The role of microstructure of extracellular proteins in dewaterability of alkaline pretreatment sludge during bioleaching.

Alkaline pre-treatment is known to enhance the acid production efficiency of sludge but adversely affects its dewatering performance. In this study, the improvement of sludge dewaterability by a novel bioleaching system with inoculating domesticated acidified sludge (AS) and its underlying mechanism were investigated. The results showed that although the addition of Fe2+ and the reduction of pH improved the dewatering performance of sludge, their effects were inferior to that of AS + Fe. The addition of AS and Fe2+ significantly reduced the specific resistance to filtration and capillary suction time of the sludge by 98.6 % and 95.5 %, respectively. This improvement in dewatering performance was achieved through the combined actions of bio-acidification, bio-oxidation, and bio-flocculation. Remarkably, under alkaline pH, microorganisms in AS remained active, leading to the formation of iron-based bioflocculants, along with a rapid pH decrease. These bioflocculants, in combination with protein (PN) in tightly bound extracellular polymeric substances (TB-EPS) through amide bonding, transformed TB-EPS from extractable to non-extractable form, reducing PN content from 12.1 mg g-1DS to 5.09 mg g-1DS and altering the protein's secondary structure. Consequently, the gel-like TB-EPS matrix effectively broke down, releasing cellular water and significantly enhancing sludge dewaterability.

Enhancement of sludge dewaterability by repeated inoculation of acidified sludge: Extracellular polymeric substances molecular structure and microbial community succession.

Improving the dewatering performance of sewage sludge is of great scientific and engineering significance in the context of accelerated urbanization and increasingly strict environmental regulations. Acidified sludge (AS) can improve sludge dewatering performance, but the dewatering effect of repeated inoculation is unclear. The effects of long-term repeated inoculation of AS on the sludge dewaterability were investigated. The molecular structure and microbial community succession of extracellular polymeric substances (EPS) are emphasized. The results revealed that increasing the inoculation ratio of AS reduced the pH, absolute value of sludge zeta potential, and sludge particle size, and the decreasing trend was more evident with prolonging treatment time. Under the conditions of 30% and 50% AS inoculation, the dewatering performance of the sludge was significantly improved (p < 0.05). Compared with the raw sludge, the specific resistance of filtration (SRF) and capillary suction time of 30% inoculation were reduced by 64.3% and 50.1% after 30 cycles, respectively. Excluding loosely bound (LB)-EPS, soluble (S)-EPS and tightly bound (TB)-EPS exhibited a visible decrease, the protein in TB-EPS was significantly related to sludge dewaterability (p < 0.05). The fluorescent components of aromatic protein and fulvic acid-like substances in TB-EPS were significantly associated with SRF, with a correlation coefficient 0.99 (p < 0.05). Both the increase in the percentages of random coil and decrease in α-helix in TB-EPS contributed to improving dewaterability. Increasing Firmicutes and decreasing Chloroflexi levels improved the sludge dewatering capacity. Repeated inoculation did not disrupt the dewatering effect of AS rather increased the feasibility of the engineering application of AS. Considering the dewatering performance and cost synthetically, 30% AS inoculated ratio is feasible for practical applications.

Sludge disintegration and phosphorus migration in anaerobic fermentation of waste activated sludge by the addition of EDTA-2Na.

The effects of the addition of EDTA-2Na on sludge disintegration and phosphorus (P) migration during anaerobic fermentation (AF) of waste activated sludge (WAS) are investigated. The efficiency of sludge disintegration was positively correlated with the dose of EDTA-2Na from 0.5-2.0 g/g SS, and an enormous quantity of P was liberated into the aqueous phase, accompanied by sludge disintegration. The proper dose of EDTA-2Na for P release from WAS was 1.5 g/g SS, with an orthophosphate concentration of 394.72 mg/L. P release was more consistent with the pseudo second-order kinetic model. The migration of P species during AF with EDTA-2Na addition was also studied. Orthophosphate was the main species in both of the liquid phase and the loosely bound extracellular polymeric substances (EPS), but organic P (OP) was much more abundant in tightly bound EPS. Inorganic P (IP) was the dominant P speciation in the solid and was mainly distributed in the fraction of non-apatite IP, which accounted for more than 62.8% of IP in the presence of EDTA-2Na. In addition, both IP and OP in the solid contributed to the accumulation of P and the former was outperformed. Furthermore, the increased total dissolved P mainly came from cells. However, the fermented sludge tended to be smaller and to have low compressibility, which is detrimental to its further treatment.

