Ministry of Housing and Urban-Rural Development

This study statistically reported the current state of sludge treatment/disposal in China from the aspects of sources, technical routes, geographical distribution, and development by using observational data after 1978. By the end of 2019, 5476 municipal wastewater treatment plants were operating in China, leading to an annual sludge productivity of 39.04 million tons (80% water content). Overall, 29.3% of the sludge in China was disposed via land application, followed by incineration (26.7%) and sanitary landfills (20.1%). Incineration, compost, thermal hydrolysis and anerobic digestion were the mainstream technologies for sludge treatment in China, with capacities of 27,122, 11,250, 8342 and 6944 t/d in 2019, respectively. Incineration and drying were preferentially constructed in East China. In contrast, sludge compost was most frequently used in Northeast China (46.5%), East China (22.4%) and Central China (12.8%), while anaerobic digestion in East China, North China and Central China. The capacities of sludge facilities exhibited a sharp increase in 2009–2019, with an overall greenhouse gas emissions in China in 2019 reached 108.18 × 108 kg CO2-equivaient emissions, and the four main technical routes contributed as: incineration (45.11%) > sanitary landfills (23.04%) > land utilization (17.64%) > building materials (14.21%). Challenges and existing problems of sludge disposal in China, including high CO2 emissions, unbalanced regional development, low stabilization and land utilization levels, were discussed. Finally, suggestions regarding potential technical and administrative measures in China, and sustainable sludge management for developing countries, were also given.

Sewage sludge biochars were obtained at different pyrolysis temperatures from 300°C to 900°C and their macro- and microscale properties were analyzed. The biochar's plant-available nutrients and humus-like substances in the water-extractable phase and fixed nutrients in the solid fraction were evaluated for their potential agronomic implications. FT-IR, Raman, XRD, XPS, and SEM techniques were used to investigate the chemical structure, functional groups, and microcrystal structure on the surface of the biochar. The results revealed minor chemical changes and dramatic mass loss in the biochar obtained at 300-500°C, whereas significant chemical changes in the biochar were obtained at 600-900°C. The concentrations of plant-available nutrients as well as fulvic- and humic-acid-like materials decreased in the biochar samples obtained at higher temperatures. These results implied that the biochar samples pyrolyzed at 300-500°C could be a direct nutrient source and used to neutralize alkaline soil. The surface area and porosity of the biochar samples increased with temperature, which increased their adsorption capacity. Rearrangement occurred at higher temperature 600-900°C, resulting in the biochar becoming increasingly polyaromatic and its graphite-like carbon becoming organized.

Chemical oxygen demand (COD) is a critical analytical parameter for water quality assessment. COD represents the degree of organic pollution in water bodies. However, the standard analytical methods for COD are time-consuming and possess low oxidation efficiency, chloride interference, and severe secondary pollution. Works performed during the last two decades have resulted in several technologies, including modified standard methods (e.g., microwave-assisted method) and new technologies or methods (e.g., electro- and photo-oxidative methods based on advanced oxidation processes) that are less time-consuming, environment friendly, and more reliable. This review is devoted in analyzing the technical features of the principal methods described in the literature to compare their performances (i.e., measuring window, reliability, and robustness) and identify the advantages and disadvantages of each method.

China has suffered frequent source water contamination accidents in the past decade, which has resulted in severe consequences to the water supply of millions of residents. The origins of typical cases of contamination are discussed in this paper as well as the emergency response to these accidents. In general, excessive pursuit of rapid industrialization and the unreasonable location of factories are responsible for the increasing frequency of accidental pollution events. Moreover, insufficient attention to environmental protection and rudimentary emergency response capability has exacerbated the consequences of such accidents. These environmental accidents triggered or accelerated the promulgation of stricter environmental protection policy and the shift from economic development mode to a more sustainable direction, which should be regarded as the turning point of environmental protection in China. To guarantee water security, China is trying to establish a rapid and effective emergency response framework, build up the capability of early accident detection, and develop efficient technologies to remove contaminants from water.

