Influence of temperature fluctuation on thermophilic anaerobic digestion of municipal organic solid waste

A laboratory-scale experiment was carried out to assess the influence of temperature fluctuation on thermophilic anaerobic digestion of municipal organic solid waste （MOSW）. Heating failure was simulated by decreasing temperature suddenly from 55 ℃ to 20 ℃ suddenly, 2 h time is needed for temperature decrease and recovery. Under the conditions of 8.0 g/（L·d） and 15 d respectively for MOSW load and retention time, following results were noted： （1） biogas production almost stopped and VFA （volatile fatty acid） accumulated rapidly, accompanied by pH decrease; （2） with low temperature （20 ℃） duration of 1, 5, 12 and 24 h, it took 3, 11, 56 and 72 h for the thermophilic anaerobic digestion system to reproduce methane after temperature fluctuation, （3） the longer the low temperature interval lasted, the more the methanogenic bacteria would decay, hydrolysis, acidification and methanogenesis were all influenced by temperature fluctuation： （4） the thermophilic microorganisms were highly resilient to temperature fluctuation.

Effective incineration technology with a new-type rotary waste incinerator

The technology of steady combustion in a new type of rotary incinerator is firstly discussed. The formation and control of HCl,NOx and SO_(2) during the incineration of sampled municipal organic solid waste are studied with the incinerator. Results showed that the new model of rotary incinerator can effectively control and reduce the pollutant formations by post combustion.

Cr(Ⅵ) reduction capability of humic acid extracted from the organic component of municipal solid waste

The capacity of humic acid extracted from organic waste （HAw） to reduce Cr（Ⅵ） was tested at pH 2.5,4 and 6 and compared with coal-derived humic acid （HAc）.HAw was more effective than HAc in reducing Cr（Ⅵ）.The kinetics of Cr（Ⅵ） reductions depended strongly on pH.The calculation of the apparent rate coefficients indicated that HAw was more efficient at reducing Cr（Ⅵ） than HAc,but was also more efficient than HAs from soil and peat.The reduction capability of HAs depends on the type of functional groups （i.e.,thiols and phenols） present,rather than the free radicals.HAw was more efficient at reducing Cr（Ⅵ） than HAc because more reactive phenols were present,i.e.,methoxy-and methyl-phenols.

Method for C/N ratio estimation using Mask R-CNN and a depth camera for organic fraction of municipal solid wastes

Fast assessment of the initial carbon to nitrogen ratio(C/N)of organic fraction of municipal solid waste(OFMSW)is an important prerequisite for automatic composting control to improve efficiency and stability of the bioconversion process.In this study,a novel approach was proposed to estimate the C/N of OFMSW,where an instance segmentation model was applied to predict the masks for the waste images.Then,by combining the instance segmentation model with the depth-camera-based volume calculation algorithm,the volumes occupied by each type of waste were obtained,therefore the C/N could be estimated based on the properties of each type of waste.First,an instance segmentation dataset including three common classes of OFMSW was built to train mask region-based convolutional neural networks(Mask R-CNN)model.Second,a volume measurement algorithm was proposed,where the measurement result of the object was derived by accumulating the volumes of small rectangular cuboids whose bottom area was calculated with the projection property.Then the calculated volume was corrected with linear regression models.The results showed that the trained instance segmentation model performed well with average precision scores AP_(50)=82.9,AP_(75)=72.5,and mask intersection over unit(Mask IoU)=45.1.A high correlation was found between the estimated C/N and the ground truth with a coefficient of determination R2=0.97 and root mean square error RMSE=0.10.The relative average error was 0.42%and the maximum error was only 1.71%,which indicated this approach has potential for practical applications.