Synergistic effect of yeast integrated with alkyl polyglucose for short-chain fatty acids production from sludge anaerobic fermentation.

An efficient strategy for short-chain fatty acid (SCFA) production from sludge anaerobic fermentation was proposed with the combination of yeast and alkyl polyglucose (APG). It revealed that the synergetic effect of yeast and APG could boost the SCFA concentration to the maximum value of 2800.34 mg COD/L within 9 days at 0.20 g/g suspended solids (SS) yeast and 0.20 g/g SS APG, which was significantly higher than that of its counterparts. Interestingly, the sludge solubilization, the biodegradability of fermentation substrate, as well as the acidification of hydrolyzed products, was evidently improved in the coexistence of APG and yeast. The activities of hydrolytic enzymes and acetate kinase were also stimulated, whereas the coenzyme F420 was inhibited. The synergetic effect of yeast and APG used in this work enriches the study of carbon resource recovery from sludge anaerobic fermentation.

Effect of potassium persulphate addition on sludge disintegration of a mesophilic anaerobic fermentation system.

Persulphates, an advanced oxidation process, has been recently used as an alternative pretreatment method to enhance short-chain fatty acids (SCFAs) yield from waste-activated sludge (WAS) anaerobic fermentation (AF). But so far, the effects of peroxydisulphate (PDS) dosages on mesophilic anaerobic fermentation are still not studied fully. Herein, we explored the influences of potassium PDS addition on mesophilic AF of WAS. Notably, the addition of PDS could drastically accelerate WAS solubilization and hydrolysis, which was proportional to the amount of PDS. The maximal total SCFAs yield of 249.14 mg chemical oxygen demand/L was obtained with 120 mg PDS/g suspended solids addition at 6 days of AF, which was 2.2-fold that of the control one. Tightly bound extracellular polymeric substances (EPSs) were transformed into loosely bound EPS and dissolved organic matters, and aromatic proteins and humic-like substances of EPSs were disintegrated, which were caused by the devastating effects of PDS treatments on EPSs disruption. The intracellular constituents of microbial cells in the sludge were released accordingly. As a result, there was release of soluble substrates derived from the disintegration of both EPSs and cells, the amounts of which were proportional to the dose of PDS. Moreover, microbial diversity and richness were both decreased in the presence of PDS, and the relative abundance of phyla Actinobacteria increased with the increase of the PDS dosage. In addition, the stability of sludge flocs was destroyed in the presence of PDS, the distribution of particle size tended to be small and dispersive, and dewaterability of the sludge was deteriorated.

Combined addition of biochar and garbage enzyme improving the humification and succession of fungal community during sewage sludge composting.

The influences of combination of garbage enzyme and biochar on total organic carbon (TOC) degradation, humification and the fungal succession during sewage sludge (SS) composting were established. Results showed that the GE and BC + GE treatments significantly increased the enzyme activity of fluorescein diacetate hydrolase (FDA) and increased the TOC degradation rate by 9.8% and 21.9% relative to control. The excitation-emission matrix (EEM) combined with the percentage fluorescence response (Pi, n) also proved that the combination of BC and GE promoted fulvic acid-like and humic-like substances production, and thus increased humification. Furthermore, the combination of BC and GE effectively decreased the relative abundance of Unclassified_k_Fugni, while increased the abundance of Ascomycota and Basidiomycota compared with control. The four genera, Pseudeurotium, Talaromyces, Trichoderma, and Penicillium, were the main fungi for the humification. Comparatively, the combined of BC and GE showed the optimal performance for TOC degradation and humification during SS composting.

Enhancements of short-chain fatty acids production via anaerobic fermentation of waste activated sludge by the combined use of persulfate and micron-sized magnetite.

The combination of persulfate (PDS) with micron-sized magnetite (Fe3O4) was introduced into the process of anaerobic fermentation (AF) to scrutinize the short chain fatty acid (SCFA) production from waste activated sludge for the first time. The synergetic effect of PDS and Fe3O4 results in the promotion of intracellular and extracellular substance liberation, augment in key hydrolases activities, and enrichment of hydrolytic and acidifying microbial population. Meanwhile, carbohydrate, amino acid, and energy metabolism as well as enzymes, are considerably accelerated. Consequently, the maximum SCFAs yield is significantly enhanced to 391.25 mg COD/L on day 8 of AF with the addition of 0.3 g Fe3O4/g SS and 0.5 g PDS/g SS, which was 2.39-folds than that of the control. The relative abundance of Actinobacteria were highly enriched and reached to 35.76% at the class level. This work affords an effective avenue to evidently boost the production of SCFAs from WAS via AF.

