热水解厌氧消化工艺的分析和应用探讨

热水解厌氧消化工艺可提高污泥的水解效果和有机物降解率,增加沼气产量;杀灭污泥中病菌;缩短厌氧消化的停留时间、提高消化池内的污泥浓度,节省占地面积和土建工程投资;同时使消化后的污泥易于脱水,污泥体积减少。与传统的厌氧消化工艺比较,热水解厌氧消化工艺强化了污泥的减量化、稳定化、无害化和资源化的处理目标,当与后续热干化工艺结合时,可降低运行成本。从热水解技术的原理和形式出发,结合实际工程方案,对热水解厌氧消化工艺的可行性和应用中的问题进行了初步探讨。     

热水解工艺气对污泥厌氧消化运行的影响

热水解作为高级厌氧消化的预处理工序,其排放的废气——工艺气,一般进入厌氧消化池进行处理。通过高安屯污泥处理中心项目运行实例,分析通入热水解工艺气的消化池与未通入热水解工艺气的消化池在有机物分解率、沼气成分、污泥理化指标、沼气产率等方面的差异,总结热水解工艺气对于厌氧消化运行的影响。针对生产运行实际,提出对于工艺气处理的相关建议。     

城镇污水污泥厌氧消化技术及能源消耗

我国城镇污水处理厂采用污泥稳定化处理的不到20%,在污泥稳定化方面与国外存在较大差距。厌氧消化技术可以实现污泥的减量化、稳定化和无害化,同时可利用沼气资源。结合《城镇污水处理厂污泥处理处置污染防治最佳可行技术指南(试行)》的编写,介绍了城镇污水处理厂的污泥厌氧消化技术、能源消耗和厌氧消化排放的污染物,为决策者和从业人员提供参考。     

注重资源利用的污泥处理处置工程实践

襄阳污泥处理工程设计规模300t/d(以含固率20%计),采用脱水污泥高温热水解、厌氧消化、机械脱水、干化处理工艺。工程实践证明:高温热水解厌氧消化有效提高了传统厌氧消化的技术水平;在高温热水解的作用下,有效杀灭了病原菌,实现了卫生化;有效提高了厌氧消化效率和处理产物的稳定化水平,处理产物不再发臭;大幅度降低了沼气中的H2S含量,提高了难溶重金属硫化物的生成比例。产物之一——生物质能源(沼气),在满足自用后,部分经提纯用于向社会车辆供气;处理产物之二——生物质炭土,用于苗木栽培和移植。两种生物质产物在环境中的消纳方式,解决了处理后的产物出路问题,诠释了污泥处理处置的全过程;同时,从产物的利用中得到经济收益,让治污投入有了效益产出,使被动治污变成为主动治污。襄阳污泥处理工程模式,为我国污泥处理探索和实践出了一条可持续、可借鉴、可复制的绿色和生态污泥处理处置之路。     

污泥热水解厌氧消化与常规厌氧消化的运行比较

热水解厌氧消化技术是近年来国内外污泥处理新的发展应用方向。选取小红门污泥处理中心项目的运行数据,比较热水解厌氧消化与常规厌氧消化的运行操作、进泥泥质、消化效果、产气量、沼气成分、附属系统等的差异,分析项目运行中存在的负荷、余热利用问题,总结热水解厌氧消化的运行特点,提出建议及进一步优化的方向。     

北京市高安屯污泥处理中心工程设计及优化

北京市高安屯污泥处理中心工程处理规模约1 850t/d,采用热水解-厌氧消化-板框脱水工艺,是亚洲最大的采用该工艺的污泥处理中心。通过对污泥接收系统、热水解系统、厌氧消化系统、板框脱水系统及沼气脱硫系统进行优化设计,使得该污泥处理中心在方便运行管理、保证施工质量等方面有了进一步提高,进而强化了污泥稳定性、减量化、无害化和资源化的处理目标。     

污泥厌氧消化沼气优化利用成本分析

介绍了国内沼气利用的情况,特别是污泥厌氧消化系统的发展前景及产生沼气的各种利用方式。对污泥厌氧消化本体及四种常见的沼气综合利用方式的成本进行了比较及综合分析,所有的数据都来源于运行实践,对其他污泥厌氧消化系统的经济运行和沼气综合利用方式的选择具有一定借鉴作用。     

