郑州市污泥堆肥处理工程的设计

郑州市污泥堆肥处理工程处理规模为600 t/d,采用好氧堆肥工艺处置三个污水处理厂的剩余污泥.介绍了工艺流程及发酵槽、混料仓、除臭系统等各处理单元的设计参数,可为相关工程提供参考.     

Quantitative effects of composting state variables on C/N ratio through GA-aided multivariate analysis

It is widely known that variation of the C/N ratio is dependent on many state variables during composting processes. This study attempted to develop a genetic algorithm aided stepwise cluster analysis (GASCA) method to describe the nonlinear relationships between the selected state variables and the C/N ratio in food waste composting. The experimental data from six bench-scale composting reactors were used to demonstrate the applicability of GASCA. Within the GASCA framework, GA searched optimal sets of both specified state variables and SCA's internal parameters; SCA established statistical nonlinear relationships between state variables and the C/N ratio; to avoid unnecessary and time-consuming calculation, a proxy table was introduced to save around 70% computational efforts. The obtained GASCA cluster trees had smaller sizes and higher prediction accuracy than the conventional SCA trees. Based on the optimal GASCA tree, the effects of the GA-selected state variables on the C/N ratio were ranged in a descending order as: NH₄⁺-N concentration > Moisture content > Ash Content > Mean Temperature > Mesophilic bacteria biomass. Such a rank implied that the variation of ammonium nitrogen concentration, the associated temperature and the moisture conditions, the total loss of both organic matters and available mineral constituents, and the mesophilic bacteria activity, were critical factors affecting the C/N ratio during the investigated food waste composting. This first application of GASCA to composting modelling indicated that more direct search algorithms could be coupled with SCA or other multivariate analysis methods to analyze complicated relationships during composting and many other environmental processes.     

造纸污泥交替式好氧厌氧堆肥实验

调节造纸污泥的水分和C/N比,经过为期50d的交替好氧厌氧堆肥处理,污泥有机质发生降解,TN、TP和TK含量都呈上升趋势,挥发性固体和有机碳分别达到60%和30%的稳定状态,堆肥的种子发芽率达到95%以上,大肠杆菌数低于国家卫生标准,实现造纸污泥无害化、稳定化和减量化的要求.腐熟的污泥堆肥成为高价值的农用产品.     

Mortality of grape phylloxera in composting organics

The effects of windrow and in-vessel Vertical Composting Unit (VCU) systems on the mortality of grape phylloxera, Daktulosphaira vitifolii (Fitch) (Hemiptera: Phylloxeridae) infesting European grapevine ( Vitis vinifera L.) root systems were tested in three experiments. No phylloxera survived the first three-week windrow period of a 12-week, four-turn, composting cycle at a representative depth of 0.75–1.0 m with temperatures between 62.2°C and 66.5°C. Some root systems survived on the windrow surface and produced new growth after 12 weeks. Phylloxera survived on these root systems for no longer than 6 weeks at temperatures between 25.5°C and 29.4°C, which are well below the upper thermal survival limit of 36°C to 40.0°C for phylloxera. Root systems surviving on the surface were destroyed when buried at 0.75–1.0 m. No phylloxera or root systems survived when exposed to shallower burial (1.0 to 0.25 m), reduced times of exposure (21 to 4 days) and lower temperatures (66.5°C to 50.8°C) in three successive windrows. This included one treatment equating to the requirements of the current Australian Standard (AS 4454) for composted products. In a third experiment, phylloxera were allowed to pass passively through a bench scale test-cell that simulated composting in a VCU. Temperatures ranged between 54.6°C and 61.4°C in the top two-thirds of the tower where phylloxera were exposed for 12–21 days. No phylloxera or root systems survived the VCU. Temperatures in both composting systems were sufficiently high to cause complete mortality of phylloxera provided that turning regimens for windrows ensure that all material is mixed to the Australian Standard. Factors other than temperature may also contribute to phylloxera mortality during composting.     