Comparative evaluation of biochar, pelelith, and garbage enzyme on nitrogenase and nitrogen-fixing bacteria during the composting of sewage sludge.

This study investigated the effects of garbage enzyme (GE), pelelith (PL), and biochar (BC) on nitrogen (N) conservation, nitrogenase (Nase) and N-fixing bacteria during the composting of sewage sludge. Results showed that the addition of GE, PL, and BC reduced NH3 emissions by 40.9%, 29.3%, and 67.4%, and increased the NO3-N contents of the end compost by 161.4, 88.2, and 105.8% relative to control, respectively, thus increasing the TN content. Three additives improved Nase, cellulase, and fluorescein diacetate hydrolase (FDA) activities and the abundances of nifH gene, and the largest increase was BC, followed by PL and GE. In addition, the additives also markedly influenced the succession of N-fixing bacteria, and significantly increased the abundance of Proteobacteria during the whole process. The BC and PL additions strengthened the sensitivity of N-fixing bacteria to environmental variables, and FDA, TN, moisture content, and NO3-N significantly affected the N-fixing bacteria at genus level.

Effects of urease inhibitors on enzymatic activities and fungal communities during the biosolids composting.

This study evaluated the influences of urease inhibitors (UIs) on nitrogen conversion, enzyme activities, and fungal communities during aerobic composting. Results showed that UI addition reduced NH3 emissions by 22.2% and 21.5% and increased the total nitrogen (TN) content by 9.7% and 14.3% for the U1 (0.5% UI of the dry weight of the mixture) and U2 (1% UI of the dry weight of the mixture) treatments, respectively. The addition of UI inhibited the enzyme activity during thermophilic stage while increased enzyme activity during the cool and maturity stages. Ascomycota, Basidiomycota and unclassified fungi were the main phyla, and Ascomycota increased significantly during the maturity period. Network analysis showed that Aspergillus, Penicillium, Trichoderma, Talaromyces, Peseudeurotium, and Exophiala were the main "connecting" genera. The redundancy analysis (RDA) showed that the fungal community was mainly influenced by temperature, DOC, pH, and urease. The results suggested that UI was an effective additive for nitrogen conservation and the increase of enzyme activity reduce nitrogen loss and promote enzyme activity during biosolids composting.

Influence of reusable polypropylene packing on ammonia and greenhouse gas emissions during sewage sludge composting-a lab-scale investigation.

Bulking agents are particularly important for sewage sludge composting. In this study, reusable polypropylene packing (RPP) was mixed with sawdust to improve composting. The effect of the mix ratio of sawdust and RPP on the physicochemical characteristics, nitrogen transformation, and emissions of greenhouse gas (GHG) as well as differences in the germination index values was detected in a lab-scale composting experiment. The results showed that the unique use of RPP as a bulking agent increased the moisture content over 70%, which resulted in poorer porosity and a less efficient O2 utilization environment and thus suppressed the degradation of organic matter. The highest CH4 9275.8 mg and lowest CO2 202.6 g emissions were detected after 25 days of composting in the treatment with RPP used as a bulking agent. When the mixing ratio of sawdust and RPP was 1:1, the temperature, oxygen supply, and dissolved organic carbon degradation were improved. The NH3, N2O, and CH4 emissions were reduced by 32.2, 18.3, and 90.7% compared with a treatment with RPP as a unique bulking agent. The RPP had no effect on conserving nitrogen during sludge composting; the total nitrogen loss was reduced from 29.3 to 18.2% when sawdust was mixed with RPP in a ratio of 1:1. Therefore, mixing RPP and sawdust in the dry weight ratio of 1:1 (sawdust: RPP) can be potentially used for reducing composting cost and improving the sewage sludge composting by reducing the amount of sawdust mixed and mitigating GHG and NH3 emissions.

Use of additives in composting informed by experience from agriculture: Effects of nitrogen fertilizer synergists on gaseous nitrogen emissions and corresponding genes (amoA and nirS).

