MSWNet:A visual deep machine learning method adopting transfer learning based upon ResNet 50 for municipal solid waste sorting

An intelligent and efficient methodology is needed owning to the continuous increase of global municipal solid waste(MSW).This is because the common methods of manual and semi-mechanical screenings not only consume large amount of manpower and material resources but also accelerate virus community transmission.As the categories of MSW are diverse considering their compositions,chemical reactions,and processing procedures,etc.,resulting in low efficiencies in MSW sorting using the traditional methods.Deep machine learning can help MSW sorting becoming into a smarter and more efficient mode.This study for the first time applied MSWNet in MSW sorting,a ResNet-50 with transfer learning.The method of cyclical learning rate was taken to avoid blind finding,and tests were repeated until accidentally encountering a good value.Measures of visualization were also considered to make the MSWNet model more transparent and accountable.Results showed transfer learning enhanced the efficiency of training time(from 741 s to 598.5 s),and improved the accuracy of recognition performance(from 88.50%to 93.50%);MSWNet showed a better performance in MSW classsification in terms of sensitivity(93.50%),precision(93.40%),F1-score(93.40%),accuracy(93.50%)and AUC(92.00%).The findings of this study can be taken as a reference for building the model MSW classification by deep learning,quantifying a suitable learning rate,and changing the data from high dimensions to two dimensions.

Effects of calcined aluminum salts on the advanced dewatering and solidification/stabilization of sewage sludge

The high moisture content （80%） in the sewage dewatered sludge is the main obstacle to disposal and recycling. A chemical dewatering and stabilization/solidification （S/S） alternative for the sludge was developed, using calcined aluminum salts （AS） as solidifier, and CaCl 2 , Na 2 SO 4 and CaSO 4 as accelerators, to enhance the mechanical compressibility making the landfill operation possible. The properties of the resultant matrixes were determined in terms of moisture contents, unconfined compressive strength, products of hydration, and toxicity characteristics. The results showed that AS exhibited a moderate pozzolanic activity, and the mortar AS 0 obtained with 5% AS and 10% CaSO 4 of AS by weight presented a moisture contents below 50%–60% and a compressive strength of （51.32 ± 2.9） kPa after 5–7 days of curing time, meeting the minimum requirement for sanitary landfill. The use of CaSO 4 obviously improved the S/S performance, causing higher strength level. X-ray diffraction, scanning electron microscopy and thermogravimetry- differential scanning calorimetry investigations revealed that a large amount of hydrates （viz., gismondine and CaCO 3 ） were present in solidified sludge, leading to the depletion of evaporable water and the enhancement of the strength. In addition, the toxicity characteristic leaching procedure （TCLP） and horizontal vibration （HJ 557-2009） leaching test were conducted to evaluate their environmental compatibility. It was found that the solidified products conformed to the toxicity characteristic criteria in China and could be safely disposed of in a sanitary landfill.

A comprehensive overview of rural solid waste management in China

This paper aims to conduct a comprehensive review of rural solid waste （RSW） in terms of character- istics, management and legislation. Survey results show that RSW generation rates range from 0.25 to 2.1 kg · （capita.d）-1 in different rural villages across regions of China. Total RSW generation has been increasing, which is far higher than official data in 2014. RSW are dominated by food residue and coal ash/cinder/dust （at approximately 70%）. Most of RSW are still discarded randomly without any treatment in China. Scattered RSW generation sources, imperfect legislation system, poor infrastructure on treat- ment and disposal are identified as the biggest challenge for RSW management currently in China. To improve RSW management, increasing financial resources, estab- lishing sorting collection and transportation network, promoting sorting collection and recycling, improving treatment technology are proposed as the possible solution.

Enhanced dewatering characteristics of waste activated sludge with Fenton pretreatment： effectiveness and statistical optimization

In this work, the enhanced dewaterabing characteristics of waste activated sludge using Fenton pretreatment was investigated in terms of effectiveness and statistical optimization. Response surface method （RSM） and central composite design （CCD） were applied to evaluate and optimize the effectiveness of important operational parameters, i.e., H202 concentrations, Fe2＋ concentrations and initial pH values. A significant quadratic polynomial model was obtained （R2= 0.9189） with capillary suction time （CST） reduction efficiency as the response. Numerical optimization based on desirability function was carried out. The optimum values for H202, Fe2, and initial pH were found to be 178 mg-g-1 VSS （volatile suspended solids）, 211mg.gI VSS and 3.8, respectively, at which CST reduction efficiency of 98.25% could be achieved. This complied well with those predicted by the established polynomial model. The results indicate that Fenton pretreatment is an effective technique for advanced waste activated sludge dewatering. The enhancement of sludge dewaterability by Fenton＇s reagent lies in the migration of sludge bound water due to the disintegration of sludge flocs and microbial cells lysis.

