Linking human settlements to economic growth: strategy for urban development in less developed countries

The United Nations Conference on the Human Environment held in Stockholm in 1972 included the urban environment as a critical problem for less developed countries. The deplorable housing conditions, lack of sanitary facilities and other essential infrastructure were considered as great a threat to the ecology as the industrial excesses and imbalances of developed countries. The continued, rapid growth of metropolitan areas has exacerbated these conditions to an urban crisis—a crisis that has a very destructive potential unless the developed countries redress the situation with a rational policy and strategy of investment in urban development. This problem of strategy is discussed in this paper.     

Monitoring techniques for odour abatement assessment

Odorous emissions from sewers and wastewater treatment plants are a complex mixture of volatile chemicals that can cause annoyance to local populations, resulting in complaints to wastewater operators. Due to the variability in hedonic tone and chemical character of odorous emissions, no analytical technique can be applied universally for the assessment of odour abatement performance. Recent developments in analytical methodologies, specifically gas chromatography, odour assessment approaches (odour wheels, the odour profile method and dynamic olfactometry), and more recently combined gas chromatography-sensory analysis, have contributed to improvements in our ability to assesses odorous emissions in terms of odorant concentration and composition. This review collates existing knowledge with the aim of providing new insight into the effectiveness of sensorial and characterisation approaches to improve our understanding of the fate of odorous emissions during odour abatement. While research in non-specific sensor array (e-nose) technology has resulted in progress in the field of continuous odour monitoring, more successful long term case-studies are still needed to overcome the early overoptimistic performance expectations. Knowledge gaps still remain with regards to the decomposition of thermally unstable volatile compounds (especially sulfur compounds), the inability to predict synergistic, antagonistic, or additive interactions among odorants in combined chemical/sensorial analysis techniques, and the long term stability of chemical sensors due to sensor drift, aging, temperature/relative humidity effects, and temporal variations. Future odour abatement monitoring will require the identification of key odorants to facilitate improved process selection, design and management.     

堆肥过程中产生的尾气

堆肥过程中产生大量的臭气,考察这些臭气的组成、含量对处理城市生活垃圾堆肥有重大意义。实验采用气相色谱质谱联用仪（GCMS）对收集的堆肥尾气进行检测,测得21种气体,其中含量较大的气体为NH3和H2S等。     

Prevention of volatile fatty acids production and limitation of odours from winery wastewaters by denitrification

The effect of the addition of nitrate to winery wastewaters to control the formation of VFA in order to prevent odours during storage and treatment was studied in batch bioreactors at different NO(3)/chemical oxygen demand (COD) ratios and at full scale in natural evaporation ponds (2 x 7000 m(2)) by measuring olfactory intensity. In the absence of nitrate, butyric acid (2304 mgL(-1)), acetic acid (1633 mgL(-1)), propionic acid (1558 mgL(-1)), caproic acid (499 mgL(-1)) and valeric acid (298 mgL(-1)) were produced from reconstituted winery wastewater. For a ratio of NO(3)/COD=0.4 gg(-1), caproic and valeric acids were not formed. The production of butyric and propionic acids was reduced by 93.3% and 72.5%, respectively, at a ratio of NO(3)/COD=0.8, and by 97.4% and 100% at a ratio of NO(3)/COD=1.2 gg(-1). Nitrate delayed and decreased butyric acid formation in relation to the oxidoreduction potential. Studies in ponds showed that the addition of concentrated calcium nitrate (NITCAL) to winery wastewaters (3526 m(3)) in a ratio of NO(3)/COD=0.8 inhibited VFA production, with COD elimination (94%) and total nitrate degradation, and no final nitrite accumulation. On the contrary, in ponds not treated with nitrate, malodorous VFA (from propionic to heptano?c acids) represented up to 60% of the COD. Olfactory intensity measurements in relation to the butanol scale of VFA solutions and the ponds revealed the pervasive role of VFA in the odour of the untreated pond as well as the clear decrease in the intensity and not unpleasant odour of the winery wastewater pond enriched in nitrates. The results obtained at full scale underscored the feasibility and safety of the calcium nitrate treatment as opposed to concentrated nitric acid.