A novel process for organic acids and nutrient recovery from municipal wastewater sludge.

In this paper, a novel process for organic acids and nutrient recovery from municipal sludge was introduced and evaluated based on laboratory-scale studies. An economical estimation for its practical application was also performed by mass balance in a full-scale plant (Q=158,000 m3 d(-1)). This novel process comprises an upflow sludge blanket-type high performance elutriated acid fermenter (5d of SRT) for organic acids recovery followed by an upflow-type crystallisation (3 h of HRT) reactor using waste lime for nutrient recovery. In the system, the fermenter is characterised by thermophilic (55 degrees C) and alkaline conditions (pH 9), contributing to higher hydrolysis/acidogenesis (0.18 g VFA(COD) g(-1) VSS(COD), 63.3% of VFA(COD)/COD produced, based on sludge characteristics of the rainy season) and pathogen-free stabilised sludge production. It also provides the optimal condition for the following crystallisation reactor. In the process, the waste lime, which is an industrial waste, can be used for pH control and cation (Ca and Mg) sources for crystallisation reaction. A cost estimation for full-scale application demonstrates that this process has economic benefits (about 67 dollars per m3 of wastewater except for the energy expense) even in the rainy season.     

污泥活性炭的制备及其用于重金属废水处理的研究进展

城市污水处理厂在处理污水的同时会产生大量的污泥,其含有大量有机物和有害物,性质不稳定,易腐化,如果处理不当,将会造成严重的环境污染和资源浪费.用城市污水处理厂污泥制备活性炭是20世纪80年代后期出现的一种新型利用途径,因其制备成本低,活性炭用途广泛,可以用于污水处理去除有毒有害物质,具有良好的环境效益和社会效益,引起国内外研究人员的关注.而有毒重金属对环境的严重威胁正逐渐成为全球性问题,活性炭吸附法是一种常用来处理重金属废水的方法.综述了国内外污泥制备活性炭的工艺方法,及在这些制备方法基础上对重金属废水的处理研究.     

Production of thermostable protease enzyme in wastewater sludge using thermophilic bacterial strains isolated from sludge.

The volume of sludge produced annually is very high and poses serious disposal problems. The traditional methods of sludge disposal produce secondary pollutants. Therefore, the alternate or suitable solution is reuse of sludge in an ecofriendly approach. Biotechnology is an interesting tool to add value to the processes involved in wastewater and wastewater sludge disposal/reuse. In this context, a study was carried out on thermophilic bacterial strains that produce thermostable proteases. The bacterial strains were first isolated from municipal wastewater sludge. In contrast to the conventional strains used in industries, like Bacillus sp., the new strains were Gram-Negative type. In semi-synthetic medium, a maximal protease activity of 5.25 IU/ml (International Unit per ml) was obtained at a pH of 8.2 and at a temperature of 60 degrees C, which is higher than the stability temperature of 37 degrees C for a similar protease obtained from the conventional producer Bacillus licheniformis. Moreover, growth and protease activity of the strains were tested in wastewater sludge. It is expected that the complexity of sludge could stimulate/enhance the protease production and their characteristics. In conclusion, reuse of wastewater sludge will help to reduce their quantity as well as the value-added products produced will replace chemical products used in industries.     

城市污泥资源化利用现状及发展探讨

随着城市污泥产量连年增长,污泥处理问题迫在眉睫。由于用地日益紧张和潜在的环境污染问题,传统的处置方法如填埋已经不符合发展要求。作为污水处理厂的伴生产物,污泥含有大量有机物、氮、磷等营养物质,经过适当处理,可以变废为宝。因此,资源化利用是解决污泥问题的主要发展趋势。通过分析国内外城市污泥的处置现状,对污泥资源化技术进行了分类,并就污泥在土地利用、建材利用、能源利用和其他方面的应用进行了详细综述,同时还分析了资源化利用存在的问题,指出污泥资源化利用和发展需要因地制宜、合理开发,需要继续提高工艺水平,推进技术创新,完善政策法规。     

城市达标污水的处置技术

城市污水处理厂达标污水水质相对于地表水环境质量标准而言,仍含有大量的污染物质,排放不当仍然是水体污染源。节水减污的再生水利用是达标污水的主要出路之一。分析了再生水利用尚存在的问题;提出达标污水出路的总体思路;重点讨论了达标污水深度处理,与再生水利用相适应的输配水管网设计,直接排江、排海处置,河口处置,区域或地域通道转移和设计等技术对策与措施。     

Beneficial reuse of precast concrete industry sludge to produce alkaline stabilized biosolids.

