Ocena możliwości unieszkodliwiania osadów koksowniczych w procesie kofermentacji

The paper presents results of research on changes in physical-chemical properties during the process of co-fermentation of coke sludge and municipal sludge. The process was carried out at 37°C for 16 days. For testing of fermentation, the mixture of raw sludge and excessive sludge was prepared with the addition of fermented sludge (control) and four mixtures of sludge coke and municipal sewage sludge in the proportions: I, II, III, IV – 1:20, 1:10, 1:6, 1:4, respectively. The content of dry matter in the control sludge during fermentation decreased by 15% and the degree of decomposition of the organic substances was 24.7%. The share of organic matter in the fermented sludge was 60%. The total biogas production in the control sludge was 4557 mL. The analysed sludge I (ratio 1: 20) showed a loss of organic dry matter by 14%, and the degree of decomposition of organic matter reached 22.5%. The share of organic matter in fermented sludge alike for the control sludge accounted for 60%. During the co-fermentation of the analysed sludge (I) the total biogas production was 4508 mL. After the co-fermentation of sludge II (1:10) the degree of decomposition of organic substances was the same as during the co-fermentation sludge I and accounted for 22.4%. The dry matter content in the sludge decreased by 16%. Also, the content of organic matter in the fermented sludge was similar as after the fermentation of mixture I and accounted for 59%. The total biogas production was 3990 mL. The reduction of organic compound in sludge III (1:6) and IV was 22.3% and 20.6%. The dry matter of sludge after the 16-day incubation decreased by 16% in the case of a mixture III and by 15% – mixture IV. The share of organic matter in the fermented sludge was 64%. The results show that it is possible to dispose the coke sludge and the municipal sludge in the co-fermentation process. In the adopted experimental conditions, the introduction of coke sludge to the municipal sludge with the ratio of 1:20, 1:10 and 1: 6 (mixture I, II and III, respectively) had no statistically significant effect on the degree of decomposition of organic compounds, the loss of dry matter, the total biogas production, the reduction of organic substances expressed by COD index, the amount of biogas per unit of dry organic matter and the methane content in biogas. The coke sludge content for co-fermentation should not cause significant changes in technical parameters of the process, so in order to maintain the correct operation of the fermentation chambers it is necessary to determine the appropriate mixing ratio of sludge.