正确的政策导向是发展可持续污泥处理技术的保障

对污泥厌氧消化技术在国内外的应用及发展情况作了简单介绍.通过与其他污泥处理工艺对比,分析了污泥厌氧消化的优缺点、污泥厌氧消化工艺的费用与收益.指出污泥厌氧消化工艺是一种可持续的实用技术,理应成为城市污水处理厂污泥稳定化处理的首选工艺.认为应对现行的《城市污水处理及污染防治技术政策》进行修改,鼓励有条件的污水处理厂在选择污泥处理工艺时优先考虑厌氧消化技术.     

多级污泥厌氧消化工艺的开发

传统污泥厌氧消化技术复杂、费用较高 ,而延时曝气的低负荷工艺投资高、能耗高。介绍了多级污泥厌氧消化工艺的开发过程 ,该工艺由水解酸化、固液分离及UASB三段构成 ,经过试验研究和工程验证 ,表明该工艺可使污泥在较短的总停留时间 (t=7d)达到稳定。     

郑州王新庄污水处理厂污泥消化系统设计与运行

郑州王新庄污水处理厂是淮河流域最大的污水处理厂(40万 m3/d),其污泥利用中温厌氧消化进行稳定处理及浓缩脱水,所产沼气用来驱动鼓风机,余热配合沼气锅炉加热消化污泥.介绍了整个污泥消化系统的设计参数、特点和运行情况,并以运行数据为依托来说明设计的合理性与不足之处,总结了消化系统设计工作应注意的几个问题.     

Potentials and limits of anaerobic digestion of sewage sludge: energy self-sufficient municipal wastewater treatment plant?

Anaerobic digestion is the only energy-positive technology widely used in wastewater treatment. Full-scale data prove that the anaerobic digestion of sewage sludge can produce biogas that covers a substantial amount of the energy consumption of a wastewater treatment plant (WWTP). In this paper, we discuss possibilities for improving the digestion efficiency and biogas production from sewage sludge. Typical specific energy consumptions of municipal WWTPs per population equivalent are compared with the potential specific production of biogas to find the required/optimal digestion efficiency. Examples of technological measures to achieve such efficiency are presented. Our findings show that even a municipal WWTP with secondary biological treatment located in a moderate climate can come close to energy self-sufficiency. However, they also show that such self-sufficiency is dependent on: (i) the strict optimization of the total energy consumption of the plant, and (ii) an increase in the specific biogas production from sewage sludge to values around 600 L per kg of supplied volatile solids.     

Sludge as source of energy and revenue.

Sludge is a residue/product from wastewater treatment plants and contains most of the contaminants released during human activities. Some stringent environmental regulations on sludge treatment and disposal exist in many countries. This has resulted in increasing interest in sludge treatment methods that encourage sludge reduction and improvement in biogas production during anaerobic digestion processes. This work demonstrates the first exploitation of valuable energy from homogenised sludge at technical scale with mass reduction. The optimal combination of sludge homogenisation at relatively low pressures using a modified high-pressure homogeniser led to the success of this unique project. Results showed that about 30% more energy could be obtained from thickened and disrupted sludge than from untreated samples. The energy produced was higher than that invested during disruption and digestion processes. About 23% sludge reduction was also observed with no increase in chemical oxygen demand. This new process can produce extra energy for local electrification and heating the digester while the sludge reduction provides economic benefits. Concentration of sludge causes reduction in investment cost on digester as well as reduction in operational time for sludge dewatering.     