Carbon chain elongation means the conversion of short-chain volatile fatty acids to medium-chain carboxylates, such as n -caproate and n -caprylate with electron donors under anaerobic condition. This bio-reaction can both expand the resource of valuable biochemicals and broaden the utilization of low-grade organic residues in a sustainable biorefinery context. Clostridium kluyveri is conventionally considered model microbe for carbon chain elongation which uses the reverse β-oxidation pathway. However, little is known about the detailed microbial structure and function of other abundant microorganism in a mixed culture (or open culture) of chain elongation. We conducted the comparative metagenomic and metatranscriptomic analysis of a chain elongation microbiome to throw light on the underlying functional microbes and alternative pathways.

The addition of various amounts of biochar to anaerobic digestion of food wastes at different ratios of inoculum to substrate (ISR) was investigated to evaluate the effect of biochar as a functional additive and to optimize the additive dosage of biochar. The biochar treatments at ISR 2, 1, and 0.8 shortened the lag phase of digestion by -20.0%-10.9%, 43.3%-54.4%, and 36.3%-54.0%, and raised the maximum methane production rate by 100%-275%, 100%-133.3%, and 33.3%-100%, respectively, compared to control without biochar. Biochar also enhanced the degradation rate of dissolved organics and volatile fatty acids. Furthermore, the amount of biochar with best effectiveness at ISR = 2, 1, and 0.8 was 2.5, 0.625, and 0.5 g g(-1)-waste, respectively. Therefore, the effectiveness of biochar depended on the additive amount of biochar and at the same time the inoculum amount, implying a complementary role of abiotic biochar to biotic inoculum.

To improve land use efficiency, urban renewal must also consider urban microclimates and heat islands. Existing research has depended on manual interpretation of high-resolution optical satellite imagery to resolve land surface temperature (LST) changes caused by urban renewal; however, the acquired ground time series data tend to be uneven and unique to specific frameworks. The objective of this study was to establish a more general framework to study LST changes caused by urban renewal using multi-source remote sensing data. Specifically, urban renewal areas during 2007–2017 were obtained by integrating Landsat and yearly Phased Array type L-band Synthetic Aperture Radar (PALSAR) images, and LST was retrieved from Landsat thermal infrared data using the generalized single-channel algorithm. Our results showed that urban renewal land (URL) area accounted for 1.88% of urban land area. Relative LST between URL and general urban land (GUL) of Liwan, Yuexiu, Haizhu, and Tianhe districts dropped by 0.88, 0.42, 0.43, and 0.10 K, respectively, whereas those of Baiyun, Huangpu, Panyu, and Luogang districts presented opposite characteristics, with a rise in the LST of 0.98, 1.03, 1.63, and 2.11 K, respectively. These results are attributable to population density, building density, and landscape pattern changes during the urban renewal process.

Transition-metal oxide (MxOy)-based persulfate (PDS) activation processes have demonstrated enormous potential for pollutant degradation in water purification. However, the mechanistic insight of PDS activation by a MxOy catalyst concerning the mediate role of the organic substrate remains obscure. Here, we demonstrated that the in situ-formed phenoxyl radical on the CuO surface can trigger efficient persulfate activation for phenol degradation. The formation of the phenoxyl radical was an inner-sphere process, which involved the successive steps of chemisorption through surface hydroxyl group substitution and the subsequent spontaneous electron transfer reaction from adsorbed phenol to CuO. The organic substrate phenol can be oxidized by the PDS molecule and surface-bound SO4•– through the nonradical and free-radical pathways, respectively. Such a unique “half-radical” mechanism resulted in an extraordinarily high PDS utilization efficiency of 188.9%. More importantly, a general rule for phenoxyl radical formation was concluded; it can be formed in the cases of organic substrates with a Hammett constant σ+ lower than −0.02 and metal ion of a 3d subshell between half-filled and fully filled. This study clarifies the mediate role of the organic substrate for interfacial PDS activation on MxOy and also gives new insights into the rational design of a highly efficient MxOy catalyst for selective phenolic/aniline pollutant degradation in wastewater.

A preliminary assessment of conditions for the industrial manufacture of a new cementitious system based on clinker-calcined clay and limestone, developed by the authors, referred as “low carbon cement” is presented. The new cement enables the substitution of more than 50% of the mass of clinker without compromising performance. The paper presents the follow-up of an industrial trial carried out in Cuba to produce 130 tonnes of the new cement at a cement plant. The new material proved to fulfill national standards in applications such as the manufacture of hollow concrete blocks and precast concrete. No major differences either in the rheological or mechanical properties were found when compared with Portland cement. Environmental assessment of the ternary cement was made, which included comparison with other blended cements produced industrially in Cuba. The new cement has proven to contribute to the reduction of above 30% of carbon emissions on cement manufacture.