Leachate treatment using a demonstration aged refuse biofilter

Approximately 7000 m^3 of aged refuse （AR） with a placement of over eight years was excavated from Shanghai Refuse Landfill, the largest landfill in China, and used for the construction of a two-stage bioreactor （AR biofilter） media for the biological treatment of 100 m3 of refuse landfill leachate. It was found that over 64% of COD, 96.9%-99.8% of NH4^＋-N, and 95.8%-99.8% of BOD5 could be removed by the AR biofilter, when the leachate with initial COD, BOD5, and NH4^＋-N concentrations were 986-4128 mg/L, 264--959 mg/L,m and 538-1583 mg/L, respectively. The corresponding concentrations in the effluent were reduced to below 30（000 mg/L, 2-12 mg/L, and 10-20 mg/L, respectively. The effluent was clear and pale yellow with suspended solid below 150 mg/L and color below 150 Pt/Co degree. Meanwhile, the total nitrogen removal was only 49%-63%, indicating a relative poor denitrification capacity of AR biofilter. The effluent pH was neutral and the population of Escherichia coli was less than 10^-1 CFU/mL. Hence, it was considered that the demonstration project can work well for the effective treatment of leachate.

Removal of Pb(Ⅱ) from aqueous solutions using waste textiles/poly(acrylic acid) composite synthesized by radical polymerization technique

Waste textiles（WTs） are the inevitable outcome of human activity and should be separated and recycled in view of sustainable development. In this work, WT was modified through grafting with acrylic acid（AA） via radical polymerization process using ceric ammonium nitrate（CAN） as an initiator and microwave and/or UV irradiation as energy supply. The acrylic acid-grafted waste textiles（WT-g-AA） thus obtained was then used as an adsorbent to remove Pb（Ⅱ） from Pb（Ⅱ）-containing wastewater. The effects of p H, initial concentrations of Pb（Ⅱ） and adsorbent dose were investigated, and around 95% Pb（Ⅱ） can be removed from the aqueous solution containing 10 mg/L at p H 6.0–8.0. The experimental adsorption isotherm data was fitted to the Langmuir model with maximum adsorption capacity of35.7 mg Pb/g WT-g-AA. The Pb-absorbed WT-g-AA was stripped using dilute nitric acid solution and the adsorption capacity of Pb-free material decreased from 95.4%（cycle 1） to91.1%（cycle 3）. It was considered that the WT-g-AA adsorption for Pb（Ⅱ） may be realized through the ion-exchange mechanism between ／COOH and Pb（Ⅱ）. The promising results manifested that WT-g-AA powder was an efficient, eco-friendly and reusable adsorbent for the removal of Pb（Ⅱ） from wastewater.

Molten hydroxide for detoxification of chlorine-containing waste: Unraveling chlorine retention efficiency and chlorine salt enrichment

Hazardous waste dechlorination reduces the potential of creating dioxins during the incineration process. To investigate the salt effect on waste dechlorination, molten hydroxides with a low melting temperature were utilized for the pre-dechlorination and decomposition of chlorine-containing organic wastes(COWs) including trichlorobenzene(TCB),perchloroethylene, hexachlorobenzene and chlordane. The results showed that a eutectic mixture of caustic sodium and potassium hydroxides(41 wt.% NaOH and 59 wt.% KOH) led to a low melting point below 300°C and a relatively high chlorine retention efficiency(CRE) with TCB as a representative COWs. The amounts of hydroxides, reaction time, and temperature all had notable influence on CRE. When the mass ratio of hydroxides to TCB reached 30:1,approximately 98.1% of the TCB was destroyed within 2.5 hr at 300°C with CRE of 71.6%.According to the residue analysis, the shapes of reaction residues were irregular with particles becoming swollen and porous. The benzene ring and C–Cl bonds disappeared, while carboxyl groups formed in the residues. The stripped chlorine was retained and condensed to form chloride salts, and the relative abundance of the chloride ions associated with the mass of TCB in residues increased from 0 to 75.0% within the 2.5 hr reaction time. The observed concentration of dioxins in residues was 5.6 ngTEQ/kg. A reaction pathway and possible additional reactions that occur in this dechlorination system were proposed. Oxidizing agents may attack TCB and facilitate hydrogenation/dechlorination reactions, making this process a promising and environmentally friendly approach for chlorine-containing organic waste treatment.