The precast concrete industry generates waste called concrete sludge during routine mixer tank washing. It is highly alkaline and hazardous, and typically disposed of by landfilling. This study examined the stabilization of municipal sewage sludge using concrete sludge as an alkaline agent. Sewage sludge was amended with 10 to 40% of concrete sludge by wet weight, and 10 and 20% of lime by dry weight of the sludge mix. Mixes containing 30 and 40% of concrete sludge with 20% lime fulfilled the primary requirements of Category 1 and 2 (Canada) biosolids of maintaining a pH of 12 for at least 72 hours. The heavy metals were below Category 1 regulatory limits. The 40% concrete sludge mix was incubated at 52 degrees C for 12 of the 72 hours to achieve the Category 1 and 2 regulations of less than 1000 fecal coliform/g solids. The nutrient content of the biosolids was 8.2, 10 and 0.6 g/kg of nitrogen, phosphorus and potassium respectively. It can be used as a top soil or augmented with potassium for use as fertilizer. The study demonstrates that concrete sludge waste can be beneficially reused to produce biosolids, providing a long-term sustainable waste management solution for the concrete industry.     

Water reuse for irrigation from waste water treatment plants with seasonal varied operation modes.

Irrigation periods are usually limited to vegetation periods. The quality requirements for treated wastewater for disposal and for reuse are different. The reuse of water for irrigation allows partly the reuse of the wastewater's nutrients (N and P). Outside the irrigation period the water must be treated for disposal, thus nutrient removal is often required in order to avoid detrimental effects on the receiving surface water body. Only wastewater treatment plants with different operation modes for different seasons can realise these requirements. The nitrification is the most sensitive biological process in the aerobic wastewater treatment process. At low water temperatures the nitrifying bacteria need several weeks to re-start full nitrification after periods without NH4-removal. Therefore it is necessary to develop options for waste water treatment plants which allow a fast re-start of the nitrification process. Based on theoretical considerations and computer simulations of the activated sludge treatment process, one possibility for implementing a wastewater treatment plant with different seasonal operation modes is evaluated.     

城市污水污泥处理处置系统的技术经济分析与评价(上)

目前国内许多城市都面临着污泥的处理和处置问题,同时也都在积极地寻求污泥妥善处理处置的途径.在进行污泥处理处置工程的规划、设计和建设中,可能遇到各种各样认识的误区和问题,需要不断地澄清、摸索和总结.结合实际工作中的体会,简要分析了国内主要的污泥处理与处置方法的技术、投资和运行成本等问题.建议城市在进行污泥处理处置规划时,应首先落实最终处置出路,在此基础上摒弃和发展地吸取国外先进的技术、政策和管理经验并与当地的资源相结合,确定能源和资源最优配置的处理处置方法.     

Process performance and change in sludge characteristics during anaerobic digestion of sewage sludge with ozonation.

A new process configuration combining anaerobic digestion with ozonation, and operated at long SRT, was studied with the objective of on-site reduction in sludge quantity and improving biogas recovery. The process performance with respect to solid reduction efficiency and other important process parameters like accumulation of inorganic solids, changes in sludge viscosity and dewatering characteristics were evaluated from the data of long term pilot scale continuous experiments conducted using a mixture of primary and secondary municipal sewage sludge. Due to sludge ozonation and long SRT, high VSS degradation efficiency of approximately 80% was achieved at a reactor solid concentration of 6.5%. A high fraction of inorganic solid (>50%) consisting mainly of acid insoluble and iron compounds was found to accumulate in the reactor. The high inorganic content accumulated in the digested sludge did not, however, contribute to the observed increase in sludge viscosity at high solid concentration. The sludge viscosity was largely found to depend on the organic solid concentration rather than the total solid content. Moreover, higher inorganic content in the digested sludge resulted in better sludge dewaterability. For a quick assessment of the economic feasibility of the new process, an economic index based on the unit cost of digested sludge disposal to unit electric cost is proposed.     

白龙港污水处理厂生物处理污泥产量分析与预测

准确了解城市污水处理厂的污泥产量,不仅对污水处理厂的运行管理有指导意义,也有利于后续污泥的处理与处置。对上海白龙港污水处理厂生物处理工艺污泥产量的设计值、实际运行值进行计算,分析不同污泥产量计算方法的特点。并对重新启用初沉池后污泥产量的变化进行了详细的测算和分析,结果表明,重新启用初沉池后污泥产量比超越初沉运行时有所减少,减轻了后续污泥处置负荷。     

Reuse of wastewater sludge with marine clay as a new resource of construction aggregates.