The Chinese High-resolution Earth Observation System (CHEOS) program has successfully launched 7 civilian satellites since 2010. These satellites are named by Gaofen (meaning high resolution in Chinese, hereafter noted as GF). To combine the advantages of high temporal and comparably high spatial resolution, diverse sensors are deployed to each satellite. GF-1 and GF-6 carry both high-resolution cameras (2 m resolution panchromatic and 8 m resolution multispectral camera), providing high spatial imaging for land use monitoring; GF-3 is equipped with a C-band multipolarization synthetic aperture radar with a spatial resolution of up to 1 meter, mostly monitoring marine targets; GF-5 carried 6 sensors including hyperspectral camera and directional polarization camera, dedicated to environmental remote sensing and climate research, such as aerosol, clouds, and greenhouse gas monitoring; and GF-7 laser altimeter system payload enables a three-dimensional surveying and mapping of natural resource and land surveying, facilitating the accumulation of basic geographic information. This study provides an overview of GF civilian series satellites, especially their missions, sensors, and applications.

Plastics are used extensively and provide great convenience in daily life. However, their stable and nonbiodegradable nature incurs challenging threats to the environment and ecosystems. It is essential that a sustainable method for plastic treatment and utilization be developed. We used low-density polyethylene (LDPE) as a precursor to synthesize a hierarchical porous carbon (HPC) through autogenic pressure carbonization followed by potassium hydroxide (KOH) activation. The noncatalytic carbonization in a closed system obtained 45% carbon residues from LDPE, which would not yield any carbon residues under normal pressure. The following KOH activation developed hierarchical porous structures in the carbon materials, which can be controlled by KOH dosage. The mechanism of carbonization and activation was proposed considering the nanostructure of carbon materials. The obtained HPC exhibited a micrometer-scale carbon sphere morphology with hierarchical pores, a large specific surface area of 3059 m2 g–1, and abundant surface functional groups. By acting as an electrode material for supercapacitors, the HPC displayed excellent electrochemical performance with a specific capacitance of 355 F g–1 at a current density of 0.2 A g–1 in 6 M KOH electrolyte, a high energy density of 9.81 W h kg–1 at a power density of 450 W kg–1, and an outstanding cycling stability. This research develops a sustainable way for plastic waste utilization and a green approach for HPC synthesis.

BACKGROUND: The recalcitrant cell walls of microalgae may limit their digestibility for bioenergy production. Considering that cellulose contributes to the cell wall recalcitrance of the microalgae Chlorella vulgaris, this study investigated bioaugmentation with a cellulolytic and hydrogenogenic bacterium, Clostridium thermocellum, at different inoculum ratios as a possible method to improve CH4 and H2 production of microalgae. RESULTS: Methane production was found to increase by 17?~?24% with the addition of C. thermocellum, as a result of enhanced cell disruption and excess hydrogen production. Furthermore, addition of C. thermocellum enhanced the bacterial diversity and quantities, leading to higher fermentation efficiency. A two-step process of addition of C. thermocellum first and methanogenic sludge subsequently could recover both hydrogen and methane, with a 9.4% increase in bioenergy yield, when compared with the one-step process of simultaneous addition of C. thermocellum and methanogenic sludge. The fluorescence peaks of excitation-emission matrix spectra associated with chlorophyll can serve as biomarkers for algal cell degradation. CONCLUSIONS: Bioaugmentation with C. thermocellum improved the degradation of C. vulgaris biomass, producing higher levels of methane and hydrogen. The two-step process, with methanogenic inoculum added after the hydrogen production reached saturation, was found to be an energy-efficiency method for hydrogen and methane production.

