wastes]. Summary report of the Eighth Polish Hydrobiologists Congress in Białystok, September 1970
Fig.3 Konin Project Diagram
