geneva
Utilization of urban wage sludge: Chine
perspectives
建议英语goroundPurpo Urbanization and industrialization in China has resulted in a dramatic increa in the volume of wastewater and wage sludge produced from wastewater treatment plants. Problems associated with wage sludge have attracted increasing attention from the public and urban planners. How to manage sludge in an economically and environmentally acceptable manner is one of the critical issues that modern societies are facing.
英语男孩名字冯玉Methods Sludge treatment systems consist of thickening, dewatering，and veral different alternative main treatments(anaerobic digestion, aerobic digestion, drying, composting, and incineration). Agricultural application, landfill, and incineration are the principal disposal methods for wage sludge in China. However, wage sludge disposal in the future should focus on resource recovery, reducing environmental impacts and saving economic costs.
Results The reu of biosolids in all scenarios can be environmentally beneficial and cost-effective. Anaerobic digestion followed by land application is the preferable options due to low economic and energy costs and material reu.
6624Conclusion It is necessary to formulate a standard suitable for the utilization of wage sludge in China.
志同道合的英文1 Introduction提供就业机会
In 2008, it is estimated that 57 billion tons of municipal wastewater was discharged in China, 58% of which came from municipal domestic wage,
while the production of municipal wastewater and dewatered wage in China incread approximately 5% per year on average from 1998 to 2009 as shown in Fig.1.Sewage sludge as an inevitable by-product of wastewater treatment process prents a number of environmental concerns. Wastewater treatment process concentrate various pollutants such as heavy metals, organic micro-pollutants, and pathogens into sludge. Sludge disposal can thereby result in the relea of toxins into the environment and subquently into the food chain. On the other hand, it has been estimated that depending on technology choice, approximately 30∼60% of wage treatment plant operating costs are related to sludge treatment activities. Therefore, the management of wage sludge in an economically and environmentally acceptable way is a matter of increasing importance.
high five
Fig. 1 Production of municipal wastewater and dewatered wage sludge in China
An ideal way to solve the issue of sludge waste is to minimize its production in biological wastewater treatment process, rather than rely on post-treatment. When mechanical wastewater treatment is
ud, a diversity of approaches for wage sludge treatment process and end u exists, each with different associated costs and environmental impacts. Strategies on end us of biosolids have traditionally been bad on cost, regulatory, environmental, and public acceptance considerations. In recent years, veral methods have been ud to evaluate their economic and environmental acceptability. Hospido et al considered land application as an acceptable option for anaerobic digested sludge by evaluating environmental and economic costs of three scenarios (land application, incineration, and
pyrolysis of dried sludge), but the environmental impact of construction was ignored. Also little detailed economic analysis information is available for other alternative scenarios. Barber ud a model comparing the environmental impacts and economic costs of different alternative treatment and disposal scenarios. Nevertheless, the transport costs associated with the full range of biosolids management options were not discusd, which may be one of the limiting factors of sludge land application in China. Few investigations have been reported on the environmental and economic impacts of pyrolysis and gasification scenario, partly due to their high cost and scarce application in practice. Therefore, more detailed papers should be investigated for an overall comparison of different treatment and end u of urban wage sludge, to determine which combinations are more sustainable.
guide
There are 1,258 municipal wastewater treatment plants(WWTPs) in China. The method of wage sludge disposal is carried out using four process: 45% of the sludge produced is being utilized in agriculture, 3.5% is being incinerated, 34.5% is landfilled including 3.5% with domestic waste, while 3.5% is ud in some other areas (Fig. 2). There are political and economic incentives to increa the agriculture application of sludge since it contains large amounts of organic matter and nutrients, such as N and P. However, the reduced availability of land, incread public comprehension of pathogen risk, the potential for food chain contamination by heavy metals, and the risk of uncertainty surrounding organic micropollutants act to limit sludge land application. Landfill is also decreasing becau of technology, economic capacity, and new legislation. Incineration due to significant dry solid volume reduction and energy recovery from the sludge can contribute to a sustainable biosolids strategy, but environmental pollution and the cost should be carefully treated. Other disposal options such as pyrolysis, gasification,combustion,and co-combustion of wage sludge with other materials and u as an energy source in the production of cement or building materials have been intensively investigated. The process which can recover energy from wage sludge will probably become the future trends of development.
Fig. 2 Ways of sludge disposal and utilization in China (2010)
Bad on the above considerations, it can be expected that studies for the treatment of wage sludge shall focus on the following aspects: safe handling, resource recovery, and low economic costs. In all the respects, the recovery of sustainable energy from wage sludge will be of obvious importance. Another issue of concern is to reduce toxins in wage sludge before the final treatment and minimize the negative impacts on human and ecosystem health. The aim of this paper is to discuss the current situation and future outlook for wage sludge treatment and disposal and estimate the environmental and economic impacts of various options from wage sludge.