Traditional Ecological Knowledge (TEK) is one of the components of the Globally Important Agricultural Heritage Systems (GIAHS), which are good examples of evolutionary adapted socio-ecosystems in human history. The Hani Rice Terraces System, located in China’s southwestern Yunnan Province, is a living example of GIAHS. The Hani Rice Terraces system has existed for more than one thousand years, following TEK related to cultivation and natural resources management, which was collected and practiced continually. Over this long time period, TEK has enabled the Hani people to manage their terraces and other natural resources in a sustainable way. This paper concentrates on the TEK transferring in the current Hani community, taking a small village, Mitian, as an example. Grouping the interviewees into three different age groups (young group, 0–30 years old; middle-age group, 31–50 years old; old group > 50 years old), we investigated their understanding and participation in 13 items of TEK in relation to rice cultivation and water utilization. The items of TEK were divided into four categories, namely “Festivals”, “Beliefs”, “Folk Songs”, and “Water Management”. From the data collected, it was learned that all the items of TEK are well known, but not necessarily practiced. Age and gender have significant influences on farmers’ understanding and participation in TEK. Our analysis suggested that both the knowledge and the practice showed declining trends from the older to the younger age group. Men and women behave differently in practices. In general, it is shown that TEK is declining in the Hani villages which will affect the rice terrace system in ways that are yet unknown. It is likely that a blended TEK, with old and new knowledge and practices, will emerge to sustain the upland rice terrace systems of Yunnan.

This study aimed at producing C6–C8 medium-chain carboxylates (MCCAs) directly from gaseous CO using mixed culture. The yield and C2–C8 product composition were investigated when CO was continuously fed with gradually increasing partial pressure. The maximal concentrations of n-caproate, n-heptylate, and n-caprylate were 1.892, 1.635, and 1.033 mmol L−1, which were achieved at the maximal production rates of 0.276, 0.442, and 0.112 mmol L−1 day−1, respectively. Microbial analysis revealed that long-term acclimation and high CO partial pressure were important to establish a CO-tolerant and CO-utilizing chain-elongating microbiome, rich in Acinetobacter, Alcaligenes, and Rhodobacteraceae and capable of forming MCCAs solely from CO. These results demonstrated that carboxylate and syngas platform could be integrated in a shared growth vessel, and could be a promising one-step technique to convert gaseous syngas to preferable liquid biochemicals, thereby avoiding the necessity to coordinate syngas fermentation to short-chain carboxylates and short-to-medium-chain elongation. Thus, this method could provide an alternative solution for the utilization of waste-derived syngas and expand the resource of promising biofuels.

The northern part of Lantau Island in Hong Kong is undergoing very rapid development following completion of the Hong Kong International Airport at Chek Lap Kok on the island. This development is adjacent to a range of steeply sloping hills that experience levels of annual rainfall in the range of 2000–2400 mm. Rainfall-induced landslides on this steeply sloping natural terrain are therefore potential hazards to property developments downslope. The objective of this study is to characterize the initiation process and the subsequent travel distance of the landslides resulting from recent rainstorms, by integrating aerial photogrammetry with GIS. These landslides, which occurred during the 18 July 1992 and 4–5 November 1993 rainstorms, were interpreted from sequential aerial photographs. Data on these landslides were collected to form a landslide database. Such data, together with information on geology, slope gradient, elevation, slope aspect, slope shape, and vegetation cover were entered into a Geographical Information System (GIS), to determine the geologic and geomorphologic characteristics of the landslide source and to estimate the travel distance of landslide debris. It is demonstrated that this integrated approach of GIS and aerial photogrammetry could serve as an effective means of landslide characterization.

The spatial structure of Beijing has changed dramatically since the reforms of the late 1970s. It is not clear, however, whether these changes have been sufficient to transform the city’s monocentric spatial structure into a polycentric one. This paper uses 2010 enterprise registered data to investigate the spatial distribution of employment in Beijing. Using a customized grid to increase the spatial resolution of our results, we explore the city’s employment density distribution and investigate potential employment subcenters. This leads to several findings. First, Beijing still has strong monocentric characteristics; second, the city has a very large employment center rather than a small central business district; third, five subcenters are identified, including four in the suburbs; and fourth, a polycentric model that includes these subcenters possesses more explanatory power than a simple monocentric model, but by only four percentage. We conclude that the spatial structure of Beijing is still quite monocentric, but may be in transition to a polycentric pattern.

