Ispitivanje uticaja korišćenja otpadnih voda iz klanice na zdravlje i proizvodnju mesa šarana (Cyprinus carpio) bezbednog za ishranu ljudi

Abstract

Meat industry is characterised by high water consumption and is undoubtedly a significant source of organic pollution of the environment. There are both ecological and financial motives for water purification which intertwine and complement each other. The use of available technology for fish farming in slaughterhouse industry is an ecological solution for removal of organically loaded water used in slaughterhouses. On the other hand, such integrated system carries certain risks mostly related to the safety of fish meat produced in this way. The aim of the research carried out in this doctoral thesis was to examine the effect of the use of wastewater from slaughterhouses on the health of carp and safety of carp meat for human consumption. The research of this doctoral thesis was carried out in several stages. A system for wastewater purification was built on the property of ‘Djurdjević’ Meat Industry in Pećinci. The efficiency of wastewater treatment plant was examined by using chemical analyses of water in different water purifying stages. After this, a fishpond was built on the same property. It was mostly supplied with the water from the system for wastewater purification from the slaughterhouse. The water from purifiers goes to pre-fishery where purified water is aerated, after which the water goes into fishpond where a part of nutrients from purifiers is used for carp nutrition. The water is then used for irrigation of the soil surrounding the slaughterhouse. This way, the fishpond has an impact on increasing the quality of purified wastewaters and reaching limit concentrations set before the inflow into a natural recipient. Carp fingerlings in good health were stocked in the fishpond. Carp was produced in optimal ambient conditions by using purified water originating from slaughterhouses and by adding well water. A good quality of meat was achieved by feeding fish balanced meals. Health condition of fish was monitored during the production cycle by diagnostic examination of the causative agent of viral, bacterial and parasitic etiology. The condition of ecosystem (water in the fishpond and sediment) for carp farming was also monitored and potential impact of microbiological condition of ecosystem on microbiological status of fish and final product, meat, was examined. The monitoring of the presence of organochlorine pesticides, radioactive elements, residues of antibiotics and sulphonamides, heavy metals and metalloids in sediment, water and fish was performed together with assessment of safety of the carp produced in this way for human consumption. The content of contaminants in the tissues of fish was observed from ecological aspect and safety of fish as food was examined. When it comes to hygienic safety aspect, the content of contaminants in meat is measured in a majority of countries and their concentration is regulated by law. Based on the concentration of the contaminants in edible tissue of fish, the safety of fish is assessed, i.e. it is determined whether it fulfils the prescribed conditions. Sampling was carried out using the same protocol in spring (April) and autumn (October). The results of the quality of water sampled from a few spots on the property of ‘Djurdjevic’ Meat Industry from Pecinci, unequivocally show the efficiency of purifiers and integrated system. Based the obtained results, the wastewater treatment plant at the ‘Djurdjevic’ Meat Industry operates with the following efficiency: 99% (spring), 98% (autumn) calculated in relation to Chemical oxygen demand (COD); 99% (spring), 99% (autumn) calculated in relation to Biochemical oxygen demand (BOD5); 84% (spring), 91% (autumn) calculated in relation to ammonia. Also, the results show that the efficiency of wastewater treatment plant was equal during both sampling, i.e. there were no significant variations in performance of wastewater treatment plant. The results of the examination showed that the water from fishpond in both spring and autumn sampling was category 3, i.e. the examined parameters do not exceed the maximum permissible concentrations for water of category 3 which can be used for breeding cyprinid species of fish. The water from melioration canal corresponds to category 2/3 which can be used for irrigation. Production parameters for carp were comparable to the results accomplished earlier using conventional methods for breeding carp. At the end of the breeding process, the average weight of a live carp from the fishpond at ‘Djurdjevic’ Meat Industry was 2,020 g. The total density of fish during fish catching was 3,270 kg/ha. Microbiological quality of water and sediment was pretty much equal in both seasons of sampling and no significant differences in the examined parameters related to the season were observed. The indicators of fecal pollution were high in the water sampled before the purifying process. The analyses of water after the purifying process show that microbiological quality of water is significantly improved. There were no Streptococcus faecalis, Proteus sp. and Pseudomonas aeruginosa in purified wastewater, and the number of other potentially pathogenic bacteria was significantly lower. The results of microbiological analyses of water from the fishpond in spring and autumn sampling showed that water was category 3. When it comes to microbiological contaminants, the efficiency of wastewater treatment plant was high for most of the examined microorganism - above 99%. The number of all examined microorganism in carp was within permissible limits and did not exceed the prescribed hygienic norms. There was no statistically significant difference in terms of microbiological quality of carp sampled in spring and in autumn. The number of sulfite-reducing clostridia, S. aureus and Listeria spp. was under the limit of detection of the methods in examined samples. Besides, pathogenic bacteria, Salmonella spp. and Listeria monocytogenes were not detected in the examined samples. It was found that the concentration of organochlorine pesticides in the samples of water was below the limit of detection for all examined organochlorine pesticides. The measured concentrations of organochlorine pesticides in the sediment and in fish were generally alike or lower than the concentrations measured in fishponds or accumulations and in both carp and other cyprinids in the examinations conducted worldwide. The activity of Cs-137 in the water samples in this research was below the limit of detection and in the samples of sediment it ranged between 2.84 and 7.66 Bq/kg, which is within the limit of normal–natural values. Based on the obtained results, carp produced in the fishpond supplied with purified wastewater from a slaughterhouse in terms of Cs-137 activity is safe for human consumption. The results of the examination of the content of tetracyclines and sulphonamides in water samples, sediments and carp meat showed that the measured concentrations were below the detection limit for each examined parameter. The analysis of the obtained results shows that the efficiency of purifiers in terms of the content of heavy metals and metalloids is high and ranges between 87 and 100%. When it comes to the content of heavy metals and metalloids, the water from the fishpond was category 3 in both spring and autumn sampling. The water from melioration canal was category 2/3, which means it can be used for irrigation. The results of the analyses of concentration of heavy metals in sediment showed that there were no statistically significant differences between samplings, with insignificantly higher values in autumn. The measured concentrations did not exceed the concentrations prescribed for the sediment. A statistically significant difference between the concentration of the examined heavy metals in the samples of fish sampled in spring and those sampled in autumn was found. The health condition of fish during experiments was satisfying. The number of parasites was not significant and not a single parasite disease was found in this examination, but the number of parasite species was as expected and typical for carp production. When it comes to viral diseases, no Spring viremia of carp or Koi herpesvirus disease was found by either laboratory diagnosis or clinical examination. Based on the obtained results presented in this thesis, purified wastewater can successfully be used for production of carp in terms of microbiological and chemical contaminants. The carp produced in such production system is in good health and completely safe for human consumption in terms of the presence of microbiological and chemical contaminants.