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U. Viesturs et al. Solid State Fermentation Systems for Bioremediation and BiodegradationConcentration of hydrogen sulphide before and after biofiltrationTable 2No.Gas flowrate (l⋅h -1 )Concentration of H 2 S (%)(before biofiltration)Concentration of H 2 S(%) (after biofiltration)Efficiency ofbiodegradation (%)1 20.0 0.023 0.019 17.42 14.6 0.033 0.021 36.43 11.2 0.016 0.006 62.5The total amount of bacteria during the compostingprocess increased, and their amount at the end of theprocess was 6 x 10 7 cells per 1 g of dry compost. At thesame time, the amount of fungi decreased from 3 x 10 3to 3 x 10 2 cells per 1 g of dry compost.IR spectra of different compost samples with themicromycetes strains Trichoderma viride and/or Trichodermalignorum as destructors of lignin and celluloseand Na-humate were studied. The characteristicabsorption band for identification of Na-humate waschosen, namely, 1390 cm -1 . In all spectra of the compost,this characteristic Na-humate peak is present, andits increasing intensity follows the composting process(Dubova et al., 2002).The biodegradation efficiency of hydrogen sulphidecould amount to 62.5% at the gas flow rate 11.2l×h -1 (Table 2).The oxidation of ammonia was realized in a solidstate reactor with the association of microorganismsthat was isolated from biologically activated sludge.The ammonia concentration in the inlet gas during theadaptation period (25 days) was maintained at valuesof 0.2–0.3 g×m -3 .After this period, the inlet gas concentration wasincreased to 0.5 g×m -3 with the ammonia load of 0.16NH 3m -3 h -1 . This stage was typical, with regular mediumrecirculation after 5 days for humification of thebed (Table 3).Owing to the high ammonia solubility, the pH wasadjusted in the liquefied phase to 7.0. As a result of thebiomass growing in the liquid phase of the reactor,NH 3was metabolized in nitrites and nitrates, and thepH control was not necessary any more. On the 25 thday of the experiment, the concentration of N-NO 3increasedto 3.5 g m -3 , which created an inhibitory effectto the nitrification process (Table 3).The removal efficiency under these conditions wasstable during 6 months and reached 95–98%. ECamounted to 0.33 g m -3 h -1 at the ammonia load 0.41g m -3 h -1 (Table 4).RE started decreasing above the ammonia concentration1.2 g m -3 , and the biofilter reached the EC 0.87 gm -3 h -1 . A considerable decrease in RE and EC wasobserved at the inlet ammonia concentration 4.1 g m -3 .Under these conditions, the microorganisms utilizedabout 25% of the inlet nitrogen amount. The ammoniaload 5.6 g NH 3m -3 h -1 decreased the EC and RE to 0.34g m -3 h -1 and 20%, respectively.Formation of nitrification products and N-NH 4 during the ammonia biodegradation processTable 3Inlet ammoniaconcentration (g⋅m -3 )Time (days) N-NO 2 (g⋅m -3 ) N-NO 3 (g⋅m -3 ) N-NH 4 (g⋅m -3 )0.2 10 0.4 0 1.20.2 15 0.3 1.0 1.20.2 20 0.2 1.3 1.30.2 25 0.2 3.5 4.20.5 30 0.2 4.7 4.20.5 35 0.1 5.1 4.40.5 40 0.1 5.3 4.554 LLU Raksti 12 (308), 2004; 1-18 47-57
U. Viesturs et al. Solid State Fermentation Systems for Bioremediation and BiodegradationExperimentAmmonia removal efficiency in one-stage biofiltration systemAmmoniaconcentrationin inlet gas(g⋅m -3 )Ammoniaconcentration inoutlet gas (g⋅m -3 )Ammoniaload(g⋅m -3 h -1 )Biologicaleliminationcapacity(g⋅m -3 h -1 )Table 4Removalefficiency(%)1 0.5 0.01 0.41 0.33 982 1.2 0.10 0.97 0.87 923 2.0 0.30 1.62 1.13 854 2.5 0.50 2.03 1.20 805 3.0 0.71 2.43 1.20 746 4.1 2.20 3.30 0.75 467 5.0 3.12 4.05 0.50 378 7.0 5.63 5.67 0.34 209 5.0 3.2 4.05 0.01 35In the two-stage biofiltration system, the partlytreated gas from the first bioreactor was passed throughthe second one. The pumped liquid with the nitrificationproducts was moved from the first column to thesecond one (Table 5). This two-stage configurationproved to be more effective for treatment of the wastegas containing a high amount of ammonia. The ammoniaRE in the two-stage biofiltration system is shownin Table 5.The two-stage biodegradation system was moreefficient not only for the total RE, but also increasedthe biological degradation level. The considerable lossof the nitrogen in this system was assumed to resultfrom the denitrification process that occurred in thesecond biofilter.ConclusionsOrganic waste: sewage sludge, ethanol factorywaste and sawdust were processed using a 3 l horizontallaboratory reactor. The reactor was specially designed,since both fermentation stages, i.e. anaerobicand aerobic, were carried out in the same equipment.The first step of the biodegradation process can berealized at the anaerobic thermophilic regime, providingthe necessary mixing of the compost.The second step of the biodegradation processshould proceed at the mesophilic aerobic regime, providingan intensive aeration of the compost. The applicationof specific adapted microorganisms’ associationsfor regulating the circulation of nitrogen-ammonificationand nitrification processes in aerobic compostingprocesses provides an effective and rapidcomposting of waste.The biofiltration system for removal of hydrogensulphide from the composting facility waste gas wasrealized in a 3 l solid state reactor. The sulphide oxidationbacteria Thiobacillus thiopharus sp.–5 were isolatedfrom biological activated sludge and immobilizedAmmonia removal efficiency in two-stage biofiltration systemBiofilter 1ammonia concentration (g⋅m -3 )Biofilter 2ammonia concentration (g⋅m -3 )inlet gas outlet gas inlet gas outlet gasRemovalefficiency (%)2.0 0.1 0.1 0 1002.5 0.3 0.3 0 1003.0 0.7 0.7 0 1004.1 1.1 1.1 0.3 92.35.2 3.2 3.2 1.4 73.17.0 5.6 5.6 2.5 64.3Table 5LLU Raksti 12 (307), 2004; 47-57 1-1855
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