Enhanced anaerobic digestion of waste-activated sludge by thermal-alkali pretreatment: a pilot-scale study.

The composition of waste-activated sludge (WAS) is complex, containing a large amount of harmful substances, which pose a threat to the environment and human health. The reduction and resource utilization of sludge has become a development demand in sludge treatment and disposal. Based on the technical bottlenecks in the practical application of direct anaerobic digestion technology, this study adopted two different thermal and thermal-alkali hydrolysis technologies to pretreat sludge. A pilot-scale experiment was conducted to investigate the experimental conditions, parameters, and effects of two hydrolysis technologies. This study showed that the optimal hydrolysis temperature was 70 °C, the hydrolysis effect and pH can reach equilibrium with the hydrolysis retention time was 4-8 h, and the optimal alkali concentration range was 0.0125-0.015 kg NaOH/kg dry-sludge. Thermal-alkali combination treatment greatly improved the performance of methane production, the addition of NaOH increased methane yield by 31.2% than that of 70 °C thermal hydrolysis. The average energy consumption is 75 kWh/m3 80% water-content sludge during the experiment. This study provides a better pretreatment strategy for exploring efficient anaerobic digestion treatment technologies suitable for southern characteristic sewage sludge.

Effects of carbonization temperature and time on the characteristics of carbonized sludge.

To investigate the influence of carbonization process parameters on the characteristics of municipal sludge carbonization products, this study selected carbonization temperatures of 300-700 °C and carbonization times of 0.5-1.5 h to carbonize municipal sludge. The results showed that with an increase in temperature and carbonization time, the sludge was carbonized more completely, and the structure and performance characteristics of the sludge changed significantly. Organic matter was continuously cracked, the amorphous nature of the material was reduced, its morphology was transformed into an increasing number of regular crystalline structures, and the content of carbon continued to decrease, from the initial 52.85 to 38.77%, while the content of inorganic species consisting continued to increase. The conductivity was reduced by 87.8%, and the degree of conversion of salt ions into their residual and insoluble states was significant. Natural water absorption in the sludge decreased from 8.13 to 1.29%, and hydrophobicity increased. The dry-basis higher calorific value decreased from 8,703 to 3,574 kJ/kg. Heavy metals were concentrated by a factor of 2-3, but the content of the available state was very low. The results of this study provide important technological support for the selection of suitable carbonization process conditions and for resource utilization.

How does trade policy uncertainty affect green innovation in the USA and China? A nonlinear perspective.

Green innovations are the most critical factor in promoting environmental sustainability worldwide. Trade can speed up the adoption of green innovations by facilitating the transfer of information, skills, and technology. However, trade policy uncertainty can create significant challenges for businesses investing in eco-innovations, leading to increased risk, reduced investment, and slower progress toward sustainable technologies. Recently, a growing number of researchers have shown their interest in finding the factors that can impact green innovations, but none have investigated the influence of trade policy uncertainty on green innovations in the USA and China. In addition, none of the past studies has relied on the nonlinear assumption. This analysis fills these gaps by examining the nonlinear impacts of trade policy uncertainty on eco-innovations in China and the USA over 2000Q1-2021Q4 by employing a nonlinear ARDL model. The finding reveals that a positive shock in trade policy uncertainty results in a decrease in green innovation in the USA and China, while a negative shock in trade policy uncertainty leads to an increase in green innovation in the USA over the long run. The nonlinear models also indicate that a positive shock in trade policy uncertainty harms green innovation in both the USA and China in the short run. The robustness of these results is confirmed by the NQARDL model, which confirms that an upsurge in trade policy uncertainty lowers green innovation in most quantiles in the USA and China in the short and long run. Conversely, negative shocks in trade policy uncertainty stimulate green innovation at most quantiles in both China and the USA, in the short and long run. Thus, policymakers need to consider the potential impact of trade policies on eco-innovations and work to create stable and predictable trade environments that support the growth of renewable technologies and other sustainable solutions.

Exploring the impact of formal and informal finance on green innovation under the lens of carbon neutrality.