The effects of two nitrogen fertilizer synergists (urease inhibitor, UI; nitrification inhibitor, NI) on NH3 and N2O emissions and the successions of the amoA and nirS genes during composting were assessed. Results showed that the UI and UI + NI treatments reduced NH3 emissions by 26.3% and 24.3%, respectively, and N2O emissions were reduced by 63.9% for UI + NI treatment but were not reduced by UI. The addition of UI and NI significantly reduced the abundance of the nirS gene during thermophilic stage, while significantly increased that of the amoA gene during maturation stage. Crenarchaeota was the principal nitrifying archaeal phylum and was significantly affected by pH. Proteobacteria was the main denitrifying bacterial phylum, whose relative abundance was higher for UI + NI treatment than the other treatments. PICRUSt analysis showed that the addition of UI and NI inhibited enzymatic activity related to N transformation during thermophilic stage while enriching enzymatic activity during maturation phase.

Composting pig manure and sawdust with urease inhibitor: succession of nitrogen functional genes and bacterial community.

Understanding the relationship between nitrogen (N) cycle and N transformation-related functional genes is crucial to reduce N loss during composting process. Urease inhibitor (UI) is widely used to reduce N loss in agriculture. However, the effects of UI on N transformation and related N functional genes during composting have not been well investigated. The goal of this study was to investigate the effects of a urease inhibitor (UI) on N functional genes and bacterial community succession during pig manure composting. Results showed that the addition of UI decreased the ammonium N content during the thermophilic stage and notably increased the total N and nitrite N contents of the final compost. The UI significantly decreased the abundances of amoA, nirS, nirK, and nosZ during the initial composting stage, while the opposite trend was observed at the maturation stage. Bacterial community richness and diversity were increased after the UI amendment, but the relative abundance of the phyla Firmicutes and Proteobacteria significantly decreased compared with control during the thermophilic stage. Redundancy analysis indicated that the evaluated environmental factors and bacterial community showed a cumulative 94.7% contribution to the total variation in N functional genes. In summary, UI addition is a recommended method for N conservation during composting, but the added forms of UI, such as delayed addition, combined with adsorbing materials, or microorganism inoculant, should be further evaluated.

Adding Phosphate Fertilizer and Apple Waste to Pig Manure during Composting Mitigates Nitrogen Gas Emissions and Improves Compost Quality.

Calcium superphosphate and apple ( Mill.) waste can be used for controlling N loss and improving compost quality during composting, whereas integrated addition of the two additives on composting process remains unexplored. Therefore, this study was conducted to investigate the effects of combined use of calcium superphosphate and apple waste on NH and NO emissions and compost quality during pig manure and wheat ( L.) straw composting. Mixtures of pig manure and wheat straw were combined with 6% phosphate fertilizer (PF), 15% apple waste (AW), 3% phosphate fertilizer + 7.5% apple waste (PA1), or 1.8% phosphate fertilizer + 10.5% apple waste (PA2) based on dry weight of the initial mixtures; a treatment with no additives served as a control (CK). The PF treatment took 3 d longer to reach thermophilic phase than the CK, PA1, and PA2 treatments. The treatments of PF and PA1 reduced NH and NO emissions by 67 and 45%, respectively. Moreover, N loss in PF and PA1 treatments (31.8 and 30.1%, respectively) was significantly less than in the CK. A pot experiment showed that application of the compost with PA1 treatment could increase plant height and dried biomass of Chinese pakchoi ( L. ssp.). We recommend adding 3% phosphate fertilizer and 7.5% apple waste to pig manure during composting.

Exploring the mechanisms of organic matter degradation and methane emission during sewage sludge composting with added vesuvianite: Insights into the prediction of microbial metabolic function and enzymatic activity.

Effect mechanisms of organic matter (OM) degradation and methane (CH4) emission during sewage sludge (SS) composting with added vesuvianite (V) were studied by high-throughput sequencing (HTS) and phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt). Results show that the addition of V accelerated the OM degradation and decreased the cumulative CH4 emissions by 33.6% relative to the control. In addition, V significantly decreased the mcrA gene abundance and the methanogen community richness at the genus level. PICRUSt also indicated that V strengthens the microbial metabolic function and enzymatic activity related to OM degradation, and reduced the enzymatic activity related to CH4 production. Methanogens community variation analysis proved the ratio of carbon and nitrogen and moisture content are the significant variables affecting CH4 emissions. Thus, optimizing the ratio of carbon and nitrogen and moisture content will decrease CH4 emission during SS composting.