Methanotrophic community structure of aged refuse and its capability for methane bio-oxidation

Aged refuse from waste landfills closed for eight years was examined and found to contain rich methanotrophs capable of biooxidation for methane. Specially, community structure and methane oxidation capability of methanotrophs in the aged refuse were studied. The amount of methanotrophs ranged 61.97×10^3-632.91×10^3 cells/g （in dry basis） in aged refuse from Shanghai Laogang Landfill. Type I and II methanotrophs were found in the aged refuse in the presence of sterilized sewage sludge and only Type I methanotrophs were detected in the presence of nitrate minimal salt medium （NMS）. The clone sequences of the pmoA gene obtained from the aged refuse were similar to the pmoA gene of Methylobacter, Methylocaldum, and Methylocystis, and two clones were distinct with known genera of Type I methanotrophs according to phylogenetic analysis. Aged refuse enriched with NMS was used for methane biological oxidation and over 93% conversions were obtained.

Pollution of hazardous substances in industrial construction and demolition wastes and their multi-path risk within an abandoned pesticide manufacturing plant

Exploration of heavy metals and organic pollutants, their leaching capacity along with health and environmental risks in contaminated industrial construction and demolition waste （ICDW） within a pesticide manufacturing plant were investigated. A maximum content of 90.8 mg·kg-1 Cd was found present in the wastes, which might originate from phosphorus rocks and industrial sulfuric acid used in pesticide production processes. An average concentration of 979.8 mg·kg-1 dichlorovos and other 11 organophosphorus pesticide were also detected. Relatively high leaching rates of around 4.14‰ were obtained from laboratory simulated ICDW using both glacial acetic acidsodium hydroxide and deionized water. Pesticide pollutants had the strongest tendency to retaining on dry bricks （leaching rate 1.68 9‰） compared to mortar-coatings, etc. due to their different physical characteristics and octanol-water partioning coefficient. Mobility of pesticide from on-site ICDW by water was spatially correlated to waste types, process sections and human activities, with a flux of leaching rate between 5.9‰ to 27.4%. Risk-based corrective action （RBCA） model was used to simulate the risk of contaminated ICDW debris randomly scattered. Oral and demlal ingestion amount by local workers was 9.8 × 10-3 and 1.9 × 10-2 mg.（kg-d）-1, respectively. Potential leaching risk to aquatic systems exceeded the limit for nearly 75% waste. Environmental and health risk exceedance was found in most ICDW, while the risk value of the most severely contaminated brick waste was 660 times beyond critical level. Implications for waste management involving construction and deconstruction work, waste transferring and regulation supplying were also provided.

Abiotic association of phthalic acid esters with humic acid of a sludge landfill

The abiotic association between phthalic acid esters （PAEs） and humic substances （HS） in sludge landfill plays an important role in the fate and stability of PAEs. An equilibrium dialysis combined with 14C-labeling was used to study the abiotic association of two abundant PAEs （diethyl phthalate and di-n-butyl phthalate） with humic acid （HA） isolated from a sludge landfill with different stabilization times and different molecular weights. Ele- mental analysis and Fourier Transform Infrared Spectro- photometer （FTIR） suggested that high KA value of HA was related to the high aromatic content and large molecular weight of HA. The results indicated that the association strength of PAEs with HA depended on both the properties of the PAEs and the characteristics of HA. The KA values of the association were strongly dependent on solution pH, and decreased dramatically as the pH was increased from 3.0 to 9.0. The results suggested that non- specific hydrophobic interaction between PAEs and HA was the main contributor to the association of the PAEs with HA. The interactive hydrogen-bonds between the HA and the PAEs molecules may also be involved in the association.

Designing an in situ remediation strategy for polluted surface water bodies through the specific regulation of microbial community

This paper proposes an in situ restoration strategy, ecosystem activation system (EAS), for selfpurification abilities of polluted water ecosystems through the specific regulation of microbial community. EAS utilizes polyhydroxyalkanoates (PHA) to modify indigenous microbial communities of polluted water bodies. Microorganisms preferentially utilizing PHA as the carbon source for their enhanced growth are defined as specific, and those with no special selectivity to PHA and raw-water dissolved organic matter are defined as non-specific and can be phased out during EAS operation. As a result, the microbial community can be regulated to the specific structure, which is beneficial for the water quality improvement. The developed model described the above principle with accounting for the growth kinetics of specific microorganisms, competitive inhabitation of specific microorganisms on non-specific microorganisms, and coupled EAS-induced self-purification of polluted water bodies. The conceptual model is believed to be a primary step toward quantitative design, operation, and optimization of EAS.