In order to reduce environmental deterioration and promote sustainable growth, green innovation-which includes ecologically friendly technology and practices-has become a top priority of policymakers worldwide. This research investigates how formal and informal finance affects green innovation in highly polluted high, middle-, and low-income economies, using data spanning from 2007 to 2021. For analyzing the empirical link between formal finance, informal finance, and green innovation, we have employed the 2SLS and GMM estimation techniques. The primary estimates of the analysis suggest that formal and informal funding methods significantly impact environment-related technologies in high-income and middle- and low-income nations. Moreover, the GDP, carbon emissions, trade openness, human capital, research and development, financial stability, and digital finance are essential factors in promoting environment-related technologies in high-, middle-, and low-income nations, respectively. The policymakers in both groups of countries should foster collaboration between the formal and informal sectors to promote green innovations, which is essential for achieving sustainable development goals.

Corporate social responsibility initiatives and their role in firms' reputation and green economic recovery through organizational trust.

Maintaining operations in the face of crises like COVID-19 is difficult. Using the stakeholder theory, this study examines the impact of corporate social responsibility (CSR) programs targeting company employees. Their social position and the likelihood of a green economic rebound (GER) are evaluated. Evidence shows that employee-focused CSR activities implemented by tourism boost organizational GER by fostering a more trusting work environment for their staff. Management and non-management staff at Chinese Tourism were polled using a non-probabilistic convenience sample and a 5-point Likert scale. Structured equation modeling was used to conduct structural analyses. Employee-focused CSR is a significant predictor of a firm reputation in the Chinese tourism industry. In addition, it is found that trust inside the organization acts as a go-between. The evidence also supports the hypothesis that a company's rising profile triggers GER. This research delves deeply into the connection between employees' perceptions of a company's employee-focused CSR initiatives, that company's reputation in the community, and employees' general enthusiasm for their job, a group that has been understudied until now. The findings are helpful for tourism management because they show them how to employ employee-focused CSR activities to strengthen connections with internal stakeholders while also using that reputation to shift to a greener way of doing business.

Effect and microbial mechanism of pharmaceutical and personal care product exposure on partial nitrification process and nitrous oxide emission.

This study focused on the short- and long-term exposure of pharmaceutical and personal care products (PPCPs) to the partial nitrification process and nitrous oxide emission. The corresponding microbial mechanisms were also explored. The results revealed a concentration-dose effect on the partial nitrification process. Moreover, the PPCP concentration of ≥2 µg/L featured inhibitory effects on the process. The solo effect of PPCP on the partial nitrification process was analyzed through microcosmic experiments, and the results revealed significant variations in PN. A dose-effect relationship existed between the PPCP concentration and N2O emission intensity. After exposure to PPCPs, the N2O emission released during the partial nitrification process was significantly reduced. Different PPCPs featured various effects in mitigating N2O emissions. Low PPCP concentrations led to a reduction in the richness and diversity of microbes, but their community structure remained significantly unchanged. High PPCP concentrations (≥5 µg/L) resulted in increased species richness and diversity, but their microbial community composition was significantly affected. The function prediction and nitrogen metabolic pathway analysis indicated that PPCP exposure led to the inhibition of the ammonia oxidation process. However, all genes encoding denitrification enzymes were upregulated. The microorganisms in the microbial community featured modular structural properties and wide synergistic relationships between genera. This study provides valuable insights into the effect of PPCP exposure on the particle nitrification process and corresponding changes in the microbial community.

Effect and mechanism of perfluorooctanoic acid (PFOA) on anaerobic digestion sludge dewaterability.

Perfluorooctanoic acid (PFOA) as nonbiodegradable organic pollutant, its presence and risks in wastewater treatment system has aroused wide concern. This study investigated the effect and underlying mechanism of PFOA on anaerobic digestion sludge (ADS) dewaterability. Long-term exposure experiments were set up to investigate the effect with various concentration of PFOA dosed. Experimental results suggested that the existence of high concentration PFOA (over 1000 µg/L) could deteriorate ADS dewaterability. The long-term exposure to 100,000 µg/L PFOA of ADS increased specific resistance filtration (SRF) by 81.57%. It was found that PFOA promoted the release of extracellular polymeric substances (EPS), which was strongly associated with sludge dewaterability. The fluorescence analysis revealed that the high PFOA concentration could significantly improve the percentage of protein-like substances and soluble microbial by-product-like content, and then further deteriorated the dewaterability. The FTIR results showed that long-term exposure of PFOA caused loose protein structure in sludge EPS, which led to loose sludge floc structure. The loose sludge floc structure aggravated the deterioration of sludge dewaterability. The solids-water distribution coefficient (Kd) decreased with the increase of initial PFOA concentration. Moreover, PFOA significantly affected microbial community structure. Metabolic function prediction results showed significant decrease of fermentation function exposed to PFOA. This study revealed that the PFOA with high concentration could deteriorated sludge dewaterability, which should be highly concerned.