[Seasonal Variation and Source Analysis of Water-soluble Inorganic Ions in Fine Particulate Matter in Zhengzhou].

In order to explore the characteristics of PM2.5 concentration and water-soluble inorganic ions in Zhengzhou City, a total of 170 PM2.5 samples were collected in the spring, summer, autumn, and winter seasons of 2016, with 30 days continuous sampling during each season. The mass concentration of PM2.5 was analyzed gravimetrically, water-soluble inorganic ions were determined by ion chromatography, and principle component analysis was employed for source apportionment. The results showed that the mass concentration of PM2.5 was 150.72µg·m-3 during the sampling period. The mass concentration was highest in winter and lowest in summer, and that of autumn is higher was higher than that of spring. The ions SO42-, NO3-, and NH4+ were the major WSIs found in PM2.5, accounting for 92.55%, 92.94%, 93.06%, and 93.15% of the total amount of the seven ions found in spring, summer, autumn, and winter, respectively. The anion-to-cation ratio was 0.886, which indicated that PM2.5 was slightly alkaline in Zhengzhou. Secondary inorganic species, including NH4+, NO3-, and SO42- were the major components of the water-soluble ions. These ions most likely existed in the form of NH4NO3 and (NH4)2SO4 during spring and summer, while they were present as NH4NO3, (NH4)2SO4 and NH4HSO4 in autumn. In addition to these three forms, NH4Cl or other forms may exist in winter. Industrial emissions, combustion, secondary transformation, soil, and construction dust were the major sources of the water-soluble ions in PM2.5.

[Interannual Variation of Metal Elements and Water-Soluble Ions in PM2.5 During Wintertime in Xinxiang and Their Source Apportionment].

To study the interannual variations of chemical composition and source apportionment, a field campaign was carried out to collect the PM2.5 temperance sample during the winter of 2015 and the winter of 2016 in Xinxiang urban areas. PM2.5 mass concentration, metal elements, and the water-soluble ions were determined and meteorological factors were recorded simultaneously. The results showed that the daily mean concentrations of PM2.5 indicated serious pollution with values of 226 µg·m-3 and 224 µg·m-3 in 2015 and 2016, respectively. The Cd and Pb elements in PM2.5 were significantly enriched, with EF more than 1000. However, compared with 2015, the enrichment effect of most metal elements showed a trend of decrease in 2016. The water-soluble ions were mainly composed of SO42-, NO3-, and NH4+. The results showed a trade-off effect between metal elements and water-soluble ions in the two study periods. The results of PCA and PMF analyses show that there were four main emission sources in Xinxiang city in winter, namely dust, secondary source, industrial source, and fossil fuel combustion source. Moreover, the main sources of PM2.5 was the mixed source of soil and building dust and secondary aerosol pollution, with contributions of 37.46% and 34.94% in the winters of 2015 and 2016, respectively.

Beneficial influences of pelelith and dicyandiamide on gaseous emissions and the fungal community during sewage sludge composting.

Reducing the emissions of NH3 and greenhouse gases (GHGs) during composting is essential for improving compost quality and controlling environmental pollution. This paper investigates the effects of pelelith (P) combined with dicyandiamide (DCD) on gaseous emissions and the fungal community diversity during sewage sludge (SS) composting. Results showed that the P and P + DCD treatments decreased the cumulative gaseous emissions by 41% and 22% for NH3, 21% and 34% for N2O, and 31.5% and 33.0% for CH4, respectively. The evolution of the fungal community analysis showed that Ascomycota and unclassified fungi dominated during the thermophilic stage, while only Ascomycota was the dominant fungal phylum during the maturity stage, composing 62%, 66%, and 73% of the total fungal community in the control, P, and P + DCD, respectively. The P and P + DCD significantly increased the fungal community richness at the genus level. Fungal community abundance was found to be significantly related to temperature, pH, organic matter, and total Kjeldahl nitrogen, which also influence the gaseous emissions during SS composting. It suggested that the combined addition of pelelith and dicyandiamide (DCD) was an effective method for reducing the emissions of NH3 and greenhouse gases during SS composting.

A novel method for sewage sludge composting using bamboo charcoal as a separating material.

