Experimental and modeling approaches for food waste composting: A review

Composting has been used as a method to dispose food waste (FW) and recycle organic matter to improve soil structure and fertility. Considering the significance of composting in FW treatment, many researchers have paid their attention on how to improve FW composting efficiency, reduce operating cost, and mitigate the associated environmental damage. This review focuses on the overall studies of FW composting, not only various parameters significantly affecting the processes and final results, but also a number of simulation approaches that are greatly instrumental in well understanding the process mechanism and/or results prediction. Implications of many key ingredients on FW composting performance are also discussed. Perspects of effective laboratory experiments and computer-based simulation are finally investigated, demonstrating many demanding areas for enhanced research efforts, which include the screening of multi-functional additives, volatile organiccompound emission control, necessity of modeling and post-modeling analysis, and usefulness of developing more conjunctive AI-based process control techniques.     

Performance of an innovative two-stage process converting food waste to hydrogen and methane

This study was conducted to evaluate the performance of an innovative two-stage process, BIOCELL, that was developed to produce hydrogen (H2) and methane (CH4) from food waste on the basis of phase separation, reactor rotation mode, and sequential batch technique. The BIOCELL process consisted of four leaching-bed reactors for H2 recovery and post-treatment and a UASB reactor for CH4 recovery. The leaching-bed reactors were operated in a rotation mode with a 2-day interval between degradation stages. The sequential batch technique was useful to optimize environmental conditions during H2 fermentation. The BIOCELL process demonstrated that, at the high volatile solids (VS) loading rate of 11.9 kg/m3 x day, it could remove 72.5% of VS and convert VS(removed) to H2 (28.2%) and CH4 (69.9%) on a chemical oxygen demand (COD) basis in 8 days. H2 gas production rate was 3.63 m3/m3 x day, while CH4 gas production rate was 1.75 m3/m3 x day. The yield values of H2 and CH4 were 0.31 and 0.21 m3/kg VS(added), respectively. Moreover, the output from the post-treatment could be used as a soil amendment. The BIOCELL process proved to be stable, reliable, and effective in resource recovery as well as waste stabilization.     

Biological solubilization and mineralization as novel approach for the pretreatment of food waste

The performance of a garbage disposal system to solubilize and mineralize food wastes through biological solubilization was evaluated through the examination of the effects of operational conditions like water supply volume, water supply frequency and aeration on the amount of waste solubilized, mineralized and accumulated in the reactor. The biological solubilization process consisted of a solubilization reactor and a circulation tank. Food waste and fresh water were supplied into the solubilization reactor with support media. Wastewater from the solubilization reactor was discharged to the circulation tank and water in the circulation tank was periodically pumped back to the solubilization reactor. In case of the total food waste loading of 16 kg m(3-1) d(-1), little carbon (0-5.7%) accumulated in the reactor as long as the system was kept under aerobic condition through large volume of water supply (higher than 3.5 lh(-1)) or applying aeration in the circulation tank. However, 42% of the loaded carbon accumulated under anaerobic condition in low water supply (less than 1.8 lh(-1)). The rest of the waste was either solubilized or mineralized. The aeration in the circulation tank, therefore, was effective to provide similar solubilization and mineralization as the large volume of water supply. However, frequency of feeding at the large volume of water supply had no significant effect on the amount of waste solubilization and mineralization.     

Isolation, identification and characterization of Bacillus amyloliquefaciens BZ-6, a bacterial isolate for enhancing oil recovery from oily sludge

Over 100 biosurfactant-producing microorganisms were isolated from oily sludge and petroleum-contaminated soil from Shengli oil field in north China. Sixteen of the bacterial isolates produced biosurfactants and reduced the surface tension of the growth medium from 71 to <30 mN m⁻¹ after 72 h of growth. These bacteria were used to treat oily sludge and the recovery efficiencies of oil from oily sludge were determined. The oil recovery efficiencies of different isolates ranged from 39% to 88%. Bacterial isolate BZ-6 was found to be the most efficient strain and the three phases (oil, water and sediment) were separated automatically after the sludge was treated with the culture medium of BZ-6. Based on morphological, physiological characteristics and molecular identification, isolate BZ-6 was identified as Bacillus amyloliquefaciens. The biosurfactant produced by isolate BZ-6 was purified and analyzed by high performance liquid chromatography-electrospray ionization tandem mass spectrometry. There were four ion peaks representing four different fengycin A homologues.     