The disposal of sludge from wastewater treatment presents highly complex problems to any municipality. Most of the sludge disposal methods have varying degrees of environmental impact. Hence, it is necessary to explore potential areas of reuse in order to alleviate sludge disposal problems and to conserve natural resources. Industrial sludge and marine clay are two forms of high-volume wastes. Using these wastes as a resource of raw materials to produce construction aggregates would enable large-scale sludge reuse. The aggregates were produced at various sludge-clay combinations containing 0, 20, 50, 80 and 100% clay contents, respectively. The pelletized aggregates displayed lower particle densities ranged between 1.48 and 2.25 g/cm3, compared to the density of granite at 2.56 g/cm3. Good 28-day concrete compressive strength of 38.5 N/mm2 achieved by the 100% sludge aggregate was comparable to the value of 38.0 N/mm2 achieved of the granite control specimens. The leachate contamination levels from the aggregates after 150 days were found acceptable when used in concrete, indicating insignificant environmental contamination. The heat flow study showed increases in heat flow at the temperatures of 480 degrees C and between 660 degrees C and 900 degrees C, indicating a need for the extension of heating time around these temperatures.     

Aspects of municipal wastewater reclamation and reuse for future water resource shortages in Taiwan.

The Water Resources Agency (WRA), Ministry of Economic Affairs (MOEA) has predicted that the annual water demand in Taiwan will reach approximately 20 billion m3 by 2021. However, the present water supply is only 18 billion m3 per year. This means that an additional 2 billion m3 have to be developed in the next 17 years. The reuse of treated wastewater effluent from municipal wastewater treatment plants could be one target for the development of new water resources. The responsible government departments already have plans to construct public sewerage systems in order to improve the quality of life of the populace and protect the environment. The treated wastewater effluent from such municipal wastewater treatment plants could be a very stable and readily available secondary type of water resource, different from the traditional types of water resources. The major areas where reclaimed municipal wastewater can be used to replace traditional fresh water resources include agricultural and landscape irrigation, street cleaning, toilet flushing, secondary industrial reuse and environmental uses. However, necessary wastewater reclamation and reuse systems have not yet been established. The requirements for their establishment include water reuse guidelines and criteria, the elimination of health risks ensuring safe use, the determination of the wastewater treatment level appropriate for the reuse category, as well as the development and application of management systems reuse. An integrated system for water reuse would be of great benefit to us all by providing more efficient ways to utilise the water resources.     

武汉市污水污泥处理与处置规划介绍

随着城市化进程加快和市政污水系统的完善,污水污泥处理与处置问题越来越突出。首先对武汉市污水污泥处理处置现状进行介绍和分析,然后预测了武汉市2010年和2020年污水污泥量,接着在此基础上确定武汉市污水污泥处理厂布局方案和处理处置工艺,最后针对污泥规划的实施和管理提出建议。     

Towards a complete recycling of phosphorus in wastewater treatment--options in Germany

Global reserves of mineral phosphorus are finite and the recycling of phosphorus from wastewater, a significant sink for phosphorus, can contribute to a more sustainable use. In Germany, Switzerland, and the Netherlands, an increasing percentage of municipal sewage sludge is incinerated and the contained phosphorus is lost. This paper reviews current technologies and shows that a complete phosphorus recovery from wastewater is technically feasible. Depending on the composition of the sewage sludge ash (SSA), there are various options for phosphorus recovery that are presented. Iron-poor SSAs can be used directly as substitute for phosphate rock in the electrothermal phosphorus process. SSAs with low heavy metal contents can be used as fertilizer without prior metal elimination. Ashes not suitable for direct recycling can be processed by thermal processes. Operators of wastewater treatment plants can additionally influence the ash composition via the selection of precipitants and the control of (indirect) dischargers. This way, they can choose the most suitable phosphorus recovery option. For sewage sludge that is co-incinerated in power plants, municipal waste incinerators or cement kilns phosphorus recovery is not possible. The phosphorus is lost forever.     