Optimization of Methane Production Based on Mixture Content of Sewage Sludge, Food Waste, and Glycerol

This paper presents bench scale experiments related to anaerobic co-digestion of aerobic sewage sludge from a pilot WWTP （waste water treatment plants）, raw glycerol from a biodiesel industry and food waste. Assays were conducted in 100 mL non-stirring penicillin vessels, at 30 ℃ and planned according to three optimization phases： （1） binary mixture of sewage sludge and FW （food waste）; （2） binary mixture of sewage sludge and glycerol; and （3） ternary mixture of sewage sludge, FW, and glycerol. In the first and second phases, the highest SMP （specific methane production） was achieved by 10% （v/v） FW and 0.5% （v/v） glycerol mixtures. The optimization of the ternary mixture during the third phase was reached by the combination of 10% （v/v） FW and 0.4% （v/v） glycerol. Despite the low SMP value, the addition of glycerol and FW contributed to doubling the SMP value of the sludge sample control.

Determination of characteristics for mechanically separated organic fraction of MsW at a full-scale anaerobic digestion plant

Anaerobic digestion(AD)as a waste management method has the potential to reduce greenhouse gas emissions while pro-ducing renewable energy,making it a viable option for managing the organic fraction of municipal solid waste(OFMSW).OFMSW characteristics can vary depending on factors such as waste source,composition and separation units.The charac-teristics of OFMSW are critical for analyzing and monitoring the AD process to optimize biogas production.In this study,the waste composition and physicochemical characteristics of the mechanically separated OFMSW(ms-OFMSW)were determined at a full-scale AD plant in Turkiye.The ms-OFMSW samples were collected monthly after mechanical separation and were subsequently sent to the anaerobic digester.The composition and physicochemical characteristics of the samples were determined by manual sorting.The results showed that the majority of the ms-OFMSW(76.45%±1.71%)was organic,while 8.99%±1.56%was recyclable and 14.56%±1.69%was non-recyclable.Loss of environmental benefits for the recyclable materials was determined using a free online tool provided by Environmental Protection Agency.Metals(399.7 GJ)and plas-tics(403.7 GJ)both saved nearly the same amount of energy while metals saved the most water(421.8 m3),with the greatest positive impact.Greenhouse benefits ranged from 3 tons to 40 tons of carbon dioxide equivalent for each waste stream.These findings suggest that efficient pre-separation units can improve the anaerobic digestibility of OFMSW,while also providing greater environmental benefits by preventing recyclable waste from the anaerobic digester.In addition to encouraging source separation applications,this study demonstrates the need for improved technologies to separate OFMSW from mixed MSW.

Effect of the rearing diet on gene expression of antimicrobial peptides in Hermetia illucens(Diptera:Stratiomyidae)

Insect proteins have been proposed for human and animal food production.Safeguarding the health status of insects in mass rearing allows to obtain high-quality products and to avoid severe economic losses due to entomopathogens.Therefore,new strategies for preserving insect health must be implemented.Modulation of the insect im-mune system through the diet is one such strategy.We evaluated gene expression of two antimicrobial peptides(one defensin and one cecropin)in Hermetia illucens(L.)(Diptera:Stratiomyidae)reared on different diets.Analyses were performed on prepupae and 10-day-old larvae reared on cereal-and municipal organic waste-based diets and on only prepupae reared on a cereal-based diet supplemented with sunflower,corn,or soybean oil.The inclusion of sunflower oil at different points in the cereal-based diet was also evalu-ated.Moreover,diet-driven differences in the inhibitory activity of the hemolymph were tested against Escherichia coli DH5αand Micrococcus yunnanensis HI55 using diffusion assays in solid media.Results showed that a municipal organic waste-based diet produced a significant overexpression of antimicrobial peptides only in prepupae.Inclusion of veg-etable oils caused an upregulation of at least one peptide,except for the corn oil.Higher expression of both genes was observed when sunflower oil was added 5 days before pupa-tion.All hemolymph samples showed an inhibitory activity against bacteria colonies.Our results suggest that municipal organic waste-based diet and vegetable oil-added diet may successfully impact the immune system of H.illucens.Such alternatives may also exist forotherspeciesofeconomic interest.