餐厨垃圾与剩余污泥协同发酵提升低C/N污水脱氮效能的中试研究

我国城镇污水处理厂进水碳源普遍偏低,严重影响生物脱氮效能。外加碳源会造成大量化学品消耗及碳排放,与双碳战略背道而驰。考察了餐厨垃圾和剩余污泥联合发酵中试装备 (规模10 t·d⁻¹) 制备挥发性脂肪酸 (VFA) 效能,并将生产的VFA发酵液投加至昆山市某城镇污水处理厂,以减少外源乙酸钠碳源投加量,以期探索城市污水与有机固废的协同、高效、低碳处理技术。结果表明：餐厨垃圾与剩余污泥体积比为7∶3时,VFA质量浓度最高,达到54.3 g·L⁻¹ (以COD计) ,乙酸和丙酸质量分数分别为36.5%和22.8%;在批次发酵中试实验中,VFA最高质量浓度达67.5 g·L⁻¹ (以COD计) ,最低质量浓度为42.4 g·L⁻¹ (以COD计) ,平均质量浓度为55.0 g·L⁻¹ (以COD计) ;对比3类碳源的反硝化实验结果,投加乙酸钠组1.5 h脱氮率为86.5%,投加发酵液组4.5 h脱氮率为81.0%,投加餐厨垃圾组仅为69.8%;根据出水总氮预警阈值 (>8 mg·L⁻¹) 补加发酵液,替代部分乙酸钠,通过实际污水厂运行数据,拟合得到发酵液投量X (m³) 与乙酸钠吨水节约量Y (g·m⁻³) 的线性关系式Y=4.9X+3.5,其中R²=0.91。该研究结果可为联合发酵制备优质碳源提升污水厂脱氮工程应用提供参考。     

The response of Escherichia coli, Bacillus subtilis, and Burkholderia cepacia WZ1 to oxidative stress of exposure to quinclorac

The activity response of the antioxidant enzymes superoxide dismutase, catalase, ATP enzyme activities of Escherichia coli (G-), Bacillus subtilis (G+), and Burkholderia cepacia WZ1 (G-) following exposure to quinclorac was investigated. The bacterial strains were treated with the different concentrations of quinclorac (1.65, 16.5, 33.0, 165.0, 330.0, and 500.0 microg L(-1)). Results obtained indicated that SOD and CAT activities of these bacteria were induced positively and obviously by quinclorac, especially to gram-positive (G+) bacteria treated by lower than 330 microg L(-1) of quinclorac. The inhibition of ATPase in E. coli K12, B. subtilis, and B. cepacia WZ1 appeared stronger with the increase of quinclorac concentration, showing a striking dose response relationship, which can, therefore, be used as an available bioindicator for quinclorac pollution. The concentration of quinclorac applied in this research had significant effects on these three bacteria at the early stage of incubation, but none of which was persistent. Native polyacrylamide gel electrophoresis and activity staining of SOD revealed that quinclorac had effects on isoforms of E. coli and B. subtilis, and on the staining intensities of the isoforms of B. cepacia WZ1. When E. coli K12 was incubated with 330 microg L(-1) of quinclorac, the upper band of the isoforms of SOD tended to become slightly more apparent at 1 h after the quinclorac treatment, but the staining activity was slightly reduced after the prolonged treatment of quinclorac. No such changes of the isoforms of B. cepacia WZ1 was observed.     

Response surface optimization of substrates for thermophilic anaerobic codigestion of sewage sludge and food waste

This study investigated the effects of food waste constituents on thermophilic (55 degrees C) anaerobic codigestion of sewage sludge and food waste by using statistical techniques based on biochemical methane potential tests. Various combinations of grain, vegetable, and meat as cosubstrate were tested, and then the data of methane potential (MP), methane production rate (MPR), and first-order kinetic constant of hydrolysis (kH) were collected for further analyses. Response surface methodology by the Box-Behnken design can verify the effects and their interactions of three variables on responses efficiently. MP was mainly affected by grain, whereas MPR and kH were affected by both vegetable and meat. Estimated polynomial regression models can properly explain the variability of experimental data with a high-adjusted R2 of 0.727, 0.836, and 0.915, respectively. By applying a series of optimization techniques, it was possible to find the proper criteria of cosubstrate. The optimal cosubstrate region was suggested based on overlay contours of overall mean responses. With the desirability contour plots, it was found that optimal conditions of cosubstrate for the maximum MPR (56.6 mL of CH4/g of chemical oxygen demand [COD]/day) were 0.71 g of COD/L of grain, 0.18 g of COD/L of vegetable, and 0.38 g of COD/L of meat by the simultaneous consideration of MP, MPR, and kH. Within the range of each factor examined, the corresponding optimal ratio of sewage sludge to cosubstrate was 71:29 as the COD basis. Elaborate discussions could yield practical operational strategies for the enhanced thermophilic anaerobic codigestion of sewage sludge and food waste.     

茅草添加与温度变化对餐厨垃圾厌氧水解产酸的影响简

比较了茅草添加在温度变化条件下对餐厨垃圾厌氧水解过程小分子有机酸产量的影响,提出一种新型餐厨垃圾的资源化方式。研究结果显示,餐厨垃圾在55℃条件下厌氧水解主要产物为乳酸,达到25.7 g/L,其干物质转化率可以达到32.1% （g TS）,而餐厨+茅草处理在同样条件下的乳酸产量为20.1 g/L,干物质转化率为25.1%。温度下降为37℃后继续进行的的厌氧水解,得到的主要产物是乙酸、丙酸和丁酸,餐厨处理和餐厨+茅草处理这两者的峰值分别为6.5、2.8、8.0和6.1 g/L、2.7 g/L和5.9 g/L。结果显示茅草添加可以在一定程度上调节水解产物的比例,而温度变化可以调控小分子有机酸的产量。本研究结果表明,厌氧水解是一种有潜力的小分子有机酸生产与餐厨垃圾资源化处理途径。     

茅草添加与温度变化对餐厨垃圾厌氧水解产酸的影响

比较了茅草添加在温度变化条件下对餐厨垃圾厌氧水解过程小分子有机酸产量的影响,提出一种新型餐厨垃圾的资源化方式。研究结果显示,餐厨垃圾在55℃条件下厌氧水解主要产物为乳酸,达到25．7g／L,其干物质转化率可以达到32．1％（gTS）,而餐厨＋茅草处理在同样条件下的乳酸产量为20．1g／L,干物质转化率为25．1％。温度下降为37℃后继续进行的的厌氧水解,得到的主要产物是乙酸、丙酸和丁酸,餐厨处理和餐厨＋茅草处理这两者的峰值分别为6．5、2．8、8．0和6．1g／L、2．7g／L和5．9g／L。结果显示茅草添加可以在一定程度上调节水解产物的比例,而温度变化可以调控小分子有机酸的产量。本研究结果表明,厌氧水解是一种有潜力的小分子有机酸生产与餐厨垃圾资源化处理途径。     

Significance of Bacillus subtilis strain SJ-101 as a bioinoculant for concurrent plant growth promotion and nickel accumulation in Brassica juncea

In this study, a nickel (Ni)-tolerant Bacillus subtilis strain SJ-101 was characterized based on the 16SrDNA homology and phylogenetic analysis. The role of this strain ascertained in facilitating Ni accumulation in the Indian mustard plant (Brassica juncea [L]. Czern and Coss) var. Pusa Bold (DIR-50), to elucidate the potential of Ni phytoremediation in combination with metal-tolerant rhizobacteria. The data revealed that the plants exposed to NiCl2 (1750 mg kg(-1)) in soil bioaugmented with strain SJ-101 have accumulated 0.147% Ni vis-à-vis 0.094% accumulation in dry biomass of the plants grown in uninoculated soil. The strain SJ-101 has also exhibited the capability of producing indole acetic acid (IAA) (55 microg ml(-1)), and solubilizing inorganic phosphate (90 microg ml(-1)) in specific culture media. The pot culture experiments clearly demonstrated the beneficial effects of bioinoculant strain SJ-101 with significant increase (p<0.05) in the plant growth attributes in untreated control soil. Furthermore, the protective effect of the strain SJ-101 against Ni phytotoxicity was evident in plants grown in soil treated with NiCl2 in concentration range of 250-1750 mg kg(-1). Thus, it is suggested that the strain SJ-101 owing to its intrinsic abilities of plant growth promotion, and attenuation of soil Ni by biosorption and bioaccumulation, could be exploited for bacteria-assisted phytoaccumulation of this toxic heavy metal from contaminated sites.     

Inactivation of Bacillus subtilis spores during ozonation in water treatment plant: influence of pre-treatment and consequences for positioning of the ozonation step

This study reports on quantitative methodology for rational selection of the ozone injection point within unit processes of conventional drinking water treatment plants to improve disinfection efficiencies. The method is based on the fact that a specific inactivation level of microorganisms is achieved at a unique value of ozone exposures, independent of ozone dose and type of water, and quantitatively described by a Delayed Chick-Watson model (C T(lag): 1.03mgl(-1), k: 1.44mg(-1)lmin(-1)). This study demonstrated this phenomenon by performing the inactivation of Bacillus subtilis (B. subtilis) spores with ozone in various types of water collected from a series of unit processes in a water treatment plant. Simple measurements of the ozone decomposition behavior in waters from each unit process of a water treatment plant can allow the quantitative evaluation of the ozone needed to achieve a required level of inactivation. This methodology will be useful for drinking water treatment plants which intend to improve the disinfection efficiencies of their ozonation process.     

Investigation of the available technologies and their feasibility for the conversion of food waste into fish feed in Hong Kong

Food waste is the largest constituent of municipal solid waste in Hong Kong, but food waste recycling is still in its infancy. With the imminent saturation of all landfill sites by 2020, multiple technologies are needed to boost up the food waste recycling rate in Hong Kong. Conversion of food waste into animal feeds is prevalent in Japan, South Korea, and Taiwan, treating over 40 % of their recycled food waste. This direction is worth exploring in Hong Kong once concerns over food safety are resolved. Fortunately, while feeding food waste to pigs and chickens poses threats to public health, feeding it to fish is considered low risk. In order to examine the feasibility of converting food waste into fish feed in Hong Kong, this paper investigates the market demand, technical viability, feed quality, regulatory hurdles, and potential contribution. The results show that a significant amount of food waste can be recycled by converting it into fish feed due to the enormous demand from feed factories in mainland China. Two conversion technologies, heat drying and black soldier fly bioconversion, are studied extensively. Black soldier fly bioconversion is preferable because the end-product, insect powder, is anticipated to gain import approval from mainland China. The authors suggest further research efforts to speed up its application for food waste recycling in urban cities.     

利用复介电常数和BPAT神经网络进行环境监测的可行性研究

土壤中的污染物成分复杂，其含量与复介电常数之间具有很强的非线性关系。以土壤样品复介电常数的实部、虚部分别作为输入，以其含水率、体密度和所含6种已知离子的浓度分别作为输出，建立BP人工神经网络。把吉泰兰地区的土壤样品数据分为训练样本集和检验样本集，网络训练后，其学习效果显示模型的性能很好，检验样本的预测结果也与实测值较好吻合，说明利用复介电常数和BP人工神经网络进行环境监测是一种好的方法。     

A facilitating framework for a developing country to adopt smart waste management in the context of circular economy

Environmental Science and Pollution Research - To achieve higher standards of sustainability, the waste management sector now requires the incorporation of circular economy (CE) principles....     

A model for the implementation of a two-shift municipal solid waste and recyclable material collection plan that offers greater convenience to residents

Separating recyclables from municipal solid waste (MSW) before collection reduces not only the quantity of MSW that needs to be treated but also the depletion of resources. However, the participation of residents is essential for a successful recycling program, and the level of participation usually depends on the degree of convenience associated with accessing recycling collection points. The residential accessing convenience (RAC) of a collection plan is determined by the proximity of its collection points to all residents and its temporal flexibility in response to resident requirements. The degree of proximity to all residents is determined by using a coverage radius that represents the maximum distance residents need to travel to access a recycling point. The temporal flexibility is assessed by the availability of proximal recycling points at times suitable to the lifestyles of all residents concerned. In Taiwan, the MSW collection is implemented at fixed locations and at fixed times. Residents must deposit their garbage directly into the collection vehicle. To facilitate the assignment of collection vehicles and to encourage residents to thoroughly separate their recyclables, in Taiwan MSW and recyclable materials are usually collected at the same time by different vehicles. A heuristic procedure including an integer programming (IP) model and ant colony optimization (ACO) is explored in this study to determine an efficient two-shift collection plan that takes into account RAC factors. The IP model has been developed to determine convenient collection points in each shift on the basis of proximity, and then the ACO algorithm is applied to determine the most effective routing plan of each shift. With the use of a case study involving a city in Taiwan, this study has demonstrated that collection plans generated using the above procedure are superior to current collection plans on the basis of proximity and total collection distance.     

纳米零价铁和零价铁对餐厨垃圾暗发酵制氢过程铁离子和酶活性的影响

通过投加不同浓度的纳米零价铁(NZVI)和零价铁(ZVI),考察了暗发酵制氢过程中铁离子组成和浓度变化、氢化酶和脱氢酶活性,研究了2种添加剂强化餐厨垃圾高温((55±1) ℃)暗发酵制氢的作用机制。结果表明：投加NZVI和ZVI均可提高餐厨垃圾暗发酵制氢性能;当投加100 mg·L⁻¹ ZVI时,产氢效果最佳,最大产氢潜力和最大产氢速率分别为425.72 mL和66.32 mL·h⁻¹,是投加NZVI实验组的1.64倍和1.34倍,代谢途径是以乙醇型发酵为主的混合型发酵;在投加NZVI和ZVI后,暗发酵制氢末端产物的Fe²⁺和Fe³⁺浓度升高,投加300 mg·L⁻¹ NZVI和100 mg·L⁻¹ ZVI实验组Fe²⁺浓度最大,是未投加实验组的2倍和1.87倍;与反应前相比,Fe²⁺显著升高,Fe³⁺由于微生物利用与转化浓度降低,同时可有效提高氢化酶活性。投加100 mg·L⁻¹ ZVI不仅可提高氢化酶活性,还可提高脱氢酶活性。以上结果可为提高餐厨垃圾等复杂有机废物的高效能源化提供参考。     

A new strategy for determination of hydroxylamine and phenol in water and waste water samples using modified nanosensor

A carbon paste electrode modified with p-chloranil and carbon nanotubes was used for the sensitive and selective voltammetric determination of hydroxylamine (HX) and phenol (PL). The oxidation of HX at the modified electrode was investigated by cyclic voltammetry (CV), chronoamperommetry, and electrochemical impedance spectroscopy. The values of the catalytic rate constant (k), and diffusion coefficient (D) for HX were calculated. Square wave voltammetric peaks current of HX and PL increased linearly with their concentrations at the ranges of 0.1–172.0 and 5.0–512.0 μmol L^?1, respectively. The detection limits for HX and PL were 0.08 and 2.0 μmol L^?1, respectively. The separation of the anodic peak potentials of HX and PL reached to 0.65 V, using square wave voltammetry. The proposed sensor was successfully applied for the determination of HX and PL in water and wastewater samples.     

Threat to food security under current levels of ground level ozone: A case study for Indian cultivars of rice

A higher ozone concentration in rural agricultural region poses threat to food production in developing countries. The present study was conducted to evaluate the growth, biomass accumulation and allocation pattern, quantitative and qualitative characteristics of grains for two tropical rice cultivars (Oryza sativa L. cv NDR 97 and Saurabh 950) at ambient O₃ concentrations at a rural site in the Indo Gangetic plains of India.Percent inhibition in number of leaves was higher for NDR 97, but in leaf area for Saurabh 950 grown in non filtered chambers (NFCs) compared to filtered chambers (FCs). Higher inhibition in root biomass was recorded in Saurabh 950 and in leaf and standing dead biomass for NDR 97. During vegetative phase, relative growth rate showed more percent inhibition in Saurabh 950, but at reproductive phase in NDR 97. Net assimilation rate showed higher values for Saurabh 950 than NDR 97 in NFCs but percent inhibition in leaf area ratio was higher for former than latter cultivar in NFCs. The ozone resistance was higher in NDR 97 during vegetative phase, but in Saurabh 950 at reproductive phase. Number of grains was higher in NDR 97 than Saurabh 950, but test weight and weight of grains m^?2 showed reverse trends. Concentrations of starch, protein, P, N, Ca, Mg and K decreased, while reducing and total soluble sugar increased in grains of both the cultivars in NFCs compared to FCs. The study concluded that under ambient condition of O₃ exposure, the two cultivars responded differently. Saurabh 950 favoured biomass translocation priority towards ear in reproductive phase and hence showed higher resistivity due to maintenance of higher test weight. NDR 97, however, showed better growth during vegetative period, but could not allocate efficiently to developing ears, hence higher number of unfilled grains in NFCs led lower test weight.