Autogenerative high pressure digestion: anaerobic digestion and biogas upgrading in a single step reactor system

Conventional anaerobic digestion is a widely applied technology to produce biogas from organic wastes and residues. The biogas calorific value depends on the CH, content which generally ranges between 55 and 65%. Biogas upgrading to so-called 'green gas', with natural gas quality, generally proceeds with add-on technologies, applicable only for biogas flows > 100 m3/h. In the concept of autogenerative high pressure digestion (AHPD), methanogenic biomass builds up pressure inside the reactor. Since CO2 has a higher solubility than CH4, it will proportion more to the liquid phase at higher pressures. Therefore, AHPD biogas is characterised by a high CH4 content, reaching equilibrium values between 90 and 95% at a pressure of 3-90 bar. In addition, also H2S and NH3 are theoretically more soluble in the bulk liquid than CO2. Moreover, the water content of the already compressed biogas is calculated to have a dew point <--10 degrees C. Ideally, high-quality biogas can be directly used for electricity and heat generation, or injected in a local natural gas distribution net. In the present study, using sodium acetate as substrate and anaerobic granular sludge as inoculum, batch-fed reactors showed a pressure increase up to 90 bars, the maximum allowable value for our used reactors. However, the specific methanogenic activity (SMA) of the sludge decreased on average by 30% compared to digestion at ambient pressure (1 bar). Other results show no effect of pressure exposure on the SMA assessed under atmospheric conditions. These first results show that the proposed AHPD process is a highly promising technology for anaerobic digestion and biogas upgrading in a single step reactor system.     

Ultrasonic sludge treatment for enhanced anaerobic digestion.

Ultrasound is the term used to describe sound energy at frequencies above 20 kHz. High-powered ultrasound can be applied to a waste stream via purpose-designed tools in order to induce cavitation. This effect results in the rupture of cellular material and reduction of particle size in the waste stream, making the cells more amenable to downstream processing. sonix is a new technology utilising high-powered, concentrated ultrasound for conditioning sludges prior to further treatment. This paper presents recent results from a number of demonstration and full-scale plants treating thickened waste activated sludge (TWAS) prior to anaerobic digestion, therefore enhancing the process. The present studies have proved that the use of ultrasound to enhance anaerobic digestion can be achieved at full scale and effectively result in the TWAS (typically difficult to digest) behaving, after sonication, as if it were a "primary" sludge. The technology presents benefits in terms of increased biogas production, better solids reduction, improved dewatering characteristics of the digested sludge mixture and relatively short payback periods of two years or less subject to the site conditions and practices applicable at that time.     

Digestion of sludge and organic waste in the sustainability concept for Malm?, Sweden.

Anaerobic digestion of sludge has been part of the treatment plant in Malm? for many years and several projects on optimisation of the digestion process have been undertaken in full scale as well as in pilot scale. In order to facilitate a more sustainable solution in the future for waste management, solid waste organic waste is sorted out from households for anaerobic treatment in a newly built city district. The system for treatment of the waste is integrated in a centralised solution located at the existing wastewater treatment plant. A new extension of the digester capacity enables separate as well as co-digestion of sludge together with urban organic waste from households, industry, restaurants, big kitchens, food stores, supermarkets, green markets etc. for biogas production and production of fertiliser. Collection and pre-treatment of different types of waste are in progress together with examination of biogas potential for different types of organic waste. Collection of household waste as well as anaerobic digestion in laboratory and pilot scale has been performed during the last year. It is demonstrated that organic household waste can be digested separately or in combination with sludge. In the latter case a higher biogas yield is found than should be expected from digestion of the two materials separately. Household waste from a system based on collection of organic waste from grinders could be digested at mesophilic conditions whereas digestion failed at thermophilic conditions.     

Life cycle assessment of an intensive sewage treatment plant in Barcelona (Spain) with focus on energy aspects

Life Cycle Assessment was used to evaluate environmental impacts associated to a full-scale wastewater treatment plant (WWTP) in Barcelona Metropolitan Area, with a treatment capacity of 2 million population equivalent, focussing on energy aspects and resources consumption. The wastewater line includes conventional pre-treatment, primary settler, activated sludge with nitrogen removal, and tertiary treatment; and the sludge line consists of thickening, anaerobic digestion, cogeneration, dewatering and thermal drying. Real site data were preferably included in the inventory. Environmental impacts of the resulting impact categories were determined by the CLM 2 baseline method. According to the results, the combustion of natural gas in the cogeneration engine is responsible for the main impact on Climate Change and Depletion of Abiotic Resources, while the combustion of biogas in the cogeneration unit accounts for a minor part. The results suggest that the environmental performance of the WWTP would be enhanced by increasing biogas production through improved anaerobic digestion of sewage sludge.     