High nitrous oxide (N2O) greenhouse gas reduction potential of Pseudomonas sp. YR02 under aerobic condition.

Aerobic environments exist widely in wastewater treatment plants (WWTP) and are unfavorable for greenhouse gas nitrous oxide (N2O) reduction. Here, a novel strain Pseudomonas sp. YR02, which can perform N2O reduction under aerobic conditions, was isolated. The successful amplification of four denitrifying genes proved its complete denitrifying ability. The inorganic nitrogen (IN) removal efficiencies (NRE) were >98.0% and intracellular nitrogen and gaseous nitrogen account for 52.6-58.4% and 41.6-47.4% of input nitrogen, respectively. The priority of IN utilization was TAN > NO3--N > NO2--N. The optimal conditions for IN and N2O removal were consistent, except for the C/N ratio, which is 15 and 5 for IN and N2O removal, respectively. The biokinetic constants analysis indicated strain YR02 had high potential to treat high ammonia and dissolved N2O wastewater. Strain YR02 bioaugmentation mitigated 98.7% of N2O emission and improved 32% NRE in WWTP, proving its application potential for N2O mitigation.

Ca-La layered double hydroxide (LDH) for selective and efficient removal of phosphate from wastewater.

Adsorption showed advantages in removing phosphorus (P) at low concentrations. Desirable adsorbents should have sufficiently high adsorption capacity and selectivity. In this study, a Ca-La layered double hydroxide (LDH) was synthesized for the first time by using a simple hydrothermal coprecipitation method for phosphate removal from wastewater. A maximum adsorption capacity of 194.04 mgP/g was achieved, ranking on the top of known LDHs. Adsorption kinetic experiments showed that 0.02 g/L Ca-La LDH could effectively reduce PO43-P from 1.0 to <0.02 mg/L within 30 min. With the copresence of bicarbonate and sulfate at concentrations 17.1 and 35.7 times of that of PO43-P, the Ca-La LDH showed promising selectivity towards phosphate (with a reduction in the adsorption capacity of <13.6%). In addition, four other (Mg-La, Co-La, Ni-La, and Cu-La) LDHs containing different divalent metal ions were synthesized by using the same coprecipitation method. Results showed much higher P adsorption performance of the Ca-La LDH than those LDHs. Field Emission Electron Microscopy (FE-SEM)-Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR), and mesoporous analysis were performed to characterize and compare the adsorption mechanisms of different LDHs. The high adsorption capacity and selectivity of the Ca-La LDH were mainly explained by selective chemical adsorption, ion exchange, and inner sphere complexation.

Improving sludge dewaterability by free nitrous acid and lysozyme pretreatment: Performances and mechanisms.

Reducing the water content of waste activated sludge (WAS) is critical for sludge treatment and disposal in wastewater treatment plants (WWTPs). In this study, a new combined conditioning processes by using lysozyme (LZM) and free nitrous acid (FNA) were proposed and demonstrated to enhance the dewaterability of WAS. The water content of sludge cake dropped from 82.82 % to 68.42 % (1 h FNA treatment + 1 h LZM treatment) and 69.52 % (6 h FNA treatment + 1 h LZM treatment) with the combined FNA and LZM treatment; and the corresponding capillary suction time (CST) reduction efficiency increased 49.29 % (1 h FNA treatment + 1 h LZM treatment) and 52.98 % (6 h FNA treatment + 1 h LZM treatment). A comprehensive investigation conducted in this study revealed the underlying mechanism of dewaterability improvement lies in the transformations of extracellular polymeric substances (EPS). The combined conditioning led to enhanced hydrophobicity in the sludge, as suggested by FTIR protein secondary structure and interfacial free energy. The reduced zeta potential and the potential barrier indicated the reduction of the repulsive force of sludge particles and the bound water content in the conditioned floc. The hydrophobicity, flow permeability and flocculability were enhanced after combined treatment, leading to the release of bound water.

The Effects of the Type of Information Played in Environmentally Themed Short Videos on Social Media on People's Willingness to Protect the Environment.