Phytotoxicity due to the agricultural use of urban wastes. Germination experiments

The inhibitory effect on germination by the organic fraction of different urban wastes was studied in two experiments: on barley (Hordeum vulgare L cv Reinete) seeds in petri dishes and on ryegrass (Lolium perenne L cv Argo) seeds in containers. The urban wastes were mixed with a calcareous soil. Fresh sewage sludge almost totally inhibited germination of barley seeds when used as substrate; fresh municipal solid waste also inhibited germination, although to a lesser degree. Both inhibitory effects were less pronounced when the products had been composted previously. Similar results were obtained when the experiments were carried out with water extracts although overall inhibition was less. Correlation between germination indices and various parameters of the products used showed that the highest indices were obtained when the organic matter of the samples was the most stable (a smaller proportion of labile carbon, carbon extracted with Na₁P₂O⁷, carbon precipitated at pH 2 and water soluble carbon in the materials and extracts). Inhibition was greater when there were greater quantities of NH^?₄, polyphenols and organic acids of low molecular weight. Yields of ryegrass obtained from high doses of urban wastes (180 t ha ^?1) mixed with a calcareous soil were less than those of the control at the first harvest, these yields being influenced negatively by the same factors as above; at the second harvest the yields with most of the products used were higher than those of the control, probably as a result of their maturation in the soil. When the water extracts of the products were added to the soil, no significant differences from the control were noted at the first harvest.     

Food waste conversion options in Singapore: Environmental impacts based on an LCA perspective

Proper management and recycling of huge volumes of food waste is one of the challenges faced by Singapore. Semakau island — the only offshore landfill of the nation — only accepts inert, inorganic solid waste and therefore a large bulk of food waste is directed to incinerators. A remaining small percent is sent for recycling via anaerobic digestion (AD), followed by composting of the digestate material. This article investigates the environmental performance of four food waste conversion scenarios — based on a life cycle assessment perspective — taking into account air emissions, useful energy from the incinerators and AD process, as well as carbon dioxide mitigation from the compost products derived from the digestate material and a proposed aerobic composting system. The life cycle impact results were generated for global warming, acidification, eutrophication, photochemical oxidation and energy use. The total normalized results showed that a small-scale proposed aerobic composting system is more environmentally favorable than incinerators, but less ideal compared to the AD process. By making full use of the AD's Recycling Phase II process alone, the Singapore Green Plan's 2012 aim to increase the recycling of food waste to 30% can easily be achieved, along with reduced global warming impacts.     

受控堆肥条件下材料需氧生物分解能力试验方法的研究

依据ISO 14 85 5 :1999《受控堆肥化条件下材料最终需氧生物分解能力———采用测定释放的二氧化碳的方法》 ,对淀粉 (St)、聚己内酯 (PCL)、聚乳酸 (PLA)、聚丁二醇丁二酸 /己二酸酯 (PBSA)、聚羟基丁烯酸戊酸酯 (PHBV )、聚乙烯醇 (PVA)、纸 (Pa)、聚乙烯 (PE) 8种材料进行了受控堆肥化条件下生物分解能力的测定。试验结果表明 ,用此方法来评价材料的堆肥能力或生物分解能力是可行的 ,且相同条件下 ,各种试样的生物分解能力大小的顺序为St >PCL >PLA >PHBV≈PBSA≈PVA >Pa。     

材料生物降解能力评价方法的研究

采用纤维素、淀粉、聚羟基丁酸酯(polyhydroxybutyrate,PHB)、聚羟基丁酸/戊酸酯[poly(hydroxybutyratecohydroxyvalerate),PHBV]、聚乙烯/淀粉共混物和聚乙烯等6种试验材料,在可控堆肥条件下通过测定释放的二氧化碳的方法,以及在水性培养液中需氧条件下分别通过测定氧气消耗量和释放的二氧化碳的方法,测定材料的生物分解能力。结果表明3种方法测得的材料生物降解百分率(%)分别依次为:纤维素(76.9)>淀粉(74.3)>PHB(73.3)>PHBV(70.5)聚乙烯/淀粉共混物(20.3)聚乙烯(0.3);PHB(78.7)>PHBV(71.2)>纤维素(70.7)聚乙烯/淀粉共混物(24.4)聚乙烯(0.3);PHB(73.6)>PHBV(72.4)>纤维素(71.9)聚乙烯/淀粉共混物(26.2)聚乙烯(0.2),在评价聚合物生物降解能力上基本具有等效性。