Bio-methane production from urban organic matter

厌氧生物处理可用于稳定水和废水净化过程中产生的污泥，用于固体废物降解和高强度工业废水的处理。有机物在厌氧条件下的降解比好氧降解具有以下优点：-它不需要氧气供应，因此具有较低的能量需求。-污泥产量减少90%，运营成本和环境影响更低。-产生沼气(主要由甲烷和二氧化碳组成)，这是一种宝贵的可再生生物燃料。在设计这些系统时，必须考虑到这样一个事实，即在液体废水的高速处理过程中，生长较慢的微生物可能会被冲走。基于利用膜将微生物留在系统中的新技术可以克服这一限制。这种结构被称为膜生物反应器(MBR)，它结合了两个功能：由保留的微生物进行生物降解，以及固体分离，即处理后的污水与负责降解的悬浮固体和微生物分离。MBR确保了高质量出水的产生，因为可以保持较高的微生物浓度；这还有一个潜在的优势，即即使在较低的运行温度下也可以进行废水处理。膜的使用还允许保留已适应特定废水类型的物种，包括那些含有否则不易降解的持久性污染物的物种。显然，膜系统是废水处理中最有前途的技术之一。由于能够在高渗透流速下工作的膜的开发，以及更紧凑、更便宜和可交换的膜组件的生产，MBR在好氧处理中的应用正在增加。然而，尽管有这些进展，膜技术也有几个重要的缺点，阻碍了其更广泛的应用。主要问题是投资和运行成本：这两者都与膜污染等运行问题密切相关，膜污染限制了可以实现的最大流速。减少膜污染的方法包括气体再循环和反冲洗，这两种方法都消耗大量的能量，减少了从厌氧系统获得的潜在能量。气体清洗也不是完全有效的，可能需要定期从反应器中取出膜进行化学清洗。这对操作成本有影响，持续使用化学试剂可能会影响膜的寿命和分离效率，因此非常希望减少这种类型的清洗频率。因此，当前研究的一个关键方面是开发和测试替代的膜清洗方法。南安普顿大学开展的这项工作将专门调查使用专门设计的支持颗粒，这种颗粒促进微生物生物量的增长，同时还提供温和的研磨清洁行动。这将与低强度超声波的应用相结合，该应用基于该大学开发的StarStream技术的改编，该技术已经赢得了一系列重大创新奖项。Starstream使用低强度超声波和低压水流中的微泡，在清洗各种表面和污垢类型方面都很有效。这两种方法的结合可能会对反应堆的性能产生协同效应，从而以较低的能量消耗实现更高的通量速率。

Anaerobic biological treatments can be used for stabilisation of the sludge produced in water and wastewater purification, in solid waste degradation and in the treatment of high-strength industrial effluents. The degradation of organic matter in anaerobic conditions has the following advantages over aerobic degradation: - It does not require an oxygen supply and consequently has a lower energy demand. - Sludge production is reduced by >90%, with lower in operational costs and environmental impacts. - It produces biogas (composed mainly of CH4 and CO2) which is a valuable renewable biofuel. In the design of these systems consideration must be given to the fact that slower-growing microorganisms may be washed out during high-rate treatment of liquid effluents. New techniques based on the utilisation of membranes to keep microorganisms in the system can overcome this limitation. This configuration is referred to as a membrane bioreactor (MBR) and combines two functions: biological degradation by the retained microorganisms, and solids separation in which the treated effluent is separated from the suspended solids and microorganisms responsible for degradation. The MBR ensures the production of high-quality effluent as a high concentration of microorganisms can be maintained; this has the further potential advantage that it may allow wastewater treatment even at lower operating temperatures. Use of membranes also allows the retention of species that have become adapted to particular wastewater types, including those that contain persistent pollutants that would otherwise not be easily degraded. It is clear that membrane systems are one of the most promising technologies in wastewater treatment. The application of MBRs for aerobic treatment is increasing, due to the development of membranes that are able to work at high permeate flow rates, and the production of more compact, cheaper and exchangeable membrane modules. Despite these advances, however, membrane technologies also have several important drawbacks which hold back their wider application. The main issues are investment and operating costs: both of which are closely linked to operational problems such as membrane fouling, which limits the maximum flow rate that can be achieved. Methods to reduce membrane fouling include gas recirculation and back-flushing, both of which consume considerable amounts of energy, reducing the potential energy gains from an anaerobic system. Gas scouring is also not completely effective, and it may be necessary periodically to remove the membrane from the reactor for chemical cleaning. This has implications for operating costs, and continual use of chemical agents may affect the membrane lifespan and separation efficiency, making it highly desirable to reduce the frequency of this type of cleaning. A key aspect of the current research is therefore to develop and test alternative methods of membrane cleaning. The work carried out by the University of Southampton will specifically investigate the use of purpose-designed support particles which encourage the growth of microbial biomass while also providing a mildly abrasive cleaning action. This will be coupled with the application of low-intensity ultrasound, based on adaptation of the StarStream technology developed at the University, which has already won a series of major awards for innovation. StarStream uses low-intensity ultrasound and micro-bubbles in a stream of low-pressure water, and is effective at cleaning a variety of surface and fouling types. The combination of these two approaches may have synergetic effects on reactor performance allowing higher flux rates to be achieved with lower energy usage.