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Wpływ diazynonu (Basudin 25EC) na proces fermentacji metanowej komunalnych osadów ściekowych

Sadecka Z., Myszograj S., Sieciechowicz A., Płuciennik-Koropczuk E.

Rocznik Ochrona Środowiska

2015

Tom 17, cz. 2

931--942

The process of methane fermentation is a labile process, sensitive to changes in the environment and susceptible to various substances which may turn out to be toxic for anaerobic biocenosis. The process may be inhibited by both the substances supplied together with the substrate and also the products resulting from the decomposition phases. The group of toxic substances which influences the fermentation process comprises heavy metals, organic compounds, ammonia nitrogen, lower organic acids, nitrogen or sulphur compounds, add to this a large group of organic micropollutants such as hormones added to fodder, disinfectants, insecticides, chemotherapeutics, antibiotics or chemical plant protection products which are all overlooked. These compounds, while occurring in the media subjected to anaerobic stabilisation, may cause a decrease in the speed of the process, possibly also causing its disruption. The inhibitory effect of various chemical compounds on the course of the fermentation process may be evaluated on the basis of the characteristics of the microorganism community, dynamics of changes in its structure and activity of the population. The determination of the activity of enzymes participating in the methane fermentation may be used to evaluate the impact of xenobiotics on the fermentation process and the efficiency of methane production. In the operational practice referring to the fermentation equipment, the impact of biotic and abiotic factors may be evaluated on the basis of changes in the process parameters. The changes in the quantity of microorganisms and the low enzymatic activity cause a decrease in the efficiency of biogas production including methane, as well as a reduction in the effectiveness of the process measured by the loss of the content of organic compounds. The paper presents the results of laboratory tests, concerning the effect of diazinon on the course of biogas production in the process of the methane fermentation of municipal sewage sludge. Diazinon is one of the representatives of phosphate insecticides and an active substance of the commercial preparation bearing the name Basudin 25EC. The effect of the preparation on the course of the process of methane fermentation of sewage sludge was studied within a dose range from 0.5 to 30 mg/ dm-3. The characteristic indicators of the course of anaerobic stabilisation of sewage sludge include the quantity and the composition of the fermentation gas in reference to the fermentation temperature and time. Based on the changes of these parameters, the inhibitive effect of diazinon contained in the Basudin 25EC technical preparation was evaluated. The biogas production in sludge with various doses of diazinon was assumed as a measure of toxicity in reference to the control sludge. The results of the studies showed that: Anaerobic microorganisms are characterised by sensitivity to the Basudin 25EC utility preparation (with a content of 25% diazinon). The first symptoms of the inhibition of the fermentation process occurred at doses of the preparation amounting to 0.5, 1 and 2 mg/dm-3. The inhibition is confirmed by a decrease in the biogas production of about 10%. The intensification of inhibition symptoms was evident at doses ranging from 4 to 8 mg/ dm-3. The reduction in biogas production ranged from 13,0–25,0%. In the sludge where the greatest dose of the preparation was applied, that is, 30 mg/ dm-3, the biogas efficiency went down from 522 dm-3/kg of dry matter to 57.0 dm-3/kg of dry matter. A 10 mg/ dm-3 dose of Basudin 25EC, causing a 60% decrease in the efficiency of biogas production (from 522 to 211 dm-3/kg of dry matter) must be regarded as toxic for the process of methane fermentation of municipal sludge sewage.