Anaerobic digestion potential for ecological and decentralised sanitation in urban areas.

The potential of anaerobic digestion in ecological and decentralised sanitation has been investigated in this research. Different anaerobic digestion systems were proposed for the treatment of sewage, grey water, black water and faeces. Moreover, mathematical models based on anaerobic digestion model no.1 (ADM1) were developed for determination of a suitable design for each system. For stable performance of an upflow anaerobic sludge blanket (UASB) reactor treating sewage, the model results indicated that optimisation of wastewater conversion to biogas (not COD removal) should be selected for determination of the hydraulic retention time (HRT) of the reactor. For the treatment of sewage or black water in a UASB septic-tank, the model results showed that the sludge removal period was the main parameter for determination of the HRT. At such HRT, both COD removal and wastewater conversion are also optimised. The model results demonstrated that for treatment of faeces in an accumulation (AC) system at temperature > or = 25 degrees C, the filling period of the system should be higher than 60 days. For maximisation of the net biogas production (i.e. reduction of biogas losses as dissolved in the effluent), the separation between grey water, urine and faeces and reduction of water consumption for faeces flushing are required. Furthermore, the faeces and kitchen organic wastes and grey water are digested in, respectively, an AC system and UASB reactor, while the urine is stored.     

Anaerobic digestion with partial ozonation minimises greenhouse gas emission from sludge treatment and disposal.

A novel anaerobic digestion process combined with partial ozonation on digested sludge was demonstrated for improving sludge digestion and biogas recovery by full-scale testing for 2 years and its performance was compared with a simultaneously operated conventional anaerobic digestion process. The novel process requires two essential modifications, which are ozonation for enhancing the biological degradability of sludge organics and concentrating of solids in the digester through a solid/liquid separation for extension of SRT. These modifications resulted in high VSS degradation efficiency of ca. 88%, as much as 1.3 times of methane production and more than 70% reduction in dewatered sludge cake production. Based on the performance, its energy demands and contribution for minimisation of greenhouse gas emission was evaluated throughout an entire study of sludge treatment and disposal schemes in a municipality for 130,000 p.e. The analysis indicated that the novel process with power generation from biogas would lead to minimal greenhouse gas emission because the extra energy production from the scheme was expected to cover all of the energy demand for the plant operation, and the remarkable reduction in dewatered sludge cake volumes makes it possible to reduce N2O discharge and consumption of fossil fuel in the subsequent sludge incineration processes.     

Minimization of greenhouse gas emission by application of anaerobic digestion process with biogas utilization.

To assess the impact on greenhouse gas emission, different process schemes for municipal sludge treatment were evaluated based on the data from pilot-scale experiments and review of annual operation reports. A modified anaerobic digestion process with partial ozonation of digested sludge to improve biological degradability and the conventional anaerobic digestion process were compared with respect to the energy demand in each process schemes. Options for beneficial use of biogas included (1) application of biogas for power production and (2) recovery as an alternative to natural gas utilization. The analysis indicated that the partial ozonation process with power production led to minimal greenhouse gas emission because the extra energy production from this scheme was expected to cover all of the energy demand for the plant operation. Moreover, the final amount of dewatered sludge cake was only 40% of that expected from the conventional process, this significantly minimizes the potential for greenhouse gas emission in the subsequent sludge incineration processes.     

碱-热法预处理改善污泥厌氧消化性能的试验研究

用传统热化学法(简称同步法)促进污泥水解,将污水厂浓缩污泥预先用NaOH处理24 h,然后再进行热处理(简称碱-热法)。以生物化学甲烷势(BMP)试验后污泥的溶解性化学需氧量(SCOD)去除率和产气量来评价碱-热法预处理对污泥厌氧消化性能的影响。BMP试验结果表明:经碱-热法处理的污泥,SCOD去除率是同步法预处理污泥SCOD去除率的1.06~1.31倍,产气量是同步法预处理污泥产气量的1.08~1.31倍。可见,碱-热法能有效提高污泥中有机物的可生化性,减少厌氧消化后污泥的剩余SCOD浓度,提高生物气产量。