Viewpoint pubs.acs.org/est
Dilemma of Sewage Sludge Treatment and Disposal in China Leiyu Feng, Jingyang Luo, and Yinguang Chen* State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China As a result, commonly used techniques for sludge treatment, such as anaerobic digestion and aerobic composting are ineffective. Anaerobic digestion/aerobic composting and land application have been widely recommended in China as the preferred method for the treatment and disposal of sewage sludge. However, the output from sludge treatment by anaerobic digestion or aerobic composting is of poor quality because of the low organic matter content. In 2013, there were about 2600 sludge treatment plants in China, but only about 60 plants had adopted anaerobic digestion processes and just 10−30 of them were actually operating,4 resulting in wasted infrastructure and treatment facilities. The treated sludge contains large amounts of nutrients, such as N, P, K, and residual organic material, and has the potential to be used as soil conditioner and fertilizer during land application. However, the high concentrations of heavy metals, POPs, and grit in the sludge, mainly from industrial wastewater and rainwater, have greatly limited its use. In the future, when making plans for the construction of wastewater treatment and recycling facilities in China, the separate treatment of municipal wastewater, rainwater, and ewage sludge, the most important byproduct of biological industrial wastewater should be considered to eliminate the wastewater treatment, is considered an important source of secondary pollution in aquatic environments, linked to health problem of sewage sludge treatment and disposal. Even if this problems and even deaths in humans. In 2012, China generated proposal were to be adopted, sludge treatment and disposal more than 68.5 billion metric tonnes of wastewater, and this is would remain a challenge. In China, most residential districts expected to rise to 78.4 billion metric tonnes in 2015.1 The have no separate discharge systems for municipal wastewater amount of sewage sludge would increase accordingly, from 30 and rainwater, and only a few industrial parks have been built million metric tonnes (at a moisture content of 80%) in 2012 with individual wastewater treatment facilities. The constructo 34 million metric tonnes in 2015.2 Historically, over 80% of tion of separate drainage pipeline networks and facilities for the sludge has not been treated and disposed of effectively and industrial wastewater treatment should be prioritized, though it safely, and this poses a great threat to the environment, is a daunting task. particularly because of the ubiquitous use of combined systems The safe treatment and disposal efficiency of sewage sludge for municipal wastewater, industrial wastewater, and rainwater in developed cities of China is expected to be 80%.5 Meanwhile, treatment. Thus, it is extremely important to set up separate there has been disproportionately low investment in sludge drainage systems to improve the efficiency and effectiveness of treatment and disposal (5.6 billion USD/year) compared with sludge treatment and disposal. The proportion of industrial wastewater entering wastewater wastewater treatment (68.8 billion USD/year) in China, unlike treatment plants (WWTPs) in China is often as high as in developed countries where there are approximately equal approximately 35.0%. Treatment of this industrial wastewater levels of investment in sludge disposal and wastewater leads to sewage sludge containing heavy metals such as Zn, Cr, treatment.5 More investment in sludge treatment and disposal and Pb, and persistent organic pollutants (POPs), such as is urgently needed in China. If not, the investment in polycyclic aromatic hydrocarbons (PAHs) and polychlorinated wastewater treatment could be in vain as the pollutants biphenyls (PCBs), seriously limiting options for disposal. For would re-enter the environment through sewage sludge. example, this type of waste cannot be applied to land as soil 3 Overall, China still faces many challenges in solving the conditioner. Also, the organic content of the sewage sludge is problem of sewage sludge treatment and disposal. usually low (less than 50%) because most of the drainage systems, especially in southern China, combine municipal wastewater, and rainwater, resulting in a high proportion of grit Received: February 2, 2015 and other inorganic matter being incorporated into the sludge.
S
© XXXX American Chemical Society
A
DOI: 10.1021/acs.est.5b01455 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
Viewpoint
Environmental Science & Technology
■
AUTHOR INFORMATION
Corresponding Author
*Phone: 86-21-65981263; fax: 86-21-65986313; e-mail:
[email protected]. Funding
Funding for this studywas provided by the National Natural Science Funds for Distinguished Young Scholar (No. 51425802), National Natural Science Foundation of China (Nos. 51108332, 51178324 and 51278354), Fundamental Research Funds for the Central Universities (No. 2013KJ017) and State Science and Technology Support Projects (No. 2012BAC11B04). Notes
The authors declare no competing financial interest.
■
REFERENCES
(1) Ministry of Environmental Protection of the People’s Republic of China. National Report on Environmental Quality of 2012. http:// www.zhb.gov.cn/gkml/hbb/qt/201306/t20130604_253201.htm. (2) Report on Sludge Treatment and Disposal Market in China, 2013. http://zt.h2o-china.com/report/2013/2013wncz_report/index. html. (3) Zhang, G.; Jing, H.; Ren, M. Z.; Zhang, S. K.; Cheng, J.; Yang, Z. R. Emission, mass balance, and distribution characteristics of PCDD/ Fs and heavy metals during cocombustion of sewage sludge and coal in power plants. Environ. Sci. Technol. 2013, 47 (4), 2123−2130. (4) Li, L. Application of anaerobic digestion in sludge disposal: Current situation and trends. China Environ. Protect. Ind. 2013, 8, 57− 59. (5) The State Council. The Twelfth Five-Year Plan of Facility Construction for Wastewater Treatment and Recycle. http://www. gov.cn/zwgk/2012-05/04/content_2129670.htm.
B
DOI: 10.1021/acs.est.5b01455 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