This study used a 2 × 2 experimental design to explore the effects of message type (non-narrative vs. narrative information) and social media metrics (high vs. low numbers of plays) of low-carbon-themed social media short videos on people's willingness to protect the environment. Subjects completed questionnaires after viewing short videos that contained different message types and social media metrics, and a final sample of 295 cases was included in the data analysis. The study found that, while the type of information (i.e., non-narrative or narrative) of the low-carbon-themed social media short videos had no direct effect on people's willingness to protect the environment, its indirect effects were significant. These indirect effects were achieved through immersion experience and social influence. Subjects who watched narrative videos had a higher level of immersion experience, which in turn was significantly and positively correlated with environmental intention; meanwhile, those who watched non-narrative videos experienced a higher level of social influence, which in turn was significantly and positively correlated with environmental intention. In addition, subjects who viewed high-volume videos experienced a more positive effect on their willingness to protect the environment. This study explored how message design could promote subjects' perceptions and positive attitudes towards environmental protection, with important managerial implications.

Impact of divalent cations on lysozyme-induced solubilisation of waste-activated sludge: Perspectives of extracellular polymeric substances and surface electronegativity.

Lysozyme hydrolysis can accelerate waste-activated sludge (WAS) solubilisation, which can significantly shorten the process and promote the efficiency of anaerobic digestion. This study investigated the impact of divalent cations on lysozyme-induced solubilisation of WAS. The performance of lysozyme pretreatment was dramatically inhibited by Mg2+ and Ca2+. Compared to the control group, the amount of net SCOD, protein, and polysaccharides released to the supernatant were reduced by 36.6%, 44.7%, and 35.8%, respectively, in the presence of divalent cations. The extracellular polymeric substance (EPS) matrix became tightly bound, resulting in fewer proteins and polysaccharides being extracted from loosely-bound EPS (LB-EPS) with divalent cations, which was detrimental to the solubilisation of WAS. Divalent cations decreased the surface electronegativity of sludge particles and prolonged the adsorption of lysozymes by sludge flocs. More than 16.6% of total lysozymes remained in the liquid phase of WAS after 240 min Mg2+ and Ca2+ strengthened the binding among proteins and polysaccharides and promoted the intermolecular cross-linking of polysaccharides. The EPS matrix formed a dense spatial reticular structure that blocked the transfer of lysozymes from the EPS matrix to the pellet. As a result, the lysozymes accumulated in LB-EPS rather than hydrolysing the microorganism's cell wall. This study provides a new perspective on the restriction of WAS pretreatment with lysozymes and optimises the method of lysozyme-induced solubilisation of WAS.

Insights into carbon recovery from excess sludge through enzyme-catalyzing hydrolysis strategy: Environmental benefits and carbon-emission reduction.

This study introduced the excellent improvement of enzyme cocktail (lysozyme and protease) on hydrolysis efficiency and the role of reducing carbon emission as an alternative carbon source. The best dosing method after optimization was to add four parts of lysozyme at 0 h and one part of protease at 1 h. The extracellular proteins and polysaccharides increased by 118% and 64% respectively under the optimal dosing mode. Enzyme cocktails reduced more organic matters and extended the distribution of sludge particles in the small particle size part. The enzymatic-treated sludge could reduce 21.09 kg CO2/t VSS if utilized to replace methanol for denitrification carbon source. Enzyme cocktails did better in enhancing both solubilization and hydrolysis than single enzymes under the optimal method. This study will provide a more integrated and comprehensive system for enzymatic pretreatment and new insight into the enzymatic pretreatment enhancing hydrolysis and reducing carbon emission.

Carbon uptake bioenergetics of PAOs and GAOs in full-scale enhanced biological phosphorus removal systems.