Traditional composting processes must be conducted with a bulking agent to ensure adequate air space for aeration. The bulking agent and composting materials are always completely mixed. A novel layered structure was introduced in sewage sludge composting, in which no bulking agent was used and bamboo charcoal was used as a separating material. Three lab-scale composting reactors (A: sawdust and sludge; B: bamboo charcoal and sludge; and C: sawdust, bamboo charcoal, and sludge) were continuously operated for 29 days. Several physicochemical parameters were investigated to evaluate the feasibility of layered composting with bamboo charcoal. The results indicated that the maximum temperatures during the thermophilic stage in treatments A, B, and C were 51.4, 50.9, and 51 °C, respectively. Layered composting with bamboo charcoal decreased the pH of the thermophilic stage from 8.98 in A to 8.75 in C, and delayed the peaks by about 120 h. The degradation rates of dissolve organic carbon (DOC) and dissolved nitrogen (DN) were 75 and 71.5% in treatment B, respectively, which were significantly higher than those of control group A (60 and 59.1%, respectively). The total NH3 emissions of treatment C (2127.8 mg) were significantly lower than those of A (2522.8 mg). Our results suggested that layered composting using bamboo charcoal as a separating material could be an alternative strategy to the traditional composting method. Moreover, layered composting combined with sawdust could effectively reduce NH3 emissions and N loss.

Insights into aggregation and transport of graphene oxide in aqueous and saturated porous media: Complex effects of cations with different molecular weight fractionated natural organic matter.

The stability of nanomaterials in aquatic environment is a critical factor that governs their fate and ecotoxicity. Meanwhile, the interaction between nanomaterials and ubiquitous natural organic matter (NOM) is a vital process that influences the transport and biological effects of nanomaterials in the environment. However, impacts of NOM on the aggregation and transport of two-dimensional nanomaterials, especially for the increasingly used graphene oxide (GO), are not well understood. Particularly, there is lack of exploration on potential impacts of the heterogeneous properties of NOM on GO behaviour, especially that induced by the wide molecular weight (MW) span of NOM. In this study, effects of several kinds of well-characterized MW fractionated Suwannee River NOM (Mf-SRNOMs) on the aggregation and transport of GO in aqueous media and saturated porous media were investigated. Our results suggest that the stability and migration capacity of GO under most investigated electrolyte conditions are promoted by all Mf-SRNOMs, and efficiencies of different Mf-SRNOMs are generally positively correlated with their MW. Primarily, mechanisms including MW-dependent steric hindrance and sorption of Mf-SRNOMs onto GO are critical in stabilizing GO, and thus facilitating its transport. However, the stronger sorption of higher Mf-SRNOMs onto the GO basal plane through π-π interaction further facilitated the cation bridging between both ends of Mf-SRNOM and GO, and resulted in heteroaggregation of NOM-GO. Moreover, the weight analysis indicated that despite the fact that high Mf-SRNOMs only occupied a small percentage of pristine-SRNOM, they showed a stronger contribution towards pristine-SRNOM's capacity in stabilizing GO, when compared with that of lower MW counterpart. These findings pointed out that complex effects of the heterogeneities of NOM and cations should be highly relevant when the aggregation and transport behaviour of two-dimensional nanomaterials is investigated, and NOM fractions that are highly aromatic and of a higher MW should receive greater attention.

Evaluation of total greenhouse gas emissions during sewage sludge composting by the different dicyandiamide added forms: Mixing, surface broadcasting, and their combination.

The aim of this work was to compare the impact of different adding forms of dicyandiamide (DCD) on NH3 and greenhouse gas (GHG) emissions during sewage sludge (SS) composting. Four treatments were set up using SS mixed with sawdust, to which DCD was then added by mixing (M), surface broadcasting (B), and a combination of the two (M+B). The treatment without DCD applied was used as the control. The results indicate that the addition of DCD slightly inhibited the organic matter (OM) degradation, but that it had no significant effect on CO2 emission. The surface mulching of DCD has no significant effect on NH3, N2O, and CH4 emissions. The mixing addition of DCD significantly increased the NH3 emission by 32.5% compared to that of the control. The N2O emission for the M and M+B treatments significantly decreased by 35.1% and 51.8%, respectively. The CH4 emission for the M and M+B treatments decreased by 33.9% and 31.8%, respectively. In addition, the total GHG emissions for the M and M+B treatments were significantly reduced by 16.7-25.7% (P < 0.05) compared to those of the control. Therefore, to reduce the total GHG emissions of the SS composting process, the addition of DCD by a combination of mixing and surface mulching is strongly recommended as a highly efficient solution.