Abstract The effects of humic acid (HA) and fulvic acid (FA) on Cu 2+ adsorption on biochar were investigated, with mechanisms confirmed by excitation-emission matrix spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy. HA loading enhanced Cu 2+ adsorption on biochar, with the maximum enhancement of 55.0% occurring at an HA loading of 100 mg-C/L. The adsorbed HA introduced many additional functional groups to biochar, thus enhancing Cu 2+ adsorption, which decreased at HA concentrations >100 mg-C/L due to self-association of HA at high loading concentrations. In contrast, FA loading caused no enhancement on Cu 2+ adsorption on biochar. FA was adsorbed through H-bonding with the functional groups of biochar, which set up a competition with Cu 2+ for adsorption on biochar. The functional groups occupied by adsorbed FA were offset by the newly introduced functional groups of FA, thus there was no net increase in the amount of Cu 2+ adsorption upon FA loading. These findings imply that, because of the enhanced adsorption of HA-loaded biochar, the amount of Cu 2+ immobilized would increase by 28.2% for mature compost and 31.9% for fresh compost if there exist interaction between biochar and HA compared with the amounts immobilized by non-interactive HA and biochar.

Land surface temperature (LST) is a critical parameter of surface energy fluxes and has become the focus of numerous studies. LST downscaling is an effective technique for supplementing the limitations of the coarse-resolution LST data. However, the relationship between LST and other land surface parameters tends to be nonlinear and spatially nonstationary, due to spatial heterogeneity. Nonlinearity and spatial nonstationarity have not been considered simultaneously in previous studies. To address this issue, we propose a multi-factor geographically weighted machine learning (MFGWML) algorithm. MFGWML utilizes three excellent machine learning (ML) algorithms, namely extreme gradient boosting (XGBoost), multivariate adaptive regression splines (MARS), and Bayesian ridge regression (BRR), as base learners to capture the nonlinear relationships. MFGWML uses geographically weighted regression (GWR), which allows for spatial nonstationarity, to fuse the three base learners’ predictions. This paper downscales the 30 m LST data retrieved from Landsat 8 images to 10 m LST data mainly based on Sentinel-2A images. The results show that MFGWML outperforms two classic algorithms, namely thermal image sharpening (TsHARP) and the high-resolution urban thermal sharpener (HUTS). We conclude that MFGWML combines the advantages of multiple regression, ML, and GWR, to capture the local heterogeneity and obtain reliable and robust downscaled LST data.

Land marketization and housing commodification have stimulated inner-city restructuring and urban expansion in China and have also induced a large amount of population displacement. Affordable housing, as part of compensation, tends to be the most common relocation housing for displaced households. It is allocated through two approaches: in-kind compensation and monetary compensation. Local government provides in-kind compensation to displaced households in the form of affordable housing, as direct compensation for demolished houses, and gives priority to those who have received monetary compensation to enable them to purchase affordable housing at a discount from the market price. The process of negotiation between local government and displaced households is complicated. As a result, uneven compensation occurs in terms of compensation approaches, as well as in how much displaced households are paid for similar new affordable houses. This study conducts a detailed analysis of the uneven displacement compensation and relocation process. It uses residential surveys conducted in Nanjing to examine uneven compensation along two dimensions: compensation approaches and the purchasing discount on new, compensated affordable housing.

Urban Land Use/Land Cover (LULC) information is essential for urban and environmental management. It is, however, very difficult to automatically extract detailed urban LULC information from remote sensing imagery, especially for a large urban area. Medium resolution imagery, such as Landsat Thematic Mapper (TM) data, cannot uncover detailed LULC information. Further, very high resolution (VHR) satellite imagery, such as IKONOS and QuickBird data, can only be applied to a small area, largely due to the data unavailability and high computation cost. As a result, little research has been conducted to extract detailed urban LULC information for a large urban area. This study, therefore, developed a three-layer classification scheme for deriving detailedurban LULC information by integrating newly launched Chinese GF-1 (medium resolution) and GF-2 (very high resolution) satellite imagery and synthetically incorporating geometry, texture, and spectral information through multi-resolution image segmentation and object-based image classification (OBIA). Homogeneous urban LULC types such as water bodies or large areas of vegetation could be derived from GF-1 imagery with 16 m and 8 m spatial resolutions, while heterogeneous urban LULC types such as industrial buildings, residential buildings, and roads could be extracted from GF-2 imagery with 3.2 m and 0.8 m spatial resolutions. The multi-resolution segmentation method and a random forest algorithm were employed to perform image segmentation and object-based image classification, respectively. An analysis of the results suggests an overall accuracy of 0.89 and 0.87 were achieved for the second and third level urban LULC classification maps, respectively. Therefore, the three-layer classification scheme has the potential to derive high accuracy urban LULC information through integrating medium and high-resolution remote sensing imagery.