Since about the 1990s China has achieved remarkable progress in urban sanitation. The country has built very extensive infrastructure for wastewater treatment, with 94.5% treatment coverage in urban areas and legally mandated nation-wide full nutrient removal implemented. However, municipal wastewater treatment plants (WWTPs) in China are still confronted with issues rooted in the unique sewage characteristics. This study compares energy recovery, cost of nutrient removal and sludge production between Chinese municipal WWTPs and those in countries with longer wastewater treatment traditions, and highlights the cause-effect relationships between Chinese sewage characteristics – high inorganic suspended solids (ISS) loads, and low COD and C/N ratio, and municipal WWTP process performance in China. Integrated design and operation guidelines for municipal WWTPs are imperative in relation to the unique sewage characteristics in China. Cost-effective measures and solutions are proposed in the paper, and the potential benefits of improving the sustainability of municipal WWTPs in China are estimated.

Substantial progress has been made providing wastewater service in urban areas in China over the past decades, resulting in essentially complete coverage for wastewater collection and treatment. In spite of rapid progress installing wastewater collection and treatment systems, China continues to be faced with the two principal components of the water crisis, namely, water pollution and water scarcity. In response, governmental policies are leading to investments supporting the rapid development of new technologies and approaches to integrated water/wastewater management. Investments in membrane technology development and manufacturers have led to widespread application of membrane technology and, contrasting with international practice, to the development of a significant indigenous manufacturing and delivery capacity. At the same time, lack of attention to collection systems has resulted in their poor condition leading to wastewater characteristics adversely impacting process performance and resource recovery opportunities. Recent policy actions are leading to correction of this situation. Biosolids management has lagged behind the develop of wastewater treatment capacity and is also adversely impacted by excessive loadings of inorganic materials due to the poor condition of some collection systems. Experience gained through significant investments in biosolids upgrades over the past 10 years has led to the development of four principal biosolids management strategies that are now being implemented. Building on the progress made addressing wastewater treatment needs in urban areas, attention is turning to rural areas where nearly 500 million people live. Two emerging water management paradigms, namely, integrated water management and resource recovery, are being implemented in China through The Concept Wastewater Treatment program and Sponge Cites. Wastewater management in China is progressing from the implementation of basic treatment, to the adoption and development of new technologies, and to the implementation of integrated solutions intended to achieve a broader range of outcomes including improved water quality, resource recovery, and increased livability. The results already being achieved, and to be anticipated in the future, will be of broad interest because of the magnitude of Chinese wastewater treatment, which allows a broad range of options to be evaluated.

China has achieved significant progress on wastewater treatment and aquatic environmental protection. However, leakage (in- and exfiltration) of sewer systems is still an issue. By using the statistical data of water and wastewater in 2016 in China, and the person loads (PLs) of water and wastewater in Singapore, the leakage fractions of hydraulic flow, organic carbon (COD), nitrogen (N) and phosphorus (P) mass loading, and in-sewer COD biological removal in the sewer systems of China (except Hong Kong, Macau and Taiwan), Shanghai, Guangzhou and Beijing were reported for the first time. The fractions of hydraulic flow infiltration (13%, Shanghai and Guangzhou) and exfiltration (39%, China) were calculated. Except Beijing, whose sewer networks are under appropriate management with small leakage fractions, the exfiltration fractions of COD (including in-sewer biological COD removal) ranged from 41% (Shanghai) to 66% (China) and averaged 55%; N ranged from 18% (Shanghai) to 48% (China) and averaged 33%; and P ranged from 23% (Shanghai and Guangzhou) to 44% (China) and averaged 30%. The exfiltrated sewage, COD, N and P not only wastes resources, but also contaminates the aquatic environment (especially groundwater) and contributes to ‘black and odorous water bodies’. In- and exfiltration in the sewer network leads to low influent COD concentration, C/N ratio and high inorganic solids and inert particulate COD concentrations of many municipal wastewater treatment plants (WWTPs) causing high cost for nutrient removal, poor resource recovery, additional reactor/settler volume requirement and other operational problems. Therefore, tackling sewer leakage is of primary importance to today's environment in China. Recommendations for the inspection of sewer systems and the rehabilitation of damaged sewers as well as the development of design and operation guidelines of municipal WWTPs tailored to the specific local sewage characteristics and other conditions are proposed.

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