This work analyzed, for the first time, the bioenergetics of PAOs and GAOs in full-scale wastewater treatment plants (WWTPs) for the uptake of different carbon sources. Fifteen samples were collected from five full-scale WWTPs. Predominance of different PAOs, i.e., Ca. Accumulibacter (0.00-0.49%), Tetrasphaera (0.37-3.94%), Microlunatus phosphovorus (0.01-0.18%), etc., and GAOs, i.e., Ca. Competibacter (0.08-5.39%), Defluviicoccus (0.05-5.34%), Micropruina (0.17-1.87%), etc., were shown by 16S rRNA gene amplicon sequencing. Despite the distinct PAO/GAO community compositions in different samples, proton motive force (PMF) was found as the key driving force (up to 90.1%) for the uptake of volatile fatty acids (VFAs, acetate and propionate) and amino acids (glutamate and aspartate) by both GAOs and PAOs at the community level, contrasting the previous understanding that Defluviicoccus have a low demand of PMF for acetate uptake. For the uptake of acetate or propionate, PAOs rarely activated F1, F0- ATPase (< 11.7%) or fumarate reductase (< 5.3%) for PMF generation; whereas, intensive involvements of these two pathways (up to 49.2% and 61.0%, respectively) were observed for GAOs, highlighting a major and community-level difference in their VFA uptake biogenetics in full-scale systems. However, different from VFAs, the uptake of glutamate and aspartate by both PAOs and GAOs commonly involved fumarate reductase and F1, F0-ATPase activities. Apart from these major and community-level differences, high level fine-scale micro-diversity in carbon uptake bioenergetics was observed within PAO and GAO lineages, probably resulting from their versatilities in employing different pathways for reducing power generation. Ca. Accumulibacter and Halomonas seemed to show higher dependency on the reverse operation of F1, F0-ATPase than other PAOs, likely due to the low involvement of glyoxylate shunt pathway. Unlike Tetrasphaera, but similar to Ca. Accumulibacter, Microlunatus phosphovorus took up glutamate and aspartate via the proton/glutamate-aspartate symporter driven by PMF. This feature was testified using a pure culture of Microlunatus phosphovorus stain NM-1. The major difference between PAOs and GAOs highlights the potential to selectively suppress GAOs for community regulation in EBPR systems. The finer-scale carbon uptake bioenergetics of PAOs or GAOs from different lineages benefits in understanding their interactions in community assembly in complex environment.

Medium chain fatty acids production from simple substrate and waste activated sludge with ethanol as the electron donor.

Production of MCFAs (Medium-chain fatty acids) from simple substrate (i.e., ethanol and acetate) and WAS with chain elongation microbiome was investigated in this study. The results showed that rapid production of MCFAs was observed when simple substrate was utilized. 1889 mg/L of caproate and 3434 mg/L of butyrate were achieved after 10 d's reaction. H2 proportion in the headspace could reach as high as 10.1% on day 8 and then declined quickly. However, when WAS was used, the bacterial consortia was not able to hydrolyze WAS efficiently, which resulted in poor MCFAs production performance. Presence of ethanol could improve the hydrolysis process to a limited degree, which resulted in solubilization of a small fraction of protein and carbohydrate. Around 33.8% and 36.9% of the total detected electrons on day 6 in the 50 mM and 100 mM tests were extracted from WAS respectively. Those results indicate that the chain elongation microbial consortia tended to receive electrons form ethanol directly other than the complex WAS.

Microbial profiles associated improving bioelectricity generation from sludge fermentation liquid via microbial fuel cells with adding fruit waste extracts.

This first-attempt study illustrated the microbial cooperative interactions related to bioelectricity generation from the mixture of sludge fermentation liquid (SFL) and fruit waste extracts (FWEs) via microbial fuel cells (MFCs). The optimal output voltages of 0.65 V for SFL-MFCs, 0.51 V for FWEs-MFCs and 0.75 V for mixture-MFCs associated with bioelectricity conversion efficiencies of 1.061, 0.718 and 1.391 kWh/kg COD were reached, respectively. FWEs addition for substrates C/N ratio optimization contributed considerably to increase SFL-fed MFCs performance via triggering a higher microbial diversity, larger relatively abundance of functional genes and microbial synergistic interactions with genera enrichment of Clostridium, Alicycliphilus, Thermomonas, Geobacter, Paludibaculum, Pseudomonas, Taibaiella and Comamonas. Furthermore, a conceptual illustration of co-locating scenario of wastewater treatment plant(s), waste sludge in situ acidogenic fermentation, fruit waste collection/crushing station and MFC plant was proposed for the first time, which provided new thinking for future waste sludge treatment toward maximizing solid reduction and power recovery.

Residual and ecological risk assessment of heavy metals in fly ash from co-combustion of excess sludge and coal.

Co-combustion of municipal excess sludge (ES) and coal provides an alternative method for disposing ES. The present study aims to investigate the residual and ecological risk of heavy metals in fly ash from co-combustion of ES and coal. The total concentration and speciation distribution of heavy metals, characterization of SEM, EDX, XRD and leaching test were carried out to assess the fly ash in this study. The results showed that the total concentrations of Cu, Zn and Mn were higher than others in fly ash, and most heavy metals were concentrated in fine particles. For Cd, Cr and Pb, the percentages of speciation of F4 and F5 were all over 90%, suggesting the relatively lower leaching toxicity. The leaching percent of all heavy metals was lower than 5% by two diluted HNO3 solutions for fly ash. The potential ecological risks increased with the decrease of particle size of fly ash, and Cd accounted for the main fraction for ecological risk despite of lower concentration in comparison to other measured heavy metals.