Greenhouse gas emission and its potential mitigation process from the waste sector in a large-scale exhibition

As one of the largest human activities, World Expo is an important source of anthropogenic Greenhouse Gas emission（GHG）, and the GHG emission and other environmental impacts of the Expo Shanghai 2010, where around 59,397 tons of waste was generated during 184 Expo running days, were assessed by life cycle assessment（LCA）. Two scenarios, i.e., the actual and expected figures of the waste sector, were assessed and compared, and 124.01 kg CO2-equivalent（CO2-eq.）, 4.43 kg SO2-eq., 4.88 kg NO-3-eq., and 3509 m3 water per ton tourist waste were found to be released in terms of global warming（GW）, acidification（AC）,nutrient enrichment（NE） and spoiled groundwater resources（SGWR）, respectively. The total GHG emission was around 3499 ton CO2-eq. from the waste sector in Expo Park, among which 86.47% was generated during the waste landfilling at the rate of 107.24 kg CO2-eq.,and CH4, CO and other hydrocarbons（HC） were the main contributors. If the waste sorting process had been implemented according to the plan scenario, around 497 ton CO2-eq.savings could have been attained. Unlike municipal solid waste, with more organic matter content, an incineration plant is more suitable for tourist waste disposal due to its high heating value, from the GHG reduction perspective.

Efficient capture of aqueous humic acid using a functionalized stereoscopic porous activated carbon based on poly(acrylic acid)/food-waste hydrogel

Stereoscopic porous carbons have shown good potential in humic acid(HA) removal. In this work, a novel stereoscopic porous activated carbon(SPAC) was designed and synthesized via the self-assembly of a hydrogel based on food waste during in-situ polymerization, vacuum drying, carbonization, and activation. Then, the SPAC was functionalized with 3-aminopropyltriethoxysilane(APTES) and the adsorption behavior of the modified SPAC(SPAC-NH_2) was studied systematically. The effects of pH, contact time, initial concentration of HA, and adsorbent dose were investigated, showing that optimal HA removal efficiency(>98.0%) could be achieved at an initial HA concentration of 100 mg/L. The experimental adsorption isotherm data was fitted to the Langmuir model with a maximum adsorption capacity of 156.0 mg HA/g SPAC-NH_2. Analysis of the mechanism indicated that the removal of HA was mainly realized through the amidization reaction between the \COOH groups of HA and the \NH_2 groups of APTES. All of the above results showed that SPAC-NH_2 powder is an efficient,eco-friendly, and reusable adsorbent which is suitable for the removal of HA from wastewater.

Indicating landfill stabilization state by using leachate property from Laogang Refuse Landfill

Variation and evolution process of leachate can be applied as a reference for landfill stabilization phase. In this work, leachates with different ages were collected from Laogang Refuse Landfill, and characterized with 14 key parameters. Simultaneously, principal component analysis （PCA） was applied to develop a synthetic parameter-F based on these 14 parameters, and a logarithm equation was simulated for the landfill stabilization process finally. It was predicted that leachates would meet Class I and Class II in standard for pollution control on the landfill site of municipal solid waste （GB 16889-1997） after 32 years and 22 years disposal under the natural attenuation in the humid and warm southern areas of China, respectively. The predication of landfill state would be more accurate and useful according to the synthetic parameter F of leachate from a working landfill.

Environmental impacts of a large-scale incinerator with mixed MSW of high water content from a LCA perspective

Large-scale incinerators are applied widely as a result of the heavy burden of municipal solid waste（MSW） generated, while strong opposition is arising from the public living nearby. A large-scale working incineration plant of 1500 ton/day was chosen for evaluation using life cycle assessment. It was found that the corresponding human toxicity impacts via soil（HTs）, human toxicity impacts via water（HTw） and human toxicity impacts via air（HTa）categories are 0.213, 2.171, and 0.012 personal equivalents（PE）, and global warming（GW100）and nutrient enrichment（NE） impacts are 0.002 and 0.001 PE per ton of waste burned for this plant. Heavy metals in flue gas, such as Hg and Pb, are the two dominant contributors to the toxicity impact categories, and energy recovery could reduce the GW100 and NE greatly. The corresponding HTs, HTw and HTa decrease to 0.087, 0.911 and 0.008 PE, and GW100 turns into savings of- 0.007 PE due to the increase of the heating value from 3935 to5811 k J/kg, if a trommel screener of 40 mm mesh size is used to pre-separate MSW. MSW sorting and the reduction of water content by physical pressure might be two promising pre-treatment methods to improve the combustion performance, and the application of stricter standards for leachate discharge and the flue gas purification process are two critical factors for improvement of the environmental profile identified in this work.