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The aim of this study was to evaluate the laboratory-scale composting of sewage sludge and pumice mixtures that were amended with sucrose. The variation in temperature, pH, NH4(+)-N, ammonia emission, bacterial community, ammonia assimilating bacteria (AAB) populations and enzymatic activity related to ammonia assimilation were detected. The addition of sucrose increased the AAB population by 2.5-3.5 times, reduced ammonia emission by 24.7-31.1% compared with the control treatment, and promoted the growth of Bacillus and Wautersiella. The activities of glutamate dehydrogenase (GDH), glutamate synthase (GS) and glutamine synthetase (GOGAT), were enhanced by the addition of sucrose. GDH made a substantial contribution to ammonia assimilation when the ammonia concentration was high (⩾1.5g/kg) in the thermophilic phase. The GS/GOGAT cycle played an important role at low ammonia concentrations (⩽1.1g/kg) in the cooling phase. These results suggested that adding sucrose to sludge compost could promote ammonia assimilation and reduce ammonia emission., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

This study aimed to investigate the role of carbon dioxide in reducing ammonia emissions. Three variations of a composting experiment were conducted in a laboratory-scale reactor, all of which exhibited the three typical composting phases. Approximately 70% of the ammonia emissions occurred within 96-144 h of the thermophilic stage. The maximum rate of change for the carbon dioxide emissions occurred at different times for different carbon source types, mixing rates, and addition times. The rate of change and total concentration of emitted carbon dioxide played a crucial role in ammonia emission due to their relationship to the intensity of ammonia assimilation. The addition of a carbon source that could be utilized by thermophilic microorganisms stimulated ammonia assimilation and thus reduced ammonia emissions. These findings suggested that the addition of a 7:3 mixture of sucrose and straw powder at 108 h is suitable for reducing ammonia emissions., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Odorous gases emitted from landfills have always been a public concern, but studies evaluating the odour contribution and the correlation between the odour concentrations are limited. The objectives of this study were to assess the odour contribution and to correlate the measured odour concentration C OD with the calculated odour concentration SOAV , which was calculated as sum of individual odour activity value ( OAV ). Odorous air samples from a landfill in Beijing were collected seasonally and measured by both gas chromatography and an olfactometer. Different from previous studies, we measured the odour threshold of 51 detected compounds using a uniform methodology to minimize the imprecision of citing odour threshold from disparate literature. The odour threshold is used to convert the individual chemical concentration into the OAV , which is used as a surrogate of the odour concentration. Evaluation of the OAV revealed that hydrogen sulfide (65.9%), dimethyl sulfide (14.4%) and trimethylamine (8.6%) contributed the most to the odour at the landfill. Moreover, the correlation between the calculated odour concentration SOAV and the measured odour concentration C OD resulted in a linear regression equation of C OD = 6.28 SOAV ( r = 0.914, n = 24, p < 0.01). Based on the scaling factor K = 6.28, the average ratio of calculated odour concentration to measured odour concentration could be improved from less than 0.2 to 1.1. By the calibration of the calculated odour concentration SOAV , it is possible to use continuous measurements of chemical concentrations to derive odour concentration for this site for monitoring purposes. [ABSTRACT FROM AUTHOR]

Abstract: Ammonia emissions during composting result in the reduced value of agronomic production and can also pollute the air. To evaluate the influence of various carbon sources on ammonia emissions, six composting experiments were carried out with different amendments of carbon sources (glucose, sucrose and straw powder). The cumulative ammonia volatilizations were reduced from 3.11 g/kg (R6) to 2.46 g/kg (R1), 2.17 g/kg (R2), 2.23 g/kg (R4) and 1.93 g/kg (R5). Compared to the control, no significant difference of ammonia emissions and carbon degradation was observed for the mixture of R3 (3.15 g/kg), which was amended with straw powder alone. The co-addition of sucrose and straw powder led to the lowest ammonia emissions. According to these results, a higher C/N ratio did not necessarily indicate an effective solution for reducing ammonia emissions, and not all readily available carbon compounds were helpful in reducing ammonia emissions. The addition of sucrose promoted the decomposition of organic carbon during the intensive stage of ammonia emissions, and the combination of straw and sucrose prolonged this promotion. Thus, the co-addition of sucrose and straw powder made it possible to reduce ammonia emissions drastically by nitrogen immobilization. [Copyright &y& Elsevier]

[Display omitted] • Effect of organic bulking agents on NH 3 , N 2 O and CH 4 from composting was evaluated. • Water-holding porosity more greatly impacted CH 4 and NH 3 than C/N and porosity. • Three bulking agents did not evidently change N 2 O emission in sludge composting. • Effect of bulking agent on genes of methane and nitrogen metabolisms was evaluated. • Continuous increase of ORP restricted denitrification gene and promoted pmoA. The effect of organic bulking agents on CO 2 , NH 3 , N 2 O and CH 4 emission and related genes was evaluated in 40 days sludge composting with wood chip, wheat straw and rice husk, respectively. The results showed wood chip had the highest C/N of 111.3, total porosity of 93.13% and aeration porosity of 78.98% among three bulking agents. Wheat straw had the highest water-holding porosity of 25.62%, which could be critical factor increasing CH 4 production and reducing NH 3 emission. Moreover, there was no significant difference in N 2 O emission rates in three composting systems with three bulking agents. RDA analysis showed a negative correlation between mcrA and NH + 4-N. Nitrate content in raw feedstock was dominant factor limiting N 2 O yield due to low amoA. The continuous increase of oxidation–reduction potential was significantly positive correlated with pmoA and negative correlation with nirK and norB , which reduced N 2 O and CH 4 production in the curing period. [ABSTRACT FROM AUTHOR]