PIFA-Mediated Dearomatizative Spirocyclization of Phenolic Biarylic Ketones via Oxidation and C-C Bond Cleavage.

The dearomatizing spirocyclization of phenolic biarylic ketones using PhI(OCOCF3)2 as oxidant is presented. The reaction affords various cyclohexadienones through C-C bond cleavage under mild conditions. Mechanistic investigations reveal that an exocyclic enol ether acts as the key intermediate in the transformation.

Deaths of colon neuroendocrine tumors are associated with increasing metastatic lymph nodes and lymph node ratio.

BACKGROUND: Colon neuroendocrine tumors (NETs) are uncommon. Currently, the impact of the number of metastatic lymph nodes (LNs) and lymph node ratio (LNR) on survival has been well investigated in other colon malignancies, but both remain nebulous for patients with colon NETs. METHODS: Surgically resected patients with histologically proven nonmetastatic colon NETs were queried from the Surveillance, Epidemiology, and End Results database between 1988 and 2011. Patients with lymph nodes involved were investigated and categorized into four LNs-based classifications (≤4, >4-10, >10-13, and >13) or three LNR-based subgroups (≤0.51, >0.51-0.71, and >0.71) according to the threshold, determined by Harrell's C statistic. Univariate and multivariate survival analyses were performed by log-rank test and Cox stepwise regression analysis, respectively. RESULTS: Eight hundred fifty-one patients met the inclusion criteria. Among them, higher LNR and LNs classification are associated with a worse prognosis. The 10-year NETs-specific survival rate was 78.3% (74.2-82.6%), 61.3% (52.4-71.7%), 40.8% (20.7-80.7%) for patients in the ≤4, >4-10, and 10-13 LNs groups, respectively. When patients were classified with LNR, the observed 10-year NETs-specific survival rate was 79.9% (74.8-85.5%) for ≤0.51, 57.4% (43.8-75.2%) for >0.51-0.71, and 40.0% (31.0-51.5%) for >0.71. In stratified analysis, higher LNs and LNR groups have worse prognosis only in patients with advanced T stage (T3-T4). Regarding stage migration, the LNR-based system did not show superiority to LNs-based classification. CONCLUSIONS: Current TNM staging classification could be improved by considering the count of metastatic nodes and LNR instead of a simple record of lymph node status (N1 or N0) for colon NETs.

Enhanced deodorization and sludge reduction in situ by a humus soil cooperated anaerobic/anoxic/oxic (A2O) wastewater treatment system.

Simultaneous sludge reduction and malodor abatement in humus soil cooperated an anaerobic/anoxic/oxic (A2O) wastewater treatment were investigated in this study. The HSR-A2O was composed of a humus soil reactor (HSR) and a conventional A2O (designated as C-A2O).The results showed that adding HSR did not deteriorate the chemical oxygen demand (COD) removal, while total phosphorus (TP) removal efficiency in HSR-A2O was improved by 18 % in comparison with that in the C-A2O. Both processes had good performance on total nitrogen (TN) removal, and there was no significant difference between them (76.8 and 77.1 %, respectively). However, NH4 (+)-N and NO3 (-)-N were reduced to 0.3 and 6.7 mg/L in HSR-A2O compared to 1.5 and 4.5 mg/L. Moreover, adding HSR induced the sludge reduction, and the sludge production rate was lower than that in the C-A2O. The observed sludge yield was estimated to be 0.32 kg MLSS/day in HSR-A2O, which represent a 33.5 % reduction compared to a C-A2O process. Activated sludge underwent humification and produced more humic acid in HSR-A2O, which is beneficial to sludge reduction. Odor abatement was achieved in HSR-A2O, ammonium (NH3), and sulfuretted hydrogen (H2S) emission decreased from 1.34 and 1.33 to 0.06 mg/m(3), 0.025 mg/m(3) in anaerobic area, with the corresponding reduction efficiency of 95.5 and 98.1 %. Microbial community analysis revealed that the relevant microorganism enrichment explained the reduction effect of humus soil on NH3 and H2S emission. The whole study demonstrated that humus soil enhanced odor abatement and sludge reduction in situ.