Optimization of municipal sludge and grease co-digestion using disintegration technologies

Many drivers tend to foster the development of renewable energy production in wastewater treatment plants as many expectations rely upon energy recovery from sewage sludge, for example through biogas use. This paper is focused on the assessment of grease waste (GW) as an adequate substrate for co-digestion with municipal sludge, as it has a methane potential of 479-710 LCH(4)/kg VS, as well as the evaluation of disintegration technologies as a method to optimize the co-digestion process. With this objective three different pre-treatments have been selected for evaluation: thermal hydrolysis, ultrasound and enzymatic treatment. Results have shown that co-digestion processes without pre-treatment had a maximum increment of 128% of the volumetric methane productivity when GW addition was 23% inlet (at 20 days of HRT and with an OLR of 3.0 kg COD/m(3)d), compared with conventional digestion of sewage sludge alone. Concerning the application of the selected disintegration technologies, all pre-treatments showed improvements in terms of methane yield (51.8, 89.5 and 57.6% more for thermal hydrolysis, ultrasound and enzymatic treatment, respectively, compared with non-pretreated wastes), thermal hydrolysis of GW and secondary sludge being the best configuration as it improved the solubilization of the organic matter and the hydrodynamic characteristics of digestates.     

Sustainable sludge management in developing countries.

Worldwide, unsanitary conditions are responsible for more than three million deaths annually. One of the reasons is the low level of sanitation in developing countries. Particularly, sludge from these regions has a high parasite concentration and low heavy metal content even though the available information is limited. Different issues needed to achieve a sustainable sludge management in developing nations are analysed. Based on this analysis some conclusions arise: sludge management plays an important role in sanitation programs by helping reduce health problems and associated risks; investments in sanitation should consider sludge management within the overall projects; the main restriction for reusing sludge is the high microbial concentration, which requires a science-based decision on the treatment process, while heavy metals are generally low; adequate sludge management needs the commitment of those sectors involved in the development and enforcement of the regulations as well as those that are directly related to its generation, treatment, reuse or disposal; current regulations have followed different approaches, based mainly on local conditions, but they favour sludge reuse to fight problems like soil degradation, reduced crop production, and the increased use of inorganic fertilizers. This paper summarises an overview of these issues.     

Experience with phosphorus removal and sludge handling and disposal in Flanders.

The way excess sludge must be disposed of is a key factor in the choice of the appropriate phosphorus removal technique at municipal wastewater treatment plants. In Europe the ongoing trend of tightening the sludge spreading rules called for a serious reduction of its agricultural utilisation and the expansion of the (co-)incineration disposal route, which led to a shift towards more sophisticated sludge handling techniques. This paper illustrates the impact of different sludge handling techniques on the performance of chemical and enhanced biological phosphorus removal at municipal WWTPs. The main conclusion is that although enhanced biological phosphorus removal is particularly sensitive to the problem of return liquors from sludge treatment processes indirect dewatering and anaerobic stabilisation cannot be discarded altogether when considering its implementation.     

利用微型动物进行污泥减量的研究进展

城市污水或工业废水的生物处理会产生大量的剩余污泥,污泥的处理费用往往成为污水处理厂的沉重负担,且不恰当的处理又会造成二次污染。开发新的污泥减量技术有着重大的社会效益和经济效益。根据生态学的原理,微型动物可以通过食物链的捕食关系达到污泥减量的效果,这方面的研究已成为国内外环境专家关注的热点。主要探讨了两段式生物反应器、直接投加微型动物和蚯蚓生态滤池三种技术的研究进展情况,并分析了各自的优缺点。     

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.     

Strategien und Potenziale zur Energieoptimierung bei der Wasserwiederverwendung

The energy and materials derived from treating sewage are becoming increasingly important worldwide and are thus progressively considered resources rather than a disposal problem. This is also apparent in the growing interest in recycling water from municipal wastewater for both non-potable and potable purposes, supplementing the drinking water supply in the latter case. However, the energy consumption of about 0.9–1.8 kWh/m³, required to recycle drinking water, is not insignificant. Due to the lack of national as well as international standardized regulatory specifications for recycled water quality, very different technical solutions for potable water reuse have been deployed worldwide. Therefore, energy-saving measures often can only be applied to internal operational optimizations and the achievable savings are rather limited. Strategies for integrated energy recovery, the increased use of anaerobic biological processes and combined heat and power (CHP) for water recycling are hence very promising. These provide opportunities for internal power provision and therefore options to reduce the specific energy requirements for potable water reuse to well below 1 kWh/m³, despite the necessary treatment processes. However, the greatest potential for energy-efficient water recycling is at the regional planning level. Recycling water is only attractive where local freshwater resources are insufficient or there is a dependency on imported water, and it is the significantly more cost-effective option than the treatment of